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CARLO JACOBONI

Professore emerito
Dipartimento di Scienze Fisiche, Informatiche e Matematiche sede ex-Fisica

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Pubblicazioni

2020 - Band transport and localised states in modelling the electric switching of chalcogenide materials [Articolo su rivista]
Brunetti, R.; Jacoboni, C.; Piccinini, E.; Rudan, M.
abstract

The role of the extended (band) states in determining the electric switching of chalcogenide materials in the amorphous phase is here analysed by means of a theoretical/simulative approach which accounts for both mobile and localised states. This goal is accomplished by including a parabolic dispersion relation for the mobile states into a set of equations of the hydrodynamic type. Simulation results have been obtained for three chalcogenides particularly appealing for technological applications. Comparison is reported with available experimental results for nanometre devices. Furthermore, a comparative analysis of the outcomes of the present model with data from other theoretical approaches based on different physical assumptions is carried out.

2017 - Time- and space-dependent electric response of Ovonic devices [Articolo su rivista]
Jacoboni, C.; Piccinini, E.; Brunetti, R.; Rudan, M.
abstract

A time- and space-dependent 1D model including the self-consistent solution of the Poisson equation is presented to study the electric response of nanometer Ovonic samples. The model accounts for the main features of the relevant microscopic processes occurring inside the material, and is easily incorporated in commercial device-simulation tools. Numerical results are presented and discussed for Ovonic samples of different lengths and material parameters, and successfully compared to recent optimized experimental results for AgInTeSb. The analysis indicates a very short intrinsic response time of Ovonic devices, of the order of tens of ps and a minimum device length of the order of 5-10 nm, in order to guarantee the device functionality. Tests on the sensitivity of the model on some physical parameters have also been carried out.

2017 - Transport scaling limits of ovonic Devices: a simulative approach [Relazione in Atti di Convegno]
Jacoboni, Carlo; Piccinini, Enrico; Brunetti, Rossella; Rudan, Massimo
abstract

The transport scaling limits of Ovonic devices are studied by means of a numerical solution of a time- and space-dependent transport models based on a set of equations that provide a good physical grasp of the microscopic process at hand. The predictivity of the approach has been confirmed through the comparison with recent experimental results where the parasitic effects have been reduced by the use of top-technology measuring equipments. The present analysis is performed for the AgInSbTe chalcogenide, since this material exibits a steep threshold-switching dynamics which makes it promising for high-speed non-volatile memory applications.

2016 - Electric Response of Ovonic Materials to Oscillating Potentials [Relazione in Atti di Convegno]
Piccinini, Enrico; Brunetti, Rossella; Rudan, Massimo; Jacoboni, Carlo
abstract

This paper presents a computational analysis, by means of a compact model, of the electric response of an Ovonic Threshold-Switch device embedded in a circuit subjected to an oscillatory bias.

2016 - Transient and Oscillating response of Ovonic devices for high-speed electronics [Articolo su rivista]
Piccinini, Enrico; Brunetti, Rossella; Bordone, Paolo; Rudan, Massimo; Jacoboni, Carlo
abstract

The electric response of Ovonic devices to a time-dependent voltage is analysed by means of a charge-transport model previously proposed by the authors. The numerical implementation of the model shows that the features of the I(V) characteristics depend not only upon the external bias, but also on more complex effects due to the interplay between intrinsic microscopic relaxation times and the inevitable parasitic elements of the system. Either stable or oscillating solutions are found according to the position of the load line. The model also allows for speculations on the potential of Ovonic materials in the design of selector devices for two-terminal non-volatile memories.

2015 - Suono: cibo dell'anima [Esposizione]
Brunetti, Rossella; Jacoboni, Carlo; Morten, Bruno
abstract

Tra tanto parlar di cibo, proviamo a parlare anche di cibo dell’anima, cioè di musica e dei suoni di cui la musica si compone. Dai tempi più antichi delle comunità umane non c’è cultura che non abbia sviluppato la propria musica e i propri strumenti per produrla, non c’è festa o banchetto, lieto o triste evento che non sia accompagnato da musica. La musica è così “innata” nell’uomo che qualcuno sostiene che forse si è cominciato a cantare prima che a parlare….Comunque sia andata il cibo dell’anima è sempre esistito per tutti, nobili, colti, ricchi, semplici o poveri. L’esplorazione della natura fisica del suono e delle possibilità di produzione ed elaborazione dei suoni hanno accompagnato lo sviluppo della scienza dalle epoche più antiche fino alla nostra era digitale. Le possibilità aperte all’impiego tecnologico e artistico dei suoni sono aumentate di pari passo con la conoscenza fisica e la capacità manipolativa del mondo sonoro. Questa eredità preziosa, che ha attraversato e coinvolto tutte le civiltà, è, come poche altre, un patrimonio planetario comune di Scienza, Tecnologia e Arte. Il progetto 2015 del ciclo La Curiosità fa lo Scienziato propone una esplorazione della natura fisica del suono, con alcuni approfondimenti tematici sulle possibilità offerte dagli strumenti musicali tradizionali e dalla voce umana e anche sulla manipolazione digitale del suono. L’ illustrazione dei contenuti scientifici e tecnologici relativi al mondo dei fenomeni sonori mostrerà come un sapere scientifico molto antico si è tramandato attraverso i secoli e si è progressivamente arricchito attraverso l’avanzamento delle Scienze e della Tecnologia, mantenendo ancora sorprendentemente “giovani” e attuali i contenuti delle antiche teorie e pratiche. Gli incontri previsti all’interno del Progetto e dedicati a platee di età diverse includono conversazioni a tema arricchite da esperimenti ed esecuzioni di brani musicali.

2014 - Electrical bistability in amorphous semiconductors: a basic analysical theory [Articolo su rivista]
Buscemi, Fabrizio; E., Piccinini; Cappelli, Andrea; Brunetti, Rossella; M., Rudan; Jacoboni, Carlo
abstract

An analytical theory of electrical bistability in amorphous semiconductors is presented and validated for chalcogenide amorphous materials.

2013 - 3D-nHD: a Hydrodynamic Model for trap-limited conduction in a 3d network [Relazione in Atti di Convegno]
Cappelli, Andrea; Brunetti, Rossella; Jacoboni, Carlo; Xiong, E. P. i. c. c. i. n. i. n. i. F.; A., Behnam; E., Pop
abstract

a 3d model for trap-limited conduction that makes use of a nonlinear resistance network is presented and applied to conduction in chalcogenide materials.

2013 - Conductive preferential paths of hot carriers in amorphous phase-change materials [Articolo su rivista]
Cappelli, Andrea; E., Piccinini; F., Xiong; A., Behnam; Brunetti, Rossella; M., Rudan; E., Pop; Jacoboni, Carlo
abstract

Charge transport properties of amorphous phase-change materials (PCM) are studied using a set of balance equations applied to a 3D random network of sites.

2013 - Multilevel modeling for charge transport in ovonic chalcogenide materials and devices [Articolo su rivista]
M., Rudan; A., Giovanardi; E., Piccinini; Buscemi, Fabrizio; Brunetti, Rossella; Cappelli, Andrea; G., Marcolini; Jacoboni, Carlo
abstract

A sound physical model for electric conduction in ovonic materials is presented.

2013 - Novel 3D random-network model for threshold switching of phase-change memories [Relazione in Atti di Convegno]
Piccinini, Enrico; Cappelli, Andrea; Xiong, Feng; Behnam, Ashkan; Buscemi, Fabrizio; Brunetti, Rossella; Rudan, Massimo; Pop, Eric; Jacoboni, Carlo
abstract

The onset of crystallization in phase-change memory devices is studied by simulating an initially amorphous sample through a disordered network of localized states. The transport of charge and electron energy is self-consistently coupled to the Poisson and the Fourier heat equations, so that crystallization sites are found at the nanoscale. Results show how Ovonic switching and crystallization are both correlated to the formation of hot-carrier conduction paths, and the conditions for the occurrence of these phenomena are investigated. The model is then validated against data from ultra-scaled carbon-nanotube-contacted devices. Device-to-device variability of macroscopically identical devices is also analyzed. publisher = {IEEE}, title = {Novel 3D random-network model for threshold switching of phase-change memories},

2012 - Hot-Carrier trap-limited transport in switching chalcogenides [Articolo su rivista]
E., Piccinini; Cappelli, Andrea; F., Buscemi; Brunetti, Rossella; D., Ielmini; M., Rudan; Jacoboni, Carlo
abstract

Hot-Carrier trap-limited transport in switching chalcogenides is studied by means of a numerical procedure which extends the traditional hydrodynamic approach used for transport in bulk semiconductor systems.

2011 - Low-field electron diffusion and noise in amorphous chalcogenides [Relazione in Atti di Convegno]
F., Buscemi; E., Piccinini; Brunetti, Rossella; M., Rudan; Jacoboni, Carlo
abstract

The low-field electric conduction in amorphous chalcogenides is here investigated by means of a Monte Carlo implementation of a full three-dimensional variable-range hopping transport model between localized states. Macroscopic features of the electrical conduction are obtained from numerical simulations and then used toestimate the linear region of the current density-voltage. The latter fits the experimentaldata. Our transport scheme also reproduces the temperature behavior of the conductivity typical of non-crystalline solids. The present investigation provides a basic schemeto be extended for the analysis of electron transport in chalcogenide glasses at high-field regimes.

2011 - Quantum electronic band to trap transitions in chalcogenides induced by electron-electron interaction [Relazione in Atti di Convegno]
F., Buscemi; E., Piccinini; F., Giovanardi; M., Rudan; Brunetti, Rossella; Jacoboni, Carlo
abstract

Charge transport in amorphous-chalcogenide materials used formanufacturing memory devices is determined by two mechanisms: hoppingof trapped electrons and motion of band electrons. Electron-electroninteraction is investigated here as one of the mechanisms mainlyresponsible for the trap-to-band transitions. The problem is tackledusing a fully quantum-mechanical approach by numerically solving thetwo-particle, time-dependent Schr\"odinger equation. The results showthat the detrapping probability increases with the current density,this supporting the interpretation by which successiveelectron-electron scattering events may play a major role in thedetermining the snap-back of the $I(V)$ characteristic in this kind ofmaterials.

2011 - Voltage snapback in amorphous-GST memory devices: transport model and validation [Articolo su rivista]
M., Rudan; F., Giovanardi; E., Piccinini; F., Buscemi; Brunetti, Rossella; Jacoboni, Carlo
abstract

Charge transport in amorphous chalcogenide-GST used for memory devices is modeled using two contributions: hopping of trapped electrons and motion of band electrons in extended states. The type of feedback that produces the snapback phenomenon is described as a filamentation in energy that is controlled by electron-electron interactions between trapped electrons and band electrons. The model thus derived is implemented within a state-of-the-art simulator. An analytical version of the model is also derived and is useful for discussing the snapback behavior and the scaling properties of the device.

2010 - Modeling of the voltage snap-back in amorphous gst memory devices [Relazione in Atti di Convegno]
M., Rudan; F., Giovanardi; T., Tsafack; X., Xiong; E., Piccinini; F., Buscemi; A., Liao; E., Pop; Brunetti, Rossella; Jacoboni, Carlo
abstract

Charge transport in amorphous chalcogenide-GST used for memory devices is modeled by means of two contributions: hopping of trapped electrons and motion of band electrons. Field-induced emission is accounted for as the mechanism mainly responsible for the trap-to-band transitions. The experimental snap-back behavior of the I(V) curves is reproduced even in the simple case of one-dimensional, uniform structures as the one considered in the paper.

2010 - Theory of Electron Transport in Semiconductors - A Pathway from Elementary Physics to Nonequilibrium Green Functions [Monografia/Trattato scientifico]
Jacoboni, Carlo
abstract

This book describes in details the theory of the electron transport in the materials and structures at the basis of modern micro- and nano-electronics. It leads and accompanies the reader, through a step-by-step derivation of all calculations, from the basic laws of classical and quantum physics up to the most modern theoretical techniques, such as nonequilibrium Green functions, to study transport properties of both semiconductor materials and modern low-dimensional and mesoscopic structures.

2009 - A new hopping model for transport in chalcogenide glasses [Relazione in Atti di Convegno]
Rudan, M.; Giovanardi, F.; Piccinini, E.; Buscemi, F.; Brunetti, R.; Jacoboni, C.
abstract

2009 - Investigation of charge transport in amorphous ge2sb2te5 using the variable-range hopping model [Relazione in Atti di Convegno]
E., Piccinini; F., Buscemi; T., Tsafack; M., Rudan; Brunetti, Rossella; Jacoboni, Carlo
abstract

Chalcogenide GST materials can suitably beexploited for manufacturing phase-change memory devices.In this paper a transport model for the amorphousphase of GST is investigated, based on the variable-range,hopping-electron model. The model is implemented bythe Monte Carlo method using the current-driven mode inboth implementations. It is applied to a device consistingof a nanometric layer of amorphous Ge2Sb2Te5 in contactwith two planar metallic electrodes. The mechanisms governingelectron transport within the device are discussedin relation to the variation of external parameters, such asoperating current and trap density.

2009 - Monte Carlo simulation of charge transport in amorphous chalcogenides [Articolo su rivista]
F., Buscemi; E., Piccinini; Brunetti, Rossella; M., Rudan; Jacoboni, Carlo
abstract

The most peculiar feature exhibited by $I(V)$ characteristics of amorphous chalcogenides materials is undoubtly its S-shape given by a negative differential-resistance behavior. In order to pursue a theoretical control of such a behavior so important for technological exploitation, in this paper we give a microscopic particle description of the charge transport across a simple device of amorphous $mathrm{Ge_2Sb_2Te_5}$ sandwiched between two planar metallic contacts. Specifically, a transport scheme based on the generalization of the variable range hopping has been implemented in a current-driven Monte Carlo simulation that allows one to investigate the aspects of the microscopic picture responsible for the electrical properties of the device. Results obtained are compared with experimental data.% and the other models available in the literature.

2009 - Monte Carlo simulation of charge transport in amorphous chalcogenides [Relazione in Atti di Convegno]
E., Piccinini; F., Buscemi; M., Rudan; Brunetti, Rossella; Jacoboni, Carlo
abstract

Chalcogenide $mathrm{Ge_2Sb_2Te_5}$ material (GST) can suitably be exploited for manufacturing phase-change memory devices. Crystalline GST exhibits an almost Ohmic I(V) curve. In contrast, the amorphous GST shows a high resistance at low biases while, above a threshold voltage, a transition takes place from a highly resistive to a conductive state, characterized by a swift rise of the current along with a voltage snap back ~cite{Pirovano2004} .A clear and correct understanding of the threshold behavior is of the utmost importance for exploiting GST in the fabrication of innovative nonvolatile memories.Experimental structural information and first-principle studies of amorphous GST suggest that the most appropriate transport picture is the one based on hopping processes through localized states~cite{Mott1961} due to a combination of tunneling and thermal excitation.A trap-conduction model is used in this work, where the current flow is due to electron hopping among donor-type traps.Transitions are accounted for according to the variable-range hopping theory. The electron phonon-assisted transition rate is evaluated according to the rate equation in ~cite{miller1960}, taking into account nonlinear effects in the electric field. The physical model summarized above is used for the first time to evaluate the electrical properties of a nanometric 3D layer of amorphous GST in contact with two metallic electrodes by means of a Monte Carlo simulation.The standard voltage-driven Monte Carlo framework has been modified into a current-driven simulation, which better compares to the typical experimental setup.The numerical procedure includes a self-consistent solution of the electric potential. The latter, in fact, has a strong influence onto the hopping rate.Results show that a realistic theoretical transport framework based on the variable-range hopping yields a complete microscopic description of the mechanism governing the threshold switching. In particular, the snap-back effect is correlated to the formation of domains of opposite charges within the device.egin{thebibliography}{9}ibitem{pirovano2004} A. Pirovano, A. Lacaita, A. Benvenuti, F. Pellizzer, and R. Bez, extit{IEEE Trans. Electron. Devices}, vol.51(3), p.452 (2004).ibitem{Mott1961} N.F. Mott and E.A. Davis, extit{Electronic Processes in Non-Crystalline Materials}, Oxford: Clarendon Press (1961).ibitem{miller1960} A. Miller and E. Abrahams, extit{Phys.

2008 - Band calculation for the exagonal and FCC Chalcogenide Ge2Sb2Te5 [Relazione in Atti di Convegno]
E., Piccinini; T., Tsafack; F., Buscemi; Brunetti, Rossella; M., Rudan; Jacoboni, Carlo
abstract

The paper addresses the calculation of the band structure fordifferent phases of the chalcogenide Ge2Sb2Te5 compound,which is raising considerable interest in view of the applications tothe nonvolatile-memory technology. The band structure is necessary fordetermining the charge- and heat-transport properties of the material.The band diagram of the face-centered cubic phase, which is the mostimportant one for the operation of phase-change memories, is shown forthe first time.

2008 - Biased Molecular Simulations for Free-Energy Mapping: A Comparison on the KcsA Channel as a Test Case [Articolo su rivista]
Piccinini, E; Ceccarelli, M; Affinito, F; Brunetti, Rossella; Jacoboni, Carlo
abstract

The calculation of free-energy landscapes in proteins is a challenge for modern numerical simulations. As to the case of potassium io channels is concerned, it is particularly interesting because of the nanometric dimensions of the selectivity filter, where the complex electrostatics is highly relevant. The present study aims at comparing three different techniques used to bias molecular dynamics simulations, namely Umbrella Sampling, Steered Molecular Dynamics, and Metadynamics, never applied all together in the past to the same channel protein. Our test case is represented by potassium ions permeating the selectivity filter in the KcsA channel

2008 - Electron decoherence in a semiconductor due to electron-phonon scattering [Relazione in Atti di Convegno]
F., Buscemi; E., Cancellieri; Bordone, Paolo; A., Bertoni; Jacoboni, Carlo
abstract

In the present work we study, by means of numerical simulations, the coherent propagation of electrons in quantum wires and focus on the effect of the introduction of roughness along the channel. We study the electron evolution both in single and coupled quantum wires in the case where the electron freely move through the channel and in the case where transport is assisted by surface acoustic waves. It has been shown that systems of coupled quantum wires can realize a complete set of quantum logic gates.However, its physical implementation is severely limited by the spreading of the wave packet and by the presence of interface roughness. Our results show that the potential of the surface acoustic wave succeeds in confining the electron wavefunction and in driving it along the channels also when interface roughness is introduced. This suggests that electron transport assisted by surface acoustic waves could be a very efficient way to realize quantum solid state devices.

2008 - Monte Carlo simulation of charge transport in amorphous GST [Relazione in Atti di Convegno]
E., Piccinini; F., Buscemi; T., Tsafack; Brunetti, Rossella; M., Rudan; Jacoboni, Carlo
abstract

A microscopic particle description of the charge transport process in amorphous GST (a-GST) is presented in this paper, based on the assumption that electrical conduction in the amorphous phase is controlled by defects and trapped carriers. The physical model has been implemented in a Monte Carlo simulation coupled to the Poisson equation for a simple device formed by a nanometric layer of amorphous GST in contact with two planar metallic electrodes. The purpose of our research is to understand how and to which amount different aspects of the microscopic picture influence the electrical properties of the device when external tunable parameters, like operating current and temperature, are varied. Moreover the role of other parameters, often almost unknown in real devices like, e.g., trap energy levels and concentration, trap spatial distribution, is analised through focused simulated experiments with the purpose of pursuing a theoretical control of the threshold behavior so much important for technological exploitation. Results obtained so far are compared with experiments, analytical models available in the literature, and the outcome of deterministic equations formulated by the Authors for the system under investigation.

2008 - Roughness effect on electron transport through quantum wires [Articolo su rivista]
E., Cancellieri; M., Rosini; Bordone, Paolo; Jacoboni, Carlo
abstract

In the present work we study, by means of numerical simulations, the coherent propagation of electrons in quantum wires and focus on the effect of the introduction of roughness along the channel. We study the electron evolution both in single and coupled quantum wires in the case where the electron freely move through the channel and in the case where transport is assisted by surface acoustic waves. It has been shown that systems of coupled quantum wires can realize a complete set of quantum logic gates.However, its physical implementation is severely limited by the spreading of the wave packet and by the presence of interface roughness. Our results show that the potential of the surface acoustic wave succeeds in confining the electron wavefunction and in driving it along the channels also when interface roughness is introduced. This suggests that electron transport assisted by surface acoustic waves could be a very efficient way to realize quantum solid state devices.

2008 - Transport anisotropy in InGaAs two-dimensional electron gases induced by indium concentration modulation [Articolo su rivista]
D., Ercolani; G., Biasiol; E., Cancellieri; M., Rosini; Jacoboni, Carlo; F., Carillo; S., Heun; L., Sorba; F., Nolting
abstract

A pronounced anisotropy is observed in the low-temperature mobility of a two-dimensional electron gas formed in an In0.75Ga0.25As/In0.75Al0.75As quantum well grown on a GaAs substrate. We show that the mobility differences along [011] and [01-1] directions are mainly due to In concentration modulations. Spatially resolved photoemission measurements show an asymmetric indium concentration modulation, correlated with the surface morphology observed by atomic force microscopy. A theoretical model considering conduction band energy modulations agrees well with the transport measurements. The identification of this mobility limiting mechanism allowed us to design and grow higher quality two-dimensional electron gas, needed for high indium content InGaAs device fabrication.

2007 - Computational analysis of current and noise properties of a single open ion channel [Articolo su rivista]
E., Piccinini; F., Affinito; Brunetti, Rossella; Jacoboni, Carlo; M., Rudan
abstract

This paper presents a computational analysis of the noise associated with the ion current in single open ion channels. The study is performed by means of a coupled molecular dynamics/Monte Carlo approach able to simulate the conduction process on the basis of all microscopic information today available from protein structural data and atomistic simulations. The case of potassium ions permeating the KcsA channel is considered in the numerical calculations. The results show a noise spectrum different from what is theoretically predicted for Poisson noise, confirmed by the existence of a correlation in ion-exit events.

2007 - Conductance of meandering wires [Articolo su rivista]
Cancellieri, E; Bertoni, A; Jacoboni, Carlo; Rosini, M; Ferrari, G.
abstract

In the past years a strong attention has been focused on the optical and transport properties of semiconductor hetero-structures owing to the possibility of tailoring material parameters such as the electron effective mass and the band gap, by changing the structure parameters. Recent experimental results on In(x)Ga(1-x)As structures cannot be explained in the framework of standard theoretical and simulative approaches for the description of carrier transport in quantum wells. In order to get a better insight of the effect of the surface roughness on the conductance, we have considered meandering quantum wires and have computed their coherent transport characteristics. We find that, at low energies, the transmission coefficient is strongly dependent on the SR parameters. The dependence of the conductance upon length of the device is also analyzed.

2007 - Effect of symmetry in the many-particle Wigner funcion [Articolo su rivista]
E., Cancellieri; Bordone, Paolo; Jacoboni, Carlo
abstract

An analysis of the Wigner function for identical particles is presented. Four situations have been considered. (i) The first is scattering process between two indistinguishable particles described by a minimum uncertainty wave packets showing the exchange and correlation effects in Wigner phase space. (ii) An equilibrium ensemble of N particles in a one-dimensional box and in a one-dimensional harmonic potential is considered second, showing that the reduced one-particle Wigner function, as a function of the energy defined in the Wigner phase space, tends to the Fermi-Dirac or to the Bose-Einstein distribution function, depending on the considered statistics. (iii) The third situation is reduced one-particle transport equation for the Wigner function, in the case of interacting particles, showing the need for the two-particle reduced Wigner function within the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy scheme. (iv) Finally, the electron-phonon interaction in the two-particle case is considered, showing coparticipation of two electrons in the interaction with the phonon bath.

2007 - Exploring free-energy profiles through ion channels: comparison on a test case [Articolo su rivista]
E., Piccinini; F., Affinito; Brunetti, Rossella; Jacoboni, Carlo; M., Ceccarelli
abstract

Abstract The calculation of free-energy profiles in proteins, and, more specifically, in ion channels, is a challenge for modern numerical simulations due both to the convergence problems associated with the electrostatics of the environment and to the difficulties in modeling the fields acting on the permeating ions. The present study is aims at comparing three different simulation techniques available in the literature on a nanometric channel protein chosen as a test case, with the purpose of establishing their real predictivity and limits.

2007 - Shot noise in single open ion channels:a computational approach based on atomistic simulations [Articolo su rivista]
Brunetti, Rossella; F., Affinito; Jacoboni, Carlo; E., Piccinini; M., Rudan
abstract

Abstract This paper presents a computational analysis of the noise associated with ion current in single open ion channels. The study is performed by means of a coupled Molecular Dynamics/Monte Carlo approach able to simulate the conduction process on the basis of all microscopic information today available from protein structural data and atomistic simulations. The case of potassium ions permeating the KcsA channel is considered in the numerical calculations. Results show a noise spectrum different from what is theoretically predicted for uncorrelated ion-exit events (Poisson noise), confirming the existence of correlation in ion motion within the channel, already evinced by atomistic structural analyses.

2006 - Electron dynamics inside short-coherence systems [Articolo su rivista]
G., Ferrari; Bordone, Paolo; Jacoboni, Carlo
abstract

We present theoretical results on electron dynamics inside nanometric systems, where the coherence of the electron ensemble is maintained in a very short region. The contacts are supposed to spoil such a coherence, therefore the interference processes between the carrier wavefunction and the internal potential profile can be affected by the proximity of the contacts. The problem has been analysed by using the Wigner-function formalism. For very short devices, transport properties, such as tunnelling through potential barriers, are significantly influenced by the distance between the contacts.

2006 - Exchange effects in the Wigner-function approach [Relazione in Atti di Convegno]
E., Cancellieri; Bordone, Paolo; Jacoboni, Carlo
abstract

In this paper, an analysis of the Wigner function (WF) for identical fermions is presented. Three situations have been analyzed. i) A scattering process between two indistinguishable electrons in minimum uncertainty wavepackets showing the exchange and correlation hole in Wigner phase space. ii) An equilibrium ensemble of N electrons in a box showing that the WF integrated over space assumes the shape of a Fermi distribution even for very small N. iii) The reduced one-particle transport-equation for the WF in the case of interacting electrons showing the first contribution to the BBGKY hierarchy.

2006 - Physical Mechanisms for ion-current levelling off in the KcsA channel through combined Monte Carlo/Molecular Dynamics simulations [Relazione in Atti di Convegno]
E., Piccinini; A., Affinito; Brunetti, Rossella; Jacoboni, Carlo; AND M., Rudan
abstract

Conduction and noise properties of potassium ions in the KcsA membrane channel are analysed by means of a combined Molecular Dynamics-Monte Carlo numerical approach. The high-voltage part of the experimental I(V) charac-teristics shows a tendency to level off which is reproduced by computational re-sults using a conduction model quite sensitive to the particular set of transition probabilities among the relevant ion occupancy configurations. Noise power spec-tra confirm the existence of correlation between consecutive ion exits from the channel.

2006 - Quantum phonon-limited high-field electron transport in semiconductors [Relazione in Atti di Convegno]
Ferrari, G; Cancellieri, E; Bordone, Paolo; Jacoboni, Carlo
abstract

A fully quantum theory of phonon-limited electron transport in semiconductors is applied to a homogeneous steady-state situation to investigate the difference between quantum results and the results of a semiclassical theory. The Wigner function is used for the quantum approach, and the Monte Carlo simulations are performed in both semiclassical and quantum theories. In the considered case, hot-electron transport in a simple silicon model at 77 K, very little difference has been found since collisional broadening changes the possible final states of the electronic transitions without altering in a significan way the total scattering rate and therefore the momentum relaxation efficiency of phonon scattering.

2006 - Wigner transport models of the electron-phonon kinetics in quantum wires [Articolo su rivista]
Nedjalkov, M; Vasileska, D; Ferry, Dk; Jacoboni, Carlo; Ringhofer, C; Dimov, I; Palankovski, V.
abstract

Two quantum-kinetic models of ultrafast electron transport in quantum wires are derived from the generalized electron-phonon Wigner equation. The various assumptions and approximations allowing one to find closed equations for the reduced electron Wigner function are discussed with an emphasis on their physical relevance. The models correspond to the Levinson and Barker-Ferry equations, now generalized to account for a space-dependent evolution. They are applied to study the quantum effects in the dynamics of an initial packet of highly nonequilibrium carriers, locally generated in the wire. The properties of the two model equations are compared and analyzed.

2005 - A simulative model for the analysis of conduction properties of ion channels based on first-principle approaches [Articolo su rivista]
F., Affinito; Brunetti, Rossella; Jacoboni, Carlo; E., Piccinini; M., Rudan; Bigiani, Albertino; P., Carloni
abstract

The calculation of free-energy profiles in proteins, and, more specifically, in ion channels, is a challenge for modern numerical simulations due both to the convergence problems associated with the electrostatics of the environment and to the difficulties in modeling the fields acting on the permeating ions. The present study is aims at comparing three different simulation techniques available in the literature on a nanometric channel protein chosen as a test case, with the purpose of establishing their real predictivity and limits.

2005 - Multiband, non-parabolic Wigner-function approach to electron transport in semiconductors [Articolo su rivista]
L., Demeio; Bordone, Paolo; Jacoboni, Carlo
abstract

In this work, we introduce a multiband transport model for quantum electron transport in semiconductors following the Wigner-function approach. By using the Bloch-Floquet decomposition of the density matrix, we obtain the Bloch-Floquet projections of the Wigner function and derive their evolution equations for energy bands of arbitrary shape. The equations of the model are very general and allow (in principle) the investigation of quantum processes in which interband transitions and/or non-parabolicity effects may occur. Finally, we present numerical applications for some particular cases in which the numerical solution can be obtained easily.

2005 - Noise properties of single open ion channels: an atomistic computational approach [Relazione in Atti di Convegno]
F., Affinito; E., Piccinini; Bigiani, Albertino; Brunetti, Rossella; Jacoboni, Carlo; AND M., Rudan
abstract

This paper presents the first results of a computational analysis of the noise associated with ion current in single open ion channels. This analysis is performed by means of a coupled Molecular Dynamics-Monte Carlo approach able to simulate the conduction process on the basis of all microscopic information today available from protein structural data and atomistic simulations. The case of potassium ions permeating the KcsA channel is considered in the numerical calculations. The obtained results evidence a noise spectrum different from what is theoretically predicted for uncorrelated ion-exit events (Poisson noise), confirming the existence of correlation in ion motion within the channel.

2004 - 30 years of HCIS [Articolo su rivista]
Jacoboni, Carlo; Bordone, Paolo
abstract

On the occasion of the 30th anniversary of the HCIS conference, we would like to provide a general, although necessarily not exhaustive, picture of how the conference has changed over the years and of how the natural evolution of research has influenced its various editions. By performing a statistical analysis of specific sets of data, we try to identify some characteristic trends that, we believe, can contribute to a better understanding of how our field of research has been developing in the last three decades. On request of the editor, we added the data relative to HCIS-13.

2004 - A simulative method for the analysis of conduction properties of ion channels based on first-principle approaches [Relazione in Atti di Convegno]
Affinito, F.; Bigiani, A.; Brunettii, R.; Carloni, P.; Jacoboni, C.; Piccinira, E.; Rudan, M.
abstract

2004 - Coherent transport in coupled quantum wires assisted by surface acoustic waves [Articolo su rivista]
Bordone, Paolo; A., Bertoni; M., Rosini; S., Reggiani; Jacoboni, Carlo
abstract

In this work we present a simulation of the coherent evolution of electrons in two coupled quantum wires assisted by surface acoustic waves. The system under study has recently been proposed as a model for a solid-state realization of quantum gates. A quantum NOT transformation and an electron beam splitter have been numerically simulated. Results show that the surface acoustic waves improve the functionality of the device by preventing the spreading of the electron wavefunction and reducing undesired reflection effects.

2004 - Influence of contacts on the electron transport dynamics inside a mesoscopic system [Articolo su rivista]
G., Ferrari; N., Giacobbi; Bordone, Paolo; Jacoboni, Carlo; A., Bertoni
abstract

In mesoscopic systems the Wigner function picture is used for studying electron quantum transport. In this work we present theoretical results on the effect of contact proximity in nanometric devices. If the correlation of the electron wavefunction vanishes inside the contact regions, the transport properties inside the device are affected. We have verified this influence analytically. The main effect is the dependence of the tunnel current through potential barriers on the distance between the contacts. Using three different simulation schemes we have observed modifications in the electron density and conductance for simple devices depending on the distance between the contacts.

2004 - Numerical simulation of an intervalley transition by the Wigner-function approach [Articolo su rivista]
L., Demeio; Bordone, Paolo; Jacoboni, Carlo
abstract

In this work we present a recently developed transport model, based on the Wigner-function approach and allowing for non-parabolic band profiles. Two scattering mechanismIs are included by means of a Boltzmann-like collision operator, describing the collisions between electrons and polar optical and intervalley phonons. The transport equation for the Wigner function is solved by the splitting-scheme algorithm. We have chosen a one-dimensional model band profile, which exhibits satellite valleys, besides the minimum at the centre of the Brillouin zone, similar to the band profile of GaAs.

2004 - Quantum dynamics of polaron formation with the Wigner-function approach [Articolo su rivista]
Brunetti, Rossella; Monastra, S; Jacoboni, Carlo
abstract

In compound semiconductor crystals with a substantial degree of ionicity Froelich interaction of charge carriers with longitudinal optical (LO) phonons is strong enough to produce detectable polaron effects. In this paper polaron effects are analysed using a quantum theory of electron transport based on the momentum- and frequency-dependent Wigner function f(w) (p, omega), defined starting from the G(<) Green function, simply related to the electron spectral function A(p,omega). The theoretical approach considers the dynamical evolution of the electron Wigner function in the presence of phonon scattering. An elaboration of the quantum dynamical equation in terms of Wigner paths formed by free flights and scattering events is used. These paths are especially suitable for a Monte Carlo solution of the transport equation for the Wigner function very similar to the semiclassical traditional Monte Carlo solution of the Boltzmann equation. Numerical results for GaAs and CdTe in a variety of physical conditions are presented.

2004 - Simulation of entanglement dynamics for a scattering between a free and a bound carrier in a quantum wire [Articolo su rivista]
Bordone, Paolo; A., Bertoni; Jacoboni, Carlo
abstract

The decoherence of a quantum system is ascribed to its enetanglement with another system considered as the environment, thus the quantitative evaluation of entanglement formation dynamics can shed light on the transition between quantum and classical behavior of a carrier that undergoes to a scattering event. We present here a numerical solution of the time-dependent 1D Schroedinger equation of a two-particle system consisting of a free carrier scattered by a bound one. The real-space entanglement between them is computed, at different times, for various initial conditions. The maximum entanglement corresponds to equal probability of transmission and reflection of the free particle.

2004 - Single electron transport and entanglement induced by surface acoustic waves versus free ballistic propagation in coupled quantum wires [Articolo su rivista]
M., Rosini; A., Bertoni; Bordone, Paolo; Jacoboni, Carlo
abstract

In this work we study the coherent propagation of electrons in quantum wires driven by surface acoustic waves, as a part of a feasibility study on a coupled quantum wires device, able to realize the basic operations needed for quantum computing. We demonstrate that the introduction of the surface acoustic wave is able to improve the devices performance. In particular, single- and double-qubit quantum gates have been simulated and better results are obtained, with respect to the free electron propagation. A further analysis reveals a strong reduction of the final undesired spatial entanglement and confirms the effectiveness of the dynamics driven by surface acoustic wave.

2004 - The Wigner-function approach to non-equilibrium electron transport [Articolo su rivista]
Jacoboni, Carlo; Bordone, Paolo
abstract

The Wigner-function (WF) approach to quantum electron transport in semiconductors is reviewed in this paper. The main definitions and properties related to the WF are presented, with a discussion of the various forms of the dynamical equations that govern its evolution. Monte Carlo solutions of such equations are also discussed. Interactions of electrons with applied fields, potential profiles, and phonons are analysed in detail. Finally, several physical applications are presented. Each topic has been developed from basic principles for the benefit of interested readers who are not experts in the particular subjects discussed in this paper.

2004 - Wigner functions for identical particles [Articolo su rivista]
E., Cancellieri; Bordone, Paolo; A., Bertoni; G., Ferrari; Jacoboni, Carlo
abstract

In this work the Wigner function approach to quantum transport developed for the single electron case is extended to a more complicated system for n indistingushable particles. In particular we study how the Monte Carlo tecnique and the Wigner paths method can be applyed to a single particle Wigner function defined for a system of n interacting particles. The numerical results are obtained for the case of a system of two particles under different conditions: two noninteracting fermions, two noninteracting bosons, two non interacting distinguishable particles and two interacting fermions.

2003 - Dinamica elettronica in sistemi mesoscopici [Abstract in Atti di Convegno]
Bordone, Paolo; Jacoboni, Carlo
abstract

Negli ultimi anni, la continua riduzione delle dimensioni dei dispositivi a semiconduttore ha reso chiaro quanto sia necessario un approccio quantistico al problema del trasporto di carica. Il metodo, basato sul formalismo della funzione di Wigner si e` mostrato particolarmente adatto a questo scopo, sia per l'analogia formale con la descrizione classica in termini di spazio delle fasi, sia per il naturale utilizzo delle condizioni al contorno. Tra i risultati principali fin' ora ottenuti si ha una possibile spiegazione della sorprendente attendibilita` dell'approccio semiclassico (equazione di Boltzmann) e l'influenza della distanza dei contatti sulla dinamica elettronica interna ad un sistema mesoscopico.

2003 - Monte Carlo analysis of electron heating in Si/SiO2 superlattices [Articolo su rivista]
Rosini, Marcello; Jacoboni, Carlo; Ossicini, Stefano
abstract

In this work, we investigate the transport properties of Si/SiO2 superlattices with a multiband one-particle Monte Carlo simulator. Using the envelope function approximation, we solve the Kronig-Penney potential along the growth direction z using a tight-binding-like analytical form; we also consider parabolic dispersion along the xy plane. The scattering mechanisms introduced in the simulator are confined optical phonons, both polar and nonpolar. Owing to the very flat shape of the bands along the growth direction, very low drift velocities are found for vertical transport. However, the simulation shows that, for oblique fields, the transport properties along the vertical direction are strongly influenced by the in-plane component of the electric field: in this way higher vertical drift velocities can be obtained. The results point out that in-plane carrier heating and multiband properties are responsible for this behavior. (C) 2002 Elsevier Science B.V. All rights reserved.

2003 - Monte Carlo simulation of quantum electron transport based on Wigner paths [Articolo su rivista]
Bordone, Paolo; A., Bertoni; Brunetti, Rossella; Jacoboni, Carlo
abstract

Advancements and improvements in the Wigner function approach to quantum electron transport are reviewed. The concept of Wigner paths allows the formulation of the Monte Carlo simulation in strict analogy with the one used in semiclassical transport theory.

2003 - NUMERICAL AND ANALYTICAL APPLICATIONS OF MULTIBAND TRANSPORT IN SEMICONDUCTORS [Relazione in Atti di Convegno]
L., Demeio; Bordone, Paolo; Jacoboni, Carlo
abstract

A multiband transport model for electron transport in semiconductors, based on the Wigner-transport approach and allowing for energy bands of arbitrary shape, is presented and applied to two simple examples: a comparison of exact and free streaming solutions of teh Wigner equation in non-parabolic regime and an interband transition in an infinite homogeneous medium.

2003 - PROXIMITY EFFECT OF THE CONTACTS ON ELECTRON TRANSPORT IN MESOSCOPIC DEVICES [Articolo su rivista]
A., Bertoni; Bordone, Paolo; G., Ferrari; N., Giacobbi; Jacoboni, Carlo
abstract

The Wigner function formalism is used for studying electron quantum transport in mesoscopic systems. In this work we show that, if the correlation of the electron wave function vanishes outside the region of interest (for example inside the contacts), then transport is affected inside the device. This property is verified analytically. Results show that, for very short devices, tunneling is actually influenced by the distance between the contacts. Modification in the electron density and conductivity have been numerically observed.

2003 - QUANTUM DYNAMICS OF POLARON FORMATION WITH THE WIGNER-FUNCTION APPROACH [Articolo su rivista]
Jacoboni, Carlo; Brunetti, Rossella; S., Monastra
abstract

In compound semiconductor crystals with a substantial degree of ionicity Froelich interaction of charge carriers with longitudinal optical phonons is strong enough to produce detectable polaron effects. In this paper polaron effects are analyzed using a quantum theory of electron transport based on the momentum and frequency-dependent Wigner function fw(p,ω), defined starting from the G< Green function, simply related to the electron spectral function A(p,ω). The theoretical approach considers the dynamical evolution of the electron Wigner function in presence of phonon scattering. An elaboration of the quantum dynamical equation in terms of Wigner paths formed by free flights and scattering events is used. These paths are especially suitable for a Monte Carlo solution of the transport equation for the Wigner function very similar to the semiclassical traditional Monte Carlo solution of the Boltzmann equation. Numerical results for GaAs and CdTe in a variety of physical conditions are presented.

2003 - Semiclassical and quantum transport in Si/SiO2 superlattices [Articolo su rivista]
Rosini, Marcello; Jacoboni, Carlo; Ossicini, Stefano
abstract

In the last few years, many research groups have been trying to develop electroluminescent devices based on silicon. In particular, it has been shown that low-dimensional structures, such as silicon clusters, quantum wires and quantum wells, are suitable for this purpose. In this work we investigate transport properties of a particular superlattice using two approaches. The first method is a Monte Carlo simulation of electron transport in the biased superlattice. The band structure is calculated using the envelope function approximation, and the scattering mechanisms introduced in the simulator are confined optical phonons. Owing to the particularly flat band structure, drift velocities are very low, but it will be shown that a parallel component of the electric field can significantly increase the vertical drift velocity. Moreover, a superlattice based device is proposed in order to obtain high recombination efficiency. Finally, a quantum calculation is introduced.

2003 - Wigner function for multiband transport in semiconductors [Articolo su rivista]
L., Demeio; L., Barletti; Bordone, Paolo; Jacoboni, Carlo
abstract

In this work we present a one-dimensional model of quantum electron transport in semiconductors that makes use of the Wigner function formalism and that takes into account the full band structure of the medium for energy bands of any shape. We introduce a multi-band Wigner function and derive the evolution equations for each component, with and without external fields, by using a Bloch states representation of the density matrix.

2003 - Wigner-path approach to nonequilibrium quantum transport [Relazione in Atti di Convegno]
Jacoboni, Carlo; Bordone, Paolo; Brunetti, Rossella
abstract

Recent developments of the application of the Wigner-path method to nonequilibrium quantum transport in mesoscopic systems are presented. The concept of wigner path allows the formulation of a Monte Carlo simulation which is quantum mechanically rigorous and yet very similar to the one used in semiclassical transport theory. Scatterings with the potential profile and with phonons are included in the path in a way that takes automatically into account all quantum effects, such as intracollisional field effect and collisional broadening.

2002 - Infinite barriers and classical force in the Wigner-function approach to quantum electron transport [Articolo su rivista]
Bordone, Paolo; A., Bertoni; Jacoboni, Carlo
abstract

In this paper some advancements in the development of the Wigner-function approach to quantum electron transport are presented. In particular we reexamined the problem of the interaction of the carriers with a potential profile with the purpose of isolating relevant differences with respect to classical dynamics. In order to simplify the notation phonon scattering has not been included. In particular, two cases are considered: (1) infinite potential barriers, and (2) the separation of the classical force from the quantum contributions in a general potential profile. (C) 2002 Elsevier Science B.V. All rights reserved.

2002 - Monte Carlo simulation of electron transport in (formula presented) superlattices: Vertical transport enhanced by a parallel field [Articolo su rivista]
Rosini, M.; Jacoboni, C.; Ossicini, S.
abstract

Considerable effort is presently devoted to develop Si quantum structures for microelectronics and nanoelectronics. In particular, well-defined (formula presented) superlattices and quantum wells are under study. We investigate here the transport properties of a (formula presented) superlattice with a multiband one-particle Monte Carlo simulator. The band structure is obtained with an analytical model and the scattering mechanisms introduced in the simulator are confined optical phonons, both polar and nonpolar. Owing to the very flat shapes of the bands along the growth direction, very low drift velocities are obtained for vertical transport. However, the simulation shows that, for oblique fields, the transport properties along the vertical direction are strongly enhanced by the in-plane component of the electric field, consequently higher vertical drift velocities can be easily obtained. © 2002 The American Physical Society.

2002 - Monte Carlo simulation of electron transport in Si/SiO2 superlattices [Relazione in Atti di Convegno]
Rosini, Marcello; Jacoboni, Carlo; Ossicini, Stefano
abstract

ABSTRACT In this work we investigate the transport properties of Si/SiO2 superlattices with a multiband one-particle Monte Carlo simulator. The band structure of the system is obtained analytically by solving the Kronig-Penney potential in a tight binding approximation along the growth direction z while we have assumed parabolic dispersion in the in-plane directions. We have introduced in the simulator confined optical phonons, both polar and non polar, as scattering mechanisms. Owing to the very flat shape of the bands along the growth direction, very low drift velocities are obtained for vertical transport. However it turns out that for oblique fields, the in-plane component of the electric field strongly influences the transport properties along the vertical direction as effect of carrier heating. In particular higher vertical drift velocities can be obtained.

2002 - Monte Carlo simulation of electron transport in Si/SiO2 superlattices: vertical transport enhanced by a parallel field [Articolo su rivista]
Rosini, Marcello; Jacoboni, Carlo; Ossicini, Stefano
abstract

Considerable effort is presently devoted to develop Si quantum structures for microelectronics and nanoelectronics. In particular, well-defined Si/SiO2 superlattices and quantum wells are under study. We investigate here the transport properties of a Si/SiO2 superlattice with a multiband one-particle Monte Carlo simulator. The band structure is obtained with an analytical model and the scattering mechanisms introduced in the simulator are confined optical phonons, both polar and nonpolar. Owing to the very flat shapes of the bands along the growth direction, very low drift velocities are obtained for vertical transport. However, the simulation shows that, for oblique fields, the transport properties along the vertical direction are strongly enhanced by the in-plane component of the electric field, consequently higher vertical drift velocities can be easily obtained.

2002 - Numerical simulation of coherent transport in quantum wires for quantum computing [Articolo su rivista]
A., Bertoni; Bordone, Paolo; Brunetti, Rossella; Jacoboni, Carlo; S., Reggiani
abstract

A solid-state implementation of a universal set of gates for quantum computation is proposed and analysed using a time-dependent 2D Schrodinger solver. The qubit is defined as the state of an electron propagating along a couple of quantum wires. The wires are suitably coupled through a potential barrier with variable height and/or width. It is shown how a proper design of the system allows the implementation of any one-qubit transformation. The two-qubit gate is realized through a Coulomb coupler able to entangle the quantum states of two electrons running in two wires of two different qubits. The simulated devices are GaAs-AlGaAs heterostructures that should be on the borderline of present semiconductor technology. An estimate of decoherence effects due to phonon scattering is also presented.

2002 - Wigner Paths for Quantum Transport [Articolo su rivista]
Bordone, Paolo; Jacoboni, Carlo
abstract

A Monte Carlo algorithm based on the concept of Wigner paths has been developed to study quantum transport in mesoscopic systems in strict analogy with the traditional Monte Carlo simulation used to solve the Boltzmann transport equation. Scatterings with both phonons and impurities can be accounted for. As regards a structure potential profile the effect of the corresponding classical force can be inserted in the dynamics of the free flight, while quantum effects due to rapid potential variations are included as a special scattering mechanism.

2002 - Wigner-function approach to multiband transport in semiconductors [Articolo su rivista]
L., Demeio; L., Barletti; A., Bertoni; Bordone, Paolo; Jacoboni, Carlo
abstract

In this work we present a one-dimensional, multi-band model for electron transport in semiconductors that makes use of the Wigner-function formalism and that allows for energy bands of any shape. A simplified two-band model is then derived from the general equations, by using the parabolic band approximation.

2001 - DYNAMICAL EQUATION AND MONTE CARLO SIMULATION OF THE TWO-TIME WIGNER FUNCTION FOR ELECTRON QUANTUM TRANSPORT [Articolo su rivista]
Brunetti, Rossella; A., Bertoni; Bordone, Paolo; Jacoboni, Carlo
abstract

Within the Wigner-function formalism for electron quantum transport in semiconductors a two-time Wigner function is defined starting from the Green-function formalism. After a proper Fourier transform a Wigner function depending on p and W as independent variables is obtained. This new Wigner function extends the Wigner formalism to the frequency domain and carries information related to the spectral density of the system. A Monte Carlo approach based on the generation of Wigner paths, already developed for the single-time Wigner function, has been extended to evaluate the momentum and energy-dependent Wigner function. Results will be shown for electrons subject to the action of an external field and in presence of scattering with optical phonons.

2001 - Numerical simulation of quantum logic gates based on quantum wires [Articolo su rivista]
Bertoni, A; Bordone, Paolo; Brunetti, Rossella; Jacoboni, Carlo; Reggiani, S.
abstract

A system based on frontier mesoscopic semiconductor technology, able to perform the basic quantum operations needed for quantum computation, is proposed. The elementary quantum bit (qubit) is defined as the state of an electron running along a couple of quantum wires coupled through a potential barrier with variable height and/or width. A proper design of the system, together with the action of Coulomb interaction of two electrons representing two different qubits, allows the implementation of basic one-qubit and two-qubit quantum logic gates. Numerical simulations confirm the correctness of the hypothesis.

2001 - Quantum transport and its simulation with the Wigner-function approach [Capitolo/Saggio]
Jacoboni, Carlo; Brunetti, Rossella; Bordone, Paolo; A., Bertoni
abstract

In this paper a review of the research performed in recent years by the group of the authors is presented. The definition and basic properties of the Wigner function are first given. Several forms of its dynamical equation are then derived with the inclusion of potential and phonon scattering. For the case of a potential V(r) the effect of the classical force, for any form of V(r), is separated from quantum effects due to rapidly varying potentials. An elaboration of the dynamical equation is introduced that leads to Wigner paths formed by free flights and scattering events. These are especially suitable for a Monte Carlo solution of the transport equation for the Wigner function very similar to the semiclassical traditional Monte Carlo simulation. The Monte Carlo simulation can be extended also to the momentum and frequency dependent Wigner function based on a two-time Green function. Several numerical results are presented throuhout the paper.

2001 - Wigner Paths Method in Quantum Transport with Dissipation [Articolo su rivista]
Bordone, Paolo; A., Bertoni; Brunetti, Rossella; Jacoboni, Carlo
abstract

The concept of Wigner paths in phase space both provides a pictorial representation of the quantum evolution of the system of interest and constitutes a useful tool for numerical solutions of the quantum equation describing the time evolution of the system. A Wigner path is defined as the path followed by a “simulative particle” carrying a σ-contribution of the Wigner function through the Wigner phase-space, and is formed by ballistic free flights separated by scattering processes (both scattering with phonons and with an arbitrary potential profile can be included), as for the case of semiclassical particles. Thus, the integral transport equation can be solved by a Monte Carlo technique by means of simulative particles following classical trajectories, in complete analogy to the “Weighted Monte Carlo” solution of the Boltzmann equation in the integral form.

2001 - Wigner-function formulation for quantum transport in semiconductors: theory and Monte Carlo approach [Articolo su rivista]
Jacoboni, Carlo; A., Bertoni; Bordone, Paolo; Brunetti, Rossella
abstract

The Wigner-function approach to the quantum theory of electron transport in mesoscopic systems is reviewed. Delta-like or particle contributions to the Wigner function evolve in time along paths formed by ballistic free flights interrupted by scattering processes as semiclassical particles. A Monte Carlo algorithm based on such Wigner paths will be presented. It extends to quantum transport the Monte Carlo procedure that proved to be very successful for the study of semiclassical transport. (C) 2001 IMACS. Published by Elsevier Science B.V. All rights reserved.

2000 - Quantum logic gates based on coherent electron transport in quantum wires [Articolo su rivista]
A., Bertoni; Bordone, Paolo; Brunetti, Rossella; Jacoboni, Carlo; S., Reggiani
abstract

It is shown that the universal set of quantum logic gates can be realized using solid-state quantum bits based on coherent electron transport in quantum wires. The elementary quantum bits are realized with a proper design of two quantum wires coupled through a potential barrier Numerical simulations show that (a) a proper design of the coupling barrier allows one to realize any one-qbit rotation and (b) Coulomb interaction between two qbits of this kind allows the implementation of the CNOT gate. These systems are based on a mature technology and seem to be integrable with conventional electronics.

2000 - TWO-QBIT GATES BASED ON COUPLED QUANTUM WIRES [Relazione in Atti di Convegno]
S., Reggiani; A., Bertoni; Bordone, Paolo; Brunetti, Rossella; Jacoboni, Carlo; M., Rudan; G., Baccarani
abstract

A solid-state implementation of a set of one- and two-qbit gates for quantum computing is proposed. the qbit is defined as the state of an electron running along two quantum wires, suitably coupled through a potential barrier with variable height and/or width. Single-qubit gates are implemented using the coupling between the two wires. The two-qbit gates have been designed using a Coulomb coupler to induce a mutual phase modulation of the two qubits. A number of runs have been perfomed using a time-dependent 2D Schroedinger solver.

1999 - Quantum transport of electrons in open nanostructures with the Wigner-function formalism [Articolo su rivista]
Bordone, Paolo; M., Pascoli; Brunetti, Rossella; A., Bertoni; Jacoboni, Carlo; A., Abramo
abstract

A theoretical Wigner-function approach to the study of quantum transport in open systems in presence of phonon scattering is presented. It is shown here that in order to solve the Wigner equation in its integral form the knowledge of the Wigner function at all points of the phase space at an initial time t0 can be substituted by the knowledge of the same function inside the region of interest at t0 and on its boundary at all times t′ less then the observation time t. The theory has been applied to calculate the current associated with electron quantum transport across given potential profiles and in presence of phonon scattering.

1999 - Quantum versus classical scattering in semiconductor charge transport: a quantitative comparison [Articolo su rivista]
A., Bertoni; Bordone, Paolo; Brunetti, Rossella; Jacoboni, Carlo; N., Sano
abstract

A first-principle analysis is presented of the effect on transport phenomena of the relaxation of the semiclassical assumptions of energy conservation and point-like nature in space/time of the scattering processes. Quantitative estimates for the quantum case have been obtained within the Wigner-function approach with the use of the concept of Wigner paths. This formulation of the transport problem, although rigorous from the point of view of quantum mechanics, is very close to the classical language, so that comparisons are very straightforward. Results of the analysis of phonon scattering show that multiple collisions reduce collisional broadening and contribute to understanding the success of the semiclassical approximation. An analogous formulation in terms of the density matrix confirms the obtained results. (C) 1999 Elsevier Science B.V. All rights reserved.

1999 - THE WIGNER FUNCTION FOR ELECTRON TRANSPORT IN MESOSCOPIC SYSTEMS [Articolo su rivista]
A., Bertoni; Bordone, Paolo; Brunetti, Rossella; Jacoboni, Carlo
abstract

The Wigner-function approach to the quantum theory of electron transport in mesoscopic systems is reviewed. Delta-like or 'particle' contributions to the Wigner function are introduced that evolve in time along 'paths' formed by ballistic free Eights separated by scattering processes like semiclassical particles. A Monte Carlo algorithm can be developed, based on such Wigner paths. Furthermore, a two-time Green function G can be used to define a Wigner function where momentum and energy are treated as independent variables. The same Monte Carlo approach would then also yield the spectral function for the electron interacting with the phonon gas.

1999 - WIGNER PATHS FOR QUANTUM TRANSPORT IN SEMICONDUCTORS [Relazione in Atti di Convegno]
Bordone, Paolo; Brunetti, Rossella; M., Pascoli; A., Bertoni; Jacoboni, Carlo
abstract

Wigner paths in phase space associated with electronic quantum transport in the Wigner-function formulation are presented and compared with Wigner trajectories, already used in the literature for the case of ballistic coherent transport. Furthermore it is indicated how Wigner paths can be profitably used for the numerical study of quantum transport in mesoscopic systems in presence of phonon scattering.

1998 - APPLICATION OF THE WIGNER-FUNCTION FORMULATION TO MESOSCOPIC SYSTEMS IN PRESENCE OF ELECTRON-PHONON INTERACTION [Articolo su rivista]
Jacoboni, Carlo; A., Abramo; Bordone, Paolo; Brunetti, Rossella; M., Pascoli
abstract

A theoretical and computational analysis of the quantum dynamics in presence of electron-phonon interaction based on the Wigner function is here applied to the study of transport in mesoscopic systems. Numerical applications are shown for a) a wavepacket scattering with phonons while crossing a potential profile and b) electrons scattering with phonons in a finite device with open boundary conditions.

1998 - MONTE CARLO SIMULATION OF SEMICONDUCTOR TRANSPORT [Capitolo/Saggio]
Jacoboni, Carlo; Brunetti, Rossella; Bordone, Paolo
abstract

The contribution is mainly related to advanced problems in Monte Carlo simulations. The first section is concerned with physical models. The fundamentals of the method are discussed in next section. Then the chapter deals with applications and results for bulk semiconductor systems, low dimensional structures and devices.

1998 - Monte Carlo Simulation of hot electrons in semiconductor devices [Capitolo/Saggio]
Jacoboni, Carlo; A., Abramo; Brunetti, Rossella
abstract

The Monte Carlo method is a very general mathematical tool for the solution of a large variety of problems. in this chapter we discuss the application of the method to high-field transport in semiconductors.

1998 - QUANTUM ELECTRON-PHONON INTERACTION FOR TRANSPORT IN OPEN NANOSTRUCTURES [Relazione in Atti di Convegno]
Bordone, Paolo; Brunetti, Rossella; M., Pascoli; Jacoboni, Carlo
abstract

Electronic quantum transport accounting for coherent propagation and electron-phonon scattering has been used to calculate the current-voltage characteristics for model nanostructures.

1998 - WIGNER PATHS AND BOUNDARY CONDITIONS FOR ELECTRON TRANSPORT IN OPEN SYSTEMS WITH ELECTRON-PHONON INTER-ACTION [Relazione in Atti di Convegno]
Jacoboni, Carlo; A., Bertoni; Bordone, Paolo; Brunetti, Rossella
abstract

Ed.IEEE, CAT.N.98X116

1998 - WIGNER PATHS AND BOUNDARY CONDITIONS FOR ELECTRON TRANSPORT IN OPEN SYSTEMS WITH ELECTRON-PHONON INTER-ACTION [Relazione in Atti di Convegno]
Jacoboni, Carlo; A., Bertoni; Bordone, Paolo; Brunetti, Rossella
abstract

A Wigner-function approach to the study of quantum transport in open systems in presence of phonon scattering is presented. Two important issues will be discussed in the paper: a) the existence of Wigner paths in phase space with many analogies with the semiclassical description of transport and b) how to deal with boundary conditions for the analysis of real open structures. Theoretical and computational results will be discussed in view of the application of this formalism to the simulation of transport in mesoscopic structures.

1998 - Wave-packet analysis of electron-phonon interaction in the Wigner formalism [Articolo su rivista]
Brunetti, Rossella; Jacoboni, Carlo
abstract

A theoretical Wigner-function approach to the study of quantum transport in open systems in presence of phonon scattering is presented. It is shown here that in order to solve the Wigner equation in its integral form the knowledge of the Wigner function at all points of the phase space at an initial time t0 can be substituted by the knowledge of the same function inside the region of interest at t0 and on its boundary at all times t′ less then the observation time t. The theory has been applied to calculate the current associated with electron quantum transport across given potential profiles and in presence of phonon scattering.

1998 - Wigner paths for electrons interacting with phonons [Articolo su rivista]
M., Pascoli; Bordone, Paolo; Brunetti, Rossella; Jacoboni, Carlo
abstract

Wigner trajectories in phase space provide a pictorial representation of the quantum evolution of a system of interest in the Wigner-function formulation of quantum mechanics with many analogies with the description of classical evolutions. The existence of Wigner trajectories has been discussed so far only for ballistic coherent electrons moving in an external potential profile. We prove in this paper the existence of Wigner paths that are defined also in the presence of electron-phonon coupling, and go over some interpretative problems related to Wigner trajectories. Wigner paths can be used to determine the evolution of the Wigner function in time during scattering processes. This general result opens new fields of application of the concept of Wigner function, mainly in connection with the numerical study of quantum transport in mesoscopic systems.

1997 - Full-band Monte Carlo analysis of hot-carrier light emission in GaAs [Articolo su rivista]
Ferretti, I; Abramo, A; Brunetti, Rossella; Jacoboni, Carlo
abstract

A computational analysis of light emission from hot carriers in GaAs due to direct intraband conduction-conduction (c-c) transitions is presented. The emission rates have been evaluated by means of a Full-Band Monte-Carlo simulator (FBMC). Results have been obtained for the emission rate as a function of the photon energy, for the emitted and absorbed light polarization along and perpendicular to the electric field direction. Comparison has been made with available experimental data in MESFETs.

1997 - Using the Wigner function for quantum transport in device simulation [Articolo su rivista]
M., Nedjalkov; I., Dimov; Bordone, Paolo; Brunetti, Rossella; Jacoboni, Carlo
abstract

The Wigner function was introduced as a generalization of the concept of distribution function for quantum statistics. The aim of this work is pushing further the formal analogy between quantum and classical approaches. The Wigner function is defined as an ensemble average, i.e., in terms of a mixture of pure states. From the point of view of basic physics, it would be very appealing to be able to define a Wigner function also for pure states and the associated expectation values for quantum observables, in strict analogy with the definition of mean value of a physical quantity in classical mechanics; then correct results for any quantum system should be recovered as appropriate superpositions of such ''pure-state'' quantities. We will show that this is actually possible, st the cost of dealing with generalized functions in place of proper functions.

1997 - Wigner function for open systems with electron-phonon interaction [Articolo su rivista]
Bordone, Paolo; A., Abramo; Brunetti, Rossella; M., Pascoli; Jacoboni, Carlo
abstract

The Wigner-function (WF) formalism is used to analyze the quantum dynamics of charge carriers in presence of electron-phonon (e-p) interaction in open mesoscopic systems making use of the perturbation theory with the external fields incorporated into the unperturbed Hamiltonian. Proper boundary conditions have been chosen and the transport phenomenon inside the device is treated in such a way that boundary conditions at finite positions are kept unaltered, even though the basis of extended scattering states is used.

1996 - Quantum Transport with electron-phonon interaction in thw Wigner-function formalism [Abstract in Atti di Convegno]
Brunetti, Rossella; Jacoboni, Carlo; M., Nedjalkov
abstract

A theory of quantum electron transport based on an extention of the Wigner function that includes electron-electron interaction is presented.

1995 - Polarization Properties of Hot-CArrier light from direct transitions [Articolo su rivista]
Brunetti, Rossella; L., Carbone; Jacoboni, Carlo; A., Lacaita; M., Fischetti
abstract

A theoretical analysis is performed of the intensity and polarization of light emission from hot carriers in semiconductors due to conduction-conduction and valence-valence band transitions.

1994 - A MULTIBAND MONTE-CARLO APPROACH TO COULOMB INTERACTION FOR DEVICE ANALYSIS [Articolo su rivista]
Abramo, A; Brunetti, Rossella; Jacoboni, Carlo; Venturi, F; Sangiorgi, E.
abstract

This paper presents an extension of the theoretical approach for both the short- and long-range components of the Coulomb interaction among carriers in semiconductors to the case of an arbitrary isotropic multiband model, devised for Monte Carlo simulation of silicon devices. The analytical and numerical aspects of the model are discussed in detail. Results for the effect of the Coulomb interaction on the carrier distribution function and on the energy-loss properties of the carrier gas are presented for the case of electrons in homogeneous and inhomogeneous silicon structures.

1994 - POLARIZATION ANALYSIS OF HOT-CARRIER LIGHT-EMISSION IN SILICON [Articolo su rivista]
Carbone, L; Brunetti, Rossella; Jacoboni, Carlo; Lacaita, A; Fischetti, M.
abstract

In this paper a theoretical-evaluation is given of the absolute intensity and polarization of light emission from silicon devices due to conduction-conduction (c-c) and valence-valence (v-v) direct transitions. The matrix elements of the momentum operator between Bloch states have been obtained from a full band-structure calculation performed with the pseudopotential method. Results have been obtained by using both analytical model distribution functions and realistic hot-carrier distributions obtained from Monte Carlo (MC) simulations based on the same band model. They show a polarization degree of a few per cent, which should be observable for these transitions.

1994 - QUANTUM-MECHANICAL EVOLUTION OF REAL-SPACE TRANSFER [Articolo su rivista]
Brunetti, Rossella; Jacoboni, Carlo; Price, Pj
abstract

A rigorous quantum-mechanical treatment of the dynamical evolution of electronic real-space transfer from a quantum well is presented, based on the density-matrix theory. A continuous electron dynamical evolution (not an abrupt collision) corresponding to a phonon absorption is analyzed here. From the evaluation of the lowest-order correction to the unperturbed density matrix, the spatial and momentum distributions can be obtained. Results will also be shown for the Wigner and Husimi functions, and it will be discussed how the present results can be used for a semiclassical modeling of real-space transfer in a Monte Carlo simulation of this effect.

1994 - TIME-RESOLVED QUANTUM-THEORY OF REAL-SPACE TRANSFER [Articolo su rivista]
Brunetti, Rossella; Jacoboni, Carlo; Price, Pj
abstract

A rigorous quantum treatment of real-space transfer for electrons from a quantum well is developed within the density matrix and Wigner function formalisms. A continuous electron dynamical evolution (not an abrupt collision) corresponding to a phonon absorption is described. From the evaluation of the lowest-order correction to the unperturbed density matrix, the spatial and momentum distributions can be evaluated. The Wigner and Husimi functions are also shown for physical situations of interest.

1993 - Monte CArlo Simulation of Silicon devices [Capitolo/Saggio]
A., Abramo; Brunetti, Rossella; C., Fiegna; Jacoboni, Carlo; Riccò, B. B.; E., Sangiorgi; F., Venturi
abstract

An overview on the theoretical background of transport physics is presented together with a discussion of the most recent improvements to the traditional scheme.

1993 - Monte Carlo simulation of carrier-carrier interaction for silicon devices [Relazione in Atti di Convegno]
A., Abramo; Brunetti, Rossella; Jacoboni, Carlo; F., Venturi; E., Sangiorgi
abstract

A Monte Carlo approach to electron-electron scattering in silicon suitable to device analysis is presented.

1992 - A MULTIBAND MODEL FOR HOLE TRANSPORT IN SILICON AT HIGH-ENERGIES [Articolo su rivista]
Abramo, A; Venturi, F; Sangiorgi, E; Fiegna, C; Ricco, B; Brunetti, Rossella; Quade, W; Jacoboni, Carlo
abstract

A new microscopic silicon model for hole transport at high electric fields featuring two valence bands in a finite Brillouin zone is presented. The band parameters and the electron-phonon coupling constants were determined by best fitting the density of states and the experimental and theoretical results for transport properties in the low and intermediate field-strength range. Hole impact ionization has been introduced following a new scheme that goes beyond the limitations contained in the Keldysh formula. The present model, coupled to an analogous model already developed for electrons, allows study of bipolar transport in silicon devices. Applications to bulk Si and Si p-MOSFETs are presented.

1992 - Quantum Transport [Capitolo/Saggio]
F., Rossi; Brunetti, Rossella; Jacoboni, Carlo
abstract

A general quantum approach to quantum transport in semiconductors is presented.

1991 - AN IMPROVED IMPACT-IONIZATION MODEL FOR HIGH-ENERGY ELECTRON-TRANSPORT IN SI WITH MONTE-CARLO SIMULATION [Articolo su rivista]
Thoma, R; Peifer, Hj; Engl, Wl; Quade, W; Brunetti, Rossella; Jacoboni, Carlo
abstract

A new model for impact ionization in Si is presented, which goes beyond the limitations of the Keldysh formula and is based on a more realistic scheme developed starting from a first-order perturbation theory. This scattering mechanism is modeled by an extended band structure which includes many bands for electrons and one band for holes in a finite Brillouin zone. Some processes have been identified to bring the dominant contribution to the scattering probability, in the present approach, for electron energies ranging up to 3 eV. Expressions for the differential and integrated scattering probabilities have been obtained which are consistent with the band model and can be included in a Monte Carlo simulation of the electron gas. Results for transport quantities are shown for a bulk material in presence of homogeneous and static electric fields under physical conditions where impact ionization influences the carrier dynamics. A comparison with theoretical and experimental data from the literature is also given.

1991 - An introduction to charge quantum transport in semiconductors and numerical approaches [Relazione in Atti di Convegno]
F., Rossi; Brunetti, Rossella; Jacoboni, Carlo
abstract

A quantum traetment of electron transport in semiconductors is presented and results will be shown from numerical procedures.

1991 - Impact ionization of electrons in si with Monte Carlo simulation [Capitolo/Saggio]
R., Thoma; H. J., Peifer; W. L., Engl; W., Quade; Brunetti, Rossella; Jacoboni, Carlo
abstract

An advanced model for impact ionization for electrons is si is presented and implemented in a Monte Carlo simulation.

1991 - MONTE-CARLO SIMULATIONS OF HIGH-ENERGY ELECTRONS AND HOLES IN SI-N-MOSFETS [Articolo su rivista]
Venturi, F; Sangiorgi, E; Brunetti, Rossella; Quade, W; Jacoboni, Carlo; Ricco, B.
abstract

Monte Carlo (MC) device simulations of high energy electrons and holes in Si-n-MOSFET's are presented. Key features of this work include the use of a suitable silicon model for carrier transport at high electric fields, an original impact ionization model, and sophisticated numerical techniques to speed up the calculation. The case of submicrometer Si-n-MOSFET's is considered as a relevant application.

1989 - A MANY-BAND SILICON MODEL FOR HOT-ELECTRON TRANSPORT AT HIGH-ENERGIES [Articolo su rivista]
Brunetti, Rossella; Jacoboni, Carlo; Venturi, F; Sangiorgi, E; Ricco, B.
abstract

A new silicon model for electron transport at high electric fields is presented. The model features an original conduction-band structure consisting of three isotropic bands together with the lowest non-parabolic band in a finite spherical Brillouin zone. The bands are given by analytic expressions whose parameters are fixed by best fitting the density of states taken from band-structure calculations. Such a model is consistently used in electron dynamics and in the evaluation of the scattering probabilities. The coupling constants to the scattering agents are determined by best fitting the available experimental data on transport properties. The effect of the new model on the results is discussed for a bulk system with particular attention to the features (e.g. the detailed shape of the electron distribution function) which are important for device applications.

1989 - Monte Carlo simulation of electron heating in scaled deep submicron MOSfets [Relazione in Atti di Convegno]
F., Venturi; E., Sangiorgi; Brunetti, Rossella; Jacoboni, Carlo; B., Riccò
abstract

A Monte Carlo study of the effects of voltage scaling on hot-electron induced effects in submicron MOSfets is presented.

1989 - Quantum theory of transient transport in semiconductors: A Monte Carlo approach [Articolo su rivista]
Brunetti, Rossella; Jacoboni, Carlo; F., Rossi
abstract

A Monte carlo method is presented for the evaluation of the density matrix from the solution of the Liouville-von neumann equation of an ensemble of noninteracting electrons in a semiconductor crystal.

1989 - The Monte Carlo Method for Semiconductor Device Simulation [Monografia/Trattato scientifico]
Jacoboni, Carlo; P., Lugli
abstract

The book contains all the information considered necessary to set up a Monte Carlo simulator of an electronic device, starting from the knowledge of basic transport physics and continuing up to the general principles of the Monte Carlo technique and its applications to the simulation of semiconductor devices.

1988 - Analysis of quantum features in transport theory from a quantum monte carlo approach [Articolo su rivista]
Brunetti, Rossella; Jacoboni, Carlo
abstract

WE PRESENT A mONTE cARLO APPROACH TO THE SOLUTION OF THE Liouvlle equation for an ensemble of carriers in semiconductors.

1987 - Effect of a perturbed acoustic-phonon distribution on hot-electron transport: a Monte Carlo analysis [Articolo su rivista]
Bordone, Paolo; Jacoboni, Carlo; P., Lugli; L., Reggiani; P., Kocevar
abstract

A Monte Carlo simulation code has been developed to study the effect of phonon perturbations in hot-electron transport in semiconductors. The modifications of carrier drift velocity and mean energy induced by the perturbed acoustic-phonon distribution are studied at low temperatures in p-Ge. Under appropriate conditions, current saturation is obtained as a result of the steady-state phonon perturbation. The Monte Carlo analysis has been complemented and compared with an analytical approach based on a heated and displaced Maxwellian distribution for the electron gas.

1986 - A Monte Carlo solution of the Liouville Equaion for quantum transport in semiconductors [Relazione in Atti di Convegno]
Brunetti, Rossella; Jacoboni, Carlo; P., Lugli; L., Reggiani
abstract

An original Monte Carlo solution of the Liouville equation for quantum transport in semiconductors is presented.

1986 - A Monte Carlo technique fro quantum transport in semiconductors [Articolo su rivista]
Jacoboni, Carlo; P., Lugli; Brunetti, Rossella; L., Reggiani
abstract

A Monte Carlo approach to solve the Liouville quation for an electron-phonon system in semiconductors is presented.

1985 - Effect of interparticle collisions on energy relaxation of carriers in semiconductors [Articolo su rivista]
Brunetti, Rossella; Jacoboni, Carlo; A., Matulionis; V., Dienys
abstract

An Ensemble Monte carlo simulation is used to calculate the dynamics of charge carriers in semiconductors in the presence of interparticle collisions.

1985 - Monte Carlo analysis of hot-phonon effects on non-polar semiconductors transport properties [Articolo su rivista]
Bordone, Paolo; Jacoboni, Carlo; P., Lugli; L., Reggiani; P., Kocevar
abstract

An iterative procedure to include phonon disturbance into a Monte Carlo algorithm is presented. Low temperature transport in p-Ge is considered. Calculations show that carrier drift velocity and mean energy increase as a result of the phonon amplification.

1984 - Analysis of the stationary and transient autocorrelation function in semiconductors [Articolo su rivista]
Brunetti, Rossella; Jacoboni, Carlo
abstract

A theoretical analysis of velocity fluctuations in semiconductors is presented both in steady state and in transient regime conditions.

1984 - Transient and Stationary properties of hot-carrier diffusivity in semiconductors [Capitolo/Saggio]
Brunetti, Rossella; Jacoboni, Carlo
abstract

The diffusion phenomena of electrons in semiconductors due to velocity fluctuations in presence og high electric fields is reviewed.

1983 - Diagonal and off-diagonal contributions to autocorrelation of velocity fluctuations in semiconductors [Articolo su rivista]
Brunetti, Rossella; Jacoboni, Carlo
abstract

A theoretical analysis of velocity fluctuations in semiconductors is presented.

1983 - The Monte Carlo method for the solution of charge transport in semiconductors with applications to cavalent materials [Articolo su rivista]
Jacoboni, Carlo; Reggiani, L.
abstract

The review presents in a comprehensive and tutorial form the basic principles of the Monte Carlo method, as applied to the solution of transport problems in semiconductors. A collection of results obtained with Monte Carlo simulations is presented for covalent semiconductors.

1982 - Prediction of negative diffusivity under transient regime conditions [Articolo su rivista]
B., Boittiaux; E., Constant; L., Reggiani; Brunetti, Rossella; Jacoboni, Carlo
abstract

we report on the possibility of a negative diffusivity under transient regime conditions.

1981 - Diffusion coeffcient of electrons in Si [Articolo su rivista]
Brunetti, Rossella; Jacoboni, Carlo; Nava, Filippo; L., Reggiani; G., Bosman; R. J. J., Zijlstra
abstract

An experimental and theoretical analysis of the diffusivity of electrons in si is presented.

1981 - Diffusion coefficient of electrons in silicon [Articolo su rivista]
Brunetti, R.; Jacoboni, C.; Nava, F.; Reggiani, L.; Bosman, G.; Zijlstra, R. J. J.
abstract

This paper reports an experimental and theoretical analysis of the diffusivity of electrons in Si as function of temperature, field strength, and field direction. Results for the longitudinal diffusion coefficient have been obtained experimentally for fields applied along 〈111〉 and 〈100〉 directions with time-of-flight and noise measurements. Calculations have been performed with the Monte Carlo procedure. The theoretical analysis, which includes an extensive discussion of the intervalley diffusion process, has yielded a revised version of the silicon model which correctly interprets both the new diffusion data and other well-established electron transport properties. The revision of the model is mainly concerned with the relative weights of f and g intervalley scattering mechanisms. In fact the interpretation of the anisotropy of the diffusion allows separate estimates of the two types of scattering through their different effects on the intervalley diffusion which comes about when electrons have different drift velocities in different valleys.

1981 - Frequency and wavevector dependent diffusion coefficient of electrons from Monte Carlo simulation [Relazione in Atti di Convegno]
Jacoboni, Carlo; L., Reggiani; Brunetti, Rossella
abstract

A general expression of a frequency and wavevector dependent diffusion coefficient for electrons is obtained and used in Monte Carlo simulations

1981 - On Intervalley diffusion of hot electrons [Articolo su rivista]
Brunetti, Rossella; Jacoboni, Carlo; L., Reggiani
abstract

A Monte Carlo analysis of intervalley diffusion in Si is presented.

1981 - The method of moments for the analysis of transient hot-carrier phenomena [Articolo su rivista]
L., Reggiani; Brunetti, Rossella; Jacoboni, Carlo
abstract

The method of moments is used to analyse the transient behavior of drift velocity and diffusion coefficient.