1,721,036 research outputs found
Semiconductor nanodevices: Facing the fascinating world of quantum mechanics
No full textThe rapidly developing field of semiconductor-based
nanomaterials and nanodevices unveils the intimate
link between low-dimensional solid-state physics and
fundamental quantum mechanics. The key tools of
electronic quantum confinement and tunnel coupling
are concepts that may be expressed and derived in
terms of the corresponding Schrödinger equation.
However, the interplay between carrier coherence and
energy dissipation/decoherence in realistic electronic
and optoelectronic nanodevices is highly non-trivial; the
conventional theoretical treatments show up intrinsic
limitations which are intimately related to the arbitrary
separation between classical and quantum world,
i.e., to the so-called measurement problem
Riedizione di un testo universitario: Un'esperienza da curatori
Full text linkNella storia di ogni buon libro di testo, le riedizioni sono testimonianza e al tempo stesso stimolo di vitalità. I due volumi di “Fisica” di P. Mazzoldi, M. Nigro e C. Voci, pubblicati per la prima volta nel 1991, sono stati subito accolti con grande apprezzamento a livello nazionale. Dopo una seconda edizione e numerose ristampe, gli autori hanno iniziato un’opera di revisione e aggiornamento, senza poterla purtroppo portare a termine. È toccato a noi, su invito della casa editrice, completare il lavoro sul secondo volume. Nel farlo, abbiamo cercato di mantenere il più possibile l’identità e l’impianto originali dell’opera e, simultaneamente, di migliorarne la fruibilità attuale. A conclusione di ogni capitolo sono stati inseriti un riepilogo dei concetti e dei risultati principali in esso contenuti e un elenco di quesiti utili a verificare la comprensione e a stimolare la riflessione su quanto appreso. Numerosi restano sia gli esempi, risolti in dettaglio, che i problemi, proposti alla fine dei capitoli. Particolare cura è stata dedicata alla rimozione dei refusi. Le figure sono in quadricromia. Alcuni contenuti opzionali e aggiuntivi sono consultabili in formato digitale
Microscopic theory of semiconductor-based optoelectronic devices
No full textSince the seminal paper by Esaki and Tsu, semiconductor-based nano metric heterostructures have been the subject of impressive theoretical and experimental activity due to their high potential impact in both fundamental research and device technology. The steady scaling down of typical space and time scales in quantum optoelectronic systems inevitably leads to a regime in which the validity of the traditional Boltzmann transport theory cannot be taken for granted and a more general quantum-transport description is imperative. In this paper, we shall review state-of-the-art approaches used in the theoretical modeling, design and optimization of optoelectronic quantum devices. The primary goal is to provide a cohesive treatment of basic quantum-transport effects, able to explain and predict the performances of new-generation semiconductor devices. With this aim, we shall review and discuss a fully three-dimensional microscopic treatment of time-dependent as well as steady-state quantum-transport phenomena, based on the density matrix formalism. This will allow us to introduce in a quite natural way the separation between coherent and incoherent processes. Starting with this general theoretical framework, we shall analyse two different types of quantum devices, namely periodically repeated structures and quantum systems with open boundaries. For devices within the first class, we will show how a proper use of periodic boundary conditions allows us to reproduce and predict their current-voltage characteristics without resorting to phenomenological parameters. For the second class of devices, we will address the relevant issue of a quantum treatment of charge transport in systems with open boundaries (electrical contacts) when studying and simulating an at least two-terminal device
Hot-carrier dynamics in semiconductor-based quantum-cascade lasers: a Monte Carlo study
No full textA microscopic analysis of the hot-carrier dynamics governing intersubband light-emitting devices is presented. In particular, a non-conventional Monte Carlo simulation scheme is adopted, which allows to directly access details of the three-dimensional carrier relaxation, without resorting to phenomenological parameters. The competition between phonon-assisted relaxation and inter-carrier scattering in quantum cascade structures, both state-of-the-art mid-infrared lasers and prototypical THz emitters, is analysed and discussed
Hot-carrier relaxation and thermalization in quantum-cascade lasers: phase coherence versus energy relaxation
No full textA global quantum simulation—steady state as well as ultrafast—of non-equilibrium carrier dynamics in semiconductor-based quantum-cascade lasers is presented. In particular, the interplay between phase coherence and energy-relaxation/dephasing processes is investigated and discussed. Our analysis shows that quantum corrections to the semiclassical scenario are minor and confirms the incoherent nature of steady-state charge transport in these structures
Microscopic modeling of THz quantum cascade lasers and other optoelectronic quantum devices
No full textThe most advanced microscopic treatments of optoelectronic quantum devices are reviewed, with special emphasis on the design and simulation of novel quantum-cascade devices operating in the Terahertz spectral region. After recalling the fundamentals of hot-electron transport versus nonequilibrium energy-relaxation and carrier-redistribution in such devices, a few simulated experiments are presented and discussed
Microscopic Modelling of Opto-Electronic Quantum Devices: A Predictive Simulation Tool
No full textA microscopic analysis of non-equilibrium phenomena in unipolar quantum devices is presented. In particular, a global Monte Carlo simulation scheme (semiclassical as well as quantum) is employed, which allows us to directly access details of the three-dimensional carrier dynamics, without resorting to phenomenological parameters. Applications to state-of-the-art mid-infrared quantum-cascade lasers and novel far-infrared emitters are discussed. The extremely good agreement between theoretical results and experimental findings demonstrates that our approach is a valid and predictive tool for the understanding of charge transport in these quantum devices
Microscopic theory of quantum-cascade lasers
No full textWe review and discuss the first fully three-dimensional study of non-equilibrium carrier dynamics governing semiconductor-based intersubband optoelectronic devices, such as quantum-cascade lasers. First, a multisubband Monte Carlo simulation scheme in a kinetic Boltzmann-like approach is presented. Then, its generalization into a density-matrix quantum-transport formalism is discussed. This allows us to directly access microscopic key features of the electron relaxation dynamics (without resorting to phenomenological parameters) as well as to investigate the nature, coherent versus incoherent, of charge injection/transport processes. Applications to state-of-the-art mid-infrared quantum-cascade lasers and novel far-infrared emitters are reviewed. The extremely good agreement between theoretical results and experimental findings demonstrates that our approach is a valid and predictive tool for the understanding of charge transport in these quantum devices
Microscopic modelling of semiconductor-based quantum devices: a predictive simulation strategy
No full textWe review and discuss the first fully three-dimensional study of non-equilibrium carrier dynamics governing semiconductor-based intersubband optoelectronic devices like, e.g., quantum-cascade lasers. First, a multisubband Monte Carlo simulation scheme in a kinetic Boltzmann-like approach is presented. Then, its generalisation into a density-matrix quantum-transport formalism is discussed. This allows us to directly access microscopic key-features of the electron relaxation dynamics (without resorting to phenomenological parameters) as well as to investigate the nature, coherent vs incoherent, of charge injection/transport processes. Besides providing a quantitative investigation into the operation of these devices, our kinetic analysis can indeed serve as a predictive tool for the evaluation of new designs and strategies. Applications are presented concerning quantum-cascade devices, both state-of-the-art mid-infrared lasers as well as novel Thz emitters
Microscopic Modeling of Energy Dissipation and Decoherence in Open Quantum Systems: Application to Semiconductor Nanodevices
No full textA general density-matrix description of energy-dissipation and decoherence phenomena in open quantum systems is presented. More specifically, contrary to the conventional single-particle correlation expansion, we shall investigate the effect of the adiabatic or Markov limit, before considering/performing any reduction procedure. Our fully operatorial approach allows us to better identify the general properties of the scattering superoperators entering our effective quantum-transport theory at various description levels. In particular, we shall show that—contrary to the semiclassical case—the conventional Markov limit does not preserve the positive-definite character of the corresponding density matrix, thus leading to highly non-physical results. To overcome this serious limitation, originally pointed out and partially solved by Davies and co-workers almost three decades ago, we shall propose an alternative and more general adiabatic procedure, which (i) in the semiclassical limit reduces to the standard Fermi's golden rule, and (ii) describes a genuine Lindblad evolution, thus providing a reliable/robust treatment of energy-dissipation and dephasing processes in semiconductor quantum device
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