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Article

Karel Král and Miroslav Menšík

In this work the experimental effect of a slow decay of the photoluminescence is studied theoretically in the case of quantum dots with an indirect energy band gap. The…

Abstract

In this work the experimental effect of a slow decay of the photoluminescence is studied theoretically in the case of quantum dots with an indirect energy band gap. The slow decay of the photoluminescence is considered as decay in time of the luminescence intensity, following the excitation of the quantum dot sample electronic system by a short optical pulse. In the presented theoretical treatment the process is studied as a single dot property. The inter-valley deformation potential interaction of the excited conduction band electrons with lattice vibrations is considered in the self-consistent Born approximation to the electronic self-energy. The theory is built on the non-equilibrium electronic quantum transport theory. The time dependence of the photoluminescence decay is estimated upon using a simple effective mass model. The numerical calculation of the considered model shows the power-law time characteristics of the photoluminescence decay in the long-time limit of the decay. We demonstrate that the nonadiabatic influence of the interaction of the conduction band electrons with the lattice vibrations provides a mechanism giving us the power-law time dependence of the photoluminescence intensity signal. This theoretical result emphasizes the role of the electron-phonon interaction in the nanostructures.

Details

World Journal of Engineering, vol. 11 no. 5
Type: Research Article
ISSN: 1708-5284

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Article

P. Degond and Y. Qiu

Presents a simplified mathematical model of electron transport in a one‐dimensional semiconductor device of N+ ‐ NN + type. The model is based on a singular…

Abstract

Presents a simplified mathematical model of electron transport in a one‐dimensional semiconductor device of N+ ‐ NN + type. The model is based on a singular perturbation approach of the kinetic equation which describes the transport processes. This so‐called Child‐Langmuir asymptotics is obtained by assuming that the injected electrons at the N + ‐ N junction on the source side have a very weak energy compared with what they are able to gain under the influence of the electric field. Formally establishes the limit model when a realistic collision model for electron‐phonon interaction is considered. Compares the results with both experiments and particle simulations.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 16 no. 3
Type: Research Article
ISSN: 0332-1649

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Article

R.K. COOK and Jeffrey FREY

A transport model has been developed which is reasonably accurate, and has proven quite efficient for the two‐dimensional numerical simulation of submicron‐scale Si and…

Abstract

A transport model has been developed which is reasonably accurate, and has proven quite efficient for the two‐dimensional numerical simulation of submicron‐scale Si and GaAs devices. In this model an approximate form of the energy‐transport equation is developed; this equation is easily included in otherwise‐conventional device simulation codes, which then require only slightly more solution time than standard models using field‐dependent transport coefficients. Calculations for 0.25 micron gate length Si and GaAs MESFET's show that velocity overshoot effects can be very important, particularly in the latter material; predicted saturation currents in the GaAs devices are almost three times larger than those that would have been predicted using conventional transport models. The model described, and its application in simulation programs, should find use in the design of submicron‐scale devices to properly take advantage of overshoot phenomena.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 1 no. 2
Type: Research Article
ISSN: 0332-1649

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Article

A. Majorana, O. Muscato and C. Milazzo

Time‐depending solutions to the Boltzmann‐Poisson system in one spatial dimension and three‐dimensional velocity space are obtained by using a recent finite difference…

Abstract

Time‐depending solutions to the Boltzmann‐Poisson system in one spatial dimension and three‐dimensional velocity space are obtained by using a recent finite difference numerical scheme. The collision operator of the Boltzmann equation models the scattering processes between electrons and phonons assumed in thermal equilibrium. The numerical solutions for bulk silicon and for a one‐dimensional n+‐n‐n+ silicon diode are compared with the Monte Carlo simulation. Further comparisons with the experimental data are shown.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 23 no. 2
Type: Research Article
ISSN: 0332-1649

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Article

P.K. Yadawa and R.R. Yadav

A simple interaction‐potential model has been established to calculate the higher order elastic constants of intermetallic YbAl2 in the temperature range from 10‐300K…

Abstract

A simple interaction‐potential model has been established to calculate the higher order elastic constants of intermetallic YbAl2 in the temperature range from 10‐300K. Temperature dependent second and third order elastic constants are used for the determination of the ultrasonic attenuation, velocity, Grüneisen numbers, Acoustic‐coupling constants, and thermal relaxation time at the different temperatures. Temperature dependency of the ultrasonic properties of YbAl2 is similar at low temperatures to that of pure metals and the low carrier heavy fermion systems ‐ LaSb, YbAs and YbP having simple NaCl‐type structures. Thermal energy density makes significant contribution to the total attenuation in the compound at the higher temperatures from 100‐300K. Effect of the magnetic field on the ultrasonic attenuation is also evaluated using the magneto resistance data. At 100K, the effect of the magnetic field becomes insignificant. The attenuation decreases with the field at 3K to 50K.

Details

Multidiscipline Modeling in Materials and Structures, vol. 5 no. 1
Type: Research Article
ISSN: 1573-6105

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Article

Orazio Muscato, Wolfgang Wagner and Vincenza Di Stefano

– The purpose of this paper is to deal with the self-heating of semiconductor nano-devices.

Abstract

Purpose

The purpose of this paper is to deal with the self-heating of semiconductor nano-devices.

Design/methodology/approach

Transport in silicon semiconductor devices can be described using the Drift-Diffusion model, and Direct Simulation Monte Carlo (MC) of the Boltzmann Transport Equation.

Findings

A new estimator of the heat generation rate to be used in MC simulations has been found.

Originality/value

The new estimator for the heat generation rate has better approximation properties due to reduced statistical fluctuations.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 33 no. 4
Type: Research Article
ISSN: 0332-1649

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Article

Orazio Muscato

Hydrodynamic‐like models are commonly used for describing carrier transport in semiconductor devices. One major problem of this formulation is how to model the production…

Abstract

Hydrodynamic‐like models are commonly used for describing carrier transport in semiconductor devices. One major problem of this formulation is how to model the production terms. In this paper the relaxation‐time approximation and the moments expansion of the production terms are checked with Monte Carlo simulations for a one dimensional n+nn+ silicon diode in the spherical parabolic band approximation.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 19 no. 3
Type: Research Article
ISSN: 0332-1649

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Article

A.M. ANILE, C. MACCORA and R.M. PIDATELLA

The effects of viscosity, previously neglected in electronic device stimulations, are studied using a non‐standard hydrodynamic model, following Anile and Pennisi. Results…

Abstract

The effects of viscosity, previously neglected in electronic device stimulations, are studied using a non‐standard hydrodynamic model, following Anile and Pennisi. Results are compared with those of Gardner.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 14 no. 1
Type: Research Article
ISSN: 0332-1649

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Article

Orazio Muscato and Wolfgang Wagner

To provide an accurate analysis of the systematic error introduced by the constant time technique free flight mechanism, due to the choice of the time step and number particles.

Abstract

Purpose

To provide an accurate analysis of the systematic error introduced by the constant time technique free flight mechanism, due to the choice of the time step and number particles.

Design/methodology/approach

A homogeneous (bulk) silicon semiconductor is studied by using direct simulation Monte Carlo (DSMC).

Findings

The systematic error turns out to be of the first order with respect to the time step. The efficiency of the method is tackled.

Research limitations/implications

The analysis is limited to the bulk case. Future researches will consider non homogeneous devices

Originality/value

An accurate analysis of an “old” free flight mechanism has been performed, and its limits have been stated.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 24 no. 4
Type: Research Article
ISSN: 0332-1649

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Article

Vitaliy Bilovol, Claudio Barbon and Bibiana Arcondo

The purpose of this paper is to investigate electrical properties of eutectic In8Sb8Te84 and In10Sb51Te39 as made thin films to evaluate their potential for non-volatile…

Abstract

Purpose

The purpose of this paper is to investigate electrical properties of eutectic In8Sb8Te84 and In10Sb51Te39 as made thin films to evaluate their potential for non-volatile phase-change memories, once the thermal measurements are very optimistic.

Design/methodology/approach

The films were deposited by pulse laser deposition technique. By using a very simple home-made cell, transversal current-voltage curves films were measured involving both voltage controlled-pulses generator and current controlled-pulses generator, employing different pulse shapes: triangular and sine shaped.

Findings

The memory effect, characteristic of a typical phase-change memory material, was observed in both materials under research. For higher tellurium content in the film, lower is the value of threshold voltage.

Research limitations/implications

Further studies on endurance, scaling and SET/RESET operations are needed.

Practical implications

The values of the key parameters, threshold voltage and hold voltage are comparable with those of Ge2Sb2Te5, GeTe and Sb2Te being considered to date as the main compounds for PCM devices.

Originality/value

The conduction mechanism in the amorphous regime is agreed with Poole–Frenkel effect in deep traps.

Details

Microelectronics International, vol. 36 no. 4
Type: Research Article
ISSN: 1356-5362

Keywords

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