Localised electronic states in semiconductor superlattices

In the case of quantum wells, the indium segregation leads to complex potential profiles that are hardly considered in the majority of the theoretical models. The authors demonstrated that the split-operator method is useful tool for obtaining the electronic properties in these cases. Particularly, they studied the influence of the indium surface segregation in optical properties of InGaAs/GaAs quantum wells. Photoluminescence measurements were carried out for a set of InGaAs/GaAs quantum wells and compared to the results obtained theoretically via split-operator method, showing a good agreement.

Study of the influence of indium segregation on the optical properties of InGaAs/GaAs quantum wells via split-operator method

This paper deals with the modeling of the electronic characteristics of semiconductor devices based on Schottky contacts in low-dimensional systems. For the capacitance-voltage characteristics, a quasi-two-dimensional quantum mechanical model is developed and validated. For the current-voltage characteristics, a unified model is presented, considering both the tunneling as well as the thermionic emission mechanisms. Our theoretical predictions suggest that for photodetection applications the use of these contacts, replacing conventional metal-semiconductor junctions, can reduce the dark current by at least one order of magnitude.

Modeling the electrical characteristics of Schottky contacts in low-dimensional heterostructure devices

Self-consistent computations of the potential profile in complex semiconductor heterostructures can be successfully applied for comprehensive simulation of the gain and the absorption spectra, for the analysis of the capture, escape, tunneling, recombination, and relaxation phenomena and as a consequence it can be used for studying dynamical behavior of semiconductor lasers and amplifiers. However, many authors use non-entirely correct ways for the application of the method. In this paper the versatile model is proposed for the investigation, optimization, and the control of parameters of the semiconductor lasers and optical amplifiers which may be employed for the creation of new generations of the high-density photonic systems for the information processing and data transfer, follower and security arrangements. The model is based on the coupled Schrodinger, Poisson's and drift-diffusion equations which allow to determine energy quantization levels and wave functions of charge carriers, take into account built-in fields, and to investigate doped MQW structures and those under external electric fields influence. In the paper the methodology of computer realization based on our model is described. Boundary conditions for each equation and consideration of the convergence for the method are included. Frequently encountered in practice approaches and errors of self-consistent computations are described. Domains of applicability of the main approaches are estimated. Application examples of the method are given. Some of regularities of the results which were discovered by using self-consistent method are discussed. Design recommendations for structure optimization in respect to managing some parameters of AMQW structures are given.

Model for self-consistent analysis of arbitrary MQW structures

I-V characteristics of Schottky contacts based on quantum wires

A theoretical model for the capacitance-voltage characteristics of strained modulation-doped field-effect transistors (MODFETs) is developed, based on a self-consistent solution of the Schrodinger and Poisson equations. We report on the first MODFET C-V simulator in which the proposed Hamiltonian takes into account the strain caused by lattice mismatch, as well as the position-dependent lattice constant and electron effective mass. It is demonstrated that the inclusion of strain-related energy terms is essential to achieve good agreement between theory and experimental data for the C-V characteristics of pseudomorphic-channel devices at high gate voltages. The model is also shown to be a useful tool to predict important device characteristics such as the transconductance.

On the capacitance-voltage modeling of strained quantum-well MODFETs

Finite superlattice with a localized state: a possible new submillimeter wave emitter, in a numerical simulation

This paper addresses the capacitance-voltage (C-V) characteristics of heterodimensional Schottky diodes, in which the Schottky metal is placed in direct contact to a two-dimensional electron gas and the confined electron behavior directly dictates the device performance. We develop a novel quasi-2D model for the C-V characteristics of the device, by starting from a self-consistent solution of the Schrodinger and Poisson equations in the growth direction. The model is validated by contrasting the theoretical results with experimental data from an AlGaAs/GaAs device fabricated in our laboratory.

Modeling the C-V characteristics of heterodimensional Schottky contacts

This paper addresses the capacitance-voltage (C-V)characteristics of heterodimensional Schottky diodes, inwhich the Schottky metal is placed in direct contact toa two-dimensional electron gas and the confinedelectron behavior directly dictates the deviceperformance. We develop a novel quasi-2D model forthe C-V characteristics of the device, by starting from aself-consistent solution of the Schrodinger and Poissonequations in the growth direction. The model isvalidated by contrasting the theoretical results withexperimental data from an AlGaAs/GaAs devicefabricated in our laboratory. 1. Introduction The properties of electrons in an inversion layerhave attracted interest since the 1930’s, when Lilienfeldconceived the field-effect transistor. Further attentionhas been motivated by the enhanced transport propertiesof the two-dimensional electron gas (2-DEG) formed atmodulation doped heterointerfaces, where the inversionlayer isquantized in the growth direction. Already inthe early 90’s High Electron-Mobility Transistors(HEMTs) based on this principle displayed poweramplification well above 100 GHz with outstandingnoise performance.This paper is concerned with devices based on afurther extension of the modulation doping concept byusing heterodimensional interfaces, i.e., interfacesbetween materials of dissimilar dimensions. In ourspecific case, this interface is a Schottky barrier laterallyconnecting a three-dimensional (3D) metal and a two-dimensional (2D) electron gas.In fact, heterodimensional diodes, transistors andphotodetectors present several attractive features such aslow capacitance due to the small effective cross-section,excellent noise and transport characteristics due to the2D electron gas and a high breakdown voltage, makingthem very promising for high-frequency applications [1-2].In order to illustrate the motivation for studyingheterodimensional devices we briefly revisit the questionof computing the thermionic emission current in suchdevices. In fact,straighforward extension of Bethe’stheory, considering both the proper two-dimensionaldensity of states as well as energyquantization in thegrowth direction for a 2-DEG with only onesignificantly populated subband, yields [3]:1 (1)kTqVexpkTEexpkTqJ A* T3 2 exp B

http://www.essderc2002.deis.unibo.it/data/id/74.pdf

Modeling the C-V Characteristics of Heterodimensional Schottky Contacts

A theoretical model for the capacitance-voltage characteristics of strained MODFETs is developed, based on a self-consistent solution of Schrodinger and Poisson equations. We report on the first MODFET C-V simulator in which the proposed Hamiltonian takes into account the strain caused by lattice mismatch, as well as the position dependeYft lattice constant and electron effective mass. It is demonstrated that the inclusion of strain­ related energy terms is essential to achieve good agreement between theory and experimental data for the C-V characteristics of pseudomorphic-channel devices at high gate voltages.

https://ieeexplore.ieee.org/iel5/10058/32252/01503556.pdf

José E. Manzoli

Papers

On the capacitance-voltage modeling of strained quantum-well MODFETs

Finite superlattice with a localized state: a possible new submillimeter wave emitter, in a numerical simulation

Modeling the C-V characteristics of heterodimensional Schottky contacts

Modeling the C-V Characteristics of Heterodimensional Schottky Contacts

Stress-Related Effects on the C-V Characteristics of Pseudomorphic MODFETs