M. A. Littlejohn

Velocity‐field characteristics of GaAs with Γc6‐Lc6‐Xc6 conduction‐band ordering

This paper describes Monte Carlo calculations of velocity‐field characteristics for GaAs using the recent experimental conduction‐band ordering of Aspnes, which places the Lc6(111) conduction‐band minima lower in energy than the Xc6(100) minima. These calculations use intervalley deformation potentials which give the best fit to recent high‐field drift velocity measurements, and at the same time give good agreement with accepted peak velocity and threshold field values.This paper describes Monte Carlo calculations of velocity‐field characteristics for GaAs using the recent experimental conduction‐band ordering of Aspnes, which places the Lc6(111) conduction‐band minima lower in energy than the Xc6(100) minima. These calculations use intervalley deformation potentials which give the best fit to recent high‐field drift velocity measurements, and at the same time give good agreement with accepted peak velocity and threshold field values.

Alloy scattering and high field transport in ternary and quaternary III–V semiconductors☆

Abstract A technique is described for the estimation of the influence of random potential alloy scattering on the high field transport properties of quaternary III–V semiconductors obtained by Monte Carlo simulation. The approach is based on an extension of a theoretical model for scattering in the ternary alloys. The magnitude of the scattering potential is an important parameter in alloy scattering, and three proposed models for calculating this potential are discussed. These are the energy bandgap difference, the electron affinity difference, and the heteropolar energy difference for the appropriate binary compounds. The technique is used in the Monte Carlo method to study the influence of alloy scattering on the transport properties of III–V quaternary alloys. The results of this study are used in a device model to estimate device parameters for FETs.

Energy bandgap and lattice constant contours of iii–v quaternary alloys

Energy band gap and lattice constant contours are presented for the nine quaternary alloys formed from Al, Ga, In and P, As, Sb. The quaternary bandgaps were obtained using an interpolation formula proposed by Moonet al. The quater nary lattice constants were obtained by use of a linear interpolation technique using the binary lattice constants as boundary values.

Velocity‐field characteristics of Ga1−xInxP1−yAsy quaternary alloys

The electron drift‐velocity–electric‐field relationship has been calculated for the Ga1−xInxP1−yAsy quaternary alloy using the Monte Carlo method. Emphasis has been placed on the compositional range for which the alloy is lattice matched to GaAs and InP. These calculations suggest that this quaternary offers promise as a material for microwave semiconductor devices, including field‐effect transistors and transferred electron devices.The electron drift‐velocity–electric‐field relationship has been calculated for the Ga1−xInxP1−yAsy quaternary alloy using the Monte Carlo method. Emphasis has been placed on the compositional range for which the alloy is lattice matched to GaAs and InP. These calculations suggest that this quaternary offers promise as a material for microwave semiconductor devices, including field‐effect transistors and transferred electron devices.

Monte Carlo calculation of the velocity‐field relationship for gallium nitride

The Monte Carlo technique has been used to calculate the velocity‐field relationship for GaN. The calculation has included polar optical scattering, acoustic scattering, piezoelectric scattering, and ionized impurity scattering. The electron mobility has also been evaluated at low fields as a function of impurity concentration.

THEORETICAL STUDY OF ELECTRON TRANSPORT IN GALLIUM NITRIDE

This paper describes characteristic electron transport properties for GaN in bulk and quantum well structures. First, ensemble Monte Carlo calculations of steady‐state electron drift velocity in bulk GaN are presented as a function of applied electric field for different lattice temperatures. At 300 K, the calculated peak steady‐state drift velocity is 2.8×107 cm/s and the threshold field is 160 kV/cm. It is found that the peak steady‐state electron drift velocity decreases only slightly by about 20% as the temperature increases from 300 to 600 K while the threshold field increases slightly by about 20%. Therefore, in addition to its high temperature stability, GaN has a low temperature coefficient making it ideal for high temperature applications. For electron transport in heterostructures, quantum mechanical calculations of the electron capture rate in GaN‐based quantum wells as a function of well thickness are also presented. An oscillatory behavior of the electron capture rate as a function of quantum...

Theory of the velocity‐field relation in AlGaAs

We present ensemble Monte Carlo calculations of the steady‐state electron drift velocity as a function of applied electric field in Al0.32 Ga0.68 As. The effect of various material parameters on the calculated velocity is assessed by varying each parameter independently by ±20%. It is found that both the optical phonon energy and intervalley separation energy alter the peak electron velocity greatly. Variations in the dielectric constants and central valley effective mass have little effect upon the peak drift velocity, but act to alter the threshold electric field. It is further found that the threshold electric field is greater in Al0.32Ga0.68As than in GaAs even though the central‐to‐satellite valley separation energy is less in AlGaAs. The combined effects of a greater central valley effective mass and a larger phonon energy in AlGaAs result in a greater threshold field. Finally, we present sets of material parameters useful in Monte Carlo models for both GaAs and AlGaAs.

Energy bandgap and lattice constant contours of iii-v quaternary alloys of the form Ax By Cz D or ABx Cy Dz

Energy bandgap and lattice constant contours are presented for the six quaternary alloys formed from Al, Ga, In and P, As, Sb, with compositions of the form Ax By C(1−y). D or ABx Cy D1−x−y . The quaternary bandgaps and lattice constants were obtained using an interpolation formula proposed by the present authors.

Velocity‐field relationship of InAs‐InP alloys including the effects of alloy scattering

The drift velocity–electric field relationship for the ternary alloy InAs1−xPx has been studied by the Monte Carlo methd. Random potential alloy scattering has been included in the calculations, along with polar optical scattering, intervalley scattering, acoustic scattering, piezoelectric scattering, and ionized impurity scattering. The low‐field electron mobility has also been calculated throughout the compositional range for the alloy.

Selective low‐pressure chemical vapor deposition of Si1−xGex alloys in a rapid thermal processor using dichlorosilane and germane

Low‐pressure chemical vapor deposition of Si1−xGex alloys in a cold wall, lamp‐heated rapid thermal processor was studied. Alloys were deposited using the reactive gases GeH4 and SiH2Cl2 in a hydrogen carrier gas. The depositions were performed at a total pressure of 2.5 Torr and at temperatures between 500 and 800 °C using GeH4:SiH2Cl2 ratios ranging from 0.025 to 1.00. Results showed that Si1−xGex alloys can be deposited selectively on silicon in SiO2. The selectivity is enhanced significantly by the addition of GeH4 in the gas stream. In this work, selective depositions were obtained when the GeH4:SiH2Cl2 gas flow ratio was greater than 0.2 regardless of the deposition temperature, corresponding to a Ge content of 20% or higher in the films as determined by Auger electron spectroscopy. An enhancement in the deposition rate was observed in agreement with earlier reports due to the addition of GeH4. The activation energy for deposition in the surface reaction limited regime varied from 20 to 30 kcal/mole...