Thermodynamic Analysis of the III–V Alloy Semiconductor Phase Diagrams

Abstract

A thermodynamic analysis was made of the pseudobinary phase diagrams of the III-V semiconductor alloys, InSb-GaSb, InAs-GaAs, and InP-GaP. The excess free energy of mixing is expressed as Bxlx2, where B is a parameter characteristic of each system and xl and x2 are the mole fractions of the end components. This homologous series of alloys showed consistent behavior in that all of the B/RT vs. composition plots were linear for both the liquids and solids. The greater part of the excess free energy of mixing of the solids appears to be in the excess entropy rather than in the enthalpy, indicating that these materials freeze with local ordering or structure rather than as homogeneous random solids. The magnitude of the departure from ideality in the solids increases from the antimonide to the arsenide and to the phosphide, which is also the order of increasing lattice mismatch between the pairs of pure components. Implications of these results in the use of the alloys in semiconductor devices are discussed.It has been recognized for many years that the III-V alloy semiconductors might be useful for fabrication of new electronic and optical devices because of the possibility of adjusting the width of the forbidden energy gap by varying the composition of the alloys (1-3). In principle, by selecting the proper combinations of III-V compounds and adjusting the composition of the mixtures, semiconductors with band gaps ranging more or less continuously from 0.18 eV (InSb) to about 2.4 eV (ALP) could be prepared. * Electrochemical Society Active Member.Whether these mixtures will be useful semiconductors will depend not only on solving such obvious problems as the growth of suitably doped single crystals, but also on whether such alloys are indeed homogeneous mixtures with properties that are smooth blends of the properties of the individual components. Thermodynamic analysis of the phase diagrams of these pseudobinary systems can give an insight into the nature of the solid alloys. This information comes from the magnitude of the departure of the systems from ideal behavior and how this depends on temperature and composition.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.122.253.228 Downloaded on 2014-10-19 to IP

Thermodynamic modeling of bulk ternary alloy crystal growth: Comparison of experiments and theory for GaInSb alloys

“…Assuming that Ga 1 À x In x Sb is a two component melt (GaSb and InSb) that is well described by this assumption, the free energy of mixing per mole is DF l mix ¼ RTðx 1 ln x 1 þ x 2 ln x 2 Þ and the heat of mixing is zero. The changes in chemical potentials are [4,10]. The solidus and liquidus lines for the ideal pseudobinary diagram are given by…”

“…These non-idealities are expressed as Bx 1 x 2 where x 1 and x 2 are the mole fractions of the components and B is an interaction parameter [10]. This interaction parameter contains enthalpy contributions to non-ideality, and for a solid it also includes distortion energy.…”

Kovalente tetraedrische Radien, Rumpfradien und Gitteranpassung

“…Die so berechneten Werte der Atomradien werden modifiziert, wenn die Radialfunktionen der Valenzelektronen auf innere Orbitale orthogonalisiert werden (HUBNER 1971).…”

Thermodynamics of solid and liquid group III-V alloys

“…Foster and Woods(3S) also calculated the pseudobinary phase diagram by assuming the liquid phase to be ideal and the activity coefficient of the two solid binary components to be given by (35) Us a fitted value for Bs that showed a small composition dependence the phase diagram was easily reproduced. Several other investigators(Z5, 2 S,JS,Jl) have also assumed that both the solid and liquid solutions are simple solutions with component activity coefficients given by equations of type Equation (35).…”

“…Several other investigators(Z5, 2 S,JS,Jl) have also assumed that both the solid and liquid solutions are simple solutions with component activity coefficients given by equations of type Equation (35). Here the parameter B was sometimes allowed to also have a temperature The procedure was to obtain the liquid B parameters from the binary phase diagrams and extend this to the ternary system.…”