Thermodynamic Analysis of the lll-V Alloy Semiconductor Phase Diagrams: I. InSb-GaSb, InAs-GaAs, and InP-GaP

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 Bx1x2, where B is a parameter characteristic of each system and x1 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. © 1971, The Electrochemical Society, Inc. All rights reserved.