Thermodynamic stability analysis of Bi-containing III-V quaternary alloys and the effect of epitaxial strain

Abstract

The thermodynamic stability of Bi-containing III-V quaternary alloys was determined using the delta lattice parameter (DLP) model in conjunction with density functional theory (DFT) calculations. The DLP model and DFT-calculated enthalpy of mixing show remarkably good agreement for the In1-yGayAs1-xBix and GaAs1-x-yBixPy systems. Binodal and spinodal isotherm contours have been constructed for these systems, as well as In1-yGayP1-xBix, In1-yGaySb1-xBix, GaAs1-x-yBixSby, InAs1-x-yBixPy and InAs1-x-yBixSby, for their unstrained and pseudomorphically strained states as a function of lattice parameter. Enhanced Bi solubility can be achieved by epitaxial growth of alloys on substrates with lattice parameters from 0.565 to 0.6058 nm. The incorporation of an anion element with a smaller atomic size also increases the Bi solubility in the Bi low concentration regime. This work elucidates the thermodynamic stability dependence for Bi-containing quaternary alloys on choice of cation, anion and strain state. It also extends the DLP model to a wider composition range.