First-principles study of the ternary semiconductor alloys (Ga,Al)(As,Sb)

Abstract

First-principles calculations are performed to study the structural, electronic, optical and thermodynamic properties of technologically important Al x Ga 1− x As, Al x Ga 1− x Sb, GaAs x Sb 1− x and AlAs x Sb 1− x ternary alloys using the full potential-linearized augmented plane wave plus local orbitals method within the density functional theory. We use both Wu–Cohen and Engel–Vosko generalized gradient approximations of the exchange-correlation energy that are based on the optimization of total energy and corresponding potential, respectively. Our investigation on the effect of composition on lattice constant, bulk modulus, ionicity, band gap, effective mass and refractive index for ternary alloys shows almost non-linear dependence on the composition. The bowing of the fundamental gap versus composition predicted by our calculations is in good agreement with available experiment data. The different roles of structural and chemical effects on the gap bowing and its variation with composition are identified and discussed. It is found that charge-exchange effect overwhelms the other contributions to the gap bowing. Besides, a regular-solution model is used to investigate the thermodynamic stability of the alloys which mainly indicates a phase miscibility gap. In addition, the quasi-harmonic Debye model is applied to determine the thermal properties at room temperature.