Effect of local strain energy to predict accurate phase diagram of III–V pseudobinary systems: case of Ga(As,Sb) and (In,Ga)As

Abstract

This work proposes an efficient and accurate methodology of ab initio thermodynamics to predict phase diagrams of III–V pseudobinary systems. The innumerable configurations of solid solutions are efficiently considered while maintaining accuracy by calculating the energies of freely relaxed configurations with the combined methodology using density functional theory calculations and cluster expansion. Then, the thermodynamic properties are calculated following a grand canonical ensemble framework that takes into account the local compositional fluctuation. The local strain energy induced by this local compositional fluctuation is found to be independent of the configuration; hence, it is calculated separately and added to the energy of a freely relaxed configuration, which significantly reduces the computational cost. This novel methodology is applied to calculate the phase diagrams of Ga(As,Sb) and (In,Ga)As, showing a good agreement with previous experimental reports. Notably, the strain energy is indispensable to predict phase diagrams accurately. It implies both the validity and the applicability of this method to other III–V pseudobinary systems. From an understanding of the crucial role of the strain energy in phase separation, an intuitive prediction is suggested through a simple estimation of the strain energy using the ratio of lattice parameters between various III–V semiconductor materials.

High-entropy alloy screening for halide perovskites

“…We confirm agreement with 42 out of 45 room temperature miscibility gap data from III–V (Fig. 1 and Table S1, ESI†) 57,58 and II–VI (Table S1, ESI†) 56 material systems. UCV correlates well with experimental III–V and II–VI mixing enthalpy (Table S1 and Fig.…”

“…Fig. 1 Experimental III-V single-phase alloy (pink circles) and multiple phase (gray Xs) data, 57,58 confirming that plotting the ES term at 300 K (or S/R) as a function of UCV leads to a phase boundary near UCV of 0.03 (black dashed line) which is useful for screening HEA that have not yet been experimentally synthesized.…”

“…54 Based on the Hume–Rothery rules for metal alloying (minimize atomic radii differences, match crystal structures, keep valency constant, and keep electronegativity constant), 55 Foster showed that lattice parameter differences could be used to predict miscibility in III–Vs and II–VIs. 56 Foster and Stringfellow used this “delta-lattice parameter” approach to correctly group the miscibility of 9 ternary II–VI 56 and 9 quaternary III–V 57 alloy systems, respectively, and the method was recently extended to correctly group the miscibility of 18 ternary III–V alloy systems, 58 confirming broad accuracy in spite of its low computational cost. To extend the delta-lattice parameter method to non-cubic structures, we draw on Zen's law: there is an empirical linear relation between molar volume and composition of a solid solution.…”