Thermal conductivity of ternary III-V semiconductor alloys: The role of mass difference and long-range order

TL;DR

This study investigates how atomic mass differences and long-range order influence thermal conductivity in ternary III-V semiconductor alloys, revealing that explicit mass treatment and alloy ordering significantly affect thermal transport predictions.

Contribution

It demonstrates the importance of explicit atomic mass treatment and alloy ordering in accurately modeling thermal conductivity of ternary III-V alloys, challenging the virtual-crystal approximation.

Findings

Explicit atomic mass treatment significantly alters thermal conductivity predictions.

Long-range order affects thermal transport, deviating from random-alloy assumptions.

Mass-difference scattering dominates over virtual-crystal approximation predictions.

Abstract

Thermal transport in bulk ternary III-V arsenide (III-As) semiconductor alloys was investigated using equilibrium molecular dynamics with optimized Albe-Tersoff empirical interatomic potentials. Existing potentials for binary AlAs, GaAs, and InAs were optimized to obtain accurate phonon dispersions and temperature-dependent thermal conductivity. Calculations of thermal transport in ternary III-Vs commonly employ the virtual-crystal approximation (VCA), where the structure is assumed to be a random alloy and all group-III atoms (cations) are treated as if they have an effective weighted-average mass. Here, we showed that is critical to treat atomic masses explicitly, and that the thermal conductivity obtained with explicit atomic masses differs considerably from the value obtained with the average VCA cation mass. The larger the difference between the cation masses, the poorer the VCA prediction for thermal conductivity. The random-alloy assumption in the VCA is also challenged, because X-ray diffraction and transmission electron microscopy show order in InGaAs, InAlAs, and GaAlAs epi-layers. We calculated thermal conductivity for three common types of order [CuPt-B, CuAu-I, and triple-period-A (TPA)] and showed that the experimental results for In$_{0.53}$Ga$_{0.47}$As and In$_{0.52}$Al$_{0.48}$As, which are lattice matched to the InP substrate, can be reproduced in molecular dynamics simulation with 2% and 8% of random disorder, respectively. Based on our results, thermal transport in ternary III-As alloys appears to be governed by the competition between mass-difference scattering, which is much more pronounced than the VCA suggests, and the long-range order that these alloys support.