Thermal Conductivity and Temperature-Induced Band Gap Renormalization in Crystalline and Amorphous Ga$_2$O$_3$

TL;DR

This study combines machine learning and first-principles calculations to analyze thermal conductivity and band gap renormalization in crystalline and amorphous Ga₂O₃, revealing significant temperature-dependent effects.

Contribution

It introduces a MTP-based computational framework for predicting thermal and electronic properties of semiconductors in both crystalline and amorphous forms.

Findings

Crystalline Ga₂O₃ shows a zero-point band gap renormalization of ~0.2 eV.

Temperature increases cause a stronger BGR in crystalline than in amorphous Ga₂O₃.

Amorphous Ga₂O₃ has a thermal conductivity near 0.9 W/m·K, much lower than crystalline Ga₂O₃.

Abstract

In the present work, we performed calculations of the lattice thermal conductivity (LTC) and electron-phonon interactions in crystalline and amorphous gallium oxide. The calculations were performed by coupling a machine-learned interatomic potential - the moment tensor potential (MTP) model - to first-principles calculations. Crystalline $\beta$-Ga$_2$O$_3$ exhibits a pronounced zero-point band gap renormalization (BGR) of $\sim 0.2\,\text{eV}$ and a BGR of $\sim 0.45\,\text{eV}$ at $700\,\text{K}$. The computed temperature dependence of BGR induced by classical nuclear motion in $\beta$-Ga$_2$O$_3$ is stronger than that in amorphous Ga$_2$O$_3$. Thermal transport calculations reveal that the LTC of amorphous Ga$_2$O$_3$ remains near $0.9\,\text{W}\cdot\text{m}^{-1}\cdot\text{K}^{-1}$ for temperatures between $300\,\text{K}$ and $700\,\text{K}$, which is approximately an order of magnitude lower than that of $\beta$-Ga$_2$O$_3$. Overall, the presented MTP-based framework provides a computationally tractable and reliable route for predicting properties of semiconductors (both crystalline and amorphous) under operating conditions relevant to microelectronics and optoelectronics.