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

Abstract

The lattice thermal conductivity (LTC) and electron-phonon interactions in crystalline and amorphous gallium oxide are herein determined by coupling a machine-learned interatomic potential, namely the moment tensor potential (MTP) model, to first-principles calculations. Crystalline ${\hat{I}}^2$-Ga${}_2$O${}_3$ exhibits a substantial band gap renormalization (BGR) of $\sim$0.45 eV at 700 K, with $\sim$0.2 eV caused by zero-point BGR. The computed temperature dependence of BGR induced by classical nuclear motion in ${\hat{I}}^2$-Ga${}_2$O${}_3$ is stronger than that in amorphous Ga${}_2$O${}_3$, with the difference in BGR reaching $\sim$0.18 eV at 900 K. Thermal transport calculations reveal that the LTC of amorphous Ga${}_2$O${}_3$ remains near $0.9$ W$\cdot$ m${}^{-1}$$\cdot$K${}^{-1}$ for temperatures between 300 K and 700 K, which is approximately an order of magnitude lower than that of crystalline ${\hat{I}}^2$-Ga${}_2$O${}_3$. Overall, the presented 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.