【International Papers】Investigating Stable Low-Energy Gallium Oxide (Ga₂O₃) Polytypes: Insights into Electronic and Optical Properties from First Principles

      Researchers from the University of Oslo have published a dissertation titled "Investigating Stable Low-Energy Gallium Oxide (Ga₂O₃) Polytypes: Insights into Electronic and Optical Properties from First Principles " in ACS Omega.

Abstract

      This study provides a comprehensive analysis of the electronic and optical properties of low-energy gallium oxide (Ga₂O₃) polytypes not considered earlier. Among these polytypes, the monoclinic structure (β-Ga₂O₃) holds significant relevance for both research and practical applications due to its superior stability under typical conditions. The primary aim of this research is to identify new and stable Ga₂O₃ polytypes that may exist under zero-temperature and zero-pressure conditions. To achieve this objective, we employ the VASP code to investigate electrical and optical properties, as well as stability assessments. Additionally, we examine phonon and thermal properties, including heat capacity, for all polytypes. This study also encompasses the computation of full elastic tensors and elastic moduli for all polytypes at 0 K, with Poisson’s and Pugh’s ratios confirming their ductile nature. Furthermore, we present the first ever report on the Raman- and infrared (IR)-active modes of these stable Ga₂O₃ polytypes. Our findings reveal that these mechanically and dynamically stable Ga₂O₃ polytypes exhibit semiconductive properties, as evidenced by electronic band structure investigations. This research offers valuable insights into the optical characteristics of Ga₂O₃ polytypes with potential applications spanning various fields.

Figure 1. Total energy (E) vs volume (V) curve for Ga₂O₃ polytypes represents all energy–volume values normalized to one formula unit (f.u.).

Figure 2. Optimized crystal structure of polytypes: (a) Ga₂O₃-M1, (b) Ga₂O₃-M2, (c) Ga₂O₃-M3, (d) Ga₂O₃-M4, (e) Ga₂O₃-M5, (f) Ga₂O₃-T, (g) Ga₂O₃–O1, (h) Ga₂O₃–O2, and (i) Ga₂O₃–O3.

Paper Link：https://doi.org/10.1021/acsomega.3c10192