Electronic and Optical Properties of Highly Complex Ga2O3 and In2O3 Polymorphs Using Approximate Quasiparticle DFT + A – 1/2

Abstract

Ga₂O₃ and In₂O₃ are among the most important wide-bandgap semiconductors for transparent electronics and ultraviolet optoelectronics. Their pronounced polymorphism necessitates a deeper understanding. In addition to assessing the stability of specific crystal structures, the central goal is to investigate the variation of material properties as a function of the actual crystal structure. The underlying atomic geometries are determined through total energy optimizations within density functional theory (DFT) using the AM05 exchange-correlation functional. To account for excitation effects in electronic systems, the formation of quasiparticles, and the underestimation of band gaps, we employ the fast, efficient, but approximate DFT + A – 1/2 method. This approach accurately predicts fundamental gaps, interband transition energies, and d-level positions for five Ga₂O₃ and five In₂O₃ polymorphs, even for structures with up to 160 atoms in the unit cell. The resulting electronic structures are further used to predict dielectric and optical spectra. The effective band masses and dielectric tensors are subsequently employed to estimate the binding energies of band-edge excitons. All results are discussed in the context of polymorph geometry and symmetry, and they are compared with available experimental and theoretical data.