Influence of Polymorphism on the Electronic Structure of Ga2O3

The search for new wide-band-gap materials is intensifying to satisfy the need for more advanced and energy-efficient power electronic devices. Ga2O3 has emerged as an alternative to SiC and GaN, sparking a renewed interest in its fundamental properties beyond the main beta-phase. Here, three polymorphs of Ga2O3, alpha, beta, and epsilon, are investigated using X-ray diffraction, X-ray photoelectron and absorption spectroscopy, and ab initio theoretical approaches to gain insights into their structure-electronic structure relationships. Valence and con- duction electronic structure as well as semicore and core states are probed, providing a complete picture of the influence of local coordination environments on the electronic structure. State-of-the-art electronic structure theory, including all-electron density functional theory and many-body perturbation theory, provides detailed understanding of the spectroscopic results. The calculated spectra provide very accurate descriptions of all experimental spectra and additionally illuminate the origin of observed spectral features. This work provides a strong basis for the exploration of the Ga2O3 polymorphs as materials at the heart of future electronic device generations.