Influence of Polymorphism on the Electronic Structure of Ga$_2$O$_3$

TL;DR

This study investigates the structural and electronic properties of three Ga$_2$O$_3$ polymorphs using experimental spectroscopy and advanced theoretical calculations to understand their potential for future electronic devices.

Contribution

It provides a comprehensive analysis of the structure-electronic relationships in Ga$_2$O$_3$ polymorphs using combined experimental and ab initio methods, which is novel.

Findings

Electronic structures vary significantly among polymorphs.

Spectroscopic data closely match theoretical predictions.

Insights into local coordination effects on electronic properties.

Abstract

The search for new wide band gap materials is intensifying to satisfy the need for more advanced and energy efficient power electronic devices. Ga$_2$O$_3$ 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 Ga$_2$O$_3$, $\alpha$, $\beta$ and $\varepsilon$, 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 conduction electronic structure as well as semi-core 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, provide 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 Ga$_2$O$_3$ polymorphs as materials at the heart of future electronic device generations.