Assessment of the (010) $\beta$-Ga$_2$O$_3$ Surface and Substrate Specification

TL;DR

This paper evaluates the (010) surface and substrate specifications of beta-Ga2O3, highlighting recent growth advances, surface features, and proposing standardization guidelines to improve film quality and control surface morphology.

Contribution

It provides a detailed analysis of the (010) surface structure of beta-Ga2O3 and offers recommendations for substrate standardization to mitigate surface ridges.

Findings

Density functional theory reveals sub-nanometer surface ordering.

Surface features include facets and ridges along specific crystallographic directions.

Recommendations aim to standardize substrates for better film quality.

Abstract

Recent breakthroughs in bulk crystal growth of the thermodynamically stable beta phase of gallium oxide ($\beta$-Ga$_2$O$_3$) have led to the commercialization of large-area beta-Ga$_2$O$_3$ substrates with subsequent epitaxy on (010) substrates producing high-quality films. Still, metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and processing of the (010) $\beta$-Ga$_2$O$_3$ surface are known to form sub-nanometer scale facets along the [001] direction as well as larger ridges with features perpendicular to the [001] direction. A density function theory calculation of the (010) surface shows an ordering of the surface as a sub-nanometer-scale feature along the [001] direction. Additionally, the general crystal structure of $\beta$-Ga$_2$O$_3$ is presented and recommendations are presented for standardizing (010) substrates to account for and control the larger-scale ridge formation.