Offcut-related step-flow and growth rate enhancement during (100) $\beta$-Ga2O3 homoepitaxy by metal-exchange catalyzed molecular beam epitaxy (MEXCAT-MBE)

TL;DR

This study demonstrates that by tuning growth parameters and substrate offcut angles, high-quality (100) β-Ga2O3 homoepitaxial layers can be grown via MEXCAT-MBE at higher rates, with step edges acting as nucleation sites.

Contribution

It introduces a method to enhance growth rates and quality of (100) β-Ga2O3 homoepitaxy using MEXCAT-MBE with substrate offcut optimization.

Findings

High-quality films grown at ~1.5 nm/min rate

Step edges serve as nucleation sites for growth

Proper substrate offcut improves growth quality

Abstract

In this work we investigate the growth of $\beta$-Ga2O3 homoepitaxial layers on top of (100) oriented substrates via indium-assisted metal exchange catalyzed molecular beam epitaxy (MEXCAT-MBE) which have exhibited prohibitively low growth rates by non-catalyzed MBE in the past. We demonstrate that the proper tuning of the MEXCAT growth parameters and the choice of a proper substrate offcut allow for the deposition of thin films with high structural quality via step-flow growth mechanism at relatively high growth rates for $\beta$-Ga2O3 homoepitaxy (i.e., around 1.5 nm/min, $\approx$45% incorporation of the incoming Ga flux), making MBE growth on this orientation feasible. Moreover, through the employment of the investigated four different (100) substrate offcuts along the [00-1] direction (i.e., 0$^\circ$, 2$^\circ$, 4$^\circ$, 6$^\circ$) we give experimental evidence on the fundamental role of the (-201) step edges as nucleation sites for growth of (100)-oriented Ga2O3 films by MBE.