In situ etching of \b{eta}-Ga2O3 using tert-butyl chloride in an MOCVD system

TL;DR

This study demonstrates in situ etching of ta-Ga2O3 films in an MOCVD system using tert-butyl chloride, revealing temperature-dependent etch regimes, anisotropic etching behavior, and surface morphology control.

Contribution

First demonstration of in situ ta-Ga2O3 etching in MOCVD using TBCl with analysis of etch mechanisms and anisotropic etching behavior.

Findings

Etch rate depends on temperature with two distinct regimes.

HCl likely acts as the primary etchant.

Etch rates scale with surface energy ratios, indicating anisotropic etching.

Abstract

In this study, we investigate in situ etching of \b{eta}-Ga2O3 in a metal-organic chemical vapor deposition (MOCVD) system using tert-Butyl chloride (TBCl). We report the successful etching of both heteroepitaxial (-201)-oriented and homoepitaxial (010)-oriented \b{eta}-Ga2O3 films over a wide range of substrate temperature, TBCl molar flows, and reactor pressures. We identify that the likely etchant is HCl (g) formed by the pyrolysis of TBCl in the hydrodynamic boundary layer above the substrate. The temperature dependence of the etch rate reveals two distinct regimes characterized by markedly different apparent activation energies. The extracted apparent activation energies suggest that at temperatures below ~800 {\deg}C the etch rate is likely limited by desorption of etch products. The relative etch rates of heteroepitaxial (-201) and homoepitaxial (010) \b{eta}-Ga2O3 were observed to scale by the ratio of the surface energies indicating an anisotropic etch. For (010) homoepitaxial films, relatively smooth post-etch surface morphology was achieved by tuning the etching parameters.