  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, while at higher
substrate temperatures chemisorption of HCl limits the etch rate. 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.
