Enhanced thickness uniformity of large-scale α-Ga2O3 epilayers grown by vertical hot-wall mist chemical vapor deposition

Smooth surface morphology and high thickness uniformity heteroepitaxy of corundum-structured (alpha-) gallium oxide (Ga2O3) crystalline thin films on 100-mm diameter c-plane sapphire substrates were successfully demonstrated using vertical hot-wall mist chemical vapor deposition (CVD). The growth rate and surface morphology of the epitaxial layers were numerically and experimentally found to be dependent on the diameter of the precursor-diluted microdroplets approaching the substrate surface. Since the microdroplet is gradually evaporated while traveling through the furnace, the growth variables such as temperature, mist-flow velocity, and substrate position were tuned to obtain a suitable diameter of microdroplets approaching the substrate. In this study, the diameter of the approaching microdroplet was approximate to 2 mu m, which was optimal for the smooth surface (root mean square roughness approximate to 1 nm) of alpha-Ga2O3 epitaxial layers with a growth rate of approximate to 230 nm/h. Due to the even flow of mist in the vertical furnace, high thickness uniformity of the alpha-Ga2O3 epitaxial layer is guaranteed on large-scale substrates, with a standard deviation of thickness as small as 28 nm, paving the way for highly reliable Ga2O3-based electric and optoelectronic devices.

Automated summary

This article presents a method for growing smooth surface and high thickness uniformity corundum-structured (alpha-) gallium oxide (Ga2O3) crystalline thin films on sapphire substrates using vertical hot-wall mist chemical vapor deposition (CVD). By tuning the growth variables and microdroplet diameter, optimal surface morphology and growth rate can be achieved. The even flow of mist in the vertical furnace ensures high thickness uniformity of the Ga2O3 epitaxial layer on large-scale substrates.