Selective Area Growth of Single-Crystalline Alpha-Gallium Oxide on a Sapphire Nanomembrane by Mist Chemical Vapor Deposition

Alpha-gallium oxide (α-Ga2O3) has been considered a promising material for efficient power semiconductors because of its large bandgap. Sapphire can be an appropriate substrate for α-Ga2O3 because the two materials have the same crystal structure. However, it is hard to obtain high-quality α-Ga2O3 thin films on sapphire due to a large lattice mismatch. Herein, we demonstrate the selective area growth of high-quality and strain-relaxed α-Ga2O3 thin films on the top of stripe-patterned sapphire nanomembranes. This process is enabled by the well-understood diffusion of adatoms to the highest surface energy plane of a sapphire nanomembrane at different growth temperatures. High-resolution transmission electron microscopy confirmed that misfit dislocations on the nanomembrane were reduced by 13% compared to those of α-Ga2O3 grown directly on a sapphire substrate. Reciprocal space mapping reveals that the sapphire nanomembrane reduces in-plane compressive strain in the film by up to 51.6%. This work paves a way for synthesizing high-quality α-Ga2O3 thin films that are promising for optoelectronic applications of high voltage and in deep ultraviolet.