Phase tailoring and wafer-scale uniform hetero-epitaxy of metastable-phased corundum α-Ga₂O₃ on sapphire

Heteroepitaxy of corundum-structured α-Ga₂O₃ is proven as an alternative strategy to solve current challenges in heat dissipation and large scale productivity for Ga₂O₃-based power electronic devices. In this work, we demonstrate low thermal budget and highly uniform epitaxy of α-Ga₂O₃ single-crystalline films on 2-inch sapphire substrate by mist-chemical vapor deposition technique. Phase tailoring is performed by tuning the growth temperature and pure phase α-Ga₂O₃ single-crystalline epilayers are achieved with atomically smooth surface and a reduced dislocation density. High-resolution transmission electron microscopic results indicate α-Ga₂O₃ growth on sapphire is semi-coherent without any impurity phases, dominated by the multiple domain matching epitaxial mode. Relaxation of strain induced by lattice misfits result in the propagation of edge dislocations along the c-axis. The wafer-scaled epilayers exhibit high crystallographic and thickness uniformity with deviations less than 3%, which stems from the formation of laminar flow on the growing front surface. The herein developed wafer-scale epitaxy in a designed vertical reactor configuration is a straightforward and economic productive scale-up approach to deliver high-quality low-cost wide-bandgap oxide semiconductors towards practical applications in power devices and solar-blind optoelectronics.