Low-Temperature Direct Growth of Few-Layer Hexagonal Boron Nitride on Catalyst-Free Sapphire Substrates.

Wide-band-gap layered semiconductor hexagonal boron nitride (h-BN) is attracting intense interest due to its unique optoelectronic properties and versatile applications in deep ultraviolet optoelectronic and two-dimensional electronic devices. However, it is still a great challenge to directly grow high-quality h-BN on dielectric substrates, and an extremely high substrate temperature or annealing is usually required. In this work, high-quality few-layer h-BN is directly grown on sapphire substrates via ion beam sputtering deposition at a relatively low temperature of 700 °C by introducing NH3 into the growth chamber. Such low growth temperature is attributed to the presence of abundant active N species, originating from the decomposition of NH3 under ion beam irradiation. To further tailor the properties of h-BN, carbon was introduced into the h-BN layer by simultaneously introducing CH4 and NH3 during the growth process, indicating the wide applicability of this approach. Moreover, a deep ultraviolet (DUV) photodetector is also fabricated from a C-doped h-BN layer and exhibits superior performance compared with an intrinsic h-BN device.