We fabricated p-i-n tunnel junction (TJ) contacts for hole injection on c-plane green micro-light-emitting diodes (micro-LEDs) by a hybrid growth approach using plasma-assisted molecular beam epitaxy (PA-MBE) and metal–organic chemical vapor deposition (MOCVD). The TJ was formed by an MBE-grown ultra-thin unintentionally doped InGaN polarization layer and an n++/n+-GaN layer on the activated p++-GaN layer prepared by MOCVD. This hybrid growth approach allowed for the realization of a steep doping interface and ultrathin depletion width for efficient inter-band tunneling. Compared to standard micro-LEDs, the TJ micro-LEDs showed a reduced device resistance, enhanced electroluminescence intensity, and a reduced efficiency droop. The size-independent J-V characteristics indicate that TJ could serve as an excellent current spreading layer. All these results demonstrated that hybrid TJ contacts contributed to the realization of high-performance micro-LEDs with long emission wavelengths.

Halide vapor phase epitaxy (HVPE) is widely used in the semiconductor industry for the growth of Si, GaAs, GaN, etc. HVPE is a non-organic chemical vapor deposition (CVD) technique, characterized by high quality growth of epitaxial layers with fast growth rate, which is versatile for the fabrication of both substrates and devices with wide applications. In this paper, we review the usage of HVPE for the growth and device applications of Ga₂O₃, with detailed discussions on a variety of technological aspects of HVPE. It is concluded that HVPE is a promising candidate for the epitaxy of large-area Ga₂O₃ substrates and for the fabrication of high power β-Ga₂O₃ devices.