Application of halide vapor phase epitaxy for the growth of ultrawide band gap Ga_2O_3

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 Ga_2O_3, 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 Ga_2O_3 substrates and for the fabrication of high power β-Ga_2O_3 devices.

High-efficiency photon-electron coupling resonant emission in GaN-based microdisks on Si

Resonance effects caused by the photon-electron interaction are a focus of attention in semiconductor optoelectronics,as they are able to increase the efficiency of emission.GaN-on-silicon microdisks can provide a perfect cavity structure for such resonance to occur.Here we report GaN-based microdisks with different diameters,based on a standard blue LED wafer on a Si substrate.A confocal photoluminescence spectroscopy is performed to analyze the properties of all microdisks.Then,we systematically study the effects of radial modes and axial modes of these microdisks on photon-electron coupling efficiency by using three-dimensional finite-difference time-domain simulations.For thick microdisks,photon-electron coupling efficiency is found to greatly depend on the distributions of both the radial modes and the axial modes,and the inclined sidewalls make significant influences on the axial mode distributions.These results are important for realization of high-efficiency resonant emission in GaN-based microcavity devices.

High-efficiency green micro-LEDs with GaN tunnel junctions grown hybrid by PA-MBE and MOCVD

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 In Ga N polarization layer and an n^(++)∕n^(+)-GaN layer on the activated p^(++)-Ga N 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.