There have been recent research advances in AlGaN-based self-assembled nanowires (NWs) as building blocks for ultraviolet (UV) optoelectronics grown by plasma-assisted molecular beam epitaxy. We review the basic growth kinetics on various foundry-compatible-metal/silicon-based substrates and the epistructure design for UV devices. We highlight the use of diffusion-barrier-metal thin film on silicon substrate as a solution to enhance device performance. NWs offer the opportunity to mitigate the detrimental quantum-confined Stark effect (QCSE), which lowers the recombination rate thereby reducing the device efficiency. On the other hand, the polarization-induced doping from the graded composition along NWs can be advantageous for eluding the inefficient doping in AlGaN-based UV devices. Sidewall surface states and the associate passivation treatment, as well as the use of ultrafast electron-microscopy characterization, are crucial investigations in shedding light on device performance under the influence of surface dangling bonds. For investigating the electrical performance of individual NWs and NWs light-emitting diode as a single entity, recent reports based on conductive atomic force microscopy measurements provide fast-prototyping in-process pass-fail evaluation and a means of improving growth for high-performance devices. Stress tests of NWs devices, crucial for reliable operation, are also discussed. Beyond applications in LEDs, an AlGaN-based NWs solar-blind photodetector demonstrated leveraging on the dislocation-free active region, reduced QCSE, enhanced light absorption, and tunable-composition features. The review opens pathways and offers insights for practical realization of AlGaN-based axial NWs devices on scalable and low-cost silicon substrates.
Group III-nitride semiconductor materials especially AlGaN are key-emerging candidates for the advancement of ultraviolet (UV) photonic devices. Numerous nanophotonics approaches using nanostructures (e.g., nanowires, nanorods, and quantum dots/disks) and nanofabrication (e.g., substrate patterning, photonic crystals, nanogratings, and surface-plasmons) have been demonstrated to address the material growth challenges and to enhance the device efficiencies of photonic devices operating at UV wavelengths. Here, we review the progress of nanophotonics implementations using nanostructured interfaces and nanofabrication approaches for the group III-nitride semiconductors to realize efficient UV-based photonic devices. The existing challenges of nanophotonics applications are presented. This review aims to provide analysis of state-of-the-art nanophotonic approaches in advancing the UV-photonic devices based on group III-nitride semiconductors.