UV-assisted room temperature operated NO₂ gas sensors were prepared from ZnO/TiO₂ core–shell nanorods decorated with Au nanoparticles synthesized by a simple low-temperature aqueous solution process.

The control of the refractive index and electrical conductivity in the dielectric layer of omnidirectional reflectors (ODRs) is essential to improve the low efficiency of AlGaN-based UV emitters. Here, we report self-assembled indium tin oxide (ITO) nanoball-embedded omnidirectional reflectors (NODRs) for use in high-efficiency AlGaN-based UV emitters at 365 nm. These NODRs consisted of a reflective Al layer, a self-assembled conducting ITO nanoball layer for current injection and spreading, and nanovoids that provided a low refractive index to achieve highly efficient UV emitters. The NODR was able to realize both high electrical conductivity and reflectivity by decreasing the average refractive index of the ITO nanoball layers. We observed diffuse reflection as well as omnidirectional reflection from the NODR UV emitters because of the corrugated interfaces of the nanovoids, ITO nanoball layer, and Al layer. These structural and optical properties of the NODRs remarkably increased the output power of a UV emitter by a Lambertian enhancement factor of 57% at an injection current of 50 mA at all emission angles compared with that of an ITO film/Al UV emitter.

GaN nanorod (GNR)-integrated photonic emitters (GIPEs) with horizontally self-arrayed GNRs were fabricated for the next generation displays. The self-array performance of GNRs was enhanced by the effective electric-field area.

We demonstrate the highly efficient, GaN-based, multiple-quantum-well light-emitting diodes (LEDs) grown on Si (111) substrates embedded with the AlN buffer layer using NH₃ growth interruption. Analysis of the materials by the X-ray diffraction omega scan and transmission electron microscopy revealed a remarkable improvement in the crystalline quality of the GaN layer with the AlN buffer layer using NH₃ growth interruption. This improvement originated from the decreased dislocation densities and coalescence-related defects of the GaN layer that arose from the increased Al migration time. The photoluminescence peak positions and Raman spectra indicate that the internal tensile strain of the GaN layer is effectively relaxed without generating cracks. The LEDs embedded with an AlN buffer layer using NH₃ growth interruption at 300 mA exhibited 40.9% higher light output power than that of the reference LED embedded with the AlN buffer layer without NH₃ growth interruption. These high performances are attributed to an increased radiative recombination rate owing to the low defect density and strain relaxation in the GaN epilayer.