Vertically oriented GaN-based air-gap distributed Bragg reflector structure fabricated using band-gap-selective photoelectrochemical etching

A three-period vertically oriented GaN-based air-gap distributed Bragg reflector structure was fabricated using band-gap-selective photoelectrochemical (PEC) etching. The epitaxial structure consisted of an ${\mathrm{Al}}_{0.08}{\mathrm{Ga}}_{0.92}\mathrm{N}∕({\mathrm{In}}_{0.04}{\mathrm{Ga}}_{0.96}\mathrm{N}∕{\mathrm{In}}_{0.07}{\mathrm{Ga}}_{0.93}\mathrm{N})$ superlattice structure, wherein the InGaN layers served as sacrificial layers during PEC etching. Microreflectance measurements yielded an average enhancement in the reflected signal of $\sim 12$ -fold over the wavelength range of 550–650 nm, when compared with the signal from a dry-etched GaN surface.