Fabrication of GaN nanowires containing n(+)-doped top layer by wet processes using electrodeless photo-assisted electrochemical etching and alkaline solution treatment

We attempted to fabricate GaN nanowires by electrodeless photo-assisted electrochemical (PEC) etching and successive alkaline solution treatment. The sample consisting of n(+)-doped and unintentionally doped GaN grown on a GaN substrate was selectively etched using a Ti mask in a mixed solution of K2S2O8 and KOH under UV light radiation. This specific layer structure required a relatively concentrated KOH solution for etching. The PEC etching resulted in the formation of a tapered cone structure of GaN with its top diameter determined by the mask size. Successive KOH treatment after PEC etching yielded GaN nanowires with diameters of about 220 nm.