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

Abstract

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 K 2 S 2 O 8 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.

Review—Progress in Electrochemical Etching of Third-Generation Semiconductors

“…It is worth noting that, in order to facilitate readers' understanding, this paper reviews various electrochemical etching processes in sections, but in practical applications, different wet etching processes can often be combined to optimize the etching results and achieve specific target. Such as in the work of Shimauchi et al, 94 GaN nanowires with a diameter of about 220 nm were prepared by a combination of electrodeless photoelectrochemical etching and continuous traditional aqueous solution etching, and the residual roughness on the etched surface was removed by continuous alkaline solution treatment, giving this nanowires a smooth etched surface; in the work of Schwab et al, 95 they used anodic oxidation etching and photoelectrochemical etching to obtain uniform and ordered GaN mesopores; anodic oxidation etching was used to obtain array mesopores, and then photoelectrochemical etching was used remove the nucleation layer on the upper part of the mesoporous layer to expose the mesoporous layer. As a result, it can be seen from the above work that the characteristics of different etching methods can be comprehensively utilized to achieve the ideal etching 80 morphology, although it requires a deep understanding of the mechanism and the influence of each etching parameter, which is not only limited to engineering exploration and is also one of the contents that can be studied in depth.…”

GaN nanowires prepared by Cu-assisted photoelectron-chemical etching

“…6,7 The two methods are both expensive and complicated to some degree. 8,9 Thus, wet etching has been demonstrated to have signicant potential to realize GaN nanowires owing to the simple experimental operation, low etching-induced damage, and material stress relief. 10,11 Currently, metal-assisted chemical wet etching (MACE) has been a terric and mature method to synthesize Si/GaAs nanowires.…”