Bias-assisted photoelectrochemical etching of p-GaN at 300 K

Abstract

Photoelectrochemical ͑PEC͒ etching of p-type GaN has been realized in room temperature, 0.1 M KOH solutions. PEC etching of GaN was achieved by applying a positive bias to the surface of the p-GaN layer through a deposited titanium mask. The applied bias reduces the field at the semiconductor surface, which induced the dissolution of the GaN. The effect of bias on etch rate and morphology was examined. It was found that insulating the Ti mask from the KOH solution with Si 3 N 4 significantly increases the etch rate. The rms roughness of the etched region decreased as the bias voltage increased. Etch rates as high as 4.4 nm/min were recorded for films etched at 2 V.

Damage characteristics of n-GaN thin film surfaces etched by ultraviolet light-assisted helium plasmas

“…2 and 3 that the additional UV light irradiation causes the morphological change in the surface and enhances the etch depth are considered to be similar to those obtained by use of the UV light-assisted wet etching technique [30][31][32]. The surface is wet-etched with a KOH aqueous solution under UV light irradiation, though the surface is hardly wet-etched only with the KOH aqueous solution.…”

“…The roughness of the surface induced by the UV light-assisted wet etching is larger than that of the as-grown surface. The reason why the UV light-assisted wet-etching occurs can be explained in terms of the upward band bending at the surface of nGaN [30][31][32]. The UV light irradiation produces electron-hole pairs in the surface.…”

Evolution of surface morphology of polar and nonpolar GaN thin films during photoelectrochemical etching

“…Thus, some volume around any electrically active defect would exhibit a decreased etch rate, provided that the reaction is limited by the number or holes produced ("carrier-limited" regime). Thus, in order to produce the smooth surfaces, sufficient holes must be present on the surface (attainable by increasing the light intensity 3 or by applying a bias 10,11 ). By maintaining the etch in the carrier-limited regime, features such as whiskers can be obtained on GaN around defective portions of the film with very short minority carrier (hole) lifetimes, and information about the defective regions of the GaN film can be ascertained in a short, inexpensive manner.…”

Electrochemical CV‐profiling of GaN

“…Wet chemical etches usually fail to etch the group III-nitrides reproducibly. There are successful reports for n-type material if photoelectrochemical (PEC) etching is used instead [3,4], whereas the reports for p-type material in literature are sparse and not very encouraging [5]. We developed a new (photo-) electrochemical etch procedure for nitrides, which we call "cyclic oxidation" and which is described in more detail elsewhere [6].…”