Removal of Dry-Etch-Induced Surface Layer Damage from p-GaN by Photoelectrochemical Etching

Abstract

A non-thermal method for removal of surface damage created by dry etching has previously been documented or n-GaN, but no such effort has been reported for p-GaN. In this study, Ga-polar p-GaN films were subjected to inductively coupled plasma reactive ion etching, creating damage near the surface and causing an inversion of the carrier type and concentration from + 5.5 × 1012 cm−2 to − 8.8 × 1010 cm−2, as measured by Hall effect. An application of the carrier-type-selective photoelectrochemical (PEC) etching technique using a KOH and K2S2O8 etch chemistry is employed in order to remove etch-face damage and recover the underlying p-GaN. We show the type selectivity of the PEC etching technique, demonstrating electroless etching of n-GaN while no interaction of the same etch chemistry with p-GaN is observed. Further, surface analysis shows that the PEC etch removes a surface layer from dry-etched p-GaN and increases its roughness substantially, from 0.64 nm to 71 nm RMS.