Crystallographic wet chemical etching of GaN

Abstract

We demonstrate well-controlled crystallographic etching of wurtzite GaN grown on c-plane sapphire using H3PO4, molten KOH, KOH dissolved in ethylene glycol, and NaOH dissolved in ethylene glycol between 90 and 180 °C, with etch rates as high as 3.2 μm/min. The crystallographic GaN etch planes are {0001}, {101̄0}, {101̄ 1̄}, {101̄ 2̄}, and {101̄3}. The vertical {101̄0} planes appear perfectly smooth when viewed with a field-effect scanning electron microscope. The activation energy is 21 kcal/mol, indicative of reaction-rate limited etching.