Doping selective lateral electrochemical etching of GaN for chemical lift-off

An electrochemical etching based on oxalic acid was developed for use in the chemical lift-off of GaN epitaxial structures. It was shown that only the Si-doped n-GaN layer was etched away, while the p-type and undoped GaN layers were not etched at all. The etch rate and the remaining structure were analyzed for various doping concentrations and etching voltages. A lateral etch rate of 12 mu m/min was achieved under 60 V for n-type doping concentration of 8x10(18) cm(-3). This doping selective etching was used to lift-off a GaN epitaxial layer patterned into 300x300 mu m(2) squares.