Patterning GaN Microstructures by Polarity-Selective Chemical Etching

We have demonstrated GaN microstructures formed by polarity-selective chemical etching in KOH solution. It was found that KOH selectively etches N-polar GaN but not Ga-polar GaN. The polarity-patterned GaN was grown by plasma-assisted molecular beam epitaxy. For intermediate etching times, hexagonal GaN pyramids were formed in the N-polar regions. With prolonged etching, the N-polar GaN can be completely removed. A one-dimensional array of GaN stripes and a two-dimensional array of hexagonal holes formed in a GaN matrix have been fabricated. Extremely smooth vertical sidewalls have been achieved along with an etch depth of up to 4 µm.