H3PO4, NaOH, and KOH solutions are found to be useful for removing nit
rogen depleted layers or damage induced by high temperature annealing
or dry etching of metalorganic chemical vapor deposition-grown (0001)G
aN/Al2O3. Solutions are selective to the (0001)plane of GaN. However,
certain flat planes etched without etch pits are exposed by wet etchin
g.