Dislocation etch pits in GaN epitaxial layers grown on sapphire substrates

Dislocations in GaN epitaxial layers grown on sapphire substrates have been studied by chemical etching. We have examined molten KOH as a defect etchant and characterized the etch pits on GaN layers. By use of molten KOH etching, etch pits were revealed on the surface of the GaN layer. All pits were hexagonal pyramids, which reflect the crystal symmetry of GaN. Results showed that molten KOH etching might be a useful method for the evaluation of the dislocations in GaN layers. The etch pit density (EPD) was typically 2 x 10(7) cm(-2).