Epitaxial layers which had been grown onto sapphire substrates were studied by means of chemical etching. Molten KOH was used as a defect etchant in order to characterize etch pits on the layers. All of the pits were in the form of hexagonal pyramids, which reflected the crystal symmetry of the GaN. The results showed that molten KOH could be a useful method for evaluating dislocations in GaN layers. The etch pit density was typically of the order of 2 x 107/cm2.

T.Kozawa, T.Kachi, T.Ohwaki, Y.Taga, N.Koide, M.Koike: Journal of the Electrochemical Society, 1996, 143[1], L17-9