Selective etching of dislocations in GaN and quantitative SEM analysis with shape-reconstruction method

Due to the differences in etch-pit morphologies, chemical etching offers a possibility to determine densities of dislocations in respect to their type. In the present paper we propose a method, which implements a simple shape-from-shading procedure, i.e. with results derived from image brightness dependence on surface slope. It allows estimation of etch-pit depth distributions from scanning electron microscopy micrographs. This method is used to obtain depth distributions from GaN surface after etching in molten KOH–NaOH eutectic mixture. Depth distributions are used to estimate densities of etch-pits related to a given dislocation type. The distributions are compared with dislocation densities determined with transmission electron microscopy.