Monocrystalline samples with a <100> orientation were investigated by means of differential thermal analysis, chemical etching, and heat treatment (950C) for various annealing times. The surface morphologies of chemically and thermally etched {100} surfaces were studied in detail with respect to the microstructure, etch-pit dimensions, defect type and density. It was found that both chemical and thermal etching techniques revealed a similar radial defect distribution pattern on the {100} surfaces, while differential thermal analysis detected a small compositional variation along the radial and axial directions. The correlation between 2 types of etch pit was considered. In the case of thermally etched samples, a kinetic study of rectangular vacancy island (thermal etch pit) formation and self-depletion was presented. On the basis of the current work, the formation rate of vacancy islands could be expressed by:

Dx2 - D02 = kt1.32exp[-E/RT]

Mechanisms were also proposed for vacancy island formation and self-depletion during heat treatment.

H.C.Zeng: Journal of Crystal Growth, 1996, 160[1-2], 119-28