Micro-defects in wafers were characterized on the basis of photoluminescence data which were obtained by means of a high-sensitivity Fourier-transform Raman spectrometer. Certain luminescence peaks were obtained, from a crystal which was pulled at a low growth rate, which were not observed in a crystal that was pulled at a normal rate. The luminescence peaks were observed in that region of the wafers where ring oxidation-induced stacking-faults formed, as well as within the ring. By comparing the behavior of annealing-induced defects (D-line and P-line), and the grown-in defects which were observed in low growth-rate crystals, it was concluded that the grown-in defects were of P-line type. On the basis of the photoluminescence intensity of the peak at 0.75eV, which was observed in crystals pulled at a low growth rate, it was deduced that the effect of the thermal history of a crystal pulled at 0.8mm/min was equivalent to annealing at 500C for 3h.

M.Hamada, T.Katoda: Japanese Journal of Applied Physics, 1996, 35[1-1A], 182-5