It was recalled that various micro-defects, which formed as a result of the condensation of native point defects and impurities, were present in dislocation-free melt-grown crystals. A computer modelling study was made here of the distribution of micro-defects in Czochralski-type crystals. The approach was based upon the main assumptions of Voronkov's theory. Values of axial temperature gradient, and cooling rate, which had been measured during crystal growth were used. It was found that the calculations quantitatively reproduced observed phenomena such as a transition, between vacancies and interstitial micro-defects, when the pulling rate was varied through a critical value. The size and shape of the regions of interstitial (A, B) defects and vacancy-related A' defects were predicted, as were the position and shape of the defect-free zone in crystals which were 8 to 16cm in diameter. By fitting the calculations to observed micro-defect patterns, the activation energy for point-defect migration was estimated to be equal to 1.3eV (for temperatures ranging from the melting point to 1273K). The radial distribution of the axial temperature gradient, near to the growth interface, could be deduced from observed micro-defect patterns.

N.I.Puzanov, A.M.Eidenzon, D.N.Puzanov: Journal of Crystal Growth, 1997, 178, 468-78