The crystals were grown by a gradually decreased pulling rate method, a special crystal growing method, and detached from a melt during the growth so as to rapidly cool the grown crystal and then to observe the appearance and disappearance of point defects at the moment of the detachment. This observation - nearly in situ observation, as it were - revealed that vacancies (Vs) were introduced through a growth interface, and interstitials (Is) were generated at an interstitial generation area, an area at which the thermal stress was increased through the increased thermal gradient, above the growth interface. In the beginning of the gradually decreased pulling rate method, since the pulling rate was high, the Vs introduced through the growth interface remained in the crystal; as the pulling rate was decreased, the generation of the Is began from the interstitial generation area, and these interstitials were recombined with the Vs introduced through the growth interface, thereby forming a first recombination area. As the concentration of the Is increased due to a lower pulling rate, a dislocation loop region began to be formed. On the growth interface side of this dislocation loop region, a V region from the growth interface and a second recombination area were similarly formed. The formation of these two recombination areas proves that the growth interface was the V region. In this paper, the point defects and secondary defects thereof were observed by our three new observation methods and the etch-pit method used in product inspection. The results of these methods were consistent with all the above phenomenon. (C) 2015 Elsevier B.V. All rights reserved.