Visualization of clusters of electrically inactive impurity atoms in n-type silicon by γ irradiation

Samples of n-type silicon grown by the Czochralski (Si-Cz) and the floating zone (Si-Fz) methods were irradiated in the initial state and also after annealing (900 degree C, 24 h), which tended to precipitate oxygen. The irradiation (with γ rays from 60Co) at 300 K was followed by annealing at 375 degree C. The electrical conductivity and the Hall coefficient were determined before and after irradiation. Moreover, a photoelectric method developed by one of the present authors was used to investigate clusters of compensating acceptor centers. Irradiation of Si-Fz not subjected to annealing increased the fraction of the volume of a crystal occupied by the space charge regions of the clusters and also the total number of charges in these clusters; these parameters were practically unaffected when Si-Cz was irradiated. On the other hand, irradiation of the material subjected to annealing enhanced the growth of clusters in Si-Cz