Peculiarities of changes in the structure and electrophysical characteristics of n-Si under the effect of various thermal treatment regimes

Abstract

Crystals of n-silicon doped with an impurity of phosphorus are studied both by the traditional metallur gical method (in the process of growth through a melt) and the nuclear transmutation method (conversion of silicon isotopes in the process of thermal neutron capture by them). The principal difference of the transmutation doping from the metallurgical doping method is that dopants are not introduced into the initial material from the outside, but are formed during the irradiation process directly from the atoms of the doped material. In order to anneal the radiation defects and activate the phosphorus-31 atoms, which exhibit donor pro perties only at lattice sites in the bulk of silicon, the transmutation-doped silicon was preliminarily subjected to the technological annealing at a temperature of 850 °С for 2 h, and then it was subjected to thermal treatments followed by the cooling with different rates. The effect of both the duration of a thermal annealing and the cooling rate from the annealing temperature to room one on the changes in the structure and electrophysical characteristics of n-Si 〈P〉 crystals doped through the melt and by the nuclear transmutation method is revealed. The appearance of dislocations in transmutationdoped Si crystals after the high-temperature annealing for 2 h and a subsequent rapid cooling is found. It is established that the high-temperature annealing for 72 h of Si samples, regardless of the method of phosphorus doping, contributes to the generation of deep donor centers, both during the slow and fast coolings, and significantly reduces the charge carrier concentration.