The effect of dislocations on the charge-carrier recombination processes in irradiated silicon

Nonequilibrium carrier recombination processes are studied in n-Si (rho = 100 to 250 Ωcm) containing higher density of dislocations introduced at plastic deformation (N/sub D/ = 1 x 103 to 1 x 107 cm -2) and after irradiation with 60Co γ-rays. The experimental results are obtained from the measurements of minority carrier lifetime (tau) by the method of conductivity modulation at a point contact. tau is shown to be very sensitive to the presence of dislocations in crystals. The dependences of tau on N/sub D/ observed in the experiment are described taking into account an increase in the effective cross section of hole capture at dislocation dangling bonds. When irradiating dislocated crystals a decrease in tau is observed and in some cases, with γ-flux increase, tau increases, too. The coefficient of radiation variation in tau in crystals with various dislocation densities is determined. The results obtained are explained taking into account the fact that the irradiation-induced radiation defects are not only additional recombination centers but that they change the dislocation recombination activity as well. (author)