Anneal dependent variations of recombination and generation lifetime in neutron irradiated MCZ Si

Transforms and competition of recombination and generation centres are revealed in neutron irradiated MCZ Si. In the as-irradiated material the recombination centres prevail and cause mono-exponential decay with nearly linear decrease of carrier lifetime from several microseconds to sub-nanoseconds with enhancement of fluence from 1012 to 3x1016 n/cm2. Isochronal 24 h anneals in the range of temperatures from 80 to 420 deg. C induce variation of the density of different deep levels, which depends on irradiation fluence. Appearance of two-exponential decays and the changes of the effective lifetimes of the initial and asymptotic decays imply the complicated transformations of radiation defects under heat treatments. Qualitatively these transforms can be understood when existence and dominance of cluster defects is assumed.