Effect of light-induced metastable defects on photocarrier lifetime

Creation and annealing of light-induced defects and their effect on photocarrier lifetime have been studied at 120 and 300 K using constant photocurrent method (CPM) and steady-state photoconductivity measurements. A hysteresis-like relation is observed between photoconductivity and light-induced defect density. This relation depends on both degradation temperature and light intensity used for the degradation. A broad, resembling a two-component distribution of defect annealing activation energies together with distribution of recombination coefficients account for the observed changes at 120 K. On the other hand, these distributions are narrower and sharply peaked at about 1 eV for the 300 K measurements. Results indicate that defects which are created at the earlier stages of the illumination have smaller annealing activation energies and higher recombination coefficient (capture cross-section) and these are better recombination centers than the defects with higher annealing activation energies.