Optical properties of electron-irradiated gallium phosphide

Results of optical absorption and photoconductivity measurements in the 0.1 to 2.4 eV range of GaP crystals irradiated with 7.5 and 50 MeV electrons are presented. The absorption of irradiated crystals near the edge can be represented by two exponential regions. In the free carrier absorption region one can observe as a result of irradiation a decrease of the power index p in the dependence α ˜ λp. Photoconductivity with long-time relaxation takes place in the spectral interval where the additional absorption is observed. The quenching of residual conductivity can be observed at hv = 1.0 eV. Variations in absorption and photoconductivity are attributed to the „tails” of density states near the zone edges arising at introduction of both point defects and disordered regions. At hv = 2.1 eV one can observe a resonance band which is attributed to intra-centre transitions on point defects. A recovery of the optical properties of GaP at annealing is studied. In heavily irradiated GaP crystals point defects can form gatherings which display themselves as disordered regions. [Russian Text Ignored.]