Effects of 3 MeV proton irradiation on the excitonic lifetime in gallium arsenide

Gallium arsenide films grown by the metalorganic chemical vapour deposition method and doped n-type with silicon to concentrations of 2/spl times/10/sup 15/ and 2/spl times/10/sup 16/ cm/sup -3/ were exposed at room temperature to 3 MeV proton irradiation in the fluence range 10/sup 9/ to 10/sup 14/ cm/sup -2/. The photoluminescence spectra of the irradiated samples were obtained in the continuous mode. The free exciton transition at 1.515 eV was observed. The lifetime associated with this transition was measured both at 4 K and at 60 K, using a time-correlated single photon counting technique. The damage constant associated with the radiative recombination lifetime of the free exciton in GaAs is (7.7/spl plusmn/2.2)/spl times/10/sup -3/ cm/sup 2/ s/sup -1/ and with the nonradiative lifetime (6.5/spl plusmn/2.7)/spl times/10/sup -3/ cm/sup 2/ s/sup -1/.