Abstract
Using 514.5-nm excitation, photoluminescent (PL) spectroscopy at 5 K was used to characterize GaAs films. In one unirradiated sample, a free exciton transition at 12250 cm/sup -1/, donor exciton transitions at 12225 and 12218 cm/sup -1/, donor hole transition at 12212 cm/sup -1/, acceptor exciton transitions at 12197, 12193, and 12183 cm/sup -1/, and a very broad transition associated with deep levels at 7300 cm/sup -1/ (0.9 eV) was observed. In another unirradiated sample, these transitions, as well as the carbon (12054 cm/sup -1/) and silicon (11980 cm/sup -1/) impurities, were observed. The photoluminescence spectrum of (1-MeV) neutron-irradiated GaAs decreased by factors of two and ten at fluences of 10/sup 13/ and 10/sup 14/ n/cm/sup 2/, respectively. An absorption tail was measured at 7.4*10/sup 14/ n/cm/sup 2/, and it is concluded that disorder is present at this fluence. The disorder introduces radiationless transitions which reduce the intensity of the PL spectrum. >
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