The photoluminescent spectrum of neutron irradiated GaAs

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^-1, donor exciton transitions at 12225 and 12218 cm^-1, donor hole transition at 12212 cm^-1, acceptor exciton transitions at 12197, 12193, and 12183 cm^-1, and a very broad transition associated with deep levels at 7300 cm^-1 (0.9 eV) was observed. In another unirradiated sample, these transitions, as well as the carbon (12054 cm ^-1) and silicon (11980 cm^-1) impurities, were observed. The photoluminescence spectrum of (1-MeV) neutron-irradiated GaAs decreased by factors of two and ten at fluences of 10¹³ and 10¹⁴ n/cm², respectively. An absorption tail was measured at 7.4×10¹⁴ n/cm², and it is concluded that disorder is present at this fluence. The disorder introduces radiationless transitions which reduce the intensity of the PL spectrum