Intrinsic defects in irradiated and annealed GaAs detected by FTIR

GaAs has been subjected to fast neutron or electron irradiations up to doses of 2×10¹⁹ n cm^–2 and 10¹⁹ e^– cm^–2 respectively and subsequently annealed to temperatures of 500°C. Infrared absorption spectra (20–700 cm^–1), measured at 20 K, show that the induced one-phonon absorption depends on the nature of the radiation. Resonant modes, at 45 cm^–1 and 119 cm^–1, and a broad line at 328 cm^–1 were found in neutron irradiated material, whereas in electron irradiated material only the 45 cm^–1 feature was detected. These spectroscopic features are interpreted as vibrational modes arising from intrinsic defect centres.