Study of electron-irradiation-induced defects in GaP by in-situ optical spectroscopy in a transmission electron microscope

Electron-irradiation-induced defects in GaP were investigated by utilizing an in-situ transmission electron microscopy/photoluminescence (TEM/PL) observation apparatus, which enables us to obtain simultaneously TEM images and PL/cathodoluminescence (CL) spectra. The results of in-situ PL/CL spectroscopy under electron-irradiation show that the luminescence intensities, measured at the wavelengths of 565, 725 and 850 nm, remain the same during irradiation at 20 K. The intensities, however, decrease by annealing at 90 K after irradiation at 20 K. The data indicate that Frenkel defects, introduced in GaP by electron-irradiation at 20 K, are no longer frozen in the temperature range from 20 to 90 K and that thermal migration of interstitial atoms results in the formation of completes associated with a non-radiative recombination center. Under electron-irradiation, the luminescence intensities measured at 90 K decrease with the electron dose. Analyses of the decrease-rates suggest that the complexes should be associated with two or more interstitial atoms.