Neutron-induced trapping levels in aluminum gallium arsenide

Abstract

Deep level transient spectroscopy (DLTS) measurements have been performed on a variety of Al_xGa_1-xAs p-n junctions prior to and following a series of fast neutron irradiations at room temperature and subsequent isochronal anneals. In contrast with electron and proton irradiated GaAs, neutron irradiation produces a single, broad featureless DLTS band which is a majority carrier trap in both n and p type material. The characteristics of this neutron-induced trap are relatively independent of growth method, dopant type and concentration. In GaAs, the thermal emission energies of the trap are 0.58 to 0.68 eV depending on the particular junction. These energies increase with Al content to 0.94 eV at 20% Al. The trap introduction rate, which also increases with Al content, is 0.7 cm_-1 in GaAs. Isochronal annealing to temperatures as high as 400‡C results in a smaller FWHM of the DLTS band, a shift in the peak to higher temperatures, and a modest decrease in magnitude. Above 400‡C the magnitude decreases rapidly, suggesting a similarity with the antisite defect, As_Ga, which has been observed to anneal in this range.