Defect Production in Electron-Irradiated, n-Type GaAs

Temperature-dependent Hall-effect measurements have been performed on pure, n-type, vapor-phase epitaxial GaAs, irradiated by 1-MeV electrons at room temperature. The energies and production rates of two dominant defect centers, C2 and C3, are as follows: E2 = EC - 0.148, E3 = EC2 = 2.0 and τ3 = 0.5 +/1 0.2 cm-1, in good agreement with deep level transient spectroscopy (DLTS) data. However, the most important result of this study is a very high production rate, τAS ≅ +/- 1 cm-1, for shallow acceptors (CAS) lying below E3. In fact, CAS is produced at a much higher rate than all of the DLTS traps observed in this energy range, providing that close to half of the primary defects in electron-irradiated GaAs are evidently not seen by DLTS. The high CAS production rate has important implications for microscopic models of C1 and C2, rendering unnecessary the assumption that one of these centers must be an acceptor in order to explain the Hall-effect results. Finally, we show that all available Hall-effect and DLTS data are consistent with CAS representing Ga-sublattice damage, which has not been observed before