Ion irradiation induced defects in epitaxial GaAs layers

We have investigated the effects of heavy ion irradiation on n-type GaAs layers, grown by molecular beam epitaxy (MBE). The ion beam we have used concerns protons (1 MeV), alpha particles (5.4 MeV), oxygen (25 MeV), iodine (200 MeV) and gold (253 MeV). The total fluence for each beam was 8 x 10(13), 1.9 x 10(12), 10(10), 10(9), 1.2 x 10(6) cm(-2), respectively. The induced damage is via displacement. Up to six different groups of deep levels were induced but in the case of heavy ions, as for instance iodine and gold they were not well resolved. Identification of the induced deep levels was attempted by comparing their Arrhenius signature with those of known levels, cited in the literature. Annealing experiments were also carried out and we have found that some of the defects recover at about 470 degrees K (200 degrees C). The annealing kinetics is first order, which means that the recovery mechanism is by close pair recombination rather than diffusion. (C) 1998 Elsevier Science Ltd. All rights reserved.