STUDIES OF ELECTRON BOMBARDMENT DAMAGE IN GAAS BY THERMALLY STIMULATED CONDUCTIVITY MEASUREMENTS

Semi-insulating, melt-grown n-type GaAs was irradiated with 1 MeV electrons of densities of 1016-1017 electrons/cm2, thereby introducing 1017-1018 cm-3 defects. The irradiation decreased the dark conductivity and the photosensitivity by about an order of magnitude, indicating that additional acceptor-like recombination centers were generated. However, no additional trapping centers were detected by thermally stimulated conductivity measurements for energies in the range 0.15-0.7 eV from either band edge. This suggests that the centers introduced had larger ionization energies than any other main trap present, namely, >0.5 eV. This is consistent with the effects of electron bombardment on luminescence in GaAs. Moreover, the calculated concentrations of the traps previously present were decreased, especially after the introduction of as many as 1018 cm-3 defects. This apparent decrease at these very high defect densities can be explained by assuming that the carriers tend to recombine via an intercenter process, rather than entering the bands. Annealing was found to remove most, but not all, of the effects of electron bombardment. © 1969 The American Institute of Physics.