Effects of Gamma Radiation on Gallium Arsenide Crystals and Gunn Diodes.

Electrical and photoluminescence measurements have been made on liquid epitaxial gallium arsenide irradiated at room temperature by 1.25 MeV Co-60 gamma rays. Both n- and p- type crystals with initial free carrier densities of 4 X 10 to the 15th power/cubic cm were subjected to a series of irradiations after each of which Hall measurements were made as a function of temperature from 77 to 300K. Photoluminescence measurements were made on irradiated and unirradiated crystals. Hall measurements on n-type crystals indicate the presence of imperfections having energy 0.13, 0.16 and 0.30 eV below the conductions band minimum in irradiated GaAs. The 0.13 and 0.16 eV levels are introduced during irradiation at roughly 1/2 the rate at which the compensating deep acceptors are introduced. New photoluminescence peaks detected in both n- and p-type crystals indicate energy levels near the center of the band gap which may also be produced by irradiation. Hall measurements on p-type crystals indicate the presence of imperfections having energy levels 0.059 and 0.10 eV above the valence band maximum in irradiated GaAs. The Hall measurements made on these crystals before irradiation indicate the presence of impurities having energy levels in the lower 0.20 eV of the band gap. (Author)