The deep levels and carrier compensation which were created in undoped metal-organic chemical vapor deposited material, by low-fluence proton irradiation (108 to 1010/cm2), were investigated by using deep-level transient spectroscopic and capacitance-voltage profiling techniques. At least 5 main electron traps were observed, after room-temperature irradiation, in addition to the EL2 which were present in the as-grown material. The irradiation generated additional EL2 defects, which annihilated at much lower temperatures than was expected for isolated EL2. Upon further increasing the fluence, the magnitude of this additional increment began to decrease. The apparent decrease in the EL2 peak was accompanied by an increase in a broad peak in the deep-level transient spectrum. This peak had a highly non-exponential capacitance transient, and it was suggested that it resulted from the interaction of the additional EL2 defects with EL6. One of the observed traps, with an energy level at Ec-0.40eV, had not previously been reported in proton-irradiated GaAs. The signature of this trap resembled that of EL5. It was quite stable at moderate annealing temperatures, and annihilated completely only at a temperature of about 600C. This level exhibited a saturation effect with increasing irradiation dose, and was believed to be related to complex defect-impurity formation. The temperature dependence of the carrier profiles revealed complex carrier compensation behaviors; including acceptor- and donor-like properties of the various traps.

H.H.Tan, J.S.Williams, C.Jagadish: Journal of Applied Physics, 1995, 78[3], 1481-7