Deep-level transient spectroscopy was used to monitor the effect of 1 to 300Mrad of 60Co -irradiation upon deep electron traps in undoped vapor-phase epitaxial n-type material. A 1Mrad -irradiated Schottky device was identical to an as-grown device; with only 2 electron traps, EL2 (Ec-0.820eV) and EL3 (Ec-0.408eV) being detected. After a dose of 5Mrad, 2 additional electron traps, EL6 (Ec-0.336eV) and E2 (Ec-0.128eV), were observed. When the dose was increased to more than 10Mrad, a third electron trap, E1 (Ec-0.033eV) was observed and the single exponential EL2 capacitance transient became a double exponential; thus indicating 2 deep levels which lay at Ec-0.820eV (EL2/EL2-A) and Ec-0.843eV (EL2-B). The trap concentration of EL2-A remained unchanged up to a dose of 50Mrad, before beginning to increase slowly as the dose was increased to more than 100Mrad. On the other hand, the EL2-B trap concentration increased to 2.6 x 1014/cm3 at 300Mrad, from 8.0 x 1012/cm3 at 10Mrad. In the case of 1MeV electron irradiation to a fluence of only 1014/cm2, EL6, E2, E1 and double exponential EL2 were detected at the same time. There was no sign of EL2-B, EL3, EL6, E2 or E1, but an additional broad U band was observed after irradiation with 1MeV neutrons. The results of  and neutron irradiation suggested that the presence of the double exponential EL2 transients was not related to EL6, E2, E1 or to the U band, and was unlikely to be due to AsGa  VGa + Asi; but was probably caused by AsGa complex defects which involved an irradiation defect. The defect concentration of E1 increased from 5.4 x 1013/cm3 at 10Mrad to 9.3 x 1014/cm3 at 100Mrad, and E2 increased from 2.1 x 1013/cm3 at 5Mrad to 6.7 x 1014/cm3 at 100Mrad.

S.T.Lai, D.Alexiev, B.D.Nener: Journal of Applied Physics, 1995, 78[6], 3686-90