Comparison of neutron and electron irradiation on the EL2 defect in GaAs

Abstract

The deep level transient spectroscopy technique has been used to study the EL2 defect in n-type semiconducting GaAs subjected to 1 MeV fast neutrons at room temperature. After neutron irradiation, the EL3 defect which is usually detected between 180 and 210 K disapperared and the EL2 defect measured between 280 and 320 K was found to remain single exponential (Ec−0.820 eV) despite the creation of a broad U band measured between 100 and 270 K. From this result, together with our earlier reports on the double exponential capacitance transient of the EL2 defect after 1 MeV electron irradiation [Lai, Nener, Faraone, Nassibian, and Hotchkis, J. Appl. Phys. 73, 640 (1993)] and the behavior of the electron irradiated EL2 defect upon isochronal annealing [Lai and Nener, J. Appl. Phys. 75, 2354 (1994)], we observe a difference in the behavior of the EL2 defect after neutron and electron irradiation. The results of the present study indicate that the EL2-B level reported in an earlier work is not due to any interaction of the stable EL2 (or EL2-A) level with either the U-band or EL6 defect. The EL2 defect is likely to be a complex defect which can manifest itself as a number of different defect levels depending on the particular details of the irradiation used. The U band is likely to be a cluster defect caused by the large number of atoms displaced from lattice sites by the fast neutrons, and is not likely to be due to any interaction mechanism between the EL2 and EL6 defects.