Negative-U, off-center OAs in GaAs and its relation to the EL3 level

Using comparative local-vibrational-mode and deep-level transient spectroscopy, we have studied the off-center O sub As defect in high-resistivity, undoped GaAs and neutron-transmutation-doped, n-type samples from the same starting material. The results fully support that this defect has a negative-U character. They also reveal that its deeper, two-electron level corresponds to the chemically unidentified EL 3 defect level in GaAs at E sub c -0.58 eV.