ELECTRICAL CHARACTERIZATION OF NEUTRON-IRRADIATION INDUCED DEFECTS IN UNDOPED EPITAXIALLY GROWN N-GAAS

Undoped n-GaAs, grown by organometallic vapor phase epitaxy, was irradiated with neutrons from a clinical p(66)/Be(40) source for a range of fluences. Deep level transient spectroscopy (DLTS), employing Pd Schottky barrier diodes, indicated that four electron traps, En1, En2, En4, and En5, with energy levels at 0.04, 0.14, 0.36, and 0.66 eV, respectively, below the conduction band were created during neutron radiation. Their introduction rates varied from 1 cm-1 for the En1 to 11 cm-1 for the En5. It was found that the En1, En2, and En4 defects have DLTS ''signatures'' similar to the E1, E2, and E3 point defects introduced during high energy electron irradiation, indicating their point defect nature. The En5 has a very large capture cross section, its emission rate exhibits a strong electric field dependence, and there are indications that it has a band-like energy.distribution, that results in a broad DLTS peak. We speculate that this trap is related to the presence of extended defects in the neutron irradiated GaAs.