Studies Of Irradiation Effects On Wide Bandgap Semiconductor

Gallium Nitride(GaN) and Silicon carbide(SiC) are promising wide bandgap materials for fabricating blue light emitting and extremely using devices. They are expected to perform in the radiation environment of military and astronautic domains. In modern device technology, electron irradiation and ion implantation are usually employed. In this article, irradiation effects of GaN and 6H-SiC have been studied.Photoluminesence (PL) measurements have been performed. n-type GaN samples irradiated with electrons having energies of 0.3MeV, 0.5MeV, lMeV and 1.7MeV were studied, in which the irradiation-induced defects by lower energies of 0.3MeV and 0.5MeV have more quenching effectivity on the blue luminescence (BL) band than on the free-exciton (FE), the donor-bound exciton(BDE) and the longitudinal phonon replicas (LO) lines. On the contrary, the defects induced by higher energies electrons with lMeV and 1.7MeV have more quenching effectivity on the FE , the BDE and the LO lines than on the (BL) band. Three new sharp lines at 478.6 nm (2.59eV), 483.3 nm (2.565eV) and 486.1nm (2.551eV) were observed in the as-irradiated n-type 6H-SiC samples after neutron, 0.5MeV and 1.7MeV electrons irradations, respectively. They remain a little after 350癈 annealing, and disappear after 500 癈 annealing, which are suggested to originate from monovacancy-like defects induced by irradiation. In the p-type neutron- and electron-irradiated 6H-SiC samples, a series of high intensity spectra due to the D-A pairs were observed by low-temperature photoluminesence. No any otherradiation related signals could be observed.0.3 and 0.5MeV electron-irradiated p-type 6H-SiC samples were studied by deep level transient spectroscopy (DLTS). In the 0.5MeV electron irradiated sample, both deep levels H1 and H2 have been observed as reported in 1.7MeV electron irradiated samples. In the 0.3MeV electron irradiated sample, however, only the deep level H1 existed. By considering the minimum energy required to displace the C atom or the Si atom in the SiC lattice, it was concluded that the generation of the H1 involves the displacement of the C atom. And the generation of the H2 involves the displacement of the Si atom. Due to the similar annealing behaviors of H1, H2 and Vc, Vsi in PAS studies, it may indicate that the H1 is attributed to Vc, and H2 is attributed to Vsi.In addition, the irradiation induced failure of GaN ultraviolet photodetector has been studied. It was concluded that the positive charge in SiO2 passivation layer on the surface and the interface states at interface, produced by ionization, were the primary reasons of the failure. The degradation of Schottky barrier is the other main reason.