Photoelectric properties of isotype and anisotype Si/GaN : O heterojunctions

Results of a comprehensive study of electrical and photoelectric properties of isotype (p-Si/p-GaN:O) and anisotype n-Si/p-GaN:O) heterojunctions are reported. The structures were fabricated by chemical vapor deposition of th in films of GaN:O solid solutions on silicon substrates by pyrolytic decomp osition of gallium monoammine chloride in the presence of water vapor. Tota l and spectral photosensitivity and photoresponse kinetics in the current m ode under forward and reverse biases, current-voltage characteristics, and saturation open-circuit photovoltage were studied. It was found that in bot h kinds of heterojunctions the charge distribution near the contacts is mai nly governed by carrier capture into interface states (with density estimat ed to be similar to 10(14)-10(15) cm(-2)) with the formation of depletion l ayers on both sides of the interface. Photosensitivity mechanisms are analy zed for anisotype and isotype heterojunctions. It is shown that the differe ntial nature of the photoresponse kinetics is related to the recharging of interface states, and the strong rise in the photoresponse signal of a bias ed anisotype heterojunction is attributed to the phototransistor effect. Th e proposed energy band models of the heterojunctions consistently describe the observed effects. (C) 2000 MAIK "Nauka/Interperiodica".