Schottky barrier characteristics and internal gain mechanism of TiO2 UV detectors.

High-responsivity metal-semiconductor-metal TiO(2) UV photodetectors with Ni and Au electrodes were fabricated identically. Their Schottky barrier heights and photocurrent gain mechanism were studied. The effective barrier height Φ and ideality factor n were evaluated according to the thermionic emission theory. The result that Φ(Ni) was lower than Φ(Au) may be attributed to the electron transfer from Ni to the TiO(2) substrate, which would lead to a dipole layer and, accordingly, decrease the barrier height. In addition, the I-V characteristics of the Ni/TiO(2)/Ni and Au/TiO(2)/Au photodetectors were observed. A significant internal gain was obtained, and the mechanism of the internal gain was studied by the phototransistor model in detail.