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4H-SiC-based metal-insulator-semiconductor (MIS) ultraviolet (UV) photodetectors with thermally grown SiO2 and evaporated Al2O3/SiO2 (A/S) films are fabricated and demonstrated as normally-off and normally-on mode devices, respectively. Ultralow dark currents of 3.25 × 10-10 and 9.75 × 10-9 A/cm2 and high UV-to-visible rejection ratios of >; 2 × 103 have been achieved at 10 V. The peak responsivities of these devices were separately 30 mA/W at 260 nm and 50 mA/W at 270 nm at 10 V. These results demonstrate that S/4H-SiC and A/S/4H-SiC MIS photodetectors are promising candidates to be applied in optoelectronic integrated circuits.

We report on the fabrication and characterization of very low-dark-current TiO2 metal-semiconductor-metal ultraviolet (UV) photodetectors (PDs) with Pt Schottky contacts. The dark current of the PDs is merely 1.28 pA at a 5-V bias, which is much better than the previously reported data. The photoconductive gain is less than one for a bias of less than 10 V. The remarkable reduction of the dark current and the gain can be attributed to the combined effect of the large Schottky barrier height produced at the Pt/TiO2 contacts and the high quality of the sputtered TiO2 films, such as low intrinsic carrier concentration, large grain size, and absence of oxygen vacancies. The PDs also display a high quantum efficiency and a large UV-to-visible rejection ratio of about three orders of magnitude.

Metal-semiconductor-metal ultraviolet (UV) photodetectors (PDs) with Au electrodes, based on TiO2 thin films prepared by radio-frequency magnetron sputtering, are fabricated and characterized. The PDs exhibit a low dark current of 9.73 pA at 5-V bias and a high breakdown voltage of over 90 V, owing to the achievement of high-quality stoichiometric TiO2 films. Meanwhile, the high responsivity with a cutoff wavelength at around 380 nm and a large UV-to-visible rejection ratio (310 versus 400 nm) of more than three orders of magnitude are obtained, which suggest that the fabricated PDs are very promising in UV detection applications.