Highly sensitive fast-response UV photodetectors based on epitaxial TiO₂ films

Epitaxial TiO₂ thin films were fabricated on LaAlO₃ single crystal substrates by RF magnetron sputtering. Ag electrodes were then evaporated on the TiO₂ thin films to form metal-semiconductor-metal photoconductive detectors. The TiO₂ photodetector exhibited a maximum photoresponse of 3.63 A W^-1 at 310 nm with a sharp cutoff wavelength at 380 nm. The ultraviolet (UV)-visible response rejection ratio (R310 nm/R390 nm) was about three orders of magnitude. The photocurrent response of the detectors scaled linearly with the applied bias and the incident light intensity. The dark current was only 0.14 nA at 10 V bias. A transient photovoltage with a rise time of ∼8 ns and a full-width at half-maximum of ∼90 ns was observed when the photodetector was under the irradiation of a 308 nm XeCl laser with 25 ns duration. The excellent performances of high responsivity and ultrahigh response speed suggest that the presented TiO ₂ detectors have promising potential in UV photodetection.