Photoresponsivity of ZnO Schottky barrier diodes

We report on the photoresponsivity of ZnO Schottky barrier diodes grown on (0001) GaN Al2 O3 substrates by plasma-assisted molecular-beam epitaxy. First, ZnO Schottky barrier diodes show a reverse saturation current of ∼ 10-8 A in the dark, and they present a large current buildup of ∼ 103 A under ultraviolet light illumination, with maintaining stable diode characteristics. Second, ZnO Schottky barrier diodes have a large bandwidth of 195 nm, where the short-wavelength cutoff and the long-wavelength cutoff are 195 and 390 nm, respectively. Third, ZnO Schottky barrier diodes have a time constant of 0.36 ms. Consequently, it is suggested that the ZnO Schottky barrier diodes are very promising for ultraviolet photodetector applications.