Ultraviolet photoresistors based on ZnO thin films grown by P-MBE

Abstract Ultraviolet photoresistors based on ZnO thin films were fabricated on sapphire substrates with MgO buffer layer by plasma-assisted molecular beam epitaxy. An extremely large dark resistance up to 4 × 10 10  Ω was obtained and the dark/photo resistance ratio is up to 2.3 × 10 5 with a light intensity of 1.3 mW/cm 2 at 370 nm. The spectral response shows a large responsivity of more than 1 Ω −1  W −1 in the UV region. The photo-resistance depends linearly on the reciprocal of the optical power density for more than two orders of magnitude. The transient response property shows a decay time of 167 μs and the relaxation mechanisms are also discussed.