Ga-doped ZnO (GZO) based ultraviolet photodetectors (PDs) were fabricated by dual ion beam sputtering with a metal-semiconductor-metal structure. The room-temperature operable PD demonstrated responsivity of 58 mA W-1 at zero bias, which is 15 times larger than that reported on similar material grown by a different physical vapour deposition process, with internal and external quantum efficiency values of ∼22.5% and 37.4%. The unbiased photodetection is attributed to the tunnelling of electrons due to heavy doping of GZO and built-in electric field due to different barriers at the two metal semiconductor contacts. The asymmetry in the electrodes was investigated by temperature-dependent current-voltage measurements.
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© 2015 The Royal Society of Chemistry.