ZnO‐based photodetector with internal photocurrent gain

The photoresponsive structures prepared by magnetron sputtering of ZnO on p‐Si substrates followed by vacuum evaporation of semitransparent Ni film on ZnO surface are investigated. The obtained Ni/n‐ZnO/p‐Si structures show high sensitivity that sharply increases with increase in applied voltage. Under a bias voltage of 5 V, the responsivities at λ  = 390 nm and λ  = 850 nm were equal to 210 and 110 A/W, which correspond to quantum efficiencies of 655 and 165, respectively. It is assumed that the observed strong response is attributed to internal gain in the Ni/n‐ZnO/p‐Si phototransistor structure containing Ni/n‐ZnO Schottky contact as the emitter junction and n‐ZnO/p‐Si heterostructure as the collector junction. The response time of the device is ∼10 –7  s. Alternative mechanisms of photocurrent multiplication in such structures are also discussed.