All oxide ultraviolet photodetectors based on a p-Cu₂O film/n-ZnO heterostructure nanowires

All-oxide ultraviolet (UV) photodetectors based on a p-Cu₂O thin film and n-ZnO nanowires were fabricated on Corning glass substrates. The p-Cu₂O film was fabricated by a sol-gel method and two-step thermal treatment on the ZnO nanowire arrays grown on ZnO doped with 5 at.% Al bottom electrode/glass for the formation of a p-n diode. The sol-gel coating of a Cu₂O layer produced the thin p-Cu₂O film with good uniformity on the ZnO nanowires and polycrystals with the (111) preferred orientation. It resulted in continuous interconnection of the ZnO nanowire arrays despite the solution process. The current-voltage (I-V) characteristics of the fabricated p-n heterostructure showed a typical rectifying behavior with a current rise at about 2 V and an I (illumination)/I (dark) ratio of about 3.89 × 10² at - 6 V. The p-Cu₂O/n-ZnO nanowire-based UV photodetectors show the responsivity of ∼ 50 A/W with a peak position at 360 nm in reverse bias, together with weak photoresponse in the visible region. Consequently, we found that the introduction of the p-type Cu₂O layer in the ZnO nanowire-based UV photodetectors provided effective all-oxide p-n junctions without degrading UV/visible selectivity.