Abstract

It is demonstrated that interface engineering in ZnO-based UV photodetectors (PDs) using an asymmetric Al₂O₃ interlayer can significantly enhance PD performance. The Al₂O₃ layer deposited by atomic layer deposition (ALD) only at the cathode/ZnO interface extends the electron tunneling distance and passivates oxygen vacancy (V_O)-related traps on the ZnO surface. This effectively suppresses the dark current (I_dark), while the photocurrent (I_photo) remains high due to the absence of the Al₂O₃ layer in the anode region. An asymmetric ZnO metal-insulator-semiconductor-metal (MISM) PD with an optimized Al₂O₃ layer thickness of 4 nm exhibits a high photo-to-dark current ratio (PDCR) of 2.31 x 10⁵, a high specific detectivity of 7.80 ´ 10¹⁴ Jones, a rapid decay time of 0.12 s, and excellent performance in harsh environments.