High-Detectivity ZnO-Based Ultraviolet Photodetector With Asymmetric Al₂O₃ Interlayer

It is demonstrated that interface engineering in ZnO-based ultraviolet (UV) photodetectors (PDs) using an asymmetric Al2O3interlayer can significantly enhance PD performance. The Al2O3layer deposited by atomic layer deposition (ALD) only at the cathode/ZnO interface extends the electron tunneling distance and passivates oxygen vacancy (${V}_{\text{O}}$)-related traps on the ZnO surface. This effectively suppresses the dark current (${I}_{\text {dark}}$), while the photocurrent (${I}_{\text {photo}}$) remains high due to the absence of the Al2O3layer in the anode region. An asymmetric ZnO metal–insulator–semiconductor–metal (MISM) PD with an optimized Al2O3layer thickness of 4 nm exhibits a high photo-to-dark current ratio (PDCR) of$2.31\times 10^{{5}}$, a high specific detectivity of$7.80\times 10^{{14}}$Jones, a rapid decay time of 0.12 s, and excellent performance in harsh environments.