Influence of buffer layer on the performance of ZnO film based photoconductive detectors

Photoconductive detectors based on zinc oxide (ZnO) thin films have garnered significant attention in optoelectronic applications owing to their simplified device architecture, well-established fabrication processes, and scalability for industrial production. The buffer layer, as a factor affecting device performance, also needs to be investigated. This study systematically investigates the critical role of the buffer layer in modulating the performance metrics of ZnO film photodetectors. Through the comparative analysis of devices fabricated on glass substrates with distinct buffer configurations (CuO monolayer vs SiO2/CuO bilayer), we reveal the substantial modulation of photoresponse characteristics. The ZnO/CuO heterostructure exhibits a suppressed dark current (reduced by 20%) and photocurrent (reduced by 67%) relative to the reference device (ZnO film photodetector or PD), accompanied by prolonged response times (τrise = 3.3 s, τdecay = 15.4 s). Introducing an SiO2 insulated layer (200 nm) can lead to charge redistribution in the CuO layer and ZnO layer, achieving an enhanced on/off ratio (Iphoto/Idark = 1.1 × 102) with accelerated decay kinetics (τdecay = 10.5 s). These performance modifications originate from the synergistic effects of type-II band alignment at the ZnO/CuO interface and interfacial capacitance modulation. This work establishes a quantitative framework for failure mode analysis in oxide-based optoelectronics, providing a critical insight for device optimization strategies.