Transient response of low-temperature ALD-grown ZnO thin film-based p–i–n UV photodetector

Abstract

This work presents an ultraviolet (UV) photodetector based on zinc oxide (ZnO) thin films grown via atomic layer deposition (ALD) technique on silica (SiO₂–Si) substrates in a p–i–n configuration (p-Si/i-SiO₂/n-ZnO). The ZnO films, deposited at 120 °C, exhibit a nanocrystalline structure with a dominant (110) orientation and a direct bandgap of 3.07 eV, indicating their suitability for UVA sensing (315–400 nm). The device exhibits a low dark current, high UV sensitivity, and stable, repeatable ON/OFF switching under 365 nm illumination at 0.05 mW cm⁻² at room temperature. I–V characteristics indicate efficient photocarrier transport. The dynamic response of the photodetector was measured at various bias voltages ranging from 0 V to 18 V. The sensitivity of the device was highest (1.17) at 0 V. At the same time, other parameters like responsivity (3.82 × 10² A W⁻¹), detectivity (7.14 × 10¹² Jones), external quantum efficiency (EQE) (1.3 × 10³ %) were found to be maximum at 18 V meanwhile the rise (0.3 s) and decay time (0.2 s) was minimum at this bias. These results demonstrate the potential of ALD–ZnO thin films for high-performance, room-temperature UV photodetectors, making them suitable for future integrated and wearable optoelectronics.