UVA-VUV broadband photodetector based on a p-hBN/n-ZnO heterojunction

Abstract

Ultraviolet (UV) photodetectors (PDs) have been extensively investigated; however, achieving high-performance photodetection in the vacuum-ultraviolet (VUV) spectral region remains relatively challenging. In this work, a p-hBN/n-ZnO heterojunction UVA-VUV broadband UV PD was fabricated with wavelength-dependent trap-assisted gain modulation. The device exhibits a stable photoresponse over a wide spectral range, from 185 to 365 nm, with responsivity increasing monotonically with increasing photon energy. Under 365 nm illumination, the relatively low absorption coefficient of ZnO allows more photons to transmit into the hBN layer, where effective photo-dissociation of trapped carriers occurs. The device achieves a responsivity of 78.87 mA/W at 1 V bias, with an external quantum efficiency (EQE) of 26.8% and a specific detectivity (D*) of 3.66 × 109 Jones. The rise and decay times are both 2.3 ms. In contrast, under 185 nm illumination, the strong absorption of higher-energy photons by the ZnO film suppresses the photo-dissociation process in hBN, prolongs the average carrier lifetime, and thereby markedly enhances the photoconductive gain. As a result, the device achieves a significantly higher responsivity of 2.82 A/W at 185 nm, corresponding to an EQE of 1893.42%, a D* of 7.95 × 1011 Jones, and rise and decay times of 3.3 and 4.4 ms at 1 V bias. Moreover, the device can operate in a self-powered mode, with responsivity reaching 0.7 mA/W at 185 nm. This work presents a promising strategy for designing and applying high-performance UVA-VUV broadband PDs.