Interface Engineering of Rare-Earth Oxide-GaN Heterojunction for Improving Vacuum-Ultraviolet Photodetection

Lutetium oxide (Lu2O3), an ultrawide bandgap (UWB) (5.5–6.2 eV) rare-Earth oxide, has been proposed as a potential material for constructing vacuum-ultraviolet (VUV) photodetectors. In this work, an ultrathin (4 nm) aluminum oxide (Al2O3) layer is deposited at the interface of Lu2O3/GaN heterojunction to fabricate a Lu2O3 VUV photovoltaic detector with high performance. At 0 V bias and under VUV illumination, the Lu2O3/Al2O3/GaN photodetector presents a photoresponsivity of 17.2 mA/W (at 192 nm), a decay time of 54.9 ms, and a detectivity of $1.2\times 10^{{12}}$ Jones. The excellent performance of the device comes from the ultrathin Al2O3 layer deposited at the heterojunction interface, which not only acts as a buffer layer but also as a hole-blocking layer, improving the quality of the photosensitive layer and the separation efficiency of photo-generated carriers. Furthermore, with an increase in the thickness of the Al2O3 layer (>4 nm), a deterioration of optoelectronic properties of the Lu2O3/Al2O3/GaN device can be observed, which is attributed to an increase in the transport distance of the photo-generated carrier and a reduction in the probability of electron tunneling. This work can provide a reference for the preparation of high-performance Lu2O3-based VUV photovoltaic detectors in the future.