Solar-Blind UV Photodetector Based on Atomic Layer-Deposited Cu₂O and Nanomembrane β-Ga₂O₃ pn Oxide Heterojunction

Herein, we present a solar-blind ultraviolet photodetector realized using atomic layer-deposited p-type cuprous oxide (Cu₂O) underneath a mechanically exfoliated n-type β-gallium oxide (β-Ga₂O₃) nanomembrane. The atomic layer deposition process of the Cu₂O film applies bis(N,N'-di-secbutylacetamidinato)dicopper(I) [Cu(⁵Bu-Me-amd)]₂ as a novel Cu precursor and water vapor as an oxidant. The exfoliated β-Ga₂O₃ nanomembrane was transferred to the top of the Cu₂O layer surface to realize a unique oxide pn heterojunction, which is not easy to realize by conventional oxide epitaxy techniques. The current-voltage (I-V) characteristics of the fabricated pn heterojunction diode show the typical rectifying behavior. The fabricated Cu₂O/β-Ga₂O₃ photodetector achieves sensitive detection of current at the picoampere scale in the reverse mode. This work provides a new approach to integrate all oxide heterojunctions using membrane transfer and bonding techniques, which goes beyond the limitation of conventional heteroepitaxy.