Two-dimensional GaN/Si heterojunctions towards high-performance UV-B photodetectors†

Two-dimensional (2D) GaN with a tunable bandgap, high electron mobility, and high chemical and thermal stabilities is an ideal choice for high-performance UV-B photodetectors (PDs). However, the realization of 2D GaN based UV-B PDs faces the challenge of simultaneously achieving large-scale preparation and band engineering. In this work, novel UV-B PDs based on wafer-scale 2D GaN/Si heterojunctions have been proposed. Wafer-scale synthesis and band engineering of 2D GaN are realized via a two-step method consisting of magnetron sputtering and high temperature ammonolysis. With well-controlled thickness, the bandgap of 2D GaN is regulated to 3.6 and 4.1 eV. Impressively, novel UV-B PDs based on 2D GaN/Si heterojunctions exhibit a photoresponsivity of 2.2 A W⁻¹ at 308 nm at 1 V, and a fast response speed with a rise/decay time of 1.3/1.1 ms, simultaneously. This work provides a resolution for high-performance UV-B PDs through the controllable growth of 2D GaN, and the proposed synthesis strategy significantly broadens the application prospects of 2D GaN in the field of UV optoelectronics.