Charge transfer doping enabled high-performance deep-ultraviolet photodetectors based on CuI/β-Ga ₂ O ₃ heterostructures for deep-ultraviolet optical communication

In this work, we report on self-driven deep-ultraviolet (DUV) photodetectors composed of CuI/β-Ga₂O₃ heterostructures, whose photodetection performance can be significantly boosted by charge transfer doping of CuI. The incorporation of MoO₃ with a high work function induces spontaneous electron withdrawal from CuI towards MoO₃, thereby increasing the work function of CuI and ultimately amplifying the junction barrier of the CuI/β-Ga₂O₃ heterostructure. As a consequence, the photoresponse parameters in terms of photovoltage responsivity, photocurrent responsivity, and specific detectivity are largely improved from 1.47 × 10⁸ V W^-1, 8.41 mA W^-1, and 8.53 × 10¹¹ Jones to as high as 9.87 × 10⁸ V W^-1, 20.59 mA W^-1, and 3.01 × 10¹² Jones, respectively. The optimal device exhibits a large current on/off ratio of exceeding 2.0 × 10⁴, an ultralow dark current of less than 1 × 10^-13 A, a high DUV/visible rejection ratio of 1.45 × 10⁴, and a relatively rapid response speed of 33.5/49.7 ms, as well. A device assembled on a plastic substrate exhibits robust mechanical flexibility. What is more, the good DUV photodetection performance enables the device to be utilized in a DUV optical communication system, functioning as a light receiver to deliver a text signal. It is expected that this DUV photodetector will find utilization in future DUV photoelectric systems.