Unipolar Barrier Photodetectors Based on Van Der Waals Heterostructure with Ultra‐High Light On/Off Ratio and Fast Speed

Abstract Unipolar barrier architecture is designed to enhance the photodetector's sensitivity by inducing highly asymmetrical barriers, a higher barrier for blocking majority carriers to depressing dark current, and a low minority carrier barrier without impeding the photocurrent flow through the channel. Depressed dark current without block photocurrent is highly desired for uncooled Long‐wave infrared (LWIR) photodetection, which can enhance the sensitivity of the photodetector. Here, an excellent unipolar barrier photodetector based on multi‐layer (ML) graphene (G) is developed, WSe 2 , and PtSe 2 (G‐WSe 2 ‐PtSe 2 ) van der Waals (vdW) heterostructure, in which extremely low dark current of 1.61×10 −13 A, a record high light on/off ≈10 9 are demonstrated at 0 V. Notably, the device exhibits ultrafast response speed with rise time τ r = 699 ns and decay time τ d = 452 ns and high‐power conversion efficiency ( η ) of 4.87%. The heterostructure demonstrates a broadband photoresponse from 365 nm to LWIR 10.6 µm at room temperature. Notably, the G‐WSe 2 ‐PtSe 2 nBn device demonstrates high photoresponsivity ( R ) of 1.8 AW −1 with 10.6 µm laser at 1 V bias in ambient air. This unipolar barrier device architecture offers an alternative way for highly sensitive free space communication.