Record high photoresponse observed in CdS-black phosphorous van der Waals heterojunction photodiode

Abstract

Two-dimensional (2D) materials have recently received great attention for their atomic thin thickness and thus derived outstanding electrical, optical and optoelectronic properties. Moreover, the dangling-bond-free surfaces of 2D materials enable the direct integration of different materials with various properties through van der Waals (vdW) forces into vdW heterostructures, providing new opportunities for constructing new type devices with superior performances. In this study, we report the vertical assembly of n-type CdS and p-type BP into p-n junctions. The electrically tunable heterojunction device shows a high current rectifying ratio up to 8×103 at a low bias voltage range of ±1 V and an ideality factor of 1.5. More interestingly, the CdS/BP vdW heterojunction exhibits an ultra-high photoresponsivity up to 9.2×105 A W−1 and an ultra-high specific detectivity of 3.2×1013 Jones with a low bias voltage of 1.0 V, which is among the highest in the reported results of 2D heterostructures. While operated at a self-powered mode, the device also exhibits excellent photodetection performances with a high photoresponsivity of 0.27 A W−1 and a high external quantum efficiency of 76%. Time-resolved photoresponse characterizations indicate that the device possesses a fast response time of about 10 ms. The developed CdS/BP vdW heterojunctions will find potential applications in the next-generation nanoscale electronics and optoelectronics applications.