Asymmetric Contacts on Narrow‐Bandgap Black Phosphorus for Self‐Driven Broadband Photodetectors

Abstract Self‐driven broadband photodetectors based on two‐dimensional (2D) materials have attracted considerable interest for their outstanding optoelectronic properties. Asymmetric contact induced potential barrier on 2D narrow‐bandgap materials is a feasible scheme for self‐driven broadband photodetectors, but has not been constructed untill now due to the band structure mismatch of the channel and metal electrodes. Herein, a self‐driven broadband photodetector is reported covering from visible to infrared spectrum by well designing the band structure of the Cr/BP/WTe₂ heterostructure with asymmetric contact architecture, constructing a huge potential barrier at the two ends of the black phosphorus (BP) channel due to the perfect ohmic and Schottky contacts at the WTe₂‐BP and Cr‐BP interfaces, respectively. The as‐fabricated device exhibits responsivity of ∼283 and ∼193 mA/W under 532 and 1550 nm illumination, respectively, under zero bias with corresponding detectivity of ∼2.3×10¹¹ and ∼1.2×10¹¹ Jones. The results demonstrate that the well‐designed band structure can be adopted to construct ideal Schottky and ohmic contact on 2D narrow‐bandgap materials to realize a self‐driven broadband photodetector. These findings highlight a simple and novel strategy for constructing predesigned band structure for further electronic and optoelectronic applications.