Self‐Driven Metal–Semiconductor–Metal WSe2 Photodetector with Asymmetric Contact Geometries.

Self‐driven photodetectors have wide applications in wireless sensor networks and wearable physiological monitoring systems. While 2D materials have different bandgaps for potential novel application fields, the self‐driven photodetectors are mainly built on PN junctions or heterostructures, whose fabrication involves doping or reliable multiple transfer steps. In this study, a novel metal–semiconductor–metal (MSM) WSe2 photodetector with asymmetric contact geometries is proposed. A high responsivity of 2.31 A W−1 is obtained under zero bias, and a large open‐circuit voltage of 0.42 V is achieved for an MSM photodetector with a large contact length difference. The MSM photodetector can overcome the disadvantage of high dark current in traditional MSM photodetectors. A small dark current of ≈1 fA along with a high detectivity of 9.16 × 1011 Jones is achieved. The working principles and finite element analysis are presented to explain the origin of the self‐driven property and its dependence on the degree of asymmetry. A self‐driven metal–semiconductor–metal (MSM) WSe2 photodetector with a planar structure by using asymmetric contact geometry is achieved. A high responsivity of 2.31 A W−1 is obtained under zero bias. The MSM photodetector avoids the disadvantage of the high dark current of traditional MSM photodetector, and a small dark current of ≈1 fA along with a detectivity of 9.16 × 1011 Jones is achieved. [ABSTRACT FROM AUTHOR]