Enhanced self-powered metal–semiconductor–metal WSe2 photodetectors with asymmetric Schottky contacts through tailored electrode thickness and positioning

Abstract

Self-powered metal–semiconductor–metal (M–S–M) photodetectors based on Schottky barrier difference have received extensive attention for their excellent photodetection performance. The Schottky barrier difference generally arises from the utilization of different metal electrodes or from variations in thickness across the ends of the two-dimensional materials, both of which represent extremely complex processes and precise control techniques. In this study, we fabricated self-powered photodetectors with a M–S–M structure using two-dimensional WSe2 nanoflakes and Au electrodes. By adjusting the thickness and positioning of the Au electrodes, a substantial difference between the two Schottky contacts of WSe2/Au and Au/WSe2 interfaces is formed due to the large Fermi-level difference between the two electrodes, which makes the M–S–M WSe2 photodetector to be used for self-powered photodetection. When irradiated with a 405 nm wavelength laser, the specific detectivity (D*) can achieve 6.35 × 1012 Jones, and the on/off ratio can reach 8 × 104. Under 808 and 1064 nm irradiation, D* reaches 5.9 × 1011 and 1.4 × 109 Jones, respectively. Furthermore, the M–S–M WSe2 photodetector, prepared on a transparent polyethylene terephthalate substrate, still achieves a D* of 5.1 × 1011 Jones under 808 nm irradiation. The results are expected to introduce an approach for self-powered photodetectors offering low cost, wide detection range, high detection performance, and broad application possibilities.