Substrate effects on the speed limiting factor of WSe photodetectors

• Published in: Physical chemistry chemical physics : PCCP 2022-10, Vol.24 (41), p.25383-2539
• Main Authors: Schedel, Christine, Strauß, Fabian, Kohlschreiber, Pia, Geladari, Olympia, Meixner, Alfred J, Scheele, Marcus
• Format: Article
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d2cp03364j

We investigate the time-resolved photoelectric response of WSe 2 crystals on glass and flexible polyimide substrates to determine the effect of a changed dielectric environment on the speed of the photodetectors. We show that varying the substrate material can alter the speed-limiting mechanism: while the detectors on polyimide are RC limited, those on glass are limited by slower excitonic diffusion processes. We attribute this to a shortening of the depletion layer at the metal electrode/WSe 2 interface caused by the higher dielectric screening of glass compared to polyimide. The photodetectors on glass show a tunable bandwidth, which can be increased to 2.6 MHz with increasing the electric field. The speed of a WSe 2 photodetector can be affected by the chosen substrate material, apparent as the detector on polyimide is independent of the applied electric field, while the one on glass can be accelerated up to a 3 dB bandwidth of 2.6 MHz.