We investigate the time-resolved photoelectric response of WSe2 crystals on common glass and flexible polyimide substrates to determine the effect of the 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/WSe2 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.
@article{arxiv.2203.14053,
title = {Substrate Effects on the Speed Limiting Factor of WSe$_2$ Photodetectors},
author = {Christine Schedel and Fabian Strauß and Pia Kohlschreiber and Olympia Geladari and Alfred J. Meixner and Marcus Scheele},
journal= {arXiv preprint arXiv:2203.14053},
year = {2022}
}