▎ 摘　　要

Simultaneous optimization of detectivity and dark current is successfully achieved by modulating the Schottky barrier height of a graphene/p-type silicon photodetector from 0.42 to 0.68 eV by doping graphene with polyethyleneimine (PEI). At a barrier height modulation of 0.26 eV, the dark current is reduced by three orders of magnitude from 980 nA to 219 pA, and the detectivity is improved by 529% at 850 nm when compared to undoped graphene/p-type silicon photodetectors. Such a significant performance enhancement confirms that the chemical doping of graphene before device fabrication is a simple yet highly efficient approach to improve the detectivity of heterojunction photodetectors.