Probing the charge and heat transfer channels in optically excited graphene -- transition metal dichalcogenide hybrids using Johnson noise thermometry

摘要

Graphene (Gr)-transition metal dichalcogenide (TMDC) hybrids are promising platforms for achieving sensitive and ultra-fast photodetection. The process of photo-detection in such van der Waals hybrids is usually dictated by the formation of excitons followed by the transfer of charge and energy from the TMDC layer to graphene, but they have not been explored simultaneously in the same device before. In this work, we have investigated optically excited Gr-WS_2 (tungsten disulfide) heterostructures using both standard electrical transport and Johnson noise thermometry. At large negative gate voltages, the experimentally observed photoresponse cannot be explained from conventional photogating but was found to host an increase in electron temperature as large as ～4 K. Time dependence of the transport and the noise reveals that the change in temperature and photoresistance can originate from distinct microscopic processes. The findings can be exploited for the development of Gr-TMDC based ultra-fast bolometers.