The transfer of electronic charge across the interface of two van der Waals crystals can underpin the operation of a new class of functional devices. Among van der Waals semiconductors, an exciting and rapidly growing
development involves the “post-transition” metal chalcogenide InSe. Here, field effect phototransistors are reported where single layer graphene is capped with n-type InSe. These device structures combine the photosensitivity of InSe with the unique electrical properties of graphene. It is shown that the light-induced transfer of charge between InSe and graphene offers an effective method to increase or decrease the carrier density in graphene, causing a change in its resistance that is gate-controllable and only weakly dependent on temperature. The charge transfer at the InSe/graphene interface is probed by Hall effect and photoconductivity measurmentes and it is demonstrated that light can induce a sign reversal of the quantum
Hall voltage and photovoltaic effects in the graphene layer. These findings demonstrate the potential of light-induced charge transfer in gate-tunable InSe/graphene phototransistors for optoelectronics and quantum
metrology.
