▎ 摘　　要

Graphene has great application prospects in the field of optoelectronics. We investigate a field effect transistor with a graphene channel. Carrier density and chemical potential of the channel can be spatially modified by topping the channel with dielectric structures consisting of pure and lithium enriched SU-8 layers. As an example, we demonstrate that application of a single-gate voltage can induce a P-N junction to a channel with an appropriate dielectric architecture. Electronic and photoelectric properties of the junction are studied. The photocurrent mapping is investigated, which clearly shows the origin of the photocurrent from the P-N junction. The proposed technology makes fabrication of graphene-based photodetectors simple and flexible, and may also be interesting for the development of future optoelectronic components using other two-dimensional materials.