Enhanced IR photodetection via photogating in graphene FET heterostructures

Recent advancements in photodetection using two-dimensional (2D) materials have demonstrated significant improvements in device performance. Amongthese, graphene field-effect transistors (GFETs) have emerged as highly promising photodetector platforms due to their low noise, broadband response, high responsivity, and ultrafast operation. GFET photodetectors exploit the photogating mechanism at a graphene/insulator/substrate interface, where photogenerated carriers in the substrate become selectively trapped at the interface under illumination The trapped charges in the substrate electrostatically induces opposite type charge carriers in the graphene channel through capacitive coupling, enabling multiple circulation cycles of induced carriers under bias and resulting in internal photoconductive gain. In this work, we demonstrate GFET photodetectors fabricated on slightly p doped-GaAs and Si wafers at room temperature, achieving responsivities on the order of 10⁶ A/W under above-bandgap excitation, while also enabling sub-bandgap detection via tail-state assisted transitions, indicating highly sensitive photodetection. This study provides a pathway toward engineering GFET photodetectors across UV–IR regimes by systematically tailoring the graphene-insulator-semiconductor interface.