Figure 3: (a) Transfer characteristic curves of the Gr/n-Si heterojunction device (Gr as drain) with V_DS of ±1 V. (b) The current and bias voltage characteristics of the Gr/Si heterojunction at various fixed V_gate values, V_gate varies in the range of -5 V to 5 V, with a step size of 1 V for each curve. The blue arrow indicates the direction of increasing V_gate. (c and d) Schematic band diagrams of the heterojunction with the electric field effect generated by the gate on the top of graphene. (c)Negative gate voltage. (d) Positive gate voltage.