(color online) (a) A pseudo-colored scanning electron microscopy (SEM) image of the silicon/graphene high-gain photodetector (top left). Photocurrent map at incident power of 17 nW shows bright photocurrent signal in the silicon/graphene region (bottom left). Photoresponsivity of the device (inset) as a function of incident power (right).^[35] (b) Schematic diagram and optical image of the graphene hybrid photodetector on lightly p-doped silicon/SiO₂ substrate (left). Responsivity at V_D = 1 V and V_G = 0 V of the device as a function of the light power (right). The transient response of the device switched on or off by an acoustic optical modulator with frequency of 10 kHz. P = ∼ 0.5 μW, V_D = 1 V, and V_G = 0 V (inset).^[37]