Graphene-Quantum-Dots-Graphene Heterojunction Waveguide Photodetector with Low Dark Current and High Speed

We propose and demonstrate a graphene-quantum-dots-graphene heterojunction photodetector with a 100-nm-thick silicon core. The measured bandwidth is $\sim 2$ MHz at 1550 nm, and a high normalized photocurrent-to-dark-current ratio (NPDR) of $\sim 8\times 10^{5}\mathrm{W}^{-1}$ is obtained, benefiting from the low dark current of 1.1 pA at a bias of 1 V.