Demonstration of a low power and high-speed graphene/silicon heterojunction near-infrared photodetector.

The structure and process of the graphene/Si heterojunction near-infrared photodetector were optimized to enhance the operating speed limit. The introduction of a well-designed structure improved the rise time from 12.6 μs to 115 ns, albeit at the expense of the responsivity, which decreased from 1.25 A W to 0.56 A W. Similarly, the falling time was improved from 38 μs to 288 ns with a sacrifice in responsivity from 1.25 A W to 0.29 A W, achieved through the introduction of Ge-induced defect-recombination centers within the well. Through a judicious well design and the introduction of recombination defect centers, the minimum pulse width could be improved from 50.6 μs to 435 ns, facilitating 2 MHz operation. This represents more than 100 times increase compared to previously reported graphene and graphene/Si hybrid photodetectors.