High Responsivity and Quantum Efficiency of Graphene/Silicon Photodiodes Achieved by Interdigitating Schottky and Gated Regions

Graphene/silicon (G/Si) heterostructures have been studied extensively in the past years for applications such as photodiodes, photodetectors, and solar cells, with a growing focus on efficiency and performance. Here, a specific contact pattern scheme with interdigitated Schottky and graphene/insulator/silicon (GIS) structures is explored to experimentally demonstrate highly sensitive G/Si photodiodes. With the proposed design, an external quantum efficiency (EQE) of >80% is achieved for wavelengths ranging from 380 to 930 nm. A maximum EQE of 98% is observed at 850 nm, where the responsivity peaks to 635 mA/W, surpassing that of conventional Si p-n photodiodes. This efficiency is attributed to the highly effective collection of charge carriers photogenerated in Si under the GIS parts of the diodes. The experimental data is supported by numerical simulations of the diodes. On the basis of these results, a definition for the "true" active area in G/Si photodiodes is proposed, which may serve toward standardization of G/Si-based optoelectronic devices.