Fig. 1. Structural diagram of Gr/Si hetero-junction photodetector

Fig. 2. Flow chart of Gr/ Si hetero-junction photodetector preparation

Fig. 3. The Raman spectrum of the Gr transfered to a patterned Si substrate surface

Fig. 4. The metallographic micrograph of the Gr/Si hetero-junction after selective etching annealing (graphene boundary along the red dotted circles)

Fig. 5. Comparison of the reverse voltage-current characteristic of large area Gr/Si hetero-junction at different drying temperatures ( before selective etching under dark condition)

Fig. 6. (a) Comparison of the reverse voltage-current characteristics of Gr/Si hetero-junction under different drying temperatures, etching and annealing processes; (b) comparison of the voltage-resistance characteristics of Gr/Si hetero-junction under different drying temperatures, etching and annealing processes( under dark condition )

Fig. 7. Metallographic micrograph of the surface of the hetero-junction after selective etching and annealing (left: after etching, right: after annealing. Red circles are relative obvious volatile impurities or possible residual PMMA glue)

Fig. 8. Reverse voltage-current characteristics and gain curves of Gr/ Si hetero-junction after selective etching and annealing

Fig. 9. (a) The SNR of the Gr/Si hetero-junction at different bias voltages. (b) The responsivity of the Gr/Si hetero-junction at different bias voltages