2.4 Photodetector constructed with the monolayer graphene directly
synthesized on Si substrate
Finally, we demonstrate the high-quality performance properties of three
different devices directly fabricated from our monolayer graphene grown
on different substrates. Figure 5a displays the schematic
diagram of our as-fabricated monolayer graphene photodetectors on Si
substrate. To evaluate the performance of the individual photodetector
in broadband detection, both visible light (532 nm) and near-infrared
light (980 nm and 1550 nm) with a fixed power density of 30
mW/cm2 are used to stimulate the graphene/Si Schottky
junctions. Figure 5b shows the I-V features of our
photodetectors under dark and light illumination at various wavelengths,
indicating the typical current rectifications in our Schottky junctions
of graphene and Si substrate.[46-47] During
illumination in the Schottky junction area, a pronounced photocurrent
can be seen at the reverse bias. Moreover, the generated photocurrent
improves immediately as the wavelength is shortened from 1550 nm to 532
nm, demonstrating the device’s good capability for photoelectric
conversion.[48]