Design and Fabrication of Nano-graphene-Si Schottky Diode and Analyzing the Effect of Graphene in its Photoresponsivity

This paper reports on the photo detection properties of graphene nano layer, based on the fabrication of graphene-Si Schottky diode. To fabricate this Schottky junction, a graphene nano layer has been deposited on Si substrate. The Si substrate is oxidized to 270 nm thickness and is patterned with a specific mask after Cr/Au deposition (the thickness of Cr/Au are 50 nm and 150 nm, respectively). The current-voltage (C-V) curves of the diode are analyzed under 670, 700 and 1100 nm illuminations and also under yellow light radiations. To investigate the photo detection properties of graphene nano layer in Schottky diode structure, 700 and 1100 nm radiations are also illuminated to the backside of the diode and then the photo-generated current under both front and back side illuminations are compared. The experiment results demonstrate that the generated currents in the front side mode and under 700 and 1100 nm illuminations have been increased about 23 and 17 times in comparison with the backside mode. This rise in the current shows the graphene effect in photo detection mechanism and also shows the great amount of photo generated current in graphene in the front side illuminations. The C-V curves of the diode under 670 nm and yellow light illuminations demonstrate not only the photo-generated current but also the photo voltage which shows graphene potential for being used as the solar cell. The optical properties of graphene are also discussed in this paper and many theories which can describe the generation of photo current in graphene are presented.