Photosensitivity of Monolayer Graphene-Base Field Effect Transistor

The optical properties and device physics of monolayer graphene under light is investigated in this study. In order to understand the change of the electronic behavior of graphene under light, it was necessary to study from the most fundamental layer with high quality. Thus, it became mandatory to develop a highly efficient, low-cost fabrication process for synthesis of high-quality monolayer graphene. The high-quality monolayer graphene was grown on a copper foil using a low-pressure chemical vapor deposition (LP-CVD) method at temperature of 1035°C for 10 minutes. Acetylene was used as the precursor gas for the synthesis of monolayer graphene. Thin Pt/Au films were, then, deposited on a silicon dioxide/silicon (SiO2/Si) substrate using electron beam (EB) lithography which served as source and drain electrodes of a transistor. The synthesized graphene was, then, transferred to a SiO2/Si substrate using PMMA (polymethyl methacrylate)-assisted method. The quality of the synthesized graphene was validated using Raman spectroscopy. No significant D peak was observed in the Raman spectra of the synthesized graphene. This result validated the high quality of the transferred graphene. Next, the photo-sensitivity of G-FET was investigated under light source of color temperature of 2856 K at room temperature. The electron transfer characteristic of the fabricated G-FET was measured under dark and light illumination conditions. Finally, the graphene-based field effect transistor G-FET demonstrated an external photo responsivity of about 200 μA/W with a maximum photocurrent attained to be 0.2 μA at an incident luminance power of 1 mW. The active detection region of this sample was 1000 × 60 μm2.