Photoelectrical response of Graphene Field Effect Transistors (GFETs)

In this work, we present Graphene Field Effect Transistors (GFETs) with photoelectrical response due to the photovoltaiceffect. Our final aim is to use a GFET to down convert an optical to a radiofrequency signal. The technological steps used for the devices fabrication as well as the photoelectrical characterization will be reported. Photoelectrical measurements were performed by using a 405 nm laser diode source, whose output beam was pulse amplitude-modulated at 1.33 kHz by means of a laser driver. The electrical signal out of the GFETs (in a common source amplifier configuration) was measured using a lock-in amplifier synchronized to the same reference frequency of the laser driver. This gave us the possibility to evaluate the optical response as a function of both the incident laser power and the DC biasing of the device. In particular, in order to explore the GFETs photovoltaic characteristics, we decided to perform low noise measurements at zero bias (VDS=0) and with VGS ranging between -2V and +2V. We found that the optical response of our device depends on the static polarization of the gate-source voltage and it shows a linear trend as a function of the incident laser power.