Graphene field effect transistors for applications in radiation detection

This thesis describes the development of a radiation detector which incorporates graphene into the device architecture through the use of FEM simulations and experiments with X-ray radiation. The device relies on sensing the changes in the local electric field arising from radiation interactions in a macroscopic absorber coupled to a graphene field effect transistor (GFET). Following an ionizing event in the electrically biased undoped semiconducting absorber, the generated charge carriers alter the local electric field which modulates the resistance of the GFET. FEM simulations were used to gain an understanding of the detector's potential performance for devices fabricated on an intrinsic silicon absorber to coincide with the experiments. In addition, experimental results of the device's response to X-ray irradiation at cryogenic temperatures, down to 4.3 K, are discussed. The X-ray source utilized during the experiments generated a continuous spectrum up to 40 keV, with a flux of 106 counts per second at 40 cm through a 1 mm diameter source collimator, when operated at 40 kV at 100 μA. A resistance change of more than 50% was observed in the GFETs between the high flux, 40 kV at 80 μA, and no flux conditions with a range of device response for intermediate flux settings. There was no radiation response from the devices which were not electrically gated. These initial results suggest that a GFET is sensitive to the amount of incident X-ray radiation.