Researchers at Graphenea, University of Utah and Kairos Sensors have examined a perovskite-based graphene field effect transistor (P-GFET) device for X-ray detection.
The device architecture consisted of a commercially available GFET-S20 chip, produced by Graphenea, with a layer of methylammonium lead iodide (MAPbI3) perovskite spin coated onto the top of it. This device was exposed to the field of a molybdenum target X-ray tube with beam settings between 20 and 60 kVp (X-ray tube voltage) and 30–300 μA (X-ray tube current). Dose measurements were taken with an ion-chamber and thermo-luminescent dosimeters and used to determine the sensitivity of the device as a function of the X-ray tube voltage and current, as well as source-drain voltage.
The X-ray tube was also simulated in this work with GEANT4 and MCNP to determine the dose rate and power incident on the device during irradiation.
These simulations were then used to determine the responsivity as a function of the X-ray tube voltage and current, as well as the source-drain voltage.
Overall, a strong positive correlation between sensitivity and source-drain voltage was found. Conversely, the sensitivity was found to decrease – roughly exponentially – as a function of both the X-ray tube current and energy. Buildup of charges at the junction was found to limit charge transfer.
Similar trends were seen with responsivity. The team reported the models used for the study as well as the feasibility of the device as a low-energy (<70 keV) X-ray photon detector.