Temperature dependence of current response to sub-terahertz radiation of AlGaN/GaN and graphene transistors

The current response to sub-terahertz radiation was studied experimentally over a wide range of temperatures for AlGaN/GaN and graphene transistors. It was found that the responsivity is enhanced at low temperatures by about an order of magnitude for AlGaN/GaN and more than two orders of magnitude for graphene transistors. However, the responsivity increase saturates at temperatures below 70–100 K. These results were explained by the temperature dependence of the charge carriers' mobility, which plays a dominant role in the current responsivity. It is also shown that in a realistic device, the access resistance may decrease the current responsivity, and in the case of high access resistance, the subthreshold swing may also affect the current responsivity. These results showed that extremely high carriers' mobility in graphene makes it very promising for high-frequency detectors.