Physical Insights Into the Effect of Substrate on Graphene RF Transistor Performance and Demonstration of Novel Inverted T-Gate Architecture

Graphene has emerged as a promising material for future radio frequency (RF) device applications due to its exceptional carrier mobility, high saturation velocity, and atomically thin structure. These properties enable ultra-fast charge transport and excellent electrostatic control, making graphene an attractive candidate for high-frequency and highspeed applications. However, the technology progress is limited by RF performance-killing agents like contact resistance, substrate parasitics, and material-to-device process flow limitations. This work provides a systematic insight into the performance limiters of graphene FETs on SiO2 and SiC substrates, grown via chemical vapor deposition (CVD) and epitaxial methods. Notably, the highest extracted cut-off frequency is 55/20 GHz on the SiC/SiO2 substrate, which reflects the superiority of SiC over SiO2 as a substrate for graphene RF devices. Additionally, the work discusses DC/RF performance degradation issues due to top gate dielectric deposition and demonstrate a unique “ Inverted TGate” device architecture to mitigate the same.