Investigation on the Effects of Gate-Source Overlap/Underlap and Source Doping Gradient of n-Type Si Cylindrical Gate-All-Around Tunnel Field-Effect Transistors

Tunnel field-effect transistor (TFET) has been considered as one of the promising next-generation transistors due to its potentially limit-breaking low subthreshold swing. In this work, we comprehensively examined the effects of the gate-source (G-S) overlap/underlap and the source doping gradient (SDG) of the n-type Si cylindrical gate-all-around (GAA) TFET by the TCAD tools. The simulation results indicate that the G-S overlapping structure has superior device performance than the G-S underlapping structure. However, increasing the G-S overlapping length does not further improve the device performance. Besides, SDG hardly affects the device characteristics of the G-S overlapping TFETs and for the G-S underlapping TFETs, larger SDG can mend the device performance.