Influence of Structural Parameters on Electrical Characteristics of Schottky Tunneling Field-Effect Transistor and Its Scalability

The influence of structural parameters, including the Schottky barrier height for electron (φBn) and channel doping (Na), on the electrical characteristics of a scaled Schottky barrier tunneling FET (SBTFET) have been clarified by numerical device simulation. The thermionic emission current (ITH) as well as the tunneling current (ITN) have been considered as the main electron injections at the source edge. Simulation results have revealed that the main conduction is ITN in the region near and above the threshold voltage (Vth). As tunneling probability is determined by φBn and the width of the triangular potential barrier at the source edge, a lower φBn with higher Na results in a better subthreshold swing (SS) with high on-state drive current (ION) at a gate length (Lg) of 50 nm. With Lg scaling down to 10 nm, however, a lower φBn has shown an increased off-state leakage current (IOFF) due to the short-channel effect (SCE), while a larger φBn can suppress the IOFF at the cost of ION. Therefore, considering SS with ION and IOFF ratio, it can be concluded that an optimum φBn exists for short-channel devices. The SBTFET showed good subthreshold performance and higher ION/IOFF than the conventional silicon-on-insulator (SOI) MOSFET in 10 nm region with the Schottky barrier height optimization.