Analysis of Current Variation with Work Function Variation in L-Shaped Tunnel-Field Effect Transistor

In this paper, an investigation is performed to analyze the L-shaped tunnel field-effect transistor (TFET) depending on a gate work function variation (WFV) with help of technology computer-aided design (TCAD) simulation. Depending on the gate voltage, the three variations occur in transfer curves. The first one is the on-state current (ION) variation, the second one is the hump current (IHUMP) variation, and the last one is ambipolar current (IAMB) variation. According to the simulation results, the ION variation is sensitive depending on the size of the tunneling region and could be reduced by increasing the tunneling region. However, the IHUMP and IAMB variations are relatively irrelevant to the size of the tunneling region. In order to analyze the cause of this difference, we investigated the band-to-band tunneling (BTBT) rate according to WFV cases. The results show that when ION is formed in L-shaped TFET, the BTBT rate relies on the WFV in the whole region of the gate because the tunnel barrier is formed in the entire area where the source and the gate meet. On the other hand, when the IHUMP and IAMB are formed in L-shaped TFET, the BTBT rate relies on the WFV in the edge of the gate.