Study of Work-Function Variation for High- $\kappa $ /Metal-Gate Ge-Source Tunnel Field-Effect Transistors

The work-function variation (WFV) in high-κ/ metal-gate (HK/MG) Ge-source tunnel FETs (TFETs) is evaluated using technology computer-aided design simulations. By matching the simulation results with the plot for the ratio of the average grain size to the gate area (i.e., the RGG plot), we find that the slope in the RGG plot for the TFET can be significantly altered depending on three main factors, namely, the gate width, average grain size, and equivalent oxide thickness. In addition, it is verified that the variation of channel potential affects the WFV-induced threshold voltage variation in HK/MG Ge-source TFETs.