Intrinsic Gate Capacitance of Ultrathin Body Nanosheets Considering Quantum Effects

• Published in: IEEE transactions on electron devices 2024-04, Vol.71 (4), p.2271-2277
• Main Authors: Yao, Ching-Wang, Lee, Yu-Chieh, Lin, Hsin-Cheng, Chou, Tao, Chung, Tsai-Yu, Wang, Li-Kai, Yang, Jen-Wei, Jan, Sun-Rong, Liu, C. W.
• Format: Article
• Language: English
• Subjects: Capacitance; Carrier density; Centroids; Charge carrier density; Fitting; intrinsic gate capacitance; Logic gates; Nanosheets; nanosheets (NSs); Quantum capacitance; quantum confinement; Solid modeling; subthreshold swing (SS); Thickness; Transistors; ultrathin body; Wave functions
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2024.3364584

Considering the wave function, the decreasing thickness of ultrathin body from 10 nm down to 2 nm increases the intrinsic gate capacitance since the centroid of carriers located at the center of the channel is extremely close to the channel/oxide interface in the ultrathin body. By the self-consistent Poisson-Schrodinger solver with 6-kp parameters calibrated with nonlocal empirical pseudo-potential method (NEPM), the centroids of wavefunctions can be used to understand the increment in intrinsic gate capacitance with decreasing body thickness. Note that the simulated channel is p-type GeSn with [Sn] ranging from 0% to 20%. Our simulation also shows that nearly ideal subthreshold swing (SS) can be achieved by ultrathin body nanosheets (NSs). Thus, the concept of intrinsic areal gate capacitance proportional to channel peripheral width has to be modified in the ultrathin body channel.