The Effects of Elliptical Gate Cross Section on Carbon Nanotube Gate-All-Around Field Effect Transistor

Hao Wang1,  Sheng Chang1,  Cheng Wang1,  Yue Hu1,  Hongyu He1,  Jin He1,  Qingxing He2,  Caixia Du2,  Shengju Zhong2
1Peking University, 2Shenzhen Huayue Terascale Chip LTD.Co.


In this paper, the gate-all-around carbon nanotube field effect transistor (FET) with elliptical shaped gate is studied with numerical simulation to explore the gate dielectric variation effects. The simulations are carried out with the three dimensional self-consistence Poisson-Schrodinger equations with the non-equilibrium Green’s function method. The on current, potential distribution, local density of states, and transmission coefficients of the devices of different geometry are examined. The performances of elliptical shaped gate device are compared to the round shaped gate ones and it is observed that the geometry has notable effects on the characteristics of the devices. Due to the enhanced gate electrostatic control, the ellipse shaped gate carbon nanotube FET delivers increased current with reduced ellipse axes. The enhanced gate control also affects the band gap profile and induces more bound states in the valence band due to steeper potential well. This effect will affect the sub threshold characteristic.