单壁碳纳米管作沟道的场效应晶体管输运特性理论研究

Theoretical Study of Transport Characteristics of Field Effect Transistor with Channel Made of Single-Walled Carbon Nanotube

为研究以单壁碳纳米管(CNT)作沟道的场效应晶体管(FET)的输运特性,采用非平衡格林函数(NEGF)理论,构建了CNTFET的电子输运模型,该方法摒弃粗糙的连续体模型,可实现CNTFET输运性质与手性指数的直接对接。以(17,0)锯齿型管为例,数值计算了CNTFET输出特性、转移特性、跨导、亚阈值摆幅、开关态电流比等电学特性;在等效栅氧化层厚度相同的情况下,对比了采用不同栅介质材料时上述电学特性在数值上的差异,发现随栅介质介电常数的增加,漏感应势垒降低效应变得显著,这不但导致开态时从源注入到漏的电子浓度增加、电流增大,也导致关态电流增大,开关态的电流比减少。研究还发现在通常的栅源和漏源电压下,沟道中出现热电子。

The field effect transistor, with a channel made of single-walled carbon nanotube, was modeled based on the non-equilibrium Green＇s function framework to theoretically study its transport characteristics. The newly-developed model outperforms the rough continuum one by directly considering the influence of CNTs chiral index on the transport properties of the CNTFET. The electrical properties of the （17,0） zigzag nanotube, including the output characteristics, transfer characteristics, trans-conductance, sub-threshold swing, and on-off current ratio, were numerically evaluated. The impacts of the different gate dielectric materials on the electrical properties of the CNTFET with the same equivalent gate oxide thickness were studied. The simulated results show that as the electric peanittivity increases, the drain induced bar- rier lowering effect becomes significant. The DIBL not only increases the electron concentration injected from the source and the on-state current, but also significantly enhances the off-state current, resulting in a reduction of the on-off ratio. Hot electrons exist in the channel of CNTFET under normal gate-source and drain-source voltages.