沟道长度及源/漏区掺杂浓度对MOS-CNTFET输运特性的影响

Influence of Channel Length and Source/Drain DopingContent on Transport Characteristics of MOS-CNTFET

碳纳米管场效应晶体管电子输运性质是其结构参量(纵向结构参量:如CNT的直径、栅介质层厚度、介质介电常数等;横向结构参量:如沟道长度、源/漏区掺杂浓度等)的复杂函数。本论文在量子力学非平衡格林函数理论框架内,通过自洽求解泊松方程和薛定谔方程以得到MOS-CNTFET电子输运特性。在此基础上系统地研究了沟道长度及源/漏区掺杂浓度对MOS-CNTFET器件的漏极导通电流、关态泄漏电流、开关态电流比、阈值电压、亚阈值摆幅及双极性传导等输运性质的影响。结果表明:当沟道长度在15 nm以上时,上述各性质受沟道长度的影响均较小,而导通电流、开关态电流比及双极性传导特性与源/漏掺杂浓度的大小有关,开关态电流比与掺杂浓度正相关,导通电流及双极性导电特性与源/漏掺杂浓度负相关。当沟道长度小于15 nm时,随沟道长度减小,漏极导通电流呈增加趋势,但同时导致器件阈值电压及开关电流比减小,关态漏电流及亚阈值摆幅增大且双极性传导现象严重,短沟道效应增强,此时,通过适当降低源/漏掺杂区掺杂浓度,可一定程度地减弱MOS-CNTFET器件短沟道效应。

We analytically addressed the transport characteristics of Mos-like carbon nantube field effect transistor （MOS-CNTFET）. The transport behavior of the MOS-CNTFET was modeled and calculated by solving the self-consistent Poison and Schrodinger equations within the non-equilibrium framework of Green＇s function. The influence of the channel length and source/drain doping content on the transport characteristics, including on-and off-current, on-off current ratio, threshold voltage swing, and ambipolar conductance, was evaluated. The simulated results show that the channel length and doping contents considerably affect the transport behavior. For example, the transport behavior depends weakly on a chan- nel length longer than 15 nm,but fairly strong on the doping contents to a varied degree.As the channel length decreased from 15 nm,the on-current slowly increased,accompanied by the decreases of threshold voltage and on-off current ratio, the increases of off-state leakage current and sub-threshold swing, and a more serious ambipolar conduction or short chan- nel effect. We suggest that an appropriate reduction of the source/drain doping content effectively weaken the short chan- nel effect of MOS-CNTFET devices.