基于梯度掺杂策略的碳纳米管场效应管性能优化

双极性传输特性是制约碳纳米管场效应管(carbon nanotube field effect transistors,CNFETs)性能提高的一个重要因素.为降低器件的双极性传输特性并获得较大的开关电流比,提出了一种漏端梯度掺杂策略,该策略不仅适合于类MOS碳纳米管场效应管(C-CNFETs),同时也适合于隧穿碳纳米管场效应管(T-CNFETs).基于非平衡格林函数的数值研究结果表明,该策略不仅能有效降低器件的双极传输特性,而且能将器件开关电流比提高数个数量级.进一步研究发现,该掺杂策略在这两类碳纳米管 关键词： 梯度掺杂 带间隧穿 双极性传输 碳纳米管场效应管

Performance optimization of carbon nanotube field effect transistors based on stair-case doping strategy

The ambipolar transporting characteristic is one of the most important factors that prevent the performance of Carbon Nanotube Field Effect Transistors (CNFETs) from further being improved. In order to reduce the ambipolar conductance and increase the ON-OFF current ratio of the device,a stair-case doping strategy in drain lead,which is suitable for not only the Conventional MOS-like CNFETs (C-CNFETs) but also Tunneling CNFET (T-CNFETs),is proposed in this paper. The non-equilibrium Greens function based simulation results show that this strategy can reduce the ambipolar conductance and increase the ON-OFF current ratio of the device effectively. Further study shows that many differences exist with using this stair-case doping strategy applied in C-CNFETs and T-CNFETs. First,the potential band pinning in stair-case doped C-CNFETs would weaken the ON-state performance of the device,while no band pinning exists in stair-case doped T-CNFETs. Second,applying such a stair-case doping strategy to both source and drain leads can further increase the device performances in C-CNFETs but not T-CNFEts. Third,the transporte property of T-CNFETs is dependent more strongly on the width of lightly doped drain region than that of C-CNFETs. However,certain device area would be costly because of using this stair-case doping strategy. So,much attention should be paid to the choice of device structure,doping concentration and lightly doped drain region width,to obtain a best tradeoff among speed,power and device area,in application.