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To make an exact research into the performance of conventional MOS-like carbon nanotube field-effect transistors (C-CNFETs) with realistic contacts, we studied the effect of Schottky contacts on the performance of C-CNFETs following a detailed analysis of contacting circumstances of C-CNFETs in circuit applications. As the research results show, conventional C-CNFETs suffer from weak subthreshold and off -state performances due to the band-to-band tunneling of holes even with Schottky contacts taken into account. Consequently, device structures based on three novel strategies, viz., an electrostatic doping strategy, a dual-gate-material strategy, and a staircase doping strategy, have been proposed. In addition, the simulation results reveal that these three device structures can improve the device performance of C-CNFETs in the form of steeper subthreshold characteristic, low enough potential off-state current, or (and) monotonic transfer characteristic. At the same time, it should be noted that the performances of these three strategies sensitively depend on the choice of tuning voltage, work function of gate material, or doping concentration of lightly doped source/drain leads, which should be paid with much attention in application.
Date of Publication: Nov. 2010