Enhancement-Mode Field-Effect Transistors and High-Speed Integrated Circuits Based on Aligned Carbon Nanotube Films

Aligned carbon nanotube (A-CNT) films are expected to be an ideal channel material for constructing field-effect transistors (FETs) that outperform conventional transistors, and multiple methods are developed to fabricate A-CNT films with high semiconducting purity, good alignment, and high density. However, the reported A-CNTs-based FETs are almost all depletion-mode FETs and suffer from poor subthreshold swing (SS). In this study, enhancement-mode (E-mode) FETs based on A-CNT films are fabricated by systematically optimizing the channel material and CNT/high-k/metal gate stack. The carrier mobility in top-gate A-CNT FETs reaches a maximum value of 1850 cm(2) V-1 s(-1), which is near that of chemical-vapor deposition grown individual CNTs and sets a record among A-CNT films. The fabricated 200 nm-gate length p-type A-CNT FETs present a SS of 73 mV dec(-1), the transconductance of 1 mS mu m(-1), and an on-current of 1.18 mA mu m(-1) at a bias of -1 V, indicating a real performance exceeding that of commercial Si-based transistors at a similar gate length. Based on the high-performance and uniform E-mode FETs, ring oscillators with stage numbers 5, 7, 9, and 11 are fabricated with an optimized design and high yield, exhibiting a record propagation gate delay of 11.3 ps among CNT- and other nanomaterial-based ICs.