Scaling of N‑Type\nField-Effect Transistors\nBased on Aligned Carbon Nanotube Arrays

Wafer-scale aligned carbon nanotubes (A-CNTs) are promising\ncandidate\nsemiconductors for building high-performance complementary metal–oxide–semiconductor\n(CMOS) transistors for future integrated circuits (ICs). A-CNT-based\np-type field-effect transistors (P-FETs) have demonstrated excellent\nperformance and scalability down to sub-10 nm nodes. However, the\ndevelopment of A-CNT n-type FETs (N-FETs) lags far behind, in regard\nto their electronic performance and device scaling. In this work,\nwe fabricated top-gated N-FETs based on A-CNTs with a scandium (Sc)-contacted\nsource and drain. High-performance A-CNT N-FETs were demonstrated\nwith record on-state current (<i>I</i><sub>on</sub>) exceeding\n1 mA/μm and peak transconductance (<i>g</i><sub>m</sub>) of 0.4 mS/μm. Interestingly, the A-CNT N-FETs exhibited abnormal\nscaling behavior owing to the lateral oxidation of low-work function\nsource/drain contacts, leading to formidable challenges to scale both\nthe gate length (<i>L</i><sub>g</sub>) and the contact length\n(<i>L</i><sub>c</sub>) at the same time. Understanding of\nthe abnormal scaling behavior contributes to seeking solutions for\nhigh-performance A-CNT N-FETs, and it paves the way for future CNT\nCMOS digital IC technology.