High performance n-doped carbon nanotube field-effect transistors

TL;DR

This paper presents a robust method for fabricating high-performance n-doped carbon nanotube FETs with tunable threshold voltages and significantly increased on-currents, achieved through potassium vapor doping and annealing.

Contribution

It introduces a reliable doping technique using potassium vapor and annealing to enhance the performance of carbon nanotube FETs, including threshold tuning and current increase.

Findings

Threshold voltage tunable from -1.3V to 0.5V

On-current increased by 10-100 times

Device resistance reduced due to improved contact

Abstract

We describe a robust technique for the fabrication of high performance vertically scaled n-doped field-effect transistors from large band gap carbon nanotubes. These devices have a tunable threshold voltage in the technologically relevant range (-1.3V < V_th < 0.5V) and can carry up to 5-6 muA of current in the on-state. We achieve such performance by exposure to potassium (K) vapor and device annealing in high vacuum. The treatment has a two-fold effect to: (i) controllably shift V_th toward negative gate biases via bulk doping of the nanotube (up to about 0.6e/nm), and (ii) increase the on-current by 1-2 orders of magnitude. This current enhancement is achieved by lowering external device resistance due to more intimate contact between K metal and doped nanotube channel in addition to potential reduction of the Schottky barrier height at the contact.