Predicted Performance Advantages of Carbon Nanotube Transistors with Doped Nanotubes as Source/Drain

TL;DR

This paper demonstrates through simulations that doping nanotubes in CNTFETs' source/drain regions can suppress ambipolar conduction, reduce leakage, and improve current delivery, extending device scaling limits.

Contribution

It introduces a novel doping approach for CNTFETs that enhances performance by eliminating Schottky barriers and controlling leakage through bandgap engineering.

Findings

Doped CNT source/drain regions suppress ambipolar conduction.

Leakage current is reduced and controlled by the nanotube bandgap.

Device current capacity is increased by eliminating Schottky barriers.

Abstract

Most carbon nanotube field-effect transistors (CNTFETs) directly attach metal source/drain contacts to an intrinsic nanotube channel. When the gate oxide thickness is reduced, such transistors display strong ambipolar conduction, even when the Schottky barrier for electrons (or for holes) is zero. The resulting leakage current, which increases exponentially with the drain voltage, constrains the potential applications of such devices. In this paper, we use numerical simulations to show that if CNT based metal-oxide-semiconductor (MOS) FETs can be achieved by using heavily doped CNT sections as source and drain, ambipolar conduction will be suppressed, leakage current will be reduced, and the scaling limit imposed by source-drain tunneling will be extended. By eliminating the Schottky barrier between the source and channel, the transistor will be capable of delivering more on-current. The leakage current of such devices will be controlled by the full bandgap of CNTs (instead of half of the bandgap for SB CNTFETs) and band-to-band tunneling. These factors will depend on the diameter of nanotubes and the power supply voltage.