Revealing and engineering contact-origin noise in ultrathin tellurium transistors

TL;DR

This study identifies the source of noise in ultrathin tellurium transistors and shows how to reduce it by adjusting the thickness of tellurium near the contacts.

Contribution

The paper introduces a contact-centric engineering strategy to suppress noise in ultrathin tellurium transistors.

Findings

Contact-origin trap-assisted tunneling dominates noise in 5 nm Te devices at room temperature.

Locally thickening the Te layer under contacts reduces noise by an order of magnitude in the nA current regime.

Noise suppression is achieved without compromising the 5 nm active channel thickness.

Abstract

Tellurium (Te) has emerged as a promising p-type semiconductor for ultrathin electronics owing to its strong air stability, excellent hole transport, narrow bandgap, and BEOL-integration compatibility. However, when the Te thickness approaches the depletion width, traps at the contact interface strongly affect carrier injection and introduce excess low-frequency noise. Here, we systematically investigate the origin of noise in ultrathin Te field-effect transistors (FETs) through bias- and temperature-dependent 1/f noise analysis. In devices with a 5 nm Te channel, contact-origin trap-assisted tunneling dominates in the low-current regime, producing deviations from the carrier-number-fluctuation (CNF) model at 300 K. Cooling to 100 K suppresses trap activation and restores typical CNF behavior, whereas 13 nm devices maintain CNF consistency at both temperatures due to screening of the contact region. To mitigate contact-origin noise, a locally thickened (13 nm) Te layer was inserted beneath the source and drain metal contact while preserving a 5 nm active Te channel. This design restores CNF behavior at room temperature, lowers the noise level in the nA current regime by an order of magnitude, and decreases the drain-bias dependence of noise by approximately twofold. The results identify near-contact traps as the primary noise source in ultrathin Te and demonstrate contact-centric engineering as an effective strategy to decouple device scaling from noise, enabling reliable, low-noise Te electronics.

This study identifies the origin of excess low-current noise in ultrathin Te FETs and suppresses it by locally modulating the Te thickness near the contacts.

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