The Effect of Dielectric Capping on Few-Layer Phosphorene Transistors: Tuning the Schottky Barrier Heights

TL;DR

This paper investigates how dielectric capping with Al2O3 affects the electronic properties of few-layer phosphorene transistors, demonstrating polarity switching due to Schottky barrier modifications caused by fixed charges in the dielectric.

Contribution

It reveals the impact of ALD-grown Al2O3 dielectric on Schottky barrier heights and transistor polarity in phosphorene devices, a novel insight into contact engineering.

Findings

Achieved high on-current of 144 mA/mm and hole mobility of 95.6 cm2/Vs.

Observed polarity switch from p-type to ambipolar with dielectric capping.

Attributed polarity change to fixed charges in ALD dielectric affecting Schottky barriers.

Abstract

Phosphorene is a unique single elemental semiconductor with two-dimensional layered structures. In this letter, we study the transistor behavior on mechanically exfoliated few-layer phosphorene with the top-gate. We achieve a high on-current of 144 mA/mm and hole mobility of 95.6 cm2/Vs. We deposit Al2O3 by atomic layer deposition (ALD) and study the effects of dielectric capping. We observe that the polarity of the transistors alternated from p-type to ambipolar with Al2O3 grown on the top. We attribute this transition to the changes for the effective Schottky barrier heights for both electrons and holes at the metal contact edges, which is originated from fixed charges in the ALD dielectric.