Locally Phase-Engineered MoTe$_2$ for Near-Infrared Photodetectors

TL;DR

This study demonstrates locally phase-engineered MoTe₂ devices that utilize a 1T'-2H junction to achieve efficient near-infrared photodetection with rapid response times, advancing all-2D optoelectronic circuitry.

Contribution

The paper introduces a novel method of creating phase-engineered MoTe₂ heterojunctions and uncovers the photovoltaic mechanism behind their photocurrent generation.

Findings

Photocurrent mainly originates from the 1T'-2H junction.

The heterojunction exhibits a fast response time of around 110-113 microseconds.

The device operates effectively over 700-1100 nm wavelength range.

Abstract

Transition metal dichalcogenides (TMDs) are ideal systems for two-dimensional (2D) optoelectronic applications, owing to their strong light-matter interaction and various band gap energies. New techniques to modify the crystallographic phase of TMDs have recently been discovered, allowing the creation of lateral heterostructures and the design of all-2D circuitry. Thus far, the potential benefits of phase-engineered TMD devices for optoelectronic applications are still largely unexplored. The dominant mechanisms involved in the photocurrent generation in these systems remain unclear, hindering further development of new all-2D optoelectronic devices. Here, we fabricate locally phase-engineered MoTe$_{2}$ optoelectronic devices, creating a metal (1T') semiconductor (2H) lateral junction and unveil the main mechanisms at play for photocurrent generation. We find that the photocurrent originates from the 1T'-2H junction, with a maximum at the 2H MoTe$_{2}$ side of the junction. This observation, together with the non-linear IV-curve, indicates that the photovoltaic effect plays a major role on the photon-to-charge current conversion in these systems. Additionally, the 1T'-2H MoTe$_{2}$ heterojunction device exhibits a fast optoelectronic response over a wavelength range of 700 nm to 1100 nm, with a rise and fall times of 113 $\mu$s and 110 $\mu$s, two orders of magnitude faster when compared to a directly contacted 2H MoTe$_{2}$ device. These results show the potential of local phase-engineering for all-2D optoelectronic circuitry.