Arrayed van der Waals Vertical Heterostructures based on 2D GaSe Grown by Molecular Beam Epitaxy

TL;DR

This paper presents a novel wafer-scale method for growing high-quality 2D GaSe heterostructures via molecular beam epitaxy, enabling advanced optoelectronic devices with high efficiency and durability.

Contribution

It introduces a controllable, scalable growth technique for 2D GaSe films with atomically sharp interfaces, advancing the fabrication of 2D heterostructures.

Findings

Successful wafer-scale growth of 2D GaSe films.

High external quantum efficiency of 23.6% in photodetectors.

Device robustness with no degradation after 1 million cycles.

Abstract

Vertically stacking two dimensional (2D) materials can enable the design of novel electronic and optoelectronic devices and realize complex functionality. However, the fabrication of such artificial heterostructures in wafer scale with an atomically-sharp interface poses an unprecedented challenge. Here, we demonstrate a convenient and controllable approach for the production of wafer-scale 2D GaSe thin films by molecular beam epitaxy. In-situ reflection high-energy electron diffraction oscillations and Raman spectroscopy reveal a layer-by-layer van der Waals epitaxial growth mode. Highly-efficient photodetector arrays were fabricated based on few-layer GaSe on Si. These photodiodes show steady rectifying characteristics and a relatively high external quantum efficiency of 23.6%. The resultant photoresponse is super-fast and robust with a response time of 60 us. Importantly, the device shows no sign of degradation after 1 million cycles of operation. Our study establishes a new approach to produce controllable, robust and large-area 2D heterostructures and presents a crucial step for further practical applications.