Enhanced THz emission and exciton transfer in monolayer MoS2/GaAs heterostructures

TL;DR

This study demonstrates that integrating monolayer MoS2 with GaAs heterostructures enhances THz emission and exciton transfer, leading to improved optoelectronic properties and potential for advanced device applications.

Contribution

It introduces a novel hybrid 2D/3D heterostructure that boosts THz emission and exciton transfer efficiency compared to traditional GaAs devices.

Findings

15% increase in THz emission over bare GaAs

Photoluminescence enhancement factor of 2.38

Doubling of optical conductivity and 50% reduction in absorption

Abstract

For designing an efficient terahertz (THz) emitter, the defect density of the semiconductors is smartly increased to reduce carrier lifetime, which subsequently lowers the overall power output of the semiconductor. To overcome this fundamental trade-off, this study presents a novel approach, by integrating a direct band gap 2D semiconductor such as monolayer MoS2 (1L-MoS2) with a well-known THz emitter, low-temperature-grown gallium arsenide (GaAs). The fabricated hybrid 2D/3D vertical van der Waals heterostructure showed a 15% higher THz emission compared to bare GaAs due to phase-coherent addition of second-order non-linear susceptibility, and overall enhancement in the electric field of laser. The photoluminescence (PL) enhancement factor of 2.38 in heterostructures at GaAs emission energy of 1.42 eV. However, the substantial quenching of PL emission for 1L-MoS2 at the energy of 1.84 eV, is attributed to the Dexter-type exciton transfer mechanism at type-I band alignment. THz time-domain spectroscopy reveals a significant increase in optoelectronic properties, such as optical conductivity becoming doubled, and a 50% reduction in absorption coefficients. The study introduces a new route for fabricating large-area and compact mixed-dimensional van der Waals heterostructures, which can be used to enhance the efficiency of conventional semiconductor technologies and THz-based optoelectronic devices.