Enhanced THz Emission and Exciton Transfer in Monolayer MoS2/GaAs Heterostructures

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 bandgap 2D semiconductor, such as monolayer MoS2 (1L‐MoS2) with a well‐known THz emitter and low‐temperature‐grown gallium arsenide (GaAs). The fabricated hybrid 2D/3D vertical van der Waals heterostructure shows a 15% higher THz emission compared to bare GaAs due to phase‐coherent addition of second‐order nonlinear susceptibility, and overall enhancement in the electric field of the 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.