Exciton and valley dynamics in WSe₂/GaAs heterostructure

Transition metal dichalcogenide (TMDC) monolayers provide an ideal platform for exciton and valley-spintronics exploration due to their unique properties. Integrating TMDC monolayers with conventional semiconductors allows for harnessing the unique properties of both materials. This strategy holds great promise for the development of advanced optoelectronics and spintronic devices. In this work, we investigated exciton and valley dynamics in WSe₂/GaAs heterostructure by employing the femtosecond pump-probe ultrafast spectroscopy. Facilitated by the charge transfer within the heterostructure, it was found that the exciton of WSe₂ exhibited much longer lifetime of nanosecond than that of the WSe₂ monolayer counterpart. Especially, a significantly long valley lifetime up to ∼ 2.7 ns was observed for trions of WSe₂ in the heterostructure even under the off-resonant excitation, which is found to be associated with the resident electrons accumulated at the interface resulting from the charge transfer and resultant interfacial electric field. Our results provide fundamental references for conventional semiconductor-integrated TMDC heterostructures that have great potential for designing novel optoelectronic and spintronic devices.