Simultaneously Regulated Highly Polarized and Long-Lived Valley Excitons in WSe₂/GaN Heterostructures

Interlayer excitons, with prolonged lifetimes and tunability, hold potential for advanced optoelectronics. Previous research on the interlayer excitons has been dominated by two-dimensional heterostructures. Here, we construct WSe₂/GaN composite heterostructures, in which the doping concentration of GaN and the twist angle of bilayer WSe₂ are employed as two ingredients for the manipulation of exciton behaviors and polarizations. The exciton energies in monolayer WSe₂/GaN can be regulated continuously by the doping levels of the GaN substrate, and a remarkable increase in the valley polarizations is achieved. Especially in a heterostructure with 4°-twisted bilayer WSe₂, a maximum polarization of 38.9% with a long lifetime is achieved for the interlayer exciton. Theoretical calculations reveal that the large polarization and long lifetime are attributed to the high exciton binding energy and large spin flipping energy during depolarization in bilayer WSe₂/GaN. This work introduces a distinctive member of the interlayer exciton with a high degree of polarization and a long lifetime.