Giant built-in electric field enabled quantum-confined Stark effects

Abstract

Quantum-confined Stark effects (QCSEs), where external or built-in electric fields modify optical transition energies1-6, have garnered significant interest due to their potential for tuning emission energies to couple with quantum dots, metasurfaces and cavities, etc1-3,7,8. However, only external electric-field-enabled QCSEs in 2D semiconductors have been reported so far1-3, owing to the challenges posed by small and uncontrollable built-in electric fields2,3, as well as charge modulation effects9-14. Here we report the first observation of giant built-in electric field-enabled QCSEs in 1L WSe2/1L graphene heterostructure (HS), based on chemical potential calculations. Electrical control of QCSEs demonstrates a maximum Stark shift of ~56.97 meV. This significant shift is attributed to enhanced built-in electric fields, resulting from the increased chemical potential difference induced by electrostatic doping. While increasing optical doping or reducing the interlayer distance, QCSEs weaken due to the reduced built-in electric fields. By leveraging efficient exciton dissociations from built-in electric fields15,16, the responsivity (R) and response speed of HS photodetectors increase by 6 orders of magnitude and 3 folds, respectively, compared to 1L WSe2. Our results offer a new avenue for expanding the tunability for excitons and exploiting the application potentials for 2D material in photodetectors, polariton transistors and quantum light sources.