Modulating the intralayer and interlayer valley excitons in WS2 through interaction with AlGaN

• Published in: Science China materials Vol. 66; no. 1; pp. 202 - 210
• Main Authors: Zeng, Xinlong, Kang, Wenyu, Zhou, Xiaowen, Li, Linglong, Xia, Yuanzheng, Liu, Haiyang, Yang, Chengbiao, Wu, Yaping, Wu, Zhiming, Li, Xu, Kang, Junyong
• Format: Journal Article
• Language: English
• Published: Beijing Science China Press 01.01.2023; Springer Nature B.V
• Subjects: Bilayers; Chemistry and Materials Science; Chemistry/Food Science; Coupling; Decay rate; Doping; Electron phonon interactions; Electron-hole interaction; Excitons; Interlayers; Materials Science; Monolayers; Polarization; Red shift; Scattering; Two dimensional materials; Valleys; interlayer exciton; valley polarization; WS; intralayer exciton; AlGaN
• ISSN: 2095-8226; 2199-4501
• DOI: 10.1007/s40843-022-2138-x

The fine-tuning of exciton transition and valley polarization process in two-dimensional materials have drawn tremendous research interest due to their rich valley-contrasting physics. Here, we demonstrate highly tunable exciton and valley characteristics in monolayer and bilayer WS 2 through coupling to AlGaN with different doping levels. A notable redshift in exciton energy is observed by interfacing WS 2 with n-type AlGaN. More interestingly, an interlayer exciton peak emerges as a result of the formation of type-II band alignment in bilayer WS2. Both the interlayer and intralayer exciton energies are tunable by the twist angle of bilayer WS 2 . A high valley polarization of 82.2% is achieved in monolayer WS 2 at 13 K by coupling with n-type AlGaN, due to the faster exciton decay rate through electron-phonon interaction and the reduced intervalley scattering by doping-induced carrier screening. The valley polarization of interlayer exciton is higher than that of the intralayer exciton, due to the suppressed intervalley scattering resulting from the reduced electron-hole interaction. This work has presented a facile and efficient technique to modulate the excitonic properties of 2D materials. The reported high valley polarization in monolayer WS 2 and the discovery of interlayer exciton in bilayer WS 2 will trigger innovative study in valley exciton physics and facilitate emerging valleytronic applications.