Epitaxial Single‐Layer MoS2 on GaN with Enhanced Valley Helicity. Issue 5 (19th December 2017)

• Record Type: Journal Article
• Authors: Wan, Yi; Xiao, Jun; Li, Jingzhen; Fang, Xin; Zhang, Kun; Fu, Lei; Li, Pan; Song, Zhigang; Zhang, Hui; Wang, Yilun; Zhao, Mervin; Lu, Jing; Tang, Ning; Ran, Guangzhao; Zhang, Xiang; Ye, Yu; Dai, Lun
• Is Part Of: Advanced materials. Volume 30:Issue 5(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-12-19
• Subjects: electron–phonon coupling -- gallium nitride -- single‐layer molybdenum disulfide -- substrate engineering -- valley helicity; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.201703888
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: Engineering the substrate of 2D transition metal dichalcogenides can couple the quasiparticle interaction between the 2D material and substrate, providing an additional route to realize conceptual quantum phenomena and novel device functionalities, such as realization of a 12‐time increased valley spitting in single‐layer WSe2 through the interfacial magnetic exchange field from a ferromagnetic EuS substrate, and band‐to‐band tunnel field‐effect transistors with a subthreshold swing below 60 mV dec −1 at room temperature based on bilayer n ‐MoS2 and heavily doped p ‐germanium, etc. Here, it is demonstrated that epitaxially grown single‐layer MoS2 on a lattice‐matched GaN substrate, possessing a type‐I band alignment, exhibits strong substrate‐induced interactions. The phonons in GaN quickly dissipate the energy of photogenerated carriers through electron–phonon interaction, resulting in a short exciton lifetime in the MoS2 /GaN heterostructure. This interaction enables an enhanced valley helicity at room temperature (0.33 ± 0.05) observed in both steady‐state and time‐resolved circularly polarized photoluminescence measurements. The findings highlight the importance of substrate engineering for modulating the intrinsic valley carriers in ultrathin 2D materials and potentially open new paths for valleytronics and valley‐optoelectronic device applications. Abstract : The epitaxially oriented growth of single‐layer MoS2 on a lattice‐matched GaN substrate is reported. The strong interlayer electron–phonon coupling in the heterostructure modulates the valley dynamics of the MoS2 . An enhanced room‐temperature valley helicity ≈0.33 ± 0.05 is observed. The ability to manipulate valley dynamics with the underlying substrate opens new opportunities for valley‐sensitive photonics and optoelectronics.