Determination of band offsets, hybridization, and exciton binding in 2D semiconductor heterostructures.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28246636.
- Also identified by DOI 10.1126/sciadv.1601832 and PMC identifier 5298850.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Combining monolayers of different two-dimensional semiconductors into heterostructures creates new phenomena and device possibilities. Understanding and exploiting these phenomena hinge on knowing the electronic structure and the properties of interlayer excitations. We determine the key unknown parameters in MoSe<sub>2</sub>/WSe<sub>2</sub> heterobilayers by using rational device design and submicrometer angle-resolved photoemission spectroscopy (μ-ARPES) in combination with photoluminescence. We find that the bands in the K-point valleys are weakly hybridized, with a valence band offset of 300 meV, implying type II band alignment. We deduce that the binding energy of interlayer excitons is more than 200 meV, an order of magnitude higher than that in analogous GaAs structures. Hybridization strongly modifies the bands at Γ, but the valence band edge remains at the K points. We also find that the spectrum of a rotationally aligned heterobilayer reflects a mixture of commensurate and incommensurate domains. These results directly answer many outstanding questions about the electronic nature of MoSe<sub>2</sub>/WSe<sub>2</sub> heterobilayers and demonstrate a practical approach for high spectral resolution in ARPES of device-scale structures.