Understanding the Origin and Implication of the Indirect-to-Direct Bandgap Transition in Multilayer InSe

Published

May 2, 2024

Author(s)

Nicholas Pike, Ruth Pachter, Michael Altvater, Chris Stevens, Matthew Klein, Joshua Hendrickson, Huairuo Zhang, Sergiy Krylyuk, Albert Davydov, Nicholas Glavin

Abstract

Indium selenide (InSe) multilayers have attracted much interest recently due to their electronic and optical properties, partially dependent on the existence of an indirect-to-direct bandgap transition that is correlated to the multilayer thickness. In this work, we investigate stacks of van der Waals-bonded multilayer InSe, ordered similarly to the γ phase of bulk InSe. We analyze the indirect-to-direct bandgap transition using first-principles methods, identifying the structural changes in the multilayer structures that cause the electronic modifications that result in this transition. We highlight differences between InSe and transition metal dichalcogenides. Our calculations confirm the thickness dependence of the cross-over between the indirect and direct bandgaps in multilayer InSe and emphasize changes in the structure and orbital nature of the valence and conduction bands. The optical spectra predictions performed at a high level of theory are compared to our thorough experimental photoluminescence characterization of our high-quality γ phase bulk InSe. These predictions are correlated to electronic transitions and elucidate the relative contributions of in-plane and out-of-plane dipoles. The insights gained from our study could contribute to the design of multicomponent heterostructures with InSe for future electronic and electrooptical devices.

Citation

Journal of Physical Chemistry C

Volume

128

Issue

19

Pub Type

Journals

Download Paper

https://doi.org/10.1021/acs.jpcc.4c01104

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Keywords

2D materials, InSe, bandgap, excitons

Citation

Pike, N. , Pachter, R. , Altvater, M. , Stevens, C. , Klein, M. , Hendrickson, J. , Zhang, H. , Krylyuk, S. , Davydov, A. and Glavin, N. (2024), Understanding the Origin and Implication of the Indirect-to-Direct Bandgap Transition in Multilayer InSe, Journal of Physical Chemistry C, [online], https://doi.org/10.1021/acs.jpcc.4c01104, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=957467 (Accessed October 28, 2025)