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Electronic and optical properties of the monolayer group-IV monochalcogenides MX (M = Ge, Sn; X = S, Se, Te)

TitleElectronic and optical properties of the monolayer group-IV monochalcogenides MX (M = Ge, Sn; X = S, Se, Te)
Publication TypeJournal Article
Year of Publication2017
AuthorsXu, Lei, Yang Ming, Wang Shi Jie, and Feng Yuan Ping
JournalPhys. Rev. B
Date Published06/2017
Keywordsblack phosphorus, excitons, films, graphene, localized wannier functions, mobility, MoS2, semiconductor, transistors, Transport

By using density-functional theory and many-body perturbation theory based first-principles calculations, we have systematically investigated the electronic and optical properties of monolayer group-IV monochalcogenides MX (M = Ge, Sn; X = S, Se, Te). All MX monolayers are predicted to be indirect gap semiconductors, except the GeSe monolayer, which has a direct gap of 1.66 eV. The carrier mobilities of MX monolayers are estimated to be on the order of 103 to 105 cm(2) V-1 s(-1), which is comparable to, and in some cases higher than, that of phosphorene using a phonon-limited scattering model. Moreover, the optical spectra of MX monolayers obtained from GW-Bethe-Salpeter equation calculations are highly orientation dependent, especially for the GeS monolayer, suggesting their potential application as a linear polarizing filter. Our results reveal that the GeSe monolayer is an attractive candidate for optoelectronic applications as it is a semiconductorwith a direct band gap, a relatively high carrier mobility, and an onset optical absorption energy in the visible light range. Finally, based on an effective-mass model with nonlocal Coulomb interaction included, we find that the excitonic effects of the GeSe monolayer can be effectively tuned by the presence of dielectric substrates. Our studies provide an improved understanding of electronic, optical, and excitonic properties of group-IV monochalcogenides monolayers and might shed light on their potential electronic and optoelectronic applications.


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