The direct bandgap of gray α -tin investigated by infrared ellipsometry

Rigo A. Carrasco, Cesy M. Zamarripa, Stefan Zollner, Jose Menendez, Stephanie A. Chastang, Jinsong Duan, Gordon J. Grzybowski, Bruce B. Claflin, Arnold M. Kiefer

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Using Fourier-transform infrared ellipsometry, the authors provide spectroscopic evidence about the valence band (VB) structure of diamond-like α-tin. The mid-infrared dielectric function of α-tin grown pseudomorphically on InSb or CdTe by molecular beam epitaxy shows a strong Ē0 peak near 0.41 eV. This peak is assigned to allowed intravalence band transitions from the Γ7- (electron-like) VB to the Γ8+v heavy hole VB and/or interband transitions from Γ7- to the Γ8+c light "hole" conduction band. The strength of this peak requires a hole density in the mid-1018 cm-3 range at room temperature, which might be caused by unintentional doping, by thermal electron-hole pair generation, or by the possibility that the L6+ conduction band might have an energy slightly lower than the Γ8+ VB maximum. Alternatively, this Ē0 peak might be enhanced by the M-shape of the Γ7- VB caused by interactions with the Γ7+ split-off hole VB. A sum-rule analysis of the dielectric function between 0.16 and 6.5 eV is consistent with a high-frequency dielectric constant of 24, which has at most a weak temperature dependence between 100 and 300 K.

Original languageEnglish (US)
Article number232104
JournalApplied Physics Letters
Volume113
Issue number23
DOIs
StatePublished - Dec 3 2018

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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