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arXiv · 2604.15553

Hole concentrations in doped gray {\alpha}-Sn on InSb and CdTe measured with infrared ellipsometry

Jaden R. Love·Carlos A. Armenta·Atlantis K. Moses·Haley B. Woolf·Jan Hrabovsky·Stefan Zollner·Aaron N. Engel·Christopher J. Palmstrøm
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Abstract

Gray tin ({\alpha}-Sn) layers with 30 nm thickness were grown on InSb (001) substrates using molecular beam epitaxy. The surface preparation of the substrates was adjusted to achieve either n-type or p-type doping in the {\alpha}-Sn layer. Fourier-transform infrared ellipsometry was used to find the temperature-dependent dielectric function of the {\alpha}-Sn layers from 0.03 to 0.8 eV and from 10 to 300 K. Because of the inverted band structure of {\alpha}-Sn, the spectra show a strong absorption peak at 0.45 eV due to transitions from the inverted {\Gamma_-^7} "electron" valence band to the {\Gamma_+^8} heavy hole valence band. Applying the Thomas-Reiche-Kuhn f-sum rule, the integrated oscillator strength of this peak was used to calculate the heavy hole concentration as a function of temperature. For a nearly intrinsic {\alpha}-Sn layer, the heavy hole concentration agrees well with predictions based on degenerate Fermi-Dirac statistics. Deviations from the intrinsic {\alpha}-Sn carrier concentrations are attributed to substrate surface preparation leading to the diffusion of donor or acceptor ions into the {\alpha}-Sn layer causing n-type or p-type doping.

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Jaden R. Love, Carlos A. Armenta, Atlantis K. Moses, Haley B. Woolf, Jan Hrabovsky, Stefan Zollner, Aaron N. Engel, Christopher J. Palmstrøm. 2026-04-16. Hole concentrations in doped gray {\alpha}-Sn on InSb and CdTe measured with infrared ellipsometry. https://arxiv.org/abs/2604.15553

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