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Electrically and optically active charge carrier traps in silicon-doped few-layer GaSe

M. Bissolo1,*, R. Li1,†, M. Ogura2, Z. Sofer3, S. Polesya2, D. Han4, A. W. Holleitner1, C. Kastl1, G. Koblmüller1,5 et al.

H. Ebert2, E. Zallo1,‡, and J. J. Finley1

  • *Contact author: michele.bissolo@tum.de
  • †Present address: Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany.
  • ‡Contact author: eugenio.zallo@tum.de
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Phys. Rev. Applied 26, 034034 – Published 16 September, 2026

DOI: https://doi.org/10.1103/8w6z-vwvm

Abstract

Understanding defects in atomically thin van der Waals (vdW) semiconductors is essential for advancing their use in next-generation optoelectronic and photovoltaic devices. Here, we apply a combination of various impedance spectroscopy techniques to two-dimensional (2D) vdW GaSe doped with silicon (Si) to reconstruct deep trap states across the full bandgap. Deep-level transient spectroscopy reveals three distinct deep states, 0.33, 0.68, and 0.24 eV, below the conduction band edge. Complementary deep-level optical spectroscopy and photocapacitance measurements identify two deep states at 1.4 and 1.8 eV below the conduction band edge and one at 2.0 eV above the valence band edge, with thermal admittance spectroscopy providing additional verification and further resolving two trap states at 0.16 eV above the valence band edge and at 0.26 eV below the conduction band edge. By comparing the experimentally extracted ionization energies with the predictions of density functional theory, our results attribute these trap states primarily to Si-related defects and metal vacancies. This work presents a comprehensive defect map of Si-doped GaSe, providing critical insights into carrier trapping mechanisms that are essential for optimizing the design of 2D material-based devices for industrial applications.

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Phys. Rev. Applied 26, 034034– Published 16 September, 2026
  • Received 8 February 2026
  • Revised 8 June 2026
  • Accepted 23 July 2026
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