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Superconductivity in substitutional Ga-hyperdoped Ge epitaxial thin films

Nature Nanotechnology volume 20, pages 1757–1763 (2025)Cite this article

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Abstract

Doping-induced superconductivity in group-IV elements may enable quantum functionalities in material systems accessible with well-established semiconductor technologies. Non-equilibrium hyperdoping of group-III atoms into C, Si or Ge can yield superconductivity; however, its origin is obscured by structural disorder and dopant clustering. Here we report the epitaxial growth of hyperdoped Ga:Ge films and trilayer heterostructures by molecular-beam epitaxy with extreme hole concentrations (nh = 4.15 × 1021 cm−3, 17.9% Ga substitution) that yield superconductivity with a critical temperature of Tc = 3.5 K. Synchrotron-based X-ray absorption and scattering methods reveal that Ga dopants are substitutionally incorporated within the Ge lattice, introducing a tetragonal distortion to the crystal unit cell. Our findings, corroborated by first-principles calculations, suggest that the structural order of Ga dopants creates a narrow band for the emergence of superconductivity in Ge, establishing hyperdoped Ga:Ge as a low-disorder, epitaxial superconductor–semiconductor platform.

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Fig. 1: Superconductivity in germanium by p-type hyperdoping.
Fig. 2: Ga dopant arrangement in Ge and modulated band structure.
Fig. 3: Cross-sectional electron microscopy reveals coherent crystalline interfaces.
Fig. 4: X-ray scattering measurement of tetragonal crystalline distortion.

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Data availability

Raw data are available via Zenodo at https://doi.org/10.5281/zenodo.17065133 (ref. 48).

References

  1. Ekimov, E. A. et al. Superconductivity in diamond. Nature 428, 542–545 (2004).

    Article  PubMed  CAS  Google Scholar 

  2. Bustarret, E. et al. Superconductivity in doped cubic silicon. Nature 444, 465–468 (2006).

    Article  PubMed  CAS  Google Scholar 

  3. Blase, X., Bustarret, E., Chapelier, C., Klein, T. & Marcenat, C. Superconducting group-IV semiconductors. Nat. Mater. 8, 375–382 (2009).

    Article  PubMed  CAS  Google Scholar 

  4. Chiodi, F., Duvauchelle, J.-E., Marcenat, C., Débarre, D. & Lefloch, F. Proximity-induced superconductivity in all-silicon superconductor/normal-metal junctions. Phys. Rev. B 96, 024503 (2017).

    Article  Google Scholar 

  5. Scappucci, G. et al. The germanium quantum information route. Nat. Rev. Mater. 6, 926–943 (2021).

    Article  CAS  Google Scholar 

  6. Sammak, A. et al. Shallow and undoped germanium quantum wells: a playground for spin and hybrid quantum technology. Adv. Func. Mater. 29, 1807613 (2019).

    Article  Google Scholar 

  7. Tosato, A. et al. Hard superconducting gap in germanium. Commun. Mater. 4, 23 (2023).

    Article  CAS  Google Scholar 

  8. Schiela, W. F., Yu, P. & Shabani, J. Progress in superconductor-semiconductor topological Josephson junctions. PRX Quantum 5, 030102 (2024).

    Article  Google Scholar 

  9. Hermannsdörfer, T. et al. Superconducting state in a gallium-doped germanium layer at low temperatures. Phys. Rev. Lett. 102, 217003 (2009).

    Article  Google Scholar 

  10. Prucnal, S. et al. Superconductivity in single-crystalline aluminum- and gallium-hyperdoped germanium. Phys. Rev. Mater. 3, 054802 (2019).

    Article  CAS  Google Scholar 

  11. Sardashti, K. et al. Tuning supercondutivity in Ge:Ga using Ga+ implantation energy. Phys. Rev. Mater. 5, 064802 (2021).

    Article  CAS  Google Scholar 

  12. Strohbeen, P. J., Brook, A. M., Sarney, W. L. & Shabani, J. Superconductivity in hyperdoped Ge by molecular beam epitaxy. AIP Adv. 13, 085118 (2023).

    Article  CAS  Google Scholar 

  13. Shabani, J. et al. Two-dimensional epitaxial superconductor-semiconductor heterostructures: a platform for topological superconducting networks. Phys. Rev. B 93, 155402 (2016).

    Article  Google Scholar 

  14. Krogstrup, P. et al. Epitaxy of semiconductor-superconductor nanowires. Nat. Mater. 14, 400–406 (2015).

    Article  PubMed  CAS  Google Scholar 

  15. Zhao, R. et al. Merged-element transmon. Phys. Rev. Appl. 14, 064006 (2020).

    Article  CAS  Google Scholar 

  16. Shim, Y.-P. & Tahan, C. Bottom-up superconducting and Josephson junction devices inside a group-IV semiconductor. Nat. Commun. 5, 4225 (2014).

    Article  PubMed  CAS  Google Scholar 

  17. Cohen, M. L. The existence of a superconducting state in semiconductors. Rev. Mod. Phys. 36, 240–243 (1964).

    Article  CAS  Google Scholar 

  18. Strohbeen, P. J. et al. Molecular beam epitaxy growth of superconducting tantalum germanide. Appl. Phys. Lett. 124, 092102 (2024).

    Article  CAS  Google Scholar 

  19. Trumbore, F. A. Solid solubilities of impurity elements in germanium and silicon. Bell Syst. Tech. J. 39, 205–233 (1960).

    Article  Google Scholar 

  20. Kesan, V., Iyer, S. & Cotte, J. Dopant incorporation in epitaxial germanium grown on Ge(100) substrates by MBE. J. Cryst. Growth 111, 847–855 (1991).

    Article  CAS  Google Scholar 

  21. Nath, S. K. et al. Tuning superconductivity in nanosecond laser-annealed boron-doped Si1−xGex epilayers. Phys. Status Solidi A 221, 2400313 (2024).

    Article  CAS  Google Scholar 

  22. Mönch, W. Role of virtual gap states and defects in metal-semiconductor contacts. Phys. Rev. Lett. 58, 1260 (1987).

    Article  PubMed  Google Scholar 

  23. Van de Walle, C. G. Band offsets at strained-layer interfaces. Mat. Res. Soc. Symp. Proc. 102, 565–570 (1988).

    Article  Google Scholar 

  24. Zhang, C. et al. Post-synthetic interstitial metal doping for efficient and stable 3D/2D heterostructured perovskite solar cells. Adv. Funct. Mater. 34, 2315897 (2024).

    Article  CAS  Google Scholar 

  25. Compaan, A., Contreras, G., Cardona, M. & Axmann, A. Raman scattering in ultra heavily doped Si and Ge: the dependence on free carrier and substitutional dopant densities. MRS Proc. 23, 117–122 (1983).

    Article  Google Scholar 

  26. Fournier-Lupien, J.-H. et al. Strain and composition effects on raman vibrational modes of silicon-germanium-tin ternary alloys. Appl. Phys. Lett. 103, 263103 (2013).

    Article  Google Scholar 

  27. Giustino, F. Electron-phonon interactions from first principles. Rev. Mod. Phys. 89, 015003 (2017).

    Article  Google Scholar 

  28. Allen, P. B. & Dynes, R. C. Transition temperature of strong-coupled superconductors reanalyzed. Phys. Rev. B 12, 905–922 (1975).

    Article  CAS  Google Scholar 

  29. McMillan, W. L. Transition temperature of strong-coupled superconductors. Phys. Rev. 167, 331–344 (1968).

    Article  CAS  Google Scholar 

  30. Anderson, P. W. Theory of dirty superconductors. J. Phys. Chem. Solids 11, 26–30 (1959).

    Article  CAS  Google Scholar 

  31. Steele, J. A. et al. How to GIWAXS: grazing incidence wide angle X-ray scattering applied to metal halide perovskite thin films. Adv. Energy Mater. 13, 2300760 (2023).

    Article  CAS  Google Scholar 

  32. McSkimin, H. J. & Andreatch Jr, P. Elastic moduli of germanium versus hydrostatic pressure at 25.0°C and –195.8°C. J. Appl. Phys. 34, 651–655 (1963).

    Article  Google Scholar 

  33. Vignaud, G. & Gibaud, A. REFLEX: a program for the analysis of specular X-ray and neutron reflectivity data. J. Appl. Crystallogr. 52, 201–213 (2019).

    Article  CAS  Google Scholar 

  34. Kresse, G. & Hafner, J. Ab initio molecular dynamics for liquid metals. Phys. Rev. B 47, 558(R) (1993).

    Article  Google Scholar 

  35. Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169 (1996).

    Article  CAS  Google Scholar 

  36. Giannozzi, P. et al. Advanced capabilities for materials modelling with QUANTUM ESPRESSO. J. Phys. Condens. Matter 29, 465901 (2017).

    Article  PubMed  CAS  Google Scholar 

  37. Perdew, J. P. et al. Restoring the density-gradient expansion for exchange in solids and surfaces. Phys. Rev. Lett. 100, 136406 (2008).

    Article  PubMed  Google Scholar 

  38. Karsai, F., Humer, M., Flage-Larsen, E., Blaha, P. & Kresse, G. Effects of electron-phonon coupling on absorption spectrum: edge of hexagonal boron nitride. Phys. Rev. B 98, 235205 (2018).

    Article  CAS  Google Scholar 

  39. Tran, F. & Blaha, P. Accurate band gaps of semiconductors and insulators with a semilocal exchange-correlation potential. Phys. Rev. Lett. 102, 226401 (2009).

    Article  PubMed  Google Scholar 

  40. Rödl, C. et al. Accurate electronic and optical properties of hexagonal germanium for optoelectronic applications. Phys. Rev. Mater. 3, 034602 (2019).

    Article  Google Scholar 

  41. Fadaly, E. M. T. et al. Direct-bandgap emission from hexagonal Ge and SiGe alloys. Nature 580, 205–209 (2020).

    Article  PubMed  CAS  Google Scholar 

  42. Togo, A. & Tanaka, I. First principles phonon calculations in materials science. Scr. Mater. 108, 1–5 (2015).

    Article  CAS  Google Scholar 

  43. van Setten, M. et al. The PseudoDojo: training and grading a 85 element optimized norm-conserving pseudopotential table. Comput. Phys. Commun. 226, 39–54 (2018).

    Article  Google Scholar 

  44. Kirby, N. M. et al. A low-background-intensity focusing small-angle X-ray scattering underlator beamline. J. Appl. Crystallogr. 46, 1670–1680 (2013).

    Article  CAS  Google Scholar 

  45. Ashiotis, G. et al. The fast azimuthal integration Python library: pyFAI. J. Appl. Crystallogr. 48, 510–519 (2015).

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  46. Rodríguez-Carvajal, J. Recent advances in magnetic structure determination by neutron powder diffraction. Phys. B: Condens. Matter 192, 55–69 (1993).

    Article  Google Scholar 

  47. Ravel, B. & Newville, M. ATHENA, ARTEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT. J. Synchrotron Radiat. 12, 537–541 (2005).

    Article  PubMed  CAS  Google Scholar 

  48. Strohbeen, P. J. Data for ‘superconductivity in substitutional Ga-hyperdoped Ge epitaxial thin films’. Zenodo https://doi.org/10.5281/zenodo.17065133 (2025).

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Acknowledgements

P.J.S. and J.S. acknowledge funding support from the United States Air Force Office of Scientific Research award number FA9550-21-1-0338. This work was partially supported by the Australian Research Council under the following grants: DE230100173 (J.A.S.), LP210200636 (Y.-H.C. and P.J.) and DE220101147 (C.V.). This research was undertaken on the X-ray absorption spectroscopy and the small-angle X-ray scattering/wide-angle X-ray scattering beamlines at the Australian Synchrotron, part of ANSTO. The XRR data reported in this paper were obtained at the Central Analytical Research Facility operated by Research Infrastructure (QUT). We acknowledge computational resources provided by the Australian National Computational Infrastructure and Pawsey Supercomputing Research Centre through the National Computational Merit Allocation Scheme. Electron microscopy was performed at the Center for Electron Microscopy and Analysis (CEMAS) at The Ohio State University. S.S.-R. acknowledges D. Huber for assisting with the TEM sample preparation. P.J. acknowledges fruitful discussions with R. McKenzie and B. Powell.

Author information

Author notes

  1. These authors contributed equally: Julian A. Steele, Patrick J. Strohbeen.

Authors and Affiliations

  1. School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland, Australia

    Julian A. Steele, Carla Verdi, Yi-Hsun Chen & Peter Jacobson

  2. Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Queensland, Australia

    Julian A. Steele, Ardeshir Baktash & Lianzhou Wang

  3. Center for Quantum Information Physics, New York University, New York, NY, USA

    Patrick J. Strohbeen, Alisa Danilenko, Jechiel van Dijk, Frederik H. Knudsen, Axel Leblanc, David Perconte & Javad Shabani

  4. School of Chemical Engineering, The University of Queensland, St Lucia, Queensland, Australia

    Ardeshir Baktash & Lianzhou Wang

  5. Institute for Theoretical Physics, ETH Zürich, Zürich, Switzerland

    Eugene Demler

  6. Department of Materials Science and Engineering, The Ohio State University, Columbus, OH, USA

    Salva Salmani-Rezaie

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  1. Julian A. Steele
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Contributions

Conceptualization: P.J., J.S. and E.D. Methodology: J.A.S., P.J.S., C.V. and S.S.-R. Investigation: J.A.S., P.J.S., C.V., A.B., A.D., Y.-H.C., J.v.D., F.H.K., A.L., D.P. and S.S.-R. Visualization: J.A.S. and P.J.S. Funding acquisition: J.A.S., P.J. and J.S. Project administration: J.A.S., P.J.S., P.J. and J.S. Supervision: J.A.S., P.J., J.S., E.D. and L.W. Writing—original draft: P.J., J.A.S. and P.J.S. Writing—review and editing: J.A.S., P.J.S., C.V., P.J. and J.S.

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Correspondence to Julian A. Steele, Peter Jacobson or Javad Shabani.

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Supplementary Figs. 1–19, Tables 1 and 2 and Discussion.

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Steele, J.A., Strohbeen, P.J., Verdi, C. et al. Superconductivity in substitutional Ga-hyperdoped Ge epitaxial thin films. Nat. Nanotechnol. 20, 1757–1763 (2025). https://doi.org/10.1038/s41565-025-02042-8

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