Superconductivity in Substitutional Ga-Hyperdoped Ge Epitaxial Thin Films

Julian A. Steele; Patrick J. Strohbeen; Carla Verdi; Ardeshir Baktash; Alisa Danilenko; Yi-Hsun Chen; Jechiel van Dijk; Frederik H. Knudsen; Axel Leblanc; David Perconte; Lianzhou Wang; Eugene Demler; Salva Salmani-Rezaie; Peter Jacobson; Javad Shabani

doi:10.1038/s41565-025-02042-8

arXiv · 2412.15421

Superconductivity in Substitutional Ga-Hyperdoped Ge Epitaxial Thin Films

Julian A. Steele·Patrick J. Strohbeen·Carla Verdi·Ardeshir Baktash·Alisa Danilenko·Yi-Hsun Chen·Jechiel van Dijk·Frederik H. Knudsen·Axel Leblanc·David Perconte·Lianzhou Wang·Eugene Demler·Salva Salmani-Rezaie·Peter Jacobson·Javad Shabani

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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 ($n_\textup{h} = 4.15 \times 10^{21}$~cm$^{-3}$, ~17.9\% Ga substitution) that yield superconductivity with a critical temperature of $T_{\textup{c}} = 3.5$~K and an out-of-plane critical field of 1~T at 270~mK. 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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Julian A. Steele, Patrick J. Strohbeen, Carla Verdi, Ardeshir Baktash, Alisa Danilenko, Yi-Hsun Chen, Jechiel van Dijk, Frederik H. Knudsen, Axel Leblanc, David Perconte, Lianzhou Wang, Eugene Demler, Salva Salmani-Rezaie, Peter Jacobson, Javad Shabani. 2024-12-19. Superconductivity in Substitutional Ga-Hyperdoped Ge Epitaxial Thin Films. https://doi.org/10.1038/s41565-025-02042-8

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