Solid-state reaction synthesis of superconducting refractory-metal germanides for Ge/SiGe quantum devices
Abstract
Solid-phase reactions offer a route to integrate superconductors into Ge/SiGe heterostructures, but forming high-quality superconducting layers near the buried Ge quantum well remains challenging. We investigate reactions of V, Ta, and Nb with elemental Ge and with the Si0.2Ge0.8 barrier of Ge/SiGe heterostructures at processing temperatures of 365-390 ∘C. Cross-sectional electron microscopy and low-temperature electrical transport show that deposition on Ge at 390 ∘C, in which approximately 2 nm metal increments are separated by growth stops for in-situ annealing, produces reactions throughout the deposited films and superconducting transitions at approximately 0.14 K for V-Ge, 2.1 K for Ta-Ge, and 2.8 K for Nb-Ge. The Nb-Ge layer has an out-of-plane critical field of approximately 0.8 T at 2.1 K. In the heterostructure samples, intermixing is confined to regions approximately 5-12 nm thick near the metal-SiGe interface, leaving a substantial residual metal layer. Microscopy and transport together suggest that this residual film dominates the measured superconducting response. These results establish low-temperature formation of superconducting refractory-metal-Ge layers while identifying the limited interfacial reaction as the principal obstacle to extending this approach toward the buried quantum well.
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BibTeX
@misc{roelofs2026solidstate,
title = {{Solid-state reaction synthesis of superconducting refractory-metal germanides for Ge/SiGe quantum devices}},
author = {Sebastiaan R. Roelofs and Jan Cornelis Wolff and Nick van Loo and Karina L. Hudson and Giordano Scappucci and Greg P. Mazur},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.05210},
eprint = {2610.05210},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.05210},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Solid-state reaction synthesis of superconducting refractory-metal germanides for Ge/SiGe quantum devices
AU - Sebastiaan R. Roelofs
AU - Jan Cornelis Wolff
AU - Nick van Loo
AU - Karina L. Hudson
AU - Giordano Scappucci
AU - Greg P. Mazur
PY - 2026
DA - 2026/10/04
PB - arXiv
DO - 10.48550/arxiv.2610.05210
UR - https://arxiv.org/abs/2610.05210
AB - Solid-phase reactions offer a route to integrate superconductors into Ge/SiGe heterostructures, but forming high-quality superconducting layers near the buried Ge quantum well remains challenging. We investigate reactions of V, Ta, and Nb with elemental Ge and with the Si_0.2Ge_0.8 barrier of Ge/SiGe heterostructures at processing temperatures of 365-390 ^∘C. Cross-sectional electron microscopy and low-temperature electrical transport show that deposition on Ge at 390 ^∘C, in which approximately 2 nm metal increments are separated by growth stops for in-situ annealing, produces reactions throughout the deposited films and superconducting transitions at approximately 0.14 K for V-Ge, 2.1 K for Ta-Ge, and 2.8 K for Nb-Ge. The Nb-Ge layer has an out-of-plane critical field of approximately 0.8 T at 2.1 K. In the heterostructure samples, intermixing is confined to regions approximately 5-12 nm thick near the metal-SiGe interface, leaving a substantial residual metal layer. Microscopy and transport together suggest that this residual film dominates the measured superconducting response. These results establish low-temperature formation of superconducting refractory-metal-Ge layers while identifying the limited interfacial reaction as the principal obstacle to extending this approach toward the buried quantum well.
ER -