Fabrication-free assessment of microwave losses in germanium-based dielectrics and superconductors
Abstract
We present a flip-chip-based sensing scheme to measure effective microwave losses associated with target materials for quantum technologies, without requiring any device fabrication on the material under test. Using this approach, we quantify the microwave losses of a strain-engineered Ge/SiGe quantum well heterostructure and investigate losses arising from its Ge substrate and intermediate layers. The quality factors of the fabricated microwave resonators agree with the losses of dielectric materials independently extracted from flip-chip sensing measurements. We further study the superconductor platinum silicon germanide (PtSiGe) prepared by thermal reaction with a deposited Pt film, finding high microwave losses that limit the suitability of the films studied here as the sole superconductor for high-quality resonator applications. By coating Pt with Nb prior to the reaction, we observe a substantial reduction in microwave loss and a nearly three-fold enhancement of the transport critical temperature. The temperature dependence of the microwave loss is consistent with gap inhomogeneity in both superconducting films. These results identify constraints on material choices, provide design guidance for microwave circuits on planar Ge heterostructures, and demonstrate a fast-turnaround testing method for new materials for superconducting quantum circuits.
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BibTeX
@misc{lu2026fabricationfree,
title = {{Fabrication-free assessment of microwave losses in germanium-based dielectrics and superconductors}},
author = {Haoran Lu and Kushagra Aggarwal and Xiangqin Wang and Pauline Drexler and Daniel Tong and Maciej W. Olszewski and Anand Ithepalli and Lingda Kong and Debdeep Jena and Peter L. McMahon and David A. Muller and Dominique Bougeard and Valla Fatemi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.28463},
eprint = {2608.28463},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.28463},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Fabrication-free assessment of microwave losses in germanium-based dielectrics and superconductors
AU - Haoran Lu
AU - Kushagra Aggarwal
AU - Xiangqin Wang
AU - Pauline Drexler
AU - Daniel Tong
AU - Maciej W. Olszewski
AU - Anand Ithepalli
AU - Lingda Kong
AU - Debdeep Jena
AU - Peter L. McMahon
AU - David A. Muller
AU - Dominique Bougeard
AU - Valla Fatemi
PY - 2026
DA - 2026/09/25
PB - arXiv
DO - 10.48550/arxiv.2608.28463
UR - https://arxiv.org/abs/2608.28463
AB - We present a flip-chip-based sensing scheme to measure effective microwave losses associated with target materials for quantum technologies, without requiring any device fabrication on the material under test. Using this approach, we quantify the microwave losses of a strain-engineered Ge/SiGe quantum well heterostructure and investigate losses arising from its Ge substrate and intermediate layers. The quality factors of the fabricated microwave resonators agree with the losses of dielectric materials independently extracted from flip-chip sensing measurements. We further study the superconductor platinum silicon germanide (PtSiGe) prepared by thermal reaction with a deposited Pt film, finding high microwave losses that limit the suitability of the films studied here as the sole superconductor for high-quality resonator applications. By coating Pt with Nb prior to the reaction, we observe a substantial reduction in microwave loss and a nearly three-fold enhancement of the transport critical temperature. The temperature dependence of the microwave loss is consistent with gap inhomogeneity in both superconducting films. These results identify constraints on material choices, provide design guidance for microwave circuits on planar Ge heterostructures, and demonstrate a fast-turnaround testing method for new materials for superconducting quantum circuits.
ER -