Germanium quantum well heterostructures have rapidly emerged as a leading platform for solid-state quantum information processing; however, material quality limits scalability, and higher structural quality, higher purity, as well as zero nuclear spin, are required. Here, we address these problems by employing the heaviest of Ge isotopes, by evaporating high-purity 76Ge radiation detector material, as utilized in fundamental neutrino particle physics experiments, to fabricate 76Ge/28Si76Ge quantum wells for quantum applications and explore the respective challenges. Specifically, we demonstrate improved results on strain-relaxed virtual Si0.2Ge0.8 substrates, forward graded from Si, with a dislocation density below 3.7⋅105 cm−2, explore nuclear spin-free solid-source molecular beam epitaxy, and demonstrate first quantum transport in 76Ge quantum wells. We demonstrate a record-level quantum well interface width of 0.3 nm by X-ray reflectivity, and quantitatively compare it to atom probe tomography and scanning transmission electron microscopy. The grown layer reveals nuclear-spin-bearing impurity concentrations below 1019 cm−3 and chemical impurity levels below 1018 cm−3, except for residual carbon attributed to the graphite crucible of the Ge source, which may reach up to 1019 cm−3. Low-temperature magneto-transport measurements yield electron mobilities of 6.1⋅104 cm2V−1s−1 at 15 mK with a carrier density of 2.2⋅1011 cm−2, indicating that residual carbon is the dominant scattering mechanism.
@article{arxiv.2603.06372,
title = {Epitaxy of strained, nuclear-spin free $^{76}$Ge quantum wells from solid source materials},
author = {Maximilian Oezkent and Chen-Hsun Lu and Lucas Becker and Sebastian Koelling and Robert H. Blick and Eloïse Rahier and Stefan Schönert and Nikolay Abrosimov and Thilo Remmele and Torsten Boeck and Georg Schwalb and Oussama Moutanabbir and Martin Albrecht and Carsten Richter and Jens Martin and Kevin-P. Gradwohl},
journal= {arXiv preprint arXiv:2603.06372},
year = {2026}
}