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arXiv · 2404.19161

Conductivity Freeze-Out in Isotopically Pure Si-28 at milli-Kelvin Temperatures

Ben T. McAllister·Zijun C. Zhao·Jeremy F. Bourhill·Maxim Goryachev·Daniel Creedon·Brett C. Johnson·Michael E. Tobar
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Abstract

Silicon is a key semiconducting material for electrical devices and hybrid quantum systems where low temperatures and zero-spin isotopic purity can enhance quantum coherence. Electrical conductivity in Si is characterised by carrier freeze out at around 40 K allowing microwave transmission which is a key component for addressing spins efficiently in silicon quantum technologies. In this work, we report an additional sharp transition of the electrical conductivity in a Si-28 cylindrical cavity at around 1 Kelvin. This is observed by measuring microwave resonator Whispering Gallery Mode frequencies and Q factors with changing temperature and comparing these results with finite element models. We attribute this change to a transition from a relaxation mechanism-dominated to a resonant phonon-less absorption-dominated hopping conduction regime. Characterising this regime change represents a deeper understanding of a physical phenomenon in a material of high interest to the quantum technology and semiconductor device community and the impact of these results is discussed.

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Ben T. McAllister, Zijun C. Zhao, Jeremy F. Bourhill, Maxim Goryachev, Daniel Creedon, Brett C. Johnson, Michael E. Tobar. 2024-04-29. Conductivity Freeze-Out in Isotopically Pure Si-28 at milli-Kelvin Temperatures. https://doi.org/10.1103/physrevapplied.21.064002

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