Germanium wafers for strained quantum wells with low disorder

Abstract

We grow strained Ge/SiGe heterostructures by reduced-pressure chemical vapor deposition on 100 mm Ge wafers. The use of Ge wafers as substrates for epitaxy enables high-quality Ge-rich SiGe strain-relaxed buffers with a threading dislocation density of (6$\pm$1)$\times$10${}^5$ cm${}^{-2}$, nearly an order of magnitude improvement compared to control strain-relaxed buffers on Si wafers. The associated reduction in short-range scattering allows for a drastic improvement of the disorder properties of the two-dimensional hole gas, measured in several Ge/SiGe heterostructure field-effect transistors. We measure an average low percolation density of (1.22$\pm$0.03)$\times$10${}^{10}$ cm${}^{-2}$, and an average maximum mobility of (3.4$\pm$0.1)$\times$10${}^6$ cm${}^2$/Vs and quantum mobility of (8.4$\pm$0.5)$\times$10${}^4$ cm${}^2$/Vs when the hole density in the quantum well is saturated to (1.65$\pm$0.02)$\times$10${}^{11}$ cm${}^{-2}$. We anticipate immediate application of these heterostructures for next-generation, higher-performance Ge spin-qubits and their integration into larger quantum processors.

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• Strong hole-photon coupling in planar Ge for probing charge degree and strongly-correlated states
• Majorana zero modes in gate-defined germanium hole nanowires
• Exploiting epitaxial strained germanium for scaling low noise spin qubits at the micron-scale
• Electrical operation of hole spin qubits in planar MOS silicon quantum dots
• Single-electron occupation in quantum dot arrays at selectable plunger gate voltage
• Microscopic analysis of proximity-induced superconductivity and metallization effects in superconductor-germanium hole nanowires
• A two-dimensional 10-qubit array in germanium with robust and localised qubit control
• Modular Autonomous Virtualization System for Two-Dimensional Semiconductor Quantum Dot Arrays
• Germanium-based hybrid semiconductor-superconductor topological quantum computing platforms: Disorder effects
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• Interband contributions to nonlinear transport in semiconductor nanostructures
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• Cancelling second order frequency shifts in Ge hole spin qubits via bichromatic control
• Ge as an orbitronic platform: giant in-plane orbital magneto-electric effect in a 2-dimensional hole gas
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