Low disordered, stable, and shallow germanium quantum wells: a playground for spin and hybrid quantum technology

Abstract

Buried-channel semiconductor heterostructures are an archetype material platform to fabricate gated semiconductor quantum devices. Sharp confinement potential is obtained by positioning the channel near the surface, however nearby surface states degrade the electrical properties of the starting material. In this paper we demonstrate a two-dimensional hole gas of high mobility ($5\times 10^5$ cm${}^2$/Vs) in a very shallow strained germanium channel, which is located only 22 nm below the surface. This high mobility leads to mean free paths $\approx 6\mu m$, setting new benchmarks for holes in shallow FET devices. Carriers are confined in an undoped Ge/SiGe heterostructure with reduced background contamination, sharp interfaces, and high uniformity. The top-gate of a dopant-less field effect transistor controls the carrier density in the channel. The high mobility, along with a percolation density of $1.2\times 10^{11}{\text{ cm}}^{-2}$, light effective mass (0.09 m${}_e$), and high g-factor (up to $7$) highlight the potential of undoped Ge/SiGe as a low-disorder material platform for hybrid quantum technologies.

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• Theory of Hole-Spin Qubits in Strained Germanium Quantum Dots
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• Squeezed hole spin qubits in Ge quantum dots with ultrafast gates at low power
• Operating semiconductor quantum processors with hopping spins
• Simultaneous single-qubit driving of semiconductor spin qubits at the fault-tolerant threshold
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• Recent advances in hole-spin qubits
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• Germanium wafers for strained quantum wells with low disorder
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• Hole Spin Qubits in Ge Nanowire Quantum Dots: Interplay of Orbital Magnetic Field, Strain, and Growth Direction
• Semiconductor materials stacks for quantum dot spin qubits
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• Hole spin manipulation in inhomogeneous and non-separable electric fields
• Ballistic supercurrent discretization and micrometer-long Josephson coupling in germanium
• Probing resonating valence bonds on a programmable germanium quantum simulator
• Electrical operation of planar Ge hole spin qubits in an in-plane magnetic field
• Strong hole-photon coupling in planar Ge for probing charge degree and strongly-correlated states
• Linear-in-momentum spin orbit interactions in planar Ge/GeSi heterostructures and spin qubits
• Enhanced orbital magnetic field effects in Ge hole nanowires
• Majorana zero modes in gate-defined germanium hole nanowires
• The emergent linear Rashba spin-orbit coupling offering the fast manipulation of hole-spin qubits in germanium
• Geometry of the dephasing sweet spots of spin-orbit qubits
• Majorana bound states in germanium Josephson junctions via phase control
• A quantum dot in germanium proximitized by a superconductor
• Atomic Quantum Technologies for Quantum Matter and Fundamental Physics Applications
• Electrical operation of hole spin qubits in planar MOS silicon quantum dots
• Direct microwave spectroscopy of Andreev bound states in planar Ge Josephson junctions
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• Anisotropic $g$-tensors in hole quantum dots: The role of the transverse confinement direction
• Microscopic analysis of proximity-induced superconductivity and metallization effects in superconductor-germanium hole nanowires
• Vanishing Zeeman energy in a two-dimensional hole gas
• Modular Autonomous Virtualization System for Two-Dimensional Semiconductor Quantum Dot Arrays
• Germanium-based hybrid semiconductor-superconductor topological quantum computing platforms: Disorder effects
• An upper and lower bound to the orientation-dependent linear Rashba spin-orbit coupling of two-dimensional hole gases in semiconductor quantum wells
• Assessing the potential of Ge/SiGe quantum dots as hosts for singlet-triplet qubits
• High quality CVD deposition of Ge layers for Ge/SiGe Quantum Well heterostructures
• Thin films as practical quantum materials: a status quo and beyond
• Dephasing of planar Ge hole spin qubits due to 1/$\text{f}$ charge noise
• Reducing disorder in Ge quantum wells by using thick SiGe barriers
• Superconductivity in Substitutional Ga-Hyperdoped Ge Epitaxial Thin Films
• Effects of spin-orbit coupling and in-plane Zeeman fields on the critical current in two-dimensional hole gas SNS junctions
• Non-equilibrium VLS-grown stable ST12-Ge thin film on Si substrate: A study on strain-induced band-engineering
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• Robust entangling gate for capacitively coupled few-electron singlet-triplet qubits
• Quantification of the heavy-hole--light-hole mixing in two-dimensional hole gases
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• Variability of hole spin qubits in planar Germanium
• Cancelling second order frequency shifts in Ge hole spin qubits via bichromatic control
• Role of anisotropic confining potential and elliptical driving in dynamics of a Ge hole qubit
• Dressed basis sets for the modeling of exchange interactions in double quantum dots
• Optical spin pumping in silicon
• Thermal activation of low-density Ga implanted in Ge