Impact of interface traps on charge noise, mobility and percolation density in Ge/SiGe heterostructures

Abstract

Hole spins in Ge/SiGe heterostructure quantum dots have emerged as promising qubits for quantum computation. The strong spin-orbit coupling (SOC), characteristic of heavy-hole states in Ge, enables fast and all-electrical qubit control. However, SOC also increases the susceptibility of spin qubits to charge noise. While qubit coherence can be significantly improved by operating at sweet spots with reduced hyperfine or charge noise sensitivity, the latter ultimately limits coherence, underlining the importance of understanding and reducing charge noise at its source. In this work, we study the voltage-induced hysteresis commonly observed in SiGe-based quantum devices and show that the dominant charge fluctuators are localized at the semiconductor-oxide interface. By applying increasingly negative gate voltages to Hall bar and quantum dot devices, we investigate how the hysteretic filling of interface traps impacts transport metrics and charge noise. We find that the gate-induced accumulation and trapping of charge at the SiGe-oxide interface leads to an increased electrostatic disorder, as probed by transport measurements, as well as the activation of low-frequency relaxation dynamics, resulting in slow drifts and increased charge noise levels. Our results highlight the importance of a conservative device tuning strategy and reveal the critical role of the semiconductor-oxide interface in SiGe heterostructures for spin qubit applications.

References in corpus (15)

• Spin relaxation and decoherence of holes in quantum dots
• The Observation of Percolation-Induced 2D Metal-Insulator Transition in a Si MOSFET
• A single hole spin with enhanced coherence in natural silicon
• Heavy hole states in Germanium hut wires
• Reducing charge noise in quantum dots by using thin silicon quantum wells
• Sweet-spot operation of a germanium hole spin qubit with highly anisotropic noise sensitivity
• Germanium wafers for strained quantum wells with low disorder
• Hole spin manipulation in inhomogeneous and non-separable electric fields
• Saturation of Two Level Systems and Charge Noise in Josephson Junction Qubits
• Tunable hole spin-photon interaction based on g-matrix modulation
• Electrical control of uniformity in quantum dot devices
• Wafer-scale low-disorder 2DEG in ${}^{28}$Si/SiGe without an epitaxial Si cap
• Linear-in-momentum spin orbit interactions in planar Ge/GeSi heterostructures and spin qubits
• Classification and magic magnetic-field directions for spin-orbit-coupled double quantum dots
• Single-electron occupation in quantum dot arrays at selectable plunger gate voltage

Cited by in corpus (11)

• Exploiting epitaxial strained germanium for scaling low noise spin qubits at the micron-scale
• Direct microwave spectroscopy of Andreev bound states in planar Ge Josephson junctions
• Compromise-Free Scaling of Qubit Speed and Coherence
• A backgate for enhanced tunability of holes in planar germanium
• Impact of surface treatments on the transport properties of germanium 2DHGs
• A dressed singlet-triplet qubit in germanium
• Variability of hole spin qubits in planar Germanium
• Control of threshold voltages in Si/SiGe quantum devices via optical illumination
• Finite Length Effects and Coulomb Interaction in Ge Quantum Well-Based Josephson Junctions Probed with Microwave Spectroscopy
• Bootstrapping, autonomous testing, and initialization system for Si/Si${}_x$Ge${}_{1-x}$ multi-quantum-dot devices
• Disentangling orbital and confinement contributions to $g$-factor in Ge/SiGe hole quantum dots