Buried unstrained germanium channels: a lattice-matched platform for quantum technology

2025/06/05 by Costa, Davide, Del Vecchio, Patrick, Hudson, Karina +6 · 4 citations
#FOS: Physical sciences #Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

paper · doi:10.48550/arxiv.2506.04724

Abstract

Ge and Si strained quantum wells have enabled the most advanced spin-qubit quantum processors, but they are deposited on defective, metamorphic SiGe substrates, which may impact device performance and scaling. Here we introduce an alternative platform, based on a heterojunction between unstrained Ge and a strained SiGe barrier, which is lattice-matched to a Ge substrate. In a structure with a 52-nm-thick strained SiGe barrier, we demonstrate a low-disorder two-dimensional hole gas with a high-mobility of 1.33×10⁵ cm²/Vs and a low percolation density of 1.4(1)×10¹⁰ cm^-2. Quantum transport measurements show that confined holes have a strong density-dependent in-plane effective mass and out-of-plane g-factor, pointing to a significant heavy-hole--light-hole mixing in agreement with theory. The expected strong spin-orbit interaction, possibility of isotopic purification, and ability to host superconducting pairing correlations make this platform appealing for fast quantum hardware and hybrid quantum systems.

Citations

• Conductance Plateaus at Quantum Hall Integer Filling Factors in Germanium Quantum Point Contacts
• Hole spin qubits in unstrained Germanium layers
• Hole-spin qubits in germanium beyond the single-particle regime
• Exploiting epitaxial strained germanium for scaling low noise spin qubits at the micron-scale
• A 300 mm foundry silicon spin qubit unit cell exceeding 99% fidelity in all operations
• Reducing disorder in Ge quantum wells by using thick SiGe barriers
• Impact of interface traps on charge noise and low-density transport properties in Ge/SiGe heterostructures
• Semiconductor spin qubits
• Materials for Silicon Quantum Dots and their Impact on Electron Spin Qubits
• High mobility SiMOSFETs fabricated in a full 300mm CMOS process
• Materials challenges and opportunities for quantum computing hardware

Cited by

• Ge hole spin control using acoustic waves
• Spin-cQED with bulk germanium spin qubits
• Electrically Tuneable Variability in Germanium Hole Spin Qubits
• Finite Length Effects and Coulomb Interaction in Ge Quantum Well-Based Josephson Junctions Probed with Microwave Spectroscopy

Related

• High Mobility SiGe/Ge 2DHG Heterostructure Quantum Wells for Semiconductor Hole Spin Qubits
• Undoped Strained Ge Quantum Well with Ultrahigh Mobility Grown by Reduce Pressure Chemical Vapor Deposition
• Reducing disorder in Ge quantum wells by using thick SiGe barriers
• Electron-hole superfluidity in strained Si/Ge type II heterojunctions
• Exploiting epitaxial strained germanium for scaling low noise spin qubits at the micron-scale