Single and double hole quantum dots in strained Ge/SiGe quantum wells.

Area of Science:

• Quantum Information Science
• Semiconductor Spintronics
• Materials Science

Background:

• Current spin-based qubit technologies are advancing, driving exploration of new material platforms for improved qubit control, coherence, and scalability.
• Semiconductor heterostructures offer promising avenues, with recent advances enabling the use of hole spins for quantum applications.

Purpose of the Study:

• To investigate undoped, strained Germanium/Silicon-Germanium (Ge/SiGe) quantum wells as a host for hole spin qubits.
• To demonstrate the fabrication and functionality of quantum dots and coupled quantum dots within this material system.

Main Methods:

• Fabrication of a simple, one-layer gated device structure using undoped, strained Ge/SiGe quantum wells.
• Characterization of quantum dot formation and inter-dot coupling within the fabricated devices.

Main Results:

• Successful demonstration of both single quantum dot formation and coupling between two adjacent quantum dots in the Ge/SiGe heterostructure.
• Observation of a low hole effective mass (m* ~ 0.08 m₀), significantly lower than electrons in Si/SiGe.
• The low effective mass suggests potential for enhanced tunnel couplings and favorable qubit-qubit interactions.

Conclusions:

• Undoped, strained Ge/SiGe quantum wells are a viable platform for hole spin qubits, offering low disorder and strong spin-orbit coupling.
• The demonstrated quantum dot structures and low effective mass indicate strong potential for scalable and high-performance qubit development.
• This approach aligns with industry-compatible semiconductor manufacturing, paving the way for practical quantum computing.