Germanium Quantum-Dot Array with Self-Aligned Electrodes for Quantum Electronic Devices.

Area of Science:

• Quantum Computing
• Semiconductor Physics
• Materials Science

Background:

• Semiconductor quantum dots (QDs) are crucial for scalable quantum registers, requiring precise positioning and independent electrode control.
• Existing silicon-based QD qubits are limited to milli-Kelvin temperatures and face fabrication challenges.
• Germanium (Ge) QDs offer potential for higher operating temperatures and relaxed fabrication, crucial for scaling quantum systems.

Purpose of the Study:

• To demonstrate scalable and tunable germanium (Ge) spherical quantum dots (QDs).
• To achieve self-alignment of Ge QDs with control electrodes for independent addressability.
• To explore Ge QDs for novel quantum electronic device designs operating at higher temperatures.

Main Methods:

• Utilized a combination of lithographic patterning and self-assembled growth.
• Employed thermal oxidation of poly-SiGe spacer islands on Si3N4/Si-ridges with fanout structures.
• Engineered coupling barriers of Si3N4/c-Si for electrically tunable QD coupling via self-aligned electrodes.

Main Results:

• Successfully fabricated multiple, size-tunable, spherical Ge QDs.
• Achieved controllable positioning, close coupling, and self-alignment with electrodes.
• Demonstrated electrical tunability of QD coupling barriers.

Conclusions:

• Ge spherical QDs offer unique scalability and tunability for quantum applications.
• The developed method enables precise placement of QDs, expanding design possibilities for quantum devices.
• This approach facilitates the development of Ge-based quantum systems with potential for higher operating temperatures.