Valley splitting in a silicon quantum device platform.

Area of Science:

• Solid State Physics
• Materials Science
• Quantum Mechanics

Background:

• A buried two-dimensional electron gas (2DEG) in silicon is formed by an atomically sharp phosphorus dopant profile (a δ-layer).
• The valley splitting of the 2DEG's most occupied bands (1Γ and 2Γ) is crucial for device properties but has been difficult to measure.
• Surface Umklapp processes can obscure measurements of this valley splitting.

Purpose of the Study:

• To directly measure the valley splitting of the 1Γ and 2Γ states in a silicon δ-layer 2DEG.
• To experimentally verify theoretical calculations of the 2DEG band structure.
• To investigate the impact of suppressing surface Umklapp processes.

Main Methods:

• Utilized direct spectroscopic measurements.
• Employed Density Functional Theory (DFT) for band structure calculations.
• Suppressed undesirable surface Umklapp processes to enable measurement.

Main Results:

• Achieved good qualitative agreement between experimental measurements and DFT calculations.
• Determined a valley splitting of 132 ± 5 meV for the 2DEG states.
• Reported effective mass, occupation, and compared dispersions and Fermi surface with DFT.

Conclusions:

• Direct measurement of valley splitting in silicon δ-layer 2DEG is now possible.
• The study provides experimental validation for DFT calculations in this system.
• Understanding valley splitting is key for advancing silicon-based quantum devices.