Determining the electronic confinement of a subsurface metallic state

Area of Science:

• Solid State Physics
• Materials Science
• Quantum Computing

Background:

• Understanding dopant profiles in semiconductors is critical for nanoscale electronics.
• Silicon with phosphorus delta-layers (Si:P δ-layers) offers high conductivity and confinement, making it promising for quantum computer applications.
• Quantitative electronic profiling of these Si:P δ-layers has been a significant challenge.

Purpose of the Study:

• To quantitatively measure the electronic profile of Si:P δ-layers.
• To investigate the nature of confined orbitals within these layers.
• To provide experimental validation for theoretical models.

Main Methods:

• Resonantly enhanced photoemission spectroscopy was employed to probe the electronic structure.
• Real-space breadth of occupied states in Si:P δ-layers was determined.
• Density functional theory (DFT) calculations were used for comparison.

Main Results:

• The occupied valley-split states (1Γ and 2Γ) of Si:P δ-layers exhibit exceptional confinement.
• The electronic profile's full width at half-maximum was measured to be 0.40–0.52 nm.
• Experimental results show excellent agreement with DFT calculations.
• The confined Si 3pz orbital loses its pz-like character, explaining the large valley splitting.

Conclusions:

• Si:P δ-layers possess extremely confined electronic profiles, ideal for quantum computing.
• The observed confinement and valley splitting are well-explained by the interplay between orbital confinement and electronic structure.
• This work provides crucial quantitative data for the development of next-generation semiconductor devices.