Electronic structure of the Ge/Si(1 0 5) hetero-interface: an ARPES and DFT study

Area of Science:

• Surface Science
• Condensed Matter Physics
• Materials Science

Background:

• The Ge/Si(105) surface is crucial for understanding strain relaxation in heteroepitaxial growth of Germanium (Ge) on Silicon (Si).
• This surface is the primary strained facet on Ge/Si(001) quantum dots, serving as a model system.

Purpose of the Study:

• To conduct a joint experimental and theoretical investigation of the electronic properties of the rebonded-step reconstructed Ge/Si(105) surface.
• To validate the rebonded-step structural model and understand surface strain relaxation mechanisms.

Main Methods:

• Utilized a vicinal surface to create a stable, single-domain Ge/Si film with large terraces and rebonded-step termination.
• Employed angle-resolved photoemission spectroscopy (ARPES) to study the electronic structure of the Ge/Si planar hetero-junction.
• Performed first-principles electronic structure calculations for theoretical validation.

Main Results:

• ARPES revealed 2D surface and film bands with energy-momentum dispersion matching the 5x4 periodicity of the system at four Ge monolayers coverage.
• Excellent agreement between experimental ARPES data and theoretical calculations confirmed the proposed rebonded-step structural model.
• Observed surface features within 1 eV below the valence band maximum, consistent with prior analyses of Ge/Si hetero-interface electronic and optical properties.

Conclusions:

• The study successfully characterized the electronic properties of the rebonded-step reconstructed Ge/Si(105) surface.
• Experimental and theoretical results validate the rebonded-step model as a key structure for strain relaxation in Ge/Si heteroepitaxy.
• Findings provide direct evidence of surface states influencing the electronic behavior of the Ge/Si hetero-interface.