Lattice parameter determination of a composition controlled Si1-x Gex layer on a Si (001) substrate using...

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• Epitaxial growth of Si(1-x)Ge(x) alloys on Si substrates is crucial for semiconductor device fabrication.
• Understanding the lattice parameters and symmetry of Si(1-x)Ge(x) is essential for predicting material properties and device performance.

Purpose of the Study:

• To determine the six lattice parameters of epitaxially grown Si(1-x)Ge(x) on a Si (001) substrate without assuming crystal symmetry.
• To investigate the relationship between germanium concentration and lattice parameters.
• To analyze the crystal symmetry and strain relaxation effects in Si(1-x)Ge(x) thin films.

Main Methods:

• Convergent-beam electron diffraction (CBED) was employed to precisely measure the lattice parameters (a, b, c, alpha, beta, gamma).
• CBED analysis was performed without prior assumptions regarding the crystal lattice symmetry.
• Ge concentrations were evaluated using the determined lattice parameters.

Main Results:

• The lattice parameter c of Si(1-x)Ge(x) was found to vary linearly with the germanium concentration.
• The crystal symmetry was observed to lower from cubic to tetragonal as germanium concentration increases.
• The study discusses the influence of strain relaxation due to specimen thinning.

Conclusions:

• The study provides accurate lattice parameter data for Si(1-x)Ge(x) alloys, essential for materials modeling.
• The observed transition to tetragonal symmetry highlights the importance of symmetry considerations in alloy characterization.
• The findings contribute to a better understanding of strain effects and composition evaluation in Si(1-x)Ge(x) epitaxial layers.