Extended point defects in crystalline materials: Ge and Si

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Materials Science

Background:

• Understanding point defects is crucial for semiconductor properties.
• Self-interstitials significantly influence diffusion and defect dynamics in crystalline materials.

Purpose of the Study:

• To characterize the fundamental nature of self-interstitial point defects in Germanium (Ge).
• To identify and differentiate various self-interstitial structures and their impact on diffusion.

Main Methods:

• Utilizing B diffusion measurements to probe defect behavior.
• Employing computational modeling to investigate defect structures and dynamics.

Main Results:

• Identification of two distinct self-interstitial forms in Ge.
• Characterization of a complex self-interstitial with high entropy (∼30 k) at the migration saddle point, termed a "morph."
• The morph structure dominates diffusion at elevated temperatures.

Conclusions:

• The "morph" defect, existing in both self-interstitial and vacancy-like forms, is proposed as a key element in diffusion and defect dynamics.
• This finding has implications for Germanium, Silicon, and potentially numerous other crystalline solids.