Structures of thermal double donors in silicon

Area of Science:

• Materials Science
• Solid State Physics
• Computational Chemistry

Background:

• Thermal double donors (TDDs) are electrically active defects in silicon, impacting its semiconductor properties.
• Understanding the atomic structures and formation energies of TDDs is crucial for silicon device fabrication and performance.
• Oxygen is a common impurity in silicon and is believed to be a key component of TDDs.

Purpose of the Study:

• To investigate the atomic structures and formation energies of oxygen chains as models for thermal double donors (TDDs) in silicon.
• To determine the specific configurations of TDDs and their associated energy states.
• To elucidate the relationship between oxygen cluster size and TDD stability.

Main Methods:

• Accurate total-energy calculations were employed to model oxygen chains in silicon.
• Density Functional Theory (DFT) or similar quantum mechanical methods were likely used for energy calculations.
• The study focused on calculating formation energies for various oxygen chain configurations.

Main Results:

• The first three TDDs (TDD0-TDD2) were identified as four-member rings with one or two adjacent interstitial oxygen atoms.
• These metastable TDDs form bistable negative-U systems with stable, inactive staggered structures.
• TDD3-TDD7 structures also feature four-member rings with interstitial oxygen atoms at both ends.
• Di-Y-lid core structures become energetically competitive only for oxygen clusters larger than ten atoms.

Conclusions:

• The study provides detailed structural and energetic information for TDD models based on oxygen chains.
• The findings clarify the nature of TDDs as bistable negative-U systems.
• The results offer insights into defect formation and stability in silicon, relevant for semiconductor technology.