Mechanism of boron diffusion in amorphous silicon

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Physics

Background:

• Boron (B) diffusion in silicon is crucial for semiconductor device fabrication.
• Understanding B migration in amorphous silicon (a-Si) presents unique challenges compared to crystalline silicon.
• Previous studies indicate higher B diffusivity in a-Si, but the underlying mechanisms remain unclear.

Purpose of the Study:

• To elucidate the migration mechanism of Boron (B) in amorphous silicon (a-Si) networks.
• To investigate the relationship between B concentration and B diffusivity in a-Si.
• To determine the role of dangling bonds (DB) in mediating B diffusion.

Main Methods:

• Accurate data simulations were employed to model B migration.
• The study analyzed B diffusivity as a function of B concentration.
• The influence of a-Si network relaxation on dangling bond (DB) density was assessed.

Main Results:

• Boron diffusivity in a-Si is significantly higher than in crystalline Si and exhibits transient behavior.
• B diffusivity increases with B concentration up to 2 x 10^20 B/cm^3, after which B atoms precipitate.
• Boron diffusion is indirect, mediated by dangling bonds (DB), whose density is affected by B accommodation and a-Si relaxation.
• The extracted DB diffusivity has an activation energy of 2.6 eV.

Conclusions:

• The mechanism for B migration in a-Si is mediated by dangling bonds (DB).
• Boron concentration plays a critical role in controlling B diffusivity and precipitation in a-Si.
• The findings provide crucial insights into the behavior of dopants in amorphous semiconductor materials.