Electronic structure calculations based on a density-functional approach have been performed for P, As, B, and Al subsitutional dopants near the Si(001)-oxide interface. The structures are geometrically optimized for each charge state. P and As geometries show a strong distortion when neutral, and regain tetrahedral local bonding when ionized. This geometry change creates an activation barrier for the release of the electron. Distorted neutral dopants may react with hydrogen during the forming gas interface passivation. In contrast, B and Al show tetrahedral bonding for all charge states. All four neutral dopants show substantial energy gain upon formation of dimer complexes near the interface. Neutral B is significantly more stable when bonded to two O atoms at the interface, while neutral P is more stable bonded to four Si atoms adjacent to the interface.
Journal of Applied Physics
- Pub Date:
- October 2005
- Surface states band structure electron density of states;
- Density functional theory local density approximation gradient and other corrections;
- Doping and impurity implantation in germanium and silicon