Ab Initio Analysis on Stability of Carbon-Hydrogen Complex in Si Crystal under Compressive Stress along [110] Direction

Abstract

We have analysed the stability of carbon (C)-hydrogen (H) complex in compressively stressed silicon (Si) single crystal with ab initio calculation. First, the relationship between tensile stress and the strain of Si crystal along [100], [110] or [111] direction was obtained. It was found that the calculated Young's modules of Si crystal agreed with experimental results within 10% difference. Next, the stable structure of C-H complex in strain-free Si crystal was investigated with calculating the total energy of several structures. It was found that the most stable structure consists of the substitutional C atom and interstitial H atom located at the nearest bond center (B) site. Binding energy of C and H atom was about 1.25 eV. Finally, we have studied the stability of C-H complex under uniaxial [110] compressive stress. Here, [110] direction is in (110) Si plane and perpendicular to (110) Si plane. Total energies were compared between complex A (C-H complex is in (110) plane) and complex B (C-H complex is in (110) plane). It was found that complex B is more stable than A from 0.25 to 15 GPa compressive stress.