Structure and charge-state-dependent instability of a hydrogen-carbon complex in silicon

We have studied the symmetry and structure of a hydrogen-carbon (H-C) complex in Si and the bonding nature of its electronic state by means of DLTS technique under uniaxial stress. Application of < 111 > and < 110 > compression stresses splitted the DLTS peak into two as ratios of 1:3 and 2:2, respectively, which were the ratios of the low-temperature peak to the high-temperature one. No splitting was observed under < 100 > stress. These results clearly indicate the trigonal symmetry of the H-C complex and the anti-bonding nature of its electronic state, and are consistent with the previously proposed model, where hydrogen occupies the bond-centered site between carbon and silicon atoms. We have studied the stability of the complex by annealing with and without reverse bias applied to the Schottky junction. The complex was unstable outside the depletion region, where it was annihilated with an activation energy of 0.7 eV, while inside it was relatively stable and the activation energy was 1.3 eV. From these results, we have concluded that the complex becomes unstable in the neutral charge state by capturing an electron from the conduction band.