Effects of charge state on stress-induced alignment and relaxation of a hydrogen-carbon complex in silicon

The local motion of hydrogen around carbon in n-type Si was studied by deep level transient spectroscopy (DLTS) under uniaxial compressive stress, combined with the technique of stress-induced alignment and subsequent relaxation. For the hydrogen-carbon (H-C) complex studied here, the hydrogen occupied the bond-centered site between silicon and carbon atoms. The H-C complex induced a donor level at 0.15 eV below the conduction band and was detected by DLTS as an electron trap. We have found that the compressive stress parallel to the C-H-Si bond raises the electronic energy of the bond. We have observed stress-induced alignment of the complex under 〈1 1 1〉 and 〈1 1 0〉 compressive stresses of 1 GPa at 250-300 K and subsequent relaxation of the alignment after removing the stress. This behavior can be understood as the motion of hydrogen under the stress from a high-energy to a low-energy bond with respect to the stress direction and the subsequent relaxation motion of hydrogen via bond-to-bond jumps in the absence of stress. By controlling the charge state of the complex with and without applying reverse bias to the Schottky junction, we have found that hydrogen moves more easily in the neutral charge state.