Motion of hydrogen in silicon revealed by deep-level transient spectroscopy under uniaxial stress

We propose a method to visualize the local motion of hydrogen in Si by combining deep-level transient spectroscopy (DLTS) under uniaxial stress with the technique of stress-induced alignment and subsequent relaxation of hydrogen-related complex defects. The model defect used is a hydrogen-carbon (H-C) complex, which has a donor level at E_c-0.15 eV in Si and can be detected by DLTS as an electron trap. The splitting behavior of the DLTS peak under compressive stresses to lift the orientational degeneracy is consistent with the atomic model in which the hydrogen atom occupies the bond-centered site between silicon and carbon atoms. We have observed the stress-induced alignment of the complex under a 〈1 1 0〉 stress of 1 GPa at 250-300 K and the subsequent relaxation of stress-induced alignment after removing the stress. This behavior can be understood as the motion of hydrogen under the stress from a high-energy bond to a low-energy bond with respect to the stress direction and the subsequent relaxing motion of hydrogen via bond-to-bond jumps under no stress. By controlling the charge state of the complex with and without applying reverse bias to the Schottky junction, we have found that the hydrogen motion is greatly influenced by the charge state of the complex and hydrogen moves more easily in the neutral charge state.