Electronically induced instability of a hydrogen-carbon complex in silicon and its dissociation mechanism

We studied, by deep-level transient spectroscopy (DLTS), the dissociation mechanism of a hydrogen-carbon (H-C) complex, which has a donor level at E_c - 0.15 eV and acts as an electron trap in crystalline silicon. On the basis of our results and a previously proposed atomic model of the H-C complex, in which the hydrogen atom resides inside a silicon-carbon bond, we have proposed the following dissociation mechanism. The complex is stable in the positive charge state, and to dissociate it needs a hydrogen jump with an activation energy of 1.3 eV to break the bond with carbon and silicon. The complex becomes neutral by capturing an electron from the conduction band or accepting an electron directly from the valence band under electronic excitation, and is consequently dissociated at an activation energy of 0.5 eV due to the loss of binding. Strong evidence for the existence of the negative charge state of hydrogen in crystalline silicon is also presented.