Au-related deep states in the presence of extended defects in n-type silicon

Deep level transient spectroscopy has been used to study Au-related levels in epitaxial n-type Si. Au was introduced by diffusion at temperatures of 800-950°C, into two groups of specimens, containing: a) oxidation induced stacking faults (OSFs), b) dislocations. In the samples diffused at the highest temperature (950°C), the well known Au acceptor level (at Ec-0.52 eV) was observed at high concentrations. However, significant changes in the majority carrier DLTS spectrum, and related changes in the activation energy of the electron emission, were observed in samples containing dislocations, and diffused with Au at temperatures <875°C. The effect was not found in the presence of OSFs in the temperature range investigated. The behaviour of the state during low-temperature annealing experiments was also strongly dependent on the temperature of Au-diffusion, and on the kind of extended defects. The results obtained in the samples free from OSFs confirm the conclusion of Morooka et al concerning existence of `high'- and `low'-temperature gold related states. On the other hand, the results obtained in the presence of OSFs indicate their stabilizing influence on the energy position of the gold acceptor, attributed to the `high'-temperature state. Moreover, the `low'-temperature Au state was found to be unstable, i.e. could transform to another state.