Structural and electrical properties of metal impurities at dislocations in silicon

The electrical properties of silicon materials containing dislocations are strongly affected by deep levels at or close to the dislocation core. Such deep levels are frequently thought to be due to metal impurities that are chemically bound to the dislocation core, segregated in the long-range strain field or precipitated at the dislocation. This paper summarizes recent experimental studies of the interaction of metal impurities with dislocations in silicon. Transmission electron microscopy and deep level transient spectroscopy are the main techniques to study precipitation at dislocations and binding or segregation of metal impurity atoms, respectively. Focus is drawn to precipitation of fast diffusing 3d transition metals where dislocations not only serve as nucleation sites but also establish fast growth kinetics. In addition, gold impurities in the strain field of dislocations give rise to an acceptor level with the capture kinetics of extended localized defects while the emission characteristics are hardly distinguished from those of the acceptor level of gold atoms in the undisturbed bulk. The results will be discussed in terms of possible response of the deep impurity level and the silicon bands to the dislocation strain field. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.