Electrical properties of dislocations and point defects in plastically deformed silicon.

Abstract

Energy levels of defect states introduced by plastic deformation of n-type silicon have been studied by capacitance transient spectroscopy. From the observed properties of the defects, it is concluded that two different types of defects are produced. The first type is interpreted as point defects located in the vicinity of, or inside, dislocations. These deep-level defects have been analyzed in a model involving level broadening due to strain fields and/or defect interaction. The analysis gives information on thermal emission rates, capture cross sections, ionization energies, and deep-level broadenings. In addition, this analysis allows for the determination of accurate defect concentrations. From the improved concentration measurements it has been possible to determine the dependence of the repulsive potential (responsible for the unusual capture mechanism) on the filling times during the capture process. The second type of defects seems to be directly related to dislocations, but their physical properties could not be determined unambiguously. Comparison of the deep-level transient spectroscopy (DLTS) and EPR results allowed tentative identification of the different DLTS lines with particular EPR spectra, and thus conclusions about the microscopic models for different defects. The quantitative comparison of defect concentrations measured by DLTS and EPR also suggests that in strongly deformed silicon, part of the EPR lines might be broadened due to imperfections in the lattice surrounding the paramagnetic center.