A bistable divacancylike defect in silicon damage cascades

Abstract

Two deep level transient spectroscopy (DLTS) electron emission signatures, previously labeled E4 and E5, have been shown to be bistable with respect to minority carrier injection at room temperature. These result from two charge state transitions of the same defect. We have performed DLTS measurements as function of annealing between 350 and 680 K, using minority carrier injection after each annealing stage to make E4 and E5 visible. We show that the E4–E5 pair is associated with defect clusters which dominate after neutron or ion damage with annealing characteristics that closely parallel to those of silicon divacancies found in damage clusters. At annealing temperatures above 500 K, the E4–E5 pair ceases to be bistable and exists after anneals in thermal equilibrium. We show that the stable E4 peak appears to be the same emission signature previously labeled the L center. The transformation of the E4–E5 bistable pair into the stable L center and a stable E5 companion level occurs at the same temperature, where it has been suggested that the divacancy becomes mobile. The similarity of the annealing of the E4–E5 pair to that of the divacancy, the dependence of the density of these defects on degree of clustering, and the insensitivity to common impurities combine to suggest that the E4–E5 pair is associated with primary defects located in the defect cluster and closely related to the familiar divacancy.