Stable and metastable configurations of iron atoms in SiGe alloys

In this study the alloy effect for iron-related defects in p-type unstrained B-doped Si_1−xGe_x (0<x<0.071) bulk crystals grown by the Czochralski technique have been analysed. This effect has been studied as the defect level splitting observed by the use of high-resolution Laplace DLTS. Two configurations of iron have been compared: isolated interstitial and paired with boron. For the interstitial configuration the alloy pattern suggests that the first- and second-nearest neighbours equally influence the defect energy level. For the iron–boron pair the observed DLTS signal is due to the ionization process of iron, and thus the alloy pattern represents the siting of iron in the more dilute samples (Si_0.98Ge_0.02), while for alloy compositions containing more Ge the signal comes from the ionization of boron, and so the observed pattern represents the siting of boron.