DLTS properties of iron defects in crystalline silicon used in solar cells

Crystalline silicon used in solar cells has been investigated using deep level transient spectroscopy (DLTS). In majority-carrier pulse sequence an interstitial iron deep level was observed. However, the investigation of this deep level peak with different filling pulsewidths shows that this level consists of two superimposed levels. The activation energies of these levels are 375 meV (F1) and 480 meV (F2). The capture cross section of the level (F1) with the lower activation energy is nearly two orders of magnitude larger than the capture cross section of defect F2. Both capture cross sections show, over a wide range, no temperature dependence indicating that nonradiative recombination mechanisms other than multiphonon emission are involved. The concentration ratio between both defects is nearly 1:2.