Cobalt related defect levels in silicon analyzed by temperature- and injection-dependent lifetime spectroscopy

Temperature- and injection-dependent lifetime spectroscopy (TIDLS) as a method to characterize point defects in silicon with several energy levels is demonstrated. An intentionally cobalt-contaminated p-type wafer was investigated by means of lifetime measurements performed at different temperatures up to 151 degrees C. Two defect energy levels were required to model the lifetime curves on basis of the Shockley-Read-Hall statistics. The detailed analysis is based on the determination of the recently introduced defect parameter solution surface (DPSS) in order to extract the underlying defect parameters. A unique solution has been found for a deep defect level located in the upper band gap half with an energy depth of E-C-E-t=0.38 +/- 0.01 eV, with a corresponding ratio of capture cross sections k=sigma(n)/sigma(p)=0.16 within the interval of uncertainty of 0.06-0.69. Additionally, a deep donor level in the lower band gap half known from the literature could be assigned to a second energy level within the DPSS analysis at E-t-E-V=0.41 +/- 0.02 eV with a corresponding ratio of capture cross sections k=sigma(n)/sigma(p)=16 +/- 3. An investigation of the temperature dependence of the capture cross section for electrons suggests that the underlying recombination process of the defect in the lower band gap half is driven by a two stage cascade capture with an activation energy of Delta E=52 +/- 2 meV. These results show that TIDLS in combination with DPSS analysis is a powerful method to characterize even multiple defect levels that are affecting carrier recombination lifetime in parallel. (c) 2007 American Institute of Physics.