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

摘要

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 ℃. 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 = σ_n/σ_p = 0.l6 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 = σ_n/σ_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 ΔE = 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.