Recombination activity of interstitial chromium and chromium-boron pairs in silicon

Abstract

The recombination activity of interstitial chromium (Cri) and pairs of interstitial chromium and substitutional boron (CriBs) in crystalline silicon is studied by combining temperature- and injection-dependent lifetime and deep-level transient spectroscopy measurements on intentionally chromium-contaminated n- and p-type silicon wafers. Cri as well as CriBs pairs are found to be one order of magnitude less recombination active than widely assumed. In the case of Cri, a defect energy level of EC−Et=0.24 eV, an electron capture cross section of σn=2×10−14 cm2, and a hole capture cross section of σp=4×10−15 cm2 are determined. For CriBs pairs, measurements on boron-doped p-type silicon result in Et−EV=0.28 eV, σn=5×10−15 cm2, and σp=1×10−14 cm2. Theoretical calculations using the Shockley–Read–Hall theory show that it depends crucially on the doping concentration whether Cri or CriBs is the more active recombination center. Using a calibration function calculated from the defect parameters determined in this study, lifetime changes measured before and after thermal dissociation of CriBs pairs can be used to determine the interstitial chromium concentration in boron-doped silicon.