Radiation-induced carbon-related defects in p-type silicon

The production and removal of carbon-related defects have been investigated in 1-MeV electron-irradiated boron-doped silicon solar cells using deep level transient spectroscopy (DLTS). In Czochralski (CZ) material, the interstitial carbon defect (hole trap at E_v+0.27 eV), C_I, decays by thermal and charge injection processes. We find that irradiation by MeV electrons creates C_I while simultaneously removing it through the minority-carrier injection process. Removal of C_I correlates with significant growth in the density of a complex reportedly consisting of carbon and oxygen (hole trap at E_v+0.38 eV). Thermal annealing produces a different DLTS signal than does minority-carrier injection indicating that the carbon and oxygen complex (C+O) is at least two species. The effective cross section for minority-carrier-induced annealing of C_I is found to be 2×10^-18 cm² in these samples.