Hydrogen-induced defects in cobalt-doped n-type silicon

Five new cobalt-hydrogen-related deep levels in cobalt-doped float-zone n-type silicon are identified. The levels are formed after wet chemical etching, polishing or remote plasma hydrogenation. We correlate the levels with the injection of hydrogen into cobalt-doped silicon by deep-level transient spectroscopy (DLTS) depth profiling and capacitance-voltage analysis. Cleaving the sample, without any wet chemical treatment, gives only one DLTS level, the well known Co acceptor at E(c) - 0.38 eV. The hydrogen-cobalt complexes show different thermal stabilities. One is stable up to 470 K, but all other defects anneal out at 400 K and lead to an increase of the cobalt acceptor concentration.