Temperature- and injection-dependent lifetime spectroscopy of copper-related defects in silicon

Temperature- and injection-dependent lifetime measurements have been made on single-crystal silicon wafers containing deliberately introduced Cu precipitates. Applying the Shockley-Read-Hall model to the data from p-type samples gives an accurate characterisation of these recombination centres in the form of two independent levels - one shallow centre near the conduction band, and one deep centre. These two levels provide a useful approximation to the distributed defect band that is known to exist in the upper band half by previous DLTS studies. In n-type silicon the situation is complicated by the Fermi-level shifting through the defect energy band with increasing temperature, altering the charge state of the precipitates, and therefore imparting a strong temperature dependence to the capture cross sections.