Lifetime-controlling recombination centers in platinum-diffused silicon

Abstract

The diffusion of Pt into Si from a silica film at temperatures between 800 and 1000 °C has been found to provide room-temperature minority-carrier lifetimes between 10 nsec and 1 μsec. Evaluation of the dependence of lifetime on ambient temperature and on majority-carrier doping concentration as well as the measurement of thermally stimulated currents indicate the presence of two recombination centers: an acceptor located 0.26 eV below the conduction band edge for n-type Si and a donor located 0.32 eV above the valence band edge for p-type Si. The concentration of electrically active Pt centers increases exponentially with increasing diffusion temperature, and is in the range 7×1013 to 7×1014 cm−3. Minority-carrier capture cross sections for the n- and p-type Si are about 1×10−14 and 6×10−15 cm2, respectively. A simple single-level Shockley-Read model incorporating these centers has been used to fit observed minority-carrier lifetime values over a wide range of temperature and to calculate the dependence of lifetime on majority-carrier doping concentration for n- and p-type Si.