Thermal-Donor-Related Isoelectronic Center in Silicon Which Can Bind up to Four Excitons

A group of photoluminescence lines recently observed in thermally treated Si was studied in detail by transient spectroscopy, excitation spectroscopy, and temperature- and excitation-density-dependent measurements. An earlier interpretation in terms of free-to-bound transitions cannot explain these results. Instead, the lines are found to be due to an inhomogeneously broadened distribution of isoelectronic centers which can bind from one to four excitons.