Proton irradiation of silicon: Complete electrical characterization of the induced recombination centers

The control of minority-carrier lifetimes in n-type silicon by means of low-dose, high-energy proton irradiation at room temperature has been investigated. The irradiation-induced defects, their electrical properties, their annealing behavior, and their relevance for carrier lifetimes have been studied by deep level transient spectroscopy (DLTS) and the open-circuit voltage decay technique. Emphasis was placed on the complete electrical characterization of the dominant recombination centers induced by the proton bombardment of silicon. The energy level position within the forbidden band, the capture cross sections, and emission rates for majority and minority carriers, as well as the defect concentration were determined for each center. By means of a special recombination selective DLTS measurement mode (double-double DLTS) it was even possible to localize in the spectra the deep centers which are relevant to minority-carrier lifetimes. The results are quantitatively discussed in the framework of Shockley–Read–Hall recombination statistics with respect to the reduction of carrier lifetimes for high- and low-injection conditions in semiconductor devices. The results have been corroborated qualitatively by the correlation of the minority-carrier lifetimes in proton-irradiated devices with the concentrations of the induced recombination centers which were influenced by different temperature treatments.