Compensating effects of platinum in n- and p-type silicon

Abstract

Spreading resistance measurements have been used to investigate compensating effects of ion-implanted and diffused platinum in both n- and p-type silicon. The conversion resistivity-platinum concentration has been obtained by solving the charge neutrality condition, which requires a knowledge of the entropy factors associated to the ionization of the two energy levels introduced by the platinum inside the silicon bandgap. We have measured entropy factor values of 25±2 and of 2±0.3 for the donor and the acceptor level, respectively, and by using these values the silicon resistivity versus platinum concentration has been calculated for different values of the substrate dopant concentration. As the platinum acceptor level is shallower than the corresponding level introduced by gold doping, a large difference in the resistivity increase induced by the two elements in n-type silicon is expected. We will show that this large difference is however smoothed by the different values of the corresponding entropy factors.