IDENTIFICATION POSSIBILITY OF METALLIC IMPURITIES IN P-TYPE SILICON BY LIFETIME MEASUREMENT

The prospect of the identification of metallic impurities in p-type si licon has been studied using the photoconductive decay lifetime measur ement technique at various high excitation levels (10(11)to 1.5 x 10(1 3) photon/pulse). The excitation level dependence of the recombination lifetime shows unique characteristics for recombination centers attri buted to Al, Cr, or Fe related levels. The unambiguous identification of iron and chromium is performed by the analysis of the excitation le vel dependence curves measured before and after a low temperature (180 degrees C) thermal treatment. The calculation of the iron concentrati on in the presence of other recombination centers is discussed. Contra ry to the low excitation case the determination of iron concentration from the lifetime measured at a high excitation level requires only on e correlation constant for a wide range of resistivity.