Accurate determination of minority carrier- and lattice scattering-mobility in silicon from photoconductance decay

Abstract

Accurate measurements of the minority carrier- and lattice scattering-diffusion constant and mobility in float zone silicon have been determined using photoconductance decay. For the more lightly doped specimens our results indicate slightly higher mobility than published majority carrier values. This is attributed to purer samples which allow a more accurate measurement of the lattice scattering mobility. In the dopant range 1015–1017 cm−3 the results for both electrons and holes are, within experimental error, equal to the majority carrier values. Unlike other methods this technique is a very direct measurement of the diffusion constant as only the thickness and decay time of the wafer need to be determined. The method is estimated to have a one standard deviation uncertainty of 2%–4% which is comparable to the best accuracy previously obtained for majority carrier measurements.