Determination of the minority-carrier lifetime in silicon ingots by photoconductivity relaxation measured at microwave frequencies

A new method for determining the bulk lifetime of minority carriers in single-crystal silicon ingots is proposed. A photoconductivity signal measured at a microwave frequency and normalized to its initial value is compared with the results of calculating the total number of excess charge carriers N(t)/N-st, where N-st corresponds to the quasi-steady-state photoconductance. The location of the point of intersection of the photoconductivity-relaxation curve and the dependence N(t = tau)/N-st determines the bulk lifetime tau = tau(v) . The measurements were performed on silicon ingots with different resistivities grown by crucibleless zone melting and the Czochralski method. The experimental data obtained agree well with the results of calculation. (C) 2004 MAIK "Nauka / Interperiodica".