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

Abstract

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)/Nst, where Nst corresponds to the quasi-steady-state photoconductance. The location of the point of intersection of the photoconductivity-relaxation curve and the dependence N(t=τ)/Nst determines the bulk lifetime τ=τv. 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.