Effect of Dislocations on the Minority Carrier Lifetime in Semiconductors

The density of random dislocations in germanium and silicon crystals has been measured by means of x-ray rocking curves and by etch pit counting. Data obtained by the two methods are in good agreement, and dislocation densities in the range ${10}^{4}$-${10}^{7}$/${\mathrm{cm}}^{2}$ were found. The minority carrier lifetime was shown to vary with the dislocation density, and the results could be expressed in terms of a recombination efficiency per unit length of dislocation line, ${\ensuremath{\sigma}}_{R}=\frac{1}{{N}_{D\ensuremath{\tau}}}$ (where ${N}_{D}=\mathrm{dislocation}\mathrm{density}$, $\ensuremath{\tau}=\mathrm{lifetime}$). ${\ensuremath{\sigma}}_{R}$ was found to decrease with increasing resistivity of germanium and was higher for silicon than for germanium of comparable purity.