Low-Temperature Recombination of Electrons and Donors inn-Type Germanium and Silicon

We give a revised calculation of the recombination cross section of a conduction electron and an ionized donor impurity in $n$-type Ge and Si at liquid-helium temperatures. The energy-band structure of Ge and Si is taken into account and we show that the polarization of the phonons, which are emitted during the recombination process, is of great importance. The calculated cross sections agree reasonably well with experiment as regards temperature dependence, although the order-of-magnitude agreement is not as good.