RECOMBINATION LIFETIMES IN HIGH-PURITY SILICON AT LOW TEMPERATURES

Transient recombination lifetimes have been measured in high-purity, n-type, float-zone silicon from 4.2°K to room temperature. Photoconductivity decay curves and quiescent electrical conductivity values have been obtained by a microwave reflection technique which does not require electrical contacts to the sample. Experiments were performed at low injection levels on unirradiated samples and after irradiation with 30-MeV electrons. An unusual feature of the data is a pronounced increase in lifetime with decreasing temperature below 45°K, similar to a trapping effect. This variation of lifetime with temperature has been explained using the two-lifetime transient analyses of Sandiford and Wertheim. The temperature dependences of the capture cross sections are calculated and compared with the theoretical predictions of Lax and with other experimental results. © 1969 The American Institute of Physics.