Temperature Dependence of Carrier Recombination Lifetime in Si Wafers

The temperature dependence of carrier recombination lifetime for n‐ and p‐type Si wafers is measured by the photoconductivity decay method in a temperature range between room temperature and about 90 K. The carrier lifetime of as‐polished wafers has very weak temperature dependence, while the carrier lifetime decreases steeply with decreasing temperature for oxidized wafers. For all samples, a slow component appears in the photoconductivity decay curves after an initial fast decay at temperatures below 150 K. From a numerical simulation, we conclude that the decrease in the carrier lifetime with decreasing temperature is due to recombination through shallow recombination centers with an energy level within 0.15 eV from the bandedge, and that the slow component is due to minority carrier traps with a small majority carrier capture cross section.