The Effect of Heat Treatment on the Bulk Lifetime of Excess Charge Carriers in Silicon †

Abstract

In a recent paper G. Bemski (1956) described the decrease of the bulk lifetime of excess charge carriers in silicon found when silicon samples were quenched from temperatures lower than 550°c to room temperature, and the complete or partial restoration of the original lifetime when the samples were annealed in the same range of temperatures. During recent months we have studied the effects of heat treatment of silicon in the range between room temperature and 1250°c. We found that bulk lifetime both in p- and n-type crystals made by the floating zone method and of n-type crystals made by the Czochralski technique might be increased by annealing at temperatures between about 300°c and 700°c. Annealing at temperatures higher than about 700°C decreased lifetime both in p- and n-type crystals. In ail cases the samples were relatively slowly cooled. The mechanism of these changes in lifetime is not well understood.