Measurement of Minority Carrier Lifetime in Silicon

Abstract

This report discusses lifetime in silicon as measured by photoconductive decay and checked by a drift technique. The source of pulsed light, the presentation system, and other instrumentation is described. Limitations on the injection level and field are discussed, as well as the problems presented by trapping, barriers, and making contact to the crystal. Lifetime in excess of 1500 μsec in p-type crystals and 2500 μsec in n-type crystals has been observed at room temperature. The photoconductive decay constant (lifetime) is reported in n-type crystals from 78° to 450°K, and in p-type crystals from 160° to 450°K. Measurements on another p-type crystal permitted calculation of the surface recombination velocity (∼3500 cm/sec at 300°K after grinding or etching with CP4) between 175° and 450°K.