On the mobility of photoexcited carriers in silicon at low temperatures

The mobility of photoexcited carriers in high resistivity n-type silicon has been measured from 4.2 °K to 300 °K. Carriers excited by infra-red radiation of about 10 μm wavelength showed hot carrier effects and had a temperature-independent mobility below 10 °K. The use of visible radiation caused the neutralization of ionized impurities and under these conditions photoexcited carriers had a mobility limited by lattice scattering only. This resulted in a mobility of 1.3 × 10 6 cm 2 sec -1 v -1 at 4.2 °K.