Picosecond recombination processes in lead selenide.

Picosecond recombination processes of photoexcited electron-hole plasma in PbSe are directly monitored by time-resolved pump-probe experiments in the wavelength range from 3 to 9 Mym. At temperatures T equal or smaller than 70 K, a rapid decrease of carrier density within 100 ps is found for excitation densities higher than 7 x 10high17 cmhighminus3. This behavior is due to recombination by stimulated emission, as is evident from comparative measurements of midinfrared luminescence spectra. At T is equal to 300 K, Auger recombination on a time scale of 2 ns is observed below the threshold of stimulated emission. The data for a carrier density of 3 x 10high18 cmhighminus3 give an Auger coefficient of c is approximately equal to 10highminus28 cmhigh6/s.