Ultrafast measurement of nonequilibrium carrier lifetime in an In_085Ga_015As/GaAs relaxed superlattice structure

We investigate the recombination time of nonequilibrium carriers in a highly excited In(0.85)Ga(0.15)As/GaAs relaxed superlattice structure by studying the time-resolved infrared reflectivity at 10.6 microm. Using a cross-correlation infrared reflectivity technique, we have measured a carrier lifetime of 2.6 +/- 0.3 ps. Lattice mismatch between In(0.85)Ga(0.15)As and GaAs layers gives rise to misfit dislocations, which act as ultrafast recombination centers and result in a dramatic decrease of the carrier lifetime.