Picosecond free-electron laser studies of Auger recombination in arsenic-rich InAs1–xSbx strained layer superlattices at 300 K

Room temperature pump-probe transmission experiments have been performed on arsenic-rich InAs/InAs1-xSbx strained layer superlattices (SLS) using a picosecond far-infrared free electron laser. With excitation frequencies well above the fundamental bandgap, near 10 µm, large excited carrier concentrations were obtained, allowing the density dependence of the recombination rate to be determined directly. The results have been interpreted in terms of an 8×8 k.p SLS energy band calculation, including the full dispersion for both k in-plane and k parallel to the growth direction. A comparison with identical measurements on epilayers of InSb, of comparable room temperature bandgap, shows that the Auger processes have been substantially suppressed in the superlattices. In the non-degenerate regime, where the Auger lifetime scales as τaug-1 = C1Ne2, a value of C1 between 10 and 100 times smaller is obtained for the SLS structures.