Effects of growth rate variations on carrier lifetime and interface structure in InAs/GaSb superlattices

InAs/GaSb superlattice samples have been grown with variations in interface design and growth rates of InAs and GaSb. Time resolved photoluminescence measurements show no decrease in Shockley-Read-Hall carrier lifetime for samples with rougher interfaces and a rise and then decrease in lifetimes with increasing growth rate. Interface growth sequences that tend to increase the effective growth rate of the superlattice result in longer lifetimes. The peak lifetime of 82 ns occurs at a growth rate of 0.5 ml/s for both InAs and GaSb. Growth rates from 0.2 to 0.8 ml/s show similar lifetimes, while those at faster growth rates show reduced lifetimes. Transmission electron microscopy and high resolution x-ray diffraction measurements show no variation in superlattice structural quality as a function of InAs and GaSb growth rates. Comparison of photoluminescence results with GaInAsSb quaternary structures suggests that changes in lifetime are not due to changes in superlattice structure, but result from point defects in the layers.