The effects of buffer layers on structural defects in InSb/AlxIn1-xSb quantum wells (QWs) have been investigated using transmission electron microscopy. Buffer layers with different nucleation layer materials (InSb or AlSb) and intermediate layer structures (Al0.09In0.91Sb/InSb strained-layer superlattice or InSb interlayer) were deposited on GaAs (001) substrates prior to the growth of InSb QW structures. Among the samples studied, the one with a 1 mum AlSb nucleation layer and a 200 nm InSb interlayer yielded the lowest densities of microtwins and dislocations in the InSb QW. (C) 2004 American Vacuum Society.