High lateral density and well-aligned quantum dot (QD) structures are self-formed by growing the (GaP)(1.5)(InP)(1.88) short period superlattices (SLs) on GaAs (3 1 1) A substrates. Growth sequence dependence of the QD structures is studied with scanning tunneling spectroscopy and time-resolved photoluminescence spectroscopy. The self-formed dot size for the GaP/InP SLs (GaP is the first growth) is smaller than that For the InP/GaP SLs (InP is the first growth). This difference is considered to be caused by the difference in the strain between the first layer and the substrate. Photoluminescence decay time for the QDs self-formed in the GaP/InP SLs is a little bit shorter than that in the InP/GaP SLs, which is explained by the enhancement of carrier localization due to the increase in overlapping of wave function.