A vertically correlated submonolayer (VCSML) InAs/GaAs quantum-dot (QD) heterostructure was studied using transmission electron microscopy, high-resolution x-ray diffraction （HRXRD) and polarization-dependent photoluminescence. The HRXRD (004) rocking curve was simulated using the Tagaki-Taupin equations. Excellent agreement between the experimental curve and the simulation is achieved assuming that indium-rich VCSML QDs are embedded in a quantum wel. (QW) with lower indium content and an observed QD coverage of 10%. In the VCSML QDs, the vertical lattice mismatch of the InAs monolayer with respect to GaAs is around 1.4%, while the lattice mismatch in the QW is negligible. The photoluminescence is transverse magnetic-polarized in the edge geometry.