We have investigated a novel approach of introducing a combined capping of quaternary alloy (InAlGaAs) and GaAs layer for the realization of stacked quantum dots (QD) heterostructure, in which the InAlGaAs act as a surface-strain-driven phase separation alloy activated by the predeposited InAs QDs. For a heterostructure sample with thin barrier thickness, high resolution transmission electron microscopy (HRTEM) image showed the stacking of QDs only upto the 5th layer and in the upper layers the dots are missing. We presume the stoppage of dot formation is due to, the uneven surface of the InAlGaAs alloy overgrown on the InAs QDs, as a result of the local compositional deviations of the Group-III atoms. In addition, we have noted the increase in dot formation time in the subsequent QD superlattice (SL) of the sample. As the growth rate is constant (0.2ML/s), this indicate that the amount of InAs material required for the formation of the dots in subsequent layer increases with decrease in barrier thickness, which is unreported till date. The barrier thickness has been varied to see its effect on stacking of QDs.