Analysis of strain-modified confinement potentials in vertically stacked InAs/GaAs quantum dot nanostructures with varying stacking period

The change in confinement potentials in InAs/GaAs quantum dot (QD) nanostructures due to the interaction of strain fields from InAs QDs has been systematically investigated as a function of vertical stacking period in the light of the 'model solid' theory of Van de Walle and Martin using the strain information obtained from finite element analysis. As the stacking period (inter-dot separation) of InAs QDs decreases, in general, the interaction of strain fields in the nanostructure increases the direct band gap in most of the QD volume while a minor volume near the apex region shows a decreased band gap. A substantially close stacking of QDs results in a type-II behaviour along the stacking direction. In the inter-dot separation regime where the influences of the minor volume in the apex region, the type-II behaviour, and quantum mechanical coupling among QDs are not significant, it is anticipated that the closer stacking of QDs would yield an increased band gap and thus increased recombination energy for blue shift in photoluminescence spectra, as experimentally observed elsewhere recently.