The effect of doping layers position on the heterojunction sharpness in (In,Al)As/AlAs quantum dots

The effect of a doping layer placed in heterostructures with an indirect bandgap (In,Al)As/AlAs quantum dots (QDs) on the heterointerface sharpness is examined. We demonstrate that growing an n (p) doped layer below the QDs layer significantly slows down (speeds up) the exciton recombination dynamics, which are highly sensitive to the heterointerface structure in these QDs, compared to an undoped structure. Placing the doped layer above the QDs layer does not affect the exciton dynamics. The experimental results are explained by an increase (decrease) in the charged vacancy formation rate in the cation sublattice, leading to either blurring or sharpening of the QD/matrix interface, depending on the increase in electron (hole) concentration at this heterointerface. The thickness of the diffuse layer at the QD/matrix heterointerface is estimated to be from 0 to 5 lattice constants, depending on the type of doped layer and its distance from the QDs.