Direct observation of electronic couplings between 1.5 μm emitting InGaAs/InGaAsP quantum dots on InP

We have estimated the vertical and lateral electronic couplings between 1.5 mu m emitting InGaAs/InGaAsP quantum dots (QDs) by the carrier lifetime dependence on energy position over the ground state photoluminescence (PL) band. The areal dot density is over 10(11)/cm(2). For a QD sample with 40 run barrier spacing, the measured carrier lifetimes are almost the same across the entire PL band, indicating the negligible lateral and vertical electronic couplings between QDs at this high dot density. However, for a QD sample with the 15 nm barrier spacing between QD layers the lifetime increases with increasing wavelength, clearly indicating the significant vertical electronic coupling between QDs.