The structural and optical properties of height-controlled InAs quantum dots (QDs) have been investigated by transmission electron microscopy (TEM) and photoluminescence (PL). By depositing 1.4 nm In0.15Ga0.85As and a 1 monolayer (ML) InAs layer with different periods on 3 ML InAs QDs, the height of InAs QDs was systematically controlled with similar lateral size. In TEM images, the indication of dislocations due to the large strain, which can be easily seen in large QDs, is not observed even for the QD sample with the highest aspect ratio (height/width). The PL peak position is shifted toward the longer wavelength with an increase in the aspect ratio of QDs. As the aspect ratio is increased, the full width at half maximum in PL measured at 10 K is decreased from 71 to 34 meV indicating that the inhomogeneous broadening caused by the fluctuation in QD size, especially the height, is significantly reduced.

Abstracts.We have reported steady-state and time-resolved PL studies of ZnS,Sel, epilayers grown on GaAs substrate by molecular beam epitaxy with various sulfur compositions around the lattice matching composition (0 < x < 0.12). We have investigated the PL decay dynamics of ZnS,Sel, epilayers, and found that the decay time of the ZnS,Se,, epilayer with sulfur composition closely lattice-matched with the substrate is longer than that of any other lattice-mismatched one. This is interpreted as indicatig that the crystalline defects induced by lattice mismatch with the substrate mainly act as nonradiative recombination centers and consequently reduce the PL lifetimes of the epilayers. These studies suggest that the lattice mismatch has a strong correlation with PL lifetimes of the ZnS,Sel, epilayers.