Experimental characterization and theoretical modeling of the strain effect on the evolution and interband transitions of InAs quantum dots grown on InxGa1−xAs (0.0⩽x⩽0.3) metamorphic pseudosubstrates on GaAs wafers

Experimental characterization and theoretical study of the interband transitions of self-assembled InAs quantum dots (QDs) grown on metamorphic pseudosubstrates of InxGa1−xAs (0.0⩽x⩽0.3) are reported. The effect of the varying underlying strain on the size distribution of InAs QDs and their photoluminescence emission wavelength is investigated by employing different substrate compositions. Atomic force microscopy images of the QDs show that the ratio of the height/lateral diameter of the QDs decreases with decreasing strain and the photoluminescence of the buried InAs QDs shows that the peak wavelength redshifts with increasing In mole fraction of the underlying pseudosubstrates. A theoretical model based on the Green’s function technique is used to calculate the density of states (DOS) of the QDs for the different samples based on the measured dot geometries. From the DOS, the electron and hole energy levels can be obtained, yielding the possible interband transitions. Good agreement between the model and the experimental results is obtained by allowing for Ga incorporation, from the substrate and barrier layers, into the InAs QDs and it is found that the necessary Ga mole fraction varies linearly with the Ga mole fraction in the underlying InxGa1−xAs pseudosubstrate.