Some aspects of emission variation in InAs quantum dots coupled with symmetric quantum wells

The photoluminescence (PL), its temperature and power dependences, as well as PL inhomogeneity and x ray diffraction (XRD) has been studied in the symmetric In0.15 Ga1-0.15 As/GaAs quantum wells with embedded InAs quantum dots (QDs) (dot-in-a-well, DWELL) with different QD densities, obtained by the variation in QD growth temperatures. It is shown that four reasons are responsible for the difference in emission intensities, PL peak positions and PL inhomogeneity in studied QD structures: (i) the high concentration of nonradiative (NR) recombination centers in the capping In0.15 Ga1-0.15 As layer at low QD growth temperatures (470 °C), (ii) the QD density and size distributions for the structures with QD grown at 490-535 °C, (iii) the high concentration of NR recombination centers in the GaAs barrier at high QD growth temperatures (535 °C), and (iv) the variation nonmonotonous of elastic strain versus QD density. XRD study confirms that with decreasing density of QDs in DWELLs from 1.1× 1011 cm-2 down to 1.3× 1010 cm-2 at the rise of QD growth temperatures the level of compressive strain in DWELLs varies nonmonotonously. The reasons of compressive strain variation and the impact of this variation on emission parameters of DWELLs have been discussed as well.