Effect of GaAs spacer layer thickness on optical properties of multi-stacked InAs/GaAs quantum dots

Effect of GaAs spacer layer thickness ($d_{\mathrm{GaAs}})$ on multi-stacked InAs/GaAs quantum dots are investigated by photoluminescence (PL) and excitation wavelength ($\lambda_{\mathrm{exc}})$ dependent pump-probe reflection spectroscopy. Dominance of light hole transition in the PL spectra is observed at smaller $d_{\mathrm{GaAs}} $(\textless 15 nm). Double maxima ($\Delta $R/R)$_{\mathrm{1}}$ and ($\Delta $R/R)$_{\mathrm{2}}$ appear in the differential reflection spectra (DRS) at intermediate $\lambda _{\mathrm{exc}}$ beyond which positive to negative reversal of the DRS is observed due to dominating effect of inter band absorption in InAs wetting layer. The $\lambda_{\mathrm{exc}}$ at which double maxima occur, and the positive to negative reversal starts is found to be dependent on $d_{\mathrm{GaAs}}$