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

Effect of GaAs spacer layer thickness (dGaAs) on multi-stacked InAs/GaAs quantum dots is investigated by photoluminescence (PL) and excitation wavelength (λexc) dependent pump-probe reflection spectroscopy. Dominance of light hole exciton transition in the PL spectra is observed at smaller dGaAs (<15 nm). Double maxima (ΔR/R)max1 and (ΔR/R)max2 appear in the differential reflection spectra (DRS) at intermediate λexc beyond which positive to negative reversal of the DRS is observed due to dominating effect of inter band absorption in InAs wetting layer. The λexc at which double maxima occur, and the positive to negative reversal starts is found to be dependent on dGaAs.