Photoreflectance and high excitation photoluminescence spectra have been me
asured at 10 K for In0.6Ga0.4As/GaAs double quantum dot structures with var
ious thicknesses of the GaAs separating layer. Several transitions between
split states, due to the dot-dot and wetting layer well-well interaction, h
ave been observed. The transitions have been identified using the results o
f the effective mass approximation calculations for double quantum wells an
d lens-shaped double quantum dots. The splitting energy of the quantum dot
transitions has been obtained as function of the GaAs barrier width. (C) 20
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