Effect of InAlGaAs and GaAs Combination Barrier Thickness on the Duration of Dot Formation in Different Layers of Stacked InAs/GaAs Quantum Dot Heterostructure Grown by MBE

Multilayer stacks of quantum dots (QDs) (10 periods) with a combination barrier layer of In_0.21Al_0.21Ga_0.58As (30 Å) and GaAs (70–180 Å) are grown by solid source molecular beam epitaxy (MBE) and reflection high-energy electron diffraction (RHEED) has been used for the in situ determination of the duration of dot formation in the QD layers. The increase in the duration of dot formation in the consecutive layers of the QD heterostructure with thinner barrier is attributed to the indium migration towards the defects in the strained QD layers. A thicker GaAs layer at 590 °C overgrown on the InAlGaAs is believed to remove the unevenness of the growth front for the subsequent QD layer resulting in good vertical stacking of islands till the final layer of the multilayer heterostructures.