Elastic-relaxation-induced barrier layer thickness undulations in InP/GaAs type-II quantum well superlattice structures

Elastic-relaxation-induced barrier layer thickness fluctuations are observed for InP/GaAs type-II quantum well (QW) superlattice structures. Crystalline and interfacial quality of superlattice structures is reasonable for thick barrier layers of GaAs, and strain is easily accommodated in the GaAs barrier layers, thus confirming the pseudomorphic growth. However, for thin GaAs barrier layers, interfacial and crystalline quality of the superlattice samples is poor, because the strain between adjacent InP QW is effectively coupled. It leads to the partial relaxation of the superlattice structures without introducing either appreciable defects/dislocations or formation of three-dimensional quantum dots. On the other hand, relaxation introduces clear undulations in GaAs barrier layer thickness for the superlattice structures with relatively thicker InP QWs and thinner GaAs barrier layers. Such undulations seem to propagate up to the surface of the superlattice structures and degrade the surface morphology of the partially relaxed short-period superlattice samples.

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