The effects of both surface segregation of In atoms and strain on the confinement profile of InGaAs/GaAs multi quantum wells

The InGaAs/GaAs quantum wells (QWs) have been investigated by optical measurements at different growth conditions. Growth temperature of samples with different layer thickness and nominal indium composition results in a graduation of the indium concentration (In) at the interfaces between the quantum wells and the barriers. The modification of the indium composition then distorts the potential profiles for higher temperature growth and can be attributed to In segregation effect. This leads to a blue-shift of the transition energies compared to a perfectly square quantum well. However, we also observe a clear dependence of the transition energies, inconsistent with a simple adjustment of exciton levels. Based on a theoretical model for interacting electron-hole pairs in the QWs, we obtain good agreement with experiment.