Indirect and direct optical transitions in In0.5Ga0.5As/GaP quantum dots

We present a study of self-assembled In0.5Ga0.5As quantum dots on GaP(001) surfaces linking growth parameters with structural, optical, and electronic properties. Quantum dot densities from 5.0 × 107 cm−2 to 1.5 × 1011 cm−2 are achieved. A ripening process during a growth interruption after In0.5Ga0.5As deposition is used to vary the quantum dot size. The main focus of this work lies on the nature of optical transitions which can be switched from low-efficient indirect to high-efficient direct ones through improved strain relief of the quantum dots by different cap layers.