Numerical analysis of transition energy shift in InAs/GaAs quantum dots induced by strain-reducing layers

The electronic structure of pyramid-like InAs/GaAs quantum dots (QDs) covered with an InGaAs strain-reducing layer is analyzed numerically, focusing on the dependence of the transition energy on the strain-reducing layer thickness. The transition energy of the QD is calculated by the effective mass approximation, taking into account the change of the strain distribution induced by the strain-reducing layer. A large transition energy redshift of more than 60 meV caused by the strain reduction in the QD is obtained, as the strain reducing layer thickness increases. Furthermore, it is found that when strain-reducing layer thickness becomes large, the transition energy redshift saturates. The calculation explains the reported experimental results correctly, which indicates that the strain reducing layer enables control of operation-wavelength over a wide range in various optical devices.