Quantum-confined Stark effects in interdiffused semiconductor quantum dots

Quantum-confined Stark effect in zero-dimensional semiconductor quantum-dot (QD) has attracted considerable interest due to the potential applications in electro-optic modulation and quantum computing. Composition interdiffusion occurs easily during the high temperature epitaxial growth or ex situ annealing treatment, therefore understanding the effects of interdiffusion is essential for device design and modeling. However, relatively little attention has been devoted to a systematic study of this effect. In this paper, the effects of isotropic interdiffusion on the optical transition energy of self-assembled InAs/GaAs QD structure under an electric field have been investigated theoretically. Our three-dimensional QD calculation is based on coupled QDs with different shapes arranged periodically in a tetragonal superlattice, taking into account the finite band offset, valence-band mixing, strain, and effective mass anisotropicity. The electron and hole Hamiltonians with the interdiffusion effect are solved in the momentum space domain. Our results show that isotropic three-dimensional In-Ga interdiffusion will makes the Stark shift become more symmetry about F = 0 in asymmetric lens-shaped and pyramidal QDs, implying the reduced build-in dipole momentum. The interdiffusion also leads to enhanced Stark shift with more prominent effects to QDs that are under larger electric fields.