ABSTRACT
Recent experiment on Stark effect spectroscopy in SADs [12] has demonstrated the existence of an inverted electron-hole alignment due to the presence of gallium diffusion in InAs SADs, and established a relation between the Stark shift and the vertical electron-hole separation. The theoretical interpretation of these experimental results is based on the assumption that the applied electric field can be treated by the second-order perturbation theory, which results in a quadratical dependence of the transition energy on the applied electric field [13],
E(F) = E(0) + p F + β F2 (1)
where p is the built-in dipole moment and β measures the polarization of the electron and hole states, i.e., the quantum confined Stark effect (QCSE). While this relation is well satisfied in many quantum systems including single SADs [13], and quantum well structures
[14,15], we show in this work that it is not valid for vertically coupled SAD structures [16] where the QCSE deviates significantly from its quadratic dependence on the electric field. The reason for this anomalous QCSE is due to the three-dimensional (3D) strain field distribution in the dots and in the coupling region, which controls the localization of hole states in the respective SADs. This effect is promising for applications in optoelectronics because interband transition energies can be significantly modulated by electric fields in quantum dot lasers and other photonic devices.
