Enhanced intraband transitions with strong electric-field asymmetry in stacked InAs/GaAs self-assembled quantum dots

Electronic properties and conduction intersubband optical transitions in vertically aligned double InAs/GaAs self-assembled quantum dots (SAD’s) are studied theoretically by using an eight-band strain-dependent $\mathbf{k}\cdot \mathbf{p}$ Hamiltonian. Because of the strain field extension into the barrier region between the stacked double SAD’s, the conduction-valence band mixing induces a very different composition of the basis $\mathbf{k}\cdot \mathbf{p}$ wave functions in the conduction band states from those in single dots. This effect enhances the oscillator strengths of the transitions between the ground 1s states and excited 2p states in conduction band compared with single SAD’s. We also show that the asymmetric dependence of the composition of the conduction band states on the applied longitudinal electric field would induce a strong field asymmetry of intraband transitions.