Enhancement of the Stark effect in coupled quantum wells for optical switching devices

Significant enhancement of the Stark effect on the electronic state and the optical dipole moments of coupled quantum wells is shown theoretically. The multiband effective mass theory (k-p), which takes into account coupling between heavy- and light-hole states of the coupled quantum wells is used. Mixing of states in the coupled quantum wells leads to the splitting of subband energy levels. An applied electric field causes repulsion between the split levels as well as the spin-splitting of the valence-subband structure. Comparison with the single quantum well shows that the optical dipole moment is substantially more reduced for the coupled quantum wells at the same electric field because of enhanced charge separation in this structure. A variational method is used to solve the exciton problem in coupled quantum wells. Calculated exciton peak positions versus electric field show very good agreement with recent experiments. Calculated exciton absorption spectra for the ground state show the quenching of the exciton peak at F=30 kV/cm at 5 K. These results may have interesting applications to low-voltage optoelectronic switching devices based on the quantum-confined Stark effect.<
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