Tunable exciton relaxation in vertically coupled semiconductor InAs quantum dots

Tunable exciton relaxation rates are observed in individual vertically coupled semiconductor quantum dots (CQDs). An applied electric field is used to tune the energy difference between the spatially direct (SD) and indirect (SI) excitons in InAs CQDs. The intensity and lifetime of the SI exciton is found to vary as a result of wave-function distribution, carrier tunneling, and phonon-mediated relaxation effects. This includes a modulation of the phonon relaxation rate between the SI and SD excitons, a consequence of momentum space restrictions resulting from the structure factor of the CQD.