Intraband relaxation via polaron decay in InAs self-assembled quantum dots

Three distinct channels for the decay of polarons in InAs quantum dots are identified using energy and temperature-dependent far-infrared pump-probe spectroscopy. For energies up to ∼53 meV a monotonic increase of the polaron relaxation time is observed, the polaron decay being shown to occur into two longitudinal acoustic phonons. Above this energy additional decay channels into two optical phonons are allowed, leading to the observed reduction of the decay time. We also demonstrate interlevel polaron transfer between the closely spaced p-like excited states, with measured transfer times in good agreement with calculations for an acoustic-phonon-mediated process.