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Creators/Authors contains: "Sooriyagoda, Rishmali"

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  1. Abstract

    A type-II InAs/AlAs$$_{0.16}$$0.16Sb$$_{0.84}$$0.84multiple-quantum well sample is investigated for the photoexcited carrier dynamics as a function of excitation photon energy and lattice temperature. Time-resolved measurements are performed using a near-infrared pump pulse, with photon energies near to and above the band gap, probed with a terahertz probe pulse. The transient terahertz absorption is characterized by a multi-rise, multi-decay function that captures long-lived decay times and a metastable state for an excess-photon energy of$$>100$$>100meV. For sufficient excess-photon energy, excitation of the metastable state is followed by a transition to the long-lived states. Excitation dependence of the long-lived states map onto a nearly-direct band gap ($$E{_g}$$Eg) density of states with an Urbach tail below$$E{_g}$$Eg. As temperature increases, the long-lived decay times increase$$<Eg, due to the increased phonon interaction of the unintentional defect states, and by phonon stabilization of the hot carriers$$>E{_g}$$>Eg. Additionally, Auger (and/or trap-assisted Auger) scattering above the onset of the plateau may also contribute to longer hot-carrier lifetimes. Meanwhile, the initial decay component shows strong dependence on excitation energy and temperature, reflecting the complicated initial transfer of energy between valence-band and defect states, indicating methods to further prolong hot carriers for technological applications.

     
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  2. null (Ed.)