Hot-carrier dynamics in InAs/AlAsSb multiple-quantum wells

TL;DR

This study investigates hot-carrier dynamics in InAs/AlAsSb quantum wells using time-resolved terahertz spectroscopy, revealing long-lived states, temperature effects, and potential pathways to prolong hot-carrier lifetimes for optoelectronic applications.

Contribution

It provides detailed insights into the temperature and excitation energy dependence of hot-carrier dynamics in InAs/AlAsSb quantum wells, highlighting mechanisms that extend carrier lifetimes.

Findings

Long-lived metastable states observed for excess photon energy >100 meV

Decay times increase with temperature due to phonon interactions

Initial energy transfer dynamics are highly dependent on excitation energy and temperature

Abstract

A type-II InAs/AlAs$_{0.16}$Sb$_{0.84}$ multiple-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 of for an excess-photon energy of $>100$ meV. 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 near-direct band gap ($E{_g}$) density of states with an Urbach tail below $E{_g}$. As temperature increases, the long-lived decay times increase $<E{_g}$, due to the increased phonon interaction of the unintentional defect states, and by phonon stabilization of the hot carriers $>E{_g}$. 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.