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

Abstract

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

Structure–Property–Performance Relationships of Cuprous Oxide Nanostructures for Dielectric Mie Resonance-Enhanced Photocatalysis

“…Fits to the transients best match a three-exponential decay with typical values of ≈1 ps for the fast decay, ≈30 ps for the intermediate decay, and ≈1 ns for the longer decay. Multi-exponential fits are limited in information, whereas converting the transient to its rate equation by relating the decaying signal strength to instantaneous excited carrier concentration n and differentiating it with respect to time gives . − Figure d shows ∂ n ( t )/∂ t for the 43-nm smaller and 145-nm larger Cu 2 O nanospheres, along with insets of four common mechanisms for excited-state population decay (labeled as SRH, RR, AS, and TAS) that can be identified by the slope of any region in the rate equation. For both 43-nm smaller and 145-nm larger Cu 2 O nanospheres, the decay dynamics is dominated by Shockley–Reed–Hall (SRH) dynamics, where the excited-state population recombines with defects in the material and has a slope of m ≈ 1.…”

Photocarrier Recombination Dynamics in Highly Scattering Cu2O Nanocatalyst Clusters

“…Similarly, the latter involves two photocarriers of the same species, where one recombines with a trap state and the resulting energy promotes the other deeper into its band through a free-carrier absorption process . Finally, a slope of m = 3 corresponds to AS, where a photoexcited electron–hole pair recombines, promoting a third photocarrier deeper into its band . The slope guides are used to highlight the dominant mechanism in various regions of the rate curves.…”

Review of the mechanisms for the phonon bottleneck effect in III–V semiconductors and their application for efficient hot carrier solar cells

“…More comprehensive and systematic research on slowed carrier relaxation in Type-I InAs/AlAsSb had been conducted by Esmaielpour et al since 2016. 26,30,36,96 This shows a transition from hot carrier relaxation dominated by conventional phonon-mediated relaxation below 90 K to inhibited radiative recombination at elevated temperatures due to spatial separation of charge carriers, where the carrier relaxation rates were estimated based on the Q values calculated from CWPL and temperature-dependent PL. 96 The decoupling of phonon-mediated relaxation could result in PBE for hot carrier populations at higher temperature even with lower carrier density.…”

“…The carrier relaxation rate was estimated based on the Q values, where slowed electron cooling rates were observed in both SQWs due to a higher steady‐state carrier densities and reduced Auger scattering. More comprehensive and systematic research on slowed carrier relaxation in Type‐ I InAs/AlAsSb had been conducted by Esmaielpour et al since 2016 26,30,36,96 . This shows a transition from hot carrier relaxation dominated by conventional phonon‐mediated relaxation below 90 K to inhibited radiative recombination at elevated temperatures due to spatial separation of charge carriers, where the carrier relaxation rates were estimated based on the Q values calculated from CWPL and temperature‐dependent PL 96 .…”