Carrier relaxation in GaAs v-groove quantum wires and the effects of localization

TL;DR

This study investigates carrier relaxation in GaAs/AlGaAs v-groove quantum wires, revealing inhibited relaxation at low temperatures due to localization effects and structural confinement, with implications for quantum wire optoelectronic performance.

Contribution

It provides experimental and theoretical insights into how structural confinement and localization affect carrier relaxation in GaAs v-groove quantum wires.

Findings

Inhibited inter-subband relaxation below 50 K due to localization.

Efficient relaxation occurs only above 30 K.

Measured radiative lifetimes are 340 ps and 160 ps for ground and excited states.

Abstract

Carrier relaxation processes have been investigated in GaAs/AlGaAs v-groove quantum wires (QWRs) with a large subband separation (46 meV). Signatures of inhibited carrier relaxation mechanisms are seen in temperature-dependent photoluminescence (PL) and photoluminescence-excitation (PLE) measurements; we observe strong emission from the first excited state of the QWR below ~50 K. This is attributed to reduced inter-subband relaxation via phonon scattering between localized states. Theoretical calculations and experimental results indicate that the pinch-off regions, which provide additional two-dimensional confinement for the QWR structure, have a blocking effect on relaxation mechanisms for certain structures within the v-groove. Time-resolved PL measurements show that efficient carrier relaxation from excited QWR states into the ground state, occurs only at temperatures > 30 K. Values for the low temperature radiative lifetimes of the ground- and first excited-state excitons have been obtained (340 ps and 160 ps respectively), and their corresponding localization lengths along the wire estimated.