Nearly intrinsic exciton lifetimes in single twin-free GaAs∕AlGaAs core-shell nanowire heterostructures

Abstract

CW and time-resolved photoluminescence measurements are used to investigate exciton recombination dynamics in GaAs∕AlGaAs heterostructure nanowires grown with a recently developed technique which minimizes twinning. A thin capping layer is deposited to eliminate the possibility of oxidation of the AlGaAs shell as a source of oxygen defects in the GaAs core. We observe exciton lifetimes of ∼1ns, comparable to high quality two-dimensional double heterostructures. These GaAs nanowires allow one to observe state filling and many-body effects resulting from the increased carrier densities accessible with pulsed laser excitation.

Carrier Lifetime and Mobility Enhancement in Nearly Defect-Free Core−Shell Nanowires Measured Using Time-Resolved Terahertz Spectroscopy

“…4 Refinements in the epitaxial growth of these nanowires are therefore essential in order for their optoelectronic and crystallographic standards to approach those of bulk material. 2,6,7 Such efforts are complicated by the fact that electrical measurements conducted on nanowires to determine charge-carrier mobility are often obscured by properties of the electrical contacts. Most contactless spectroscopic probes of nanowires to date have relied upon low-temperature photoluminescence measurements to characterize optoelectronic quality by measuring excitonic dynamics and radiative quantum efficiency.…”

“…1 However, the large surface-to-volume ratio inherent to nanowires results in the presence of surface traps offering easy access to carrier and exciton recombination pathways. 2,3 In addition, one-temperature growth techniques have been shown to cause a significant twin-defect (stacking-defect) density within the nanowires. 4 Refinements in the epitaxial growth of these nanowires are therefore essential in order for their optoelectronic and crystallographic standards to approach those of bulk material.…”

Origin of radiative recombination and manifestations of localization effects in GaAs/GaNAs core/shell nanowires

“…This NRR can be either surface-related or caused by bulk defects acting as NRR centers. The former is known to be enhanced in nanostructures due to a large surface-to-volume ratio and is particularly severe in the GaAs NWs where surface passivation by either an outer shell [32][33][34] or treatments with sulfide-based chemicals 35,36 were utilized to improve their internal quantum efficiency. On the other hand, dilute nitrides are known to suffer from NRR via defects in the bulk promoted by the presence of N. [20][21][22]37 Importance of these processes for the studied NWs was evaluated from timeresolved PL measurements.…”

Nature of heterointerfaces in GaAs/InAs and InAs/GaAs axial nanowire heterostructures

“…͓DOI: 10.1063/1.2978959͔ Semiconductor nanowires ͑NWs͒ are promising onedimensional ͑1D͒ nanostructures due to their potential applications in nanoscale electronic and optoelectronic devices. [1][2][3] These 1D nanostructures are generally induced by the vaporliquid-solid ͑VLS͒ mechanism using metallic nanoparticles such as Au. 4,5 Heterogeneous nucleation of a solid from a liquid metal is a well studied process in which the solid nucleates preferentially on the solid surface of a nucleant.…”