Abstract
The passivation influence by ligands coverage with trioctylphosphine oxide (TOPO) and TOPO including colloidal CdSe/ZnS quantum dots (QDs) on optical properties of the semiconductor heterostructure, namely an array of InP nanowires (NWs) with InAsP nanoinsertion grown by Au-assisted molecular beam epitaxy on Si (111) substrates, was investigated. A significant dependence of the photoluminescence (PL) dynamics of the InAsP insertions on the ligand type was shown, which was associated with the changes in the excitation translation channels in the heterostructure. This change was caused by a different interaction of the ligand shells with the surface of InP NWs, which led to the formation of different interfacial low-energy states at the NW-ligand boundary, such as surface-localized antibonding orbitals and hybridized states that were energetically close to the radiating state and participate in the transfer of excitation. It was shown that the quenching of excited states associated with the capture of excitation to interfacial low-energy traps was compensated by the increasing role of the “reverse transfer” mechanism. As a result, the effectiveness of TOPO-CdSe/ZnS QDs as a novel surface passivation coating was demonstrated.
Highlights
We have investigated the influence of the ligand coverage of trioctylphosphine oxide (TOPO) and quasi-Langmuir layer of TOPO-CdSe/ZnS quantum dots (QDs) on PL dynamics of the InP/InAsP/InP
We note the role of the TOPO-CdSe/ZnS QDs layer as a novel effective surface passivation coating for NWs
The spectroscopic measurements showed that the presence of the TOPO ligand led to a hypsochromic shift of the PL maximum, an increase in the decay time, and a significant quenching of the luminescence
Summary
The optical, electrical, thermal, and mechanical properties of semiconductor nanowires (NWs) are currently being actively investigated for use in solar cells, photoemitters, detectors, nanogenerators, etc. Large band gap InP NWs containing smaller band gap InAsP insertion attracted an increasing attention due to their applications in infrared photodetection and optical communication [3,4]. InAsP can be tailored by adjusting the alloy composition and, in particular, can cover the 1.30–1.55 mkm wavelength range. The high surface-to-volume ratio of NWs makes effective surface passivation critical for device applications. Wet chemical treatments and the atomic layer deposition of Al2 O3 , AlN, TiN, GaN, and TiO2 on InP nanowires
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