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Carrier dynamics in InP nanopillar arrays fabricated by low-damage etching
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
Department of solid state physics, Lund University.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
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2013 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 21, 212106- p.Article in journal (Refereed) Published
Abstract [en]

We present a comprehensive characterization of the optical quality of InP nanopillars (NPs) fabricated by a top down approach using micro-photoluminescence (mu-PL), time-resolved PL, and cathodoluminescence (CL). A lattice matched InGaAs layer provided beneath the 1 mu m tall NPs functions as a "detector" in CL for monitoring carrier diffusion in InP NP. Carrier feeding to the InGaAs layer indicated by a double exponential PL decay is confirmed through CL mapping. Carrier lifetimes of over 1 ns and the appreciably long diffusion lengths (400-700 nm) in the InP NPs indicate very low surface damage making them attractive for optoelectronic applications.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2013. Vol. 102, no 21, 212106- p.
Keyword [en]
Surface Recombination Velocity, Indium-Phosphide Nanowires, Wave-Guides, Superlattices, Luminescence, Spectroscopy, Passivation
National Category
Nano Technology Physical Sciences
URN: urn:nbn:se:kth:diva-117747DOI: 10.1063/1.4808447ISI: 000320620400037ScopusID: 2-s2.0-84879115969OAI: diva2:602916
Swedish Research Council, 349-2007-8664EU, FP7, Seventh Framework Programme, 248855Knut and Alice Wallenberg Foundation

QC 20130806. Updated from submitted to published.

Available from: 2013-02-04 Created: 2013-02-04 Last updated: 2013-08-06Bibliographically approved
In thesis
1. Top-down Fabrication Technologies for High Quality III-V Nanostructures
Open this publication in new window or tab >>Top-down Fabrication Technologies for High Quality III-V Nanostructures
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

III-V nanostructures have attracted substantial research effort due to their interesting physical properties and their applications in new generation of ultrafast and high efficiency nanoscale electronic and photonic components. The advances in nanofabrication methods including growth/synthesis have opened up new possibilities of realizing one dimensional (1D) nanostructures as building blocks of future nanoscale devices. For processing of semiconductor nanostructure devices, simplicity, cost effectiveness, and device efficiency are key factors. A number of methods are being pursued to fabricate high quality III-V nanopillar/nanowires, quantum dots and nano disks. Further, high optical quality nanostructures in these materials together with precise control of shapes, sizes and array geometries make them attractive for a wide range of optoelectronic/photonic devices.

This thesis work is focused on top-down approaches for fabrication of high optical quality nanostructures in III-V materials. Dense and uniform arrays of nanopillars are fabricated by dry etching using self-assembly of colloidal SiO2 particles for masking. The physico-chemistry of etching and the effect of etch-mask parameters are investigated to control the shape, aspect ratios and spatial coverage of the nanopillar arrays. The optimization of etch parameters and the utilization of erosion of etch masks is evaluated to obtain desired pillar shapes from cylindrical to conical. Using this fabrication method, high quality nanopillar arrays were realized in several InP-based and GaAs-based structures, including quantum wells and multilayer heterostructures. Optical properties of these pillars are investigated using different optical spectroscopic techniques. These nanopillars, single and in arrays, show excellent photoluminescence (PL) at room temperature and the measured PL line-widths are comparable to the as-grown wafer, indicating the high quality of the fabricated nanostructures. The substrate-free InP nanopillars have carrier life times similar to reference epitaxial layers, yet an another indicator of high material quality. InGaAs layer, beneath the pillars is shown to provide several useful functions. It effectively blocks the PL from the InP substrate, serves as a sacrificial layer for generation of free pillars, and as a “detector” in cathodoluminescence (CL) measurements. Diffusion lengths independently determined by time resolved photoluminescence (TRPL) and CL measurements are consistent, and carrier feeding to low bandgap InGaAs layer is evidenced by CL data. Total reflectivity measurements show that nanopillar arrays provide broadband antireflection making them good candidates for photovoltaic applications.  A novel post etch, sulfur-oleylamine (S-OA) based chemical process is developed to etch III-V materials with monolayer precision, in an inverse epitaxial manner along with simultaneous surface passivation. The process is applied to push the limits of top-down fabrication and InP-based high optical quality nanowires with aspect ratios more than 50, and nanostructures with new topologies (nanowire meshes and in-plane wires) are demonstrated.  The optimized process technique is used to fabricate nanopillars in InP-based multilayers (InP/InGaAsP/InP and InP/InGaAs/InP). Such multilayer nanopillars are not only attractive for broad-band absorption in solar cells, but are also ideal to generate high optical quality nanodisks of these materials. Finally, the utility of a soft stamping technique to transfer free nanopillars/wires and nanodisks onto Si substrate is demonstrated. These nanostructures transferred onto Si with controlled densities, from low to high, could provide a new route for material integration on Si.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xvi, 75 p.
III-V nanostructures, colloidal lithography, top-down fabrication, dry etching, quantum well, multilayer structures, nanowires, nanopillars, nanodisks, mono-layer etching, surface passivation, photoluminescence, carrier life time, total reflectivity, photonic crystals, nanomesh
National Category
Physical Sciences Nano Technology
urn:nbn:se:kth:diva-117766 (URN)978-91-7501-633-7 (ISBN)
Public defence
2013-02-25, Sal/Hall C1, KTH-ICT, Electrum, Isafjordsgatan 26, Kista, 10:00 (English)

QC 20130205

Available from: 2013-02-05 Created: 2013-02-04 Last updated: 2013-11-11Bibliographically approved

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