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Fabrication of Submicrometer InP Pillars by Colloidal Lithography and Dry Etching
KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Halvledarmaterial, HMA.
KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Halvledarmaterial, HMA.
KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Halvledarmaterial, HMA.
KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Halvledarmaterial, HMA.
2010 (engelsk)Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, nr 9, s. II896-II899Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

A simple method for the fabrication of submicrometer InP pillars with large surface area coverage has been developed based on a combination of colloidal lithography and inductively coupled plasma (ICP) etching technique using Cl-2/H-2/CH4/Ar chemistry. Pillars with different sizes could be fabricated by using colloidal SiO2 particles with different sizes dispersed on the sample serving as masks. Pillars with lateral diameters as small as 60 nm and aspect ratios as high as 10: 1 have been obtained. The effects of etch parameters such as radio-frequency power, ICP power, and etching time on pillar fabrication are investigated. By a suitable choice of etch parameters and utilizing erosion of colloidal (mask) SiO2 particle during etching, the height of the pillars as well as their shape can be modified from nearly cylindrical to conical shapes. Such a control on the shape of the structures in addition to the large surface coverage could be useful for applications in photovoltaics and for the fabrication of photonic crystals. For instance, continuous grading of the refractive index can be obtained for surfaces covered with conical pillars, which can be used as antireflecting surfaces in solar cells or for light extraction in light emitting diodes.

sted, utgiver, år, opplag, sider
2010. Vol. 157, nr 9, s. II896-II899
Emneord [en]
LIGHT-EMITTING-DIODES, NATURAL LITHOGRAPHY, ARRAYS, GAAS, NANOPILLARS, EFFICIENCY, PARTICLES, NANOWIRE, CRYSTAL, MASK
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-30290DOI: 10.1149/1.3464764ISI: 000280348300044Scopus ID: 2-s2.0-77955816667OAI: oai:DiVA.org:kth-30290DiVA, id: diva2:399373
Forskningsfinansiär
Swedish Research Council
Merknad
QC 20110222Tilgjengelig fra: 2011-02-22 Laget: 2011-02-22 Sist oppdatert: 2017-12-11bibliografisk kontrollert
Inngår i avhandling
1. Top-down Fabrication Technologies for High Quality III-V Nanostructures
Åpne denne publikasjonen i ny fane eller vindu >>Top-down Fabrication Technologies for High Quality III-V Nanostructures
2013 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2013. s. xvi, 75
Emneord
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
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-117766 (URN)978-91-7501-633-7 (ISBN)
Disputas
2013-02-25, Sal/Hall C1, KTH-ICT, Electrum, Isafjordsgatan 26, Kista, 10:00 (engelsk)
Opponent
Veileder
Merknad

QC 20130205

Tilgjengelig fra: 2013-02-05 Laget: 2013-02-04 Sist oppdatert: 2013-11-11bibliografisk kontrollert

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