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Nanostructuring of InP by colloidal lithography and ICP etching for photovoltaic applications
KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Semiconductor Materials, HMA (Closed 20120101).
KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Semiconductor Materials, HMA (Closed 20120101).
KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Semiconductor Materials, HMA (Closed 20120101).ORCID iD: 0000-0002-2069-2820
KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Semiconductor Materials, HMA (Closed 20120101).
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2011 (English)In: Conference Proceedings - International Conference on Indium Phosphide and Related Materials, 2011Conference paper (Refereed)
Abstract [en]

We demonstrate a simple and cost effective method to fabricate InP nanopillars using silica particles as masks for etching InP. Oxygen plasma treatment of InP surfaces before dispersion of colloidal mask particles improved surface wettability significantly and helped in uniform coverage of the particles over large areas. Pillars with varied sizes were fabricated by dispersing colloidal SiO2 with different sizes on the sample and/or by reducing size of particles after dispersion. Nanopillars with different heights and shapes from near cylindrical to conical were obtained by varying etch process parameters and by progressive erosion of colloidal SiO 2 particle (mask). Pillars with aspect ratios in excess of 15:1 have been obtained. Investigations are also made on regular close packed hexagonal structures with wide area coverage. Size reduction of colloidal particles after dispersion is used to overcome the lag effect observed in the etching of close packed structures. The demonstrated nanostructuring method is attractive for producing photonic crystals and antireflecting surfaces in solar cells.

Place, publisher, year, edition, pages
, Conference Proceedings - International Conference on Indium Phosphide and Related Materials, ISSN 10928669
Keyword [en]
Close packed; Close packed structures; Colloidal lithography; Colloidal masks; Colloidal particle; Cost-effective methods; Different heights; Different sizes; Etch process; Hexagonal structures; ICP etching; InP; Lag effects; Nano-structuring; Nanopillars; Oxygen plasma treatments; Photovoltaic applications; Silica particles; Size reductions; Surface wettability; Uniform coverage; Wide area
National Category
Nano Technology Other Physics Topics
URN: urn:nbn:se:kth:diva-104535ScopusID: 2-s2.0-84863231917ISBN: 978-3-8007-3356-9OAI: diva2:564997
Compound Semiconductor Week (CSW/IPRM), 2011 and 23rd International Conference on Indium Phosphide and Related Materials, Berlin, 22-26 May 2011

QC 20140905

Available from: 2012-11-05 Created: 2012-11-05 Last updated: 2014-09-05Bibliographically 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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