Change search
ReferencesLink to record
Permanent link

Direct link
Wafer-Scale Self-Organized InP Nanopillars with Controlled Orientation for Photovoltaic Devices
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.ORCID iD: 0000-0002-2069-2820
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA. Universität Stuttgart, Germany.
Aalto University.
Aalto University.
Show others and affiliations
2015 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 26, no 41, 415304Article in journal (Refereed) Published
Abstract [en]

A unique wafer-scale self-organization process for generation of InP nanopillars is demonstrated, which is based on maskless ion-beam etching (IBE) of InP developed to obtain the nanopillars, where the height, shape, and orientation of the nanopillars can be varied by controlling the processing parameters. The fabricated InP nanopillars exhibit broadband suppression of the reflectance, 'black InP,' a property useful for solar cells. The realization of a conformal p-n junction for carrier collection, in the fabricated solar cells, is achieved by a metalorganic vapor phase epitaxy (MOVPE) overgrowth step on the fabricated pillars. The conformal overgrowth retains the broadband anti-reflection property of the InP nanopillars, indicating the feasibility of this technology for solar cells. Surface passivation of the formed InP nanopillars using sulfur-oleylamine solution resulted in improved solar-cell characteristics. An open-circuit voltage of 0.71 V and an increase of 0.13 V compared to the unpassivated device were achieved.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015. Vol. 26, no 41, 415304
National Category
Nano Technology
URN: urn:nbn:se:kth:diva-155199DOI: 10.1088/0957-4484/26/41/415304ISI: 000363433700008PubMedID: 26403979ScopusID: 2-s2.0-84947475230OAI: diva2:760117
EU, FP7, Seventh Framework Programme, 248855Swedish Research Council, 349-2007-8664Swedish Research Council, 621-2014-5078

Updated from manuscript to article in journal.

QC 20160203

Available from: 2014-11-03 Created: 2014-11-03 Last updated: 2016-02-17Bibliographically approved
In thesis
1. Ensemble and Individual III-V Semiconductor Nanopillars: Optical Properties and Applications
Open this publication in new window or tab >>Ensemble and Individual III-V Semiconductor Nanopillars: Optical Properties and Applications
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Optical properties of semiconductor nanowires (NWs)/nanopillars (NPs), as individual or ensemble, have attracted significant research interest in recent years. Their potential applications range from solid-state lighting, photovoltaics, lasing and nonlinear optics to sensing and life sciences. Many of III-V NWs/NPs are particularly interesting for optoelectronic and photovoltaic applications, because of their direct band gap, high refractive index and superior electrical properties. These properties are beneficial for use in next generation solar cells by reducing the active cell thickness, while maintaining high efficiency. Furthermore, high second order nonlinearity coefficients of many III-V materials, for example GaAs and GaP, enhanced electric fields and tight confinement of optical modes make nanowaveguide geometries ideal for nonlinear effects.

The focus of this thesis is on the fabrication of III-V NPs, their optical properties and applications. Different methods for fabrication of NPs (top-down approach) are proposed. The fabricated NPs show a broadband suppression of reflectance, which is particularly an interesting feature for photovoltaic applications. The effect of the shape and geometry of GaAs NPs on their reflectance spectra is investigated and the experimental data show a very good agreement with the simulations. In order to decrease surface recombination in the fabricated GaAs NPs, a sulfur-based chemical passivation method was used, resulting in the recovery of photoluminescence (PL) linewidth and enhancing the PL intensity for more than an order of magnitude. Moreover, a unique wafer-scale self-organization process for generation of InP NPs is demonstrated. As a proof of concept, the self-organized InP NPs were used to fabricate solar cell devices. For fabrication of InP NP solar cells, epitaxial overgrowth of NPs arrays was used to realize p-n junctions. A significant increase in the open circuit voltage (0.13 V) of the NP solar cell was obtained after surface passivation.

Second-harmonic generation (SHG) was experimentally observed from GaP NP waveguides (single and in arrays) with vertical geometry. The generated second- harmonic light was analyzed with respect to the size of the NP waveguides and the corresponding effects of surface and bulk nonlinearities. In case of individual NPs, SHG was analyzed considering different modal excitations in GaP NPs. It was demonstrated that by varying the NP diameter and changing the pump polarization, it is possible to alter the field distribution of the radiated SHG light. The importance of tight confinement of the pump in the NP waveguides and consequently the longitudinal component of the electric field in this geometry is shown. A method was proposed to distinguish between surface and bulk contributions in SHG, which also addressed how to employ surface SHG to enhance the generated light. The proposed method was used to estimate the nonlinear coefficient and the effective thickness of the nonlinear region at the surface of GaP NP waveguides. Based on these findings, the corresponding nonlinear coefficient at the surface is estimated to be approximately 15 times higher, compared to the bulk. These findings, suggest that NPs/NWs (in this case GaP NPs) are potential alternatives for future nonlinear nanophotonic devices. Additionally, the SHG light from single GaP NPs are promising candidates for ultrafast light sources at nanoscopic scale, with potential applications in sensing, bio and single cell/ molecular imaging.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. xiii, 68 p.
TRITA-ICT/MAP AVH, ISSN 1653-7610 ; 2014:14
nanopillar, nanowires, nanophotonics, nanofabrication, III-V semiconductors, photovoltaics, second-harmonic generation, top-down approach, colloidal lithography, antireflection, modal dispersion, polarization, nanowaveguide, indium phosphide, gallium arsenide, gallium phosphide
National Category
Nano Technology
Research subject
urn:nbn:se:kth:diva-155205 (URN)978-91-7595-333-5 (ISBN)
Public defence
2014-11-26, Sal/hall 205, Electrum, KTH-ICT, Kista, 10:00 (English)

QC 20141104

Available from: 2014-11-04 Created: 2014-11-03 Last updated: 2014-11-04Bibliographically approved

Open Access in DiVA

references(101 kB)11 downloads
File information
File name REFERENCES01.pdfFile size 101 kBChecksum SHA-512
Type referencesMimetype application/pdf

Other links

Publisher's full textPubMedScopus

Search in DiVA

By author/editor
Sanatinia, RezaBerrier, AudreyAnand, Srinivasan
By organisation
Semiconductor Materials, HMA
In the same journal
Nano Technology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 311 hits
ReferencesLink to record
Permanent link

Direct link