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Open Access Nano Express

Polarized photoreflectance and photoluminescence spectroscopy of InGaAs/GaAs quantum rods grown with As2 and As4 sources

Ramūnas Nedzinskas1*, Bronislovas Čechavičius1, Julius Kavaliauskas1, Vytautas Karpus1, Gintaras Valušis1, Lianhe Li2, Suraj P Khanna23 and Edmund H Linfield2

Author Affiliations

1 Optoelectronics Department, Semiconductor Physics Institute, Center for Physical Sciences and Technology, A. Goštauto 11, Vilnius, 01108, Lithuania

2 School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK

3 CSIR-National Physical Laboratory, 110012, Dr. K. S. Krishnan Marg New Delhi, India

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Nanoscale Research Letters 2012, 7:609  doi:10.1186/1556-276X-7-609

Published: 5 November 2012

Abstract

We report photoreflectance (PR) and photoluminescence (PL) investigations of the electronic and polarization properties of different aspect ratio (height/diameter) InGaAs quantum rods (QRs) embedded in InGaAs quantum wells (QWs). These nanostructures were grown by molecular beam epitaxy using As2or As4sources. The impact of the As source on the spectral and polarization features of the QR- and QW-related interband transitions was investigated and explained in terms of the carrier confinement effects caused by variation of composition contrast between the QR material and the surrounding well. Polarized PR and PL measurements reveal that the polarization has a preferential direction along the <a onClick="popup('http://www.nanoscalereslett.com/content/7/1/609/mathml/M1','MathML',630,470);return false;" target="_blank" href="http://www.nanoscalereslett.com/content/7/1/609/mathml/M1">View MathML</a> crystal axis with a large optical anisotropy of about 60% in the (001) plane for high aspect ratio (4.1:1) InGaAs QRs. As a result, in PL spectra, the transverse magnetic mode dominated <a onClick="popup('http://www.nanoscalereslett.com/content/7/1/609/mathml/M2','MathML',630,470);return false;" target="_blank" href="http://www.nanoscalereslett.com/content/7/1/609/mathml/M2">View MathML</a>-cleaved surfaces (TM[001]>TE[110]), whereas the transverse electric mode prevailed for (110)-cleaved surfaces (<a onClick="popup('http://www.nanoscalereslett.com/content/7/1/609/mathml/M3','MathML',630,470);return false;" target="_blank" href="http://www.nanoscalereslett.com/content/7/1/609/mathml/M3">View MathML</a>). This strong optical anisotropy in the (001) plane is interpreted in terms of the hole wavefunction orientation along the <a onClick="popup('http://www.nanoscalereslett.com/content/7/1/609/mathml/M4','MathML',630,470);return false;" target="_blank" href="http://www.nanoscalereslett.com/content/7/1/609/mathml/M4">View MathML</a> direction for high aspect ratio QRs.

Keywords:
InGaAs quantum rods; Optical transitions; Electronic structure; Photoreflectance; Photoluminescence; Optical anisotropy; 78.55.Cr; 78.67.Hc; 78.67.Qa