[en] The model of hopping excitons in semiconductors proposed by Baranovskii et al (1998 Phys. Rev. B 58 13081) has been modified and applied to explain sharp lines observed in micro-photoluminescence (μ-PL) spectra of GaInNAs alloys and their changes with excitation power and temperature. Instead of two types of recombination centres (radiative and nonradiative centres) introduced by Baranovskii et alwe have proposed one kind of localization centre with radiative and nonradiative rates. Such a modification is justifiable due to our recent experimental observations for GaInNAs alloys and allows us to explain the fast thermal quenching of localized emission from this alloy. Our simulations clearly show that the individual sharp PL lines observed at low temperatures appear for this material due to exciton hopping between localization centres. Taking into account saturation effects and the exciton dissociation phenomenon, it has been shown that the observed changes in power- and temperature dependent μ-PL spectra can be excellently reproduced by the modified model.
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[en] In this study we apply time resolved photoluminescence and contactless electroreflectance to study the carrier collection efficiency of a GaInNAsSb/GaAs quantum well (QW). We show that the enhancement of photoluminescence from GaInNAsSb quantum wells annealed at different temperatures originates not only from (i) the improvement of the optical quality of the GaInNAsSb material (i.e., removal of point defects, which are the source of nonradiative recombination) but it is also affected by (ii) the improvement of carrier collection by the QW region. The total PL efficiency is the product of these two factors, for which the optimal annealing temperatures are found to be ∼700 °C and ∼760 °C, respectively, whereas the optimal annealing temperature for the integrated PL intensity is found to be between the two temperatures and equals ∼720 °C. We connect the variation of the carrier collection efficiency with the modification of the band bending conditions in the investigated structure due to the Fermi level shift in the GaInNAsSb layer after annealing.
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[en] Low temperature micro-photoluminescence (μ-PL) has been applied to study GaInNAs bulklike layers grown on GaAs substrates with various crystallographic orientations [(100), (111)A, (311)A, (411)A, and (511)A]. At low excitation conditions, the μ-PL spectra show sharp PL lines of ∝100-300 μeV widths. The density of these lines changes from sample to sample as well as from place to place within one sample. When the excitation power is increased, an additional smooth PL band appears at the higher-energy side. This band is located ∝30-100 meV above the band of sharp PL lines and is attributed to free exciton/carrier recombination. The sharp PL lines are attributed to the recombination of localized excitons trapped at local potential minima. These lines are not resolved in macro-PL spectra because of their high density. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
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Physica Status Solidi. C, Current Topics in Solid State Physics (Online); ISSN 1610-1642; 
; v. 8(5); p. 1655-1658
; v. 8(5); p. 1655-1658
[en] This work presents the influence of the growth parameters such as growth temperature and the gas phase composition on the material quality and nitrogen content in the triple quantum wells 3·InGaAsN/GaAs obtained by atmospheric pressure metal organic vapour phase epitaxy AP-MOVPE. The structural and optical properties of the obtained heterostructures were examined using high resolution X-Ray diffraction (HRXRD), contactless electro-reflectance spectroscopy CER, photoluminescence PL, secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM). (authors)
Source
Vajda, J. (ed.) (Institute of Nuclear and Physical Engineering, Institute of Electronics and Photonics, Faculty of Electrical Engineering and Information Technology, Slovak Univ. of Technology, Bratislava (Slovakia)); Jamnicky, I. (ed.) (Dept. of Physics,, Faculty of Electrical Engineering, University of Zilina, Zilina (Slovakia)); Institute of Nuclear and Physical Engineering, Institute of Electronics and Photonics, Faculty of Electrical Engineering and Information Technology, Slovak Univ. of Technology, Bratislava (Slovakia); Alumni Club of the Faculty of Electrical Engineering and Information Technology, Slovak University of Technology, Bratislava (Slovakia); Dept. of Physics, Faculty of Electrical Engineering, University of Zilina, Zilina (Slovakia); Slovak Physical Society, Bratislava (Slovakia); Institute of Physics, Slovak Academy of Sciences, Bratislava (Slovakia); Slovak Physical Society, Bratislava (Slovakia); Institut Francais-Slovaque, Bratislava (Slovakia). Funding organisation: Sponsors: Slovenske Elektrarne, a. s., Bratislava (Slovakia); Slovak Nuclear Society, Trnava (Slovakia); Institut Francais Slovaquie, Bratislava (Slovakia); 369 p; ISBN 978-80-227-3720-3; ; 28 May 2012; p. 125-128; APCOM 2012: 18. International Conference on Applied Physics of Condensed Matter; Strbske Pleso (Slovakia); 20-22 Jun 2012; GRANTS N N515 607539; POIG.01.01.02-00-008/08-04; WUT-S10019; SK-PL-0017-09; Also available from http://kf.elf.stuba.sk/∼apcom/apcom12/proceedings/; 6 figs., 5 refs.
; 28 May 2012; p. 125-128; APCOM 2012: 18. International Conference on Applied Physics of Condensed Matter; Strbske Pleso (Slovakia); 20-22 Jun 2012; GRANTS N N515 607539; POIG.01.01.02-00-008/08-04; WUT-S10019; SK-PL-0017-09; Also available from http://kf.elf.stuba.sk/∼apcom/apcom12/proceedings/; 6 figs., 5 refs.
[en] In this work we present detailed studies of the influence of nitrogen and antimony on the optical quality of InNAs(Sb) alloys. We employed photoluminescence, photoreflectance and positron annihilation spectroscopy to reveal the role of antimony and nitrogen on the improvement/degradation of the optical qualities of InNAs(Sb) alloys. A series of 1 μm-thick InNAs(Sb) layers with different nitrogen and antimony concentrations were grown by molecular beam epitaxy. The results of these investigations show that Sb atoms serve as a surfactant which effectively improves the optical quality of InNAsSb alloys. The influence of nitrogen on the optical quality however is not the same as to what has been reported for other dilute nitrides. We observed an improvement of the optical quality for some nitrogen contents. These issues are comprehensively examined and explained. (paper)
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[en] The influence of antimony on the optical quality of InGaN/GaN multi-quantum well (MQW) grown by metalorganic chemical vapor deposition has been investigated by means of photoluminescence and time-resolved photoluminescence for a set of samples obtained for the Sb/(In+Ga) flow ratio varying from 0% to 0.12%. It has been observed that by using proper Sb flow it is possible to improve the optical properties of InGaN/GaN MQWs; however, too large Sb flows cause their optical quality to deteriorate. The Sb-related improvement of optical properties has been observed as (i) ∼30% increase of PL intensity, (ii) reduction of temperature-induced photoluminescence quenching and (iii) elongation of PL decay time by 30%. The atomic force microscopy study and second ion mass spectrometry profiles show that optical quality improvement is connected with surfactant properties of antimony. (paper)
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[en] It is shown that localized emission from GaInNAs quantum wells (QW) is composed of sharp photoluminescence (PL) lines. Spectral position of these PL lines varies in a very broad range (∼150 meV) but the activation energy of each line is the same within the experimental uncertainty and equals ∼11 meV. This value is higher than in bulk GaInNAs (∼6 meV) and corresponds very well to electron–hole attraction in GaInNAs QW. It means that the source of these sharp PL lines are excitons localized on deep centres, which can recombine radiatively while the thermal energy is smaller than the Coulomb attraction between electrons and holes. Because of this the localized emission composing of sharp PL lines is observed at low temperatures and quenched much faster for GaInNAs layers than GaInNAs/GaAs QWs. (fast track communication)
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[en] The temperature dependence of carrier dynamics in GaNxAs1−yPy alloys has been investigated by time resolved photoluminescence. This investigation has shown that the decay time constant does not change significantly up to 100 K, and then starts to decrease rapidly above this temperature. Additionally, the decay times at the high-energy side of the spectrum decrease faster than those at the low-energy side. The effects have been explained by the interplay between carrier capture by radiative and nonradiative recombination centers. Detailed simulations show that the effect of carrier localization in the investigated materials is better described by double-scale potential fluctuations that are related to (i) distribution of localized states energy and (ii) bandgap fluctuations. In addition, it was observed that the increase in nitrogen concentration leads to a shorter decay time at room temperature, which is attributed to a larger concentration of non-radiative recombination centers. Furthermore, a post-growth annealing step leads to a longer decay time at room temperature, which is attributed to a reduction in non-radiative recombination centers. At low temperatures, the role of non-radiative centers is suppressed, and therefore the decay time does not differ significantly for samples with either different nitrogen concentrations or in both the as-grown and annealed samples
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