Strong luminescence from strain relaxed InGaN/GaN nanotips for highly efficient light emitters

Chang, Hsiu-Ju; Hsieh, Ya‐Ping; Chen, T. T.; Chen, Y. F.; Liang, Chi‐Te; Lin, Tai‐Yuan; Tseng, Shao-Chin; Chen, L. C.

doi:10.1364/oe.15.009357

Cited by 45 publications

(23 citation statements)

References 26 publications

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“…[3][4][5][6][7][8][9][10][11][12] The fabrication method has typically involved "top-down" patterning by etching an initially planar epitaxial structure containing InGaN/GaN QWs, although studies of directly grown nano-columnar structures have also been reported. 12 Correlations between spectroscopic results and numerical simulations of strain relaxation in the QWs were included in the reports by Yu et al 9 and Kawakami et al 10 The authors of Ref.…”

Section: Introductionmentioning

confidence: 99%

Strain relaxation in InGaN/GaN micro-pillars evidenced by high resolution cathodoluminescence hyperspectral imaging

Xie

Chen

Edwards

et al. 2012

Journal of Applied Physics

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This version is available at https://strathprints.strath.ac.uk/40400/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the A size-dependent strain relaxation and its effects on the optical properties of InGaN/GaN multiple quantum wells (QWs) in micro-pillars have been investigated through a combination of high spatial resolution cathodoluminescence (CL) hyperspectral imaging and numerical modeling. The pillars have diameters (d) ranging from 2 to 150 lm and were fabricated from a III-nitride light-emitting diode (LED) structure optimized for yellow-green emission at $560 nm. The CL mapping enables us to investigate strain relaxation in these pillars on a sub-micron scale and to confirm for the first time that a narrow ( 2 lm) edge blue-shift occurs even for the large InGaN/GaN pillars (d > 10 lm). The observed maximum blue-shift at the pillar edge exceeds 7 nm with respect to the pillar centre for the pillars with diameters in the 2-16 lm range. For the smallest pillar (d ¼ 2 lm), the total blue-shift at the edge is 17.5 nm including an 8.2 nm "global" blue-shift at the pillar centre in comparison with the unetched wafer. By using a finite element method with a boundary condition taking account of a strained GaN buffer layer which was neglected in previous simulation works, the strain distribution in the QWs of these pillars was simulated as a function of pillar diameter. The blue-shift in the QWs emission wavelength was then calculated from the strain-dependent changes in piezoelectric field, and the consequent modification of transition energy in the QWs. The simulation and experimental results agree well, confirming the necessity for considering the strained buffer layer in the strain simulation. These results provide not only significant insights into the mechanism of strain relaxation in these micro-pillars but also practical guidance for design of micro/nano LEDs.

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Section: Introductionmentioning

confidence: 99%

Strain relaxation in InGaN/GaN micro-pillars evidenced by high resolution cathodoluminescence hyperspectral imaging

Xie

Chen

Edwards

et al. 2012

Journal of Applied Physics

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“…This blue-shift may be induced by reduction of the piezoelectric field caused by strain relaxation. 42 The PL full-width-half-maximum (FWHM) is narrower for the thick buffer structure (600 nm) than for the other structures, for both AlGaN/GaN and InAlN/GaN-based heterostructures. Results from comparative analysis of the different characteristics of the RT-PL peaks of the AlGaN/ GaN and InAlN/GaN-based heterostructures are shown in Fig.…”

Section: Resultsmentioning

confidence: 98%

Comparative Structural Characterization of Thin Al0.2Ga0.8 N/GaN and In0.17Al0.83N/GaN Heterostructures Grown on Si(111), by MBE, with Variation of Buffer Thickness

Chowdhury

Borisov

Chow

et al. 2015

Journal of Elec Materi

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We report growth, by plasma-assisted molecular beam epitaxy, of thin Al 0.2 Ga 0.8 N/GaN and In 0.17 Al 0.83 N/GaN heterostructures on Si(111) substrate with three different buffer thickness (600, 400, and 200 nm). Successful growth by critical optimization of growth conditions was followed by comparative characterization of these heterostructures by use of high resolution x-ray diffraction (HRXRD), including reciprocal space mapping (RSM), room-temperature photoluminescence (RT-PL), and high resolution transmission electron microscopy (HRTEM). The effect of different buffer thickness on the threading dislocation (TD) density of a thin 1.5 nm Al 0.2 Ga 0.8 N/In 0.17 Al 0.83 N-1.25 nm GaN-1.5 nm Al 0.2 Ga 0.8 N/In 0.17 Al 0.83 N heterostructure, was also studied. Analysis revealed increasing tensile strain with decreasing buffer thickness for AlGaN-based samples; this was confirmed by the red-shift of the GaN RT-PL peak. Reduced strain in lattice-matched InAlN-based samples resulted in a blue-shift of the GaN RT-PL peak; this was indicative of better crystallographic quality than for the AlGaN/GaN samples, which was proved by XRD-FWHM and RSM results. A substantial reduction of TD density from approximately 10 10 to 10 8 cm À2 with increasing buffer thickness resulted in a smooth thin active region for both thick buffer structures whereas the latticematched InAlN/GaN-based thick buffer resulted in less effect on TD and a smooth and prominent thin active region.

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“…It can make carriers bound and reduce the capture probability of unirradiative recombination centre, luminescence efficiency has been enhanced. In general, even though InGaN/GaN MQWs has bigger dislocation density, it has higher luminescence quantum efficiency [5]. Therefore, In-composition fluctuation and phase separation are significant.…”

Section: Resultsmentioning

confidence: 99%

Influence of Rapid Thermal Annealing on the Characteristics of InGaN/GaN MQWs

et al. 2016

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Abstract. N-type InGaN/GaN multiple-quantum-wells (MQWs) were grown on sapphire substrates by metal organic chemical vapor deposition (MOCVD). The crystal quality and optical properties of samples after rapid thermal annealing (RTA) at different temperatures in a range from 400 to 800 are investigated by X-ray diffraction (XRD) and photoluminescence (PL) spectrum. The experimental results show that the peaks of InGaN, InN and In can be observed in all samples. And the results are induced by the phase separation and In-clusters. The luminescence peak of the samples annealed showed a red shift. It is caused by strain stress relaxation during the RTA process. Furthermore, some defects can be eliminated and the best annealing temperature is from 500 to 700 .

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Strong luminescence from strain relaxed InGaN/GaN nanotips for highly efficient light emitters

Cited by 45 publications

References 26 publications

Strain relaxation in InGaN/GaN micro-pillars evidenced by high resolution cathodoluminescence hyperspectral imaging

Strain relaxation in InGaN/GaN micro-pillars evidenced by high resolution cathodoluminescence hyperspectral imaging

Comparative Structural Characterization of Thin Al0.2Ga0.8 N/GaN and In0.17Al0.83N/GaN Heterostructures Grown on Si(111), by MBE, with Variation of Buffer Thickness

Influence of Rapid Thermal Annealing on the Characteristics of InGaN/GaN MQWs

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