High-Resolution 128&amp;lt;tex&amp;gt;$times$&amp;lt;/tex&amp;gt;96 Nitride Microdisplay

Choi, H. W.; Jeon, Chan‐Wook; Dawson, Martin D.

doi:10.1109/led.2004.826541

Cited by 76 publications

(62 citation statements)

References 15 publications

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“…Clearly, further improvement of spatial resolution and simulation accuracy will enable a much better understanding of the mechanism of strain relaxation in the micro-GaN pillars, which is critically important to the design of novel micro/nano pixellated LED devices for a wide range of applications. 4,[16][17][18][19] This study focuses on the strain relaxation process in micro-pillars fabricated from an LED wafer optimized for emission at yellow-green wavelengths ($560 nm). These micro-pillars had a fixed height of 1.1 lm, and diameters systematically varied from 2 to 150 lm.…”

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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“…The sapphire face of the wafer was polished prior to device fabrication. Details of the fabrication sequence have been described in [3]. The 128 x 96 spherical microlens array was fabricated by the photoresist-reflow method on the polished sapphire face of the LED wafer, a schematic of which is showed in Figure 1(a).…”

Section: Methodsmentioning

confidence: 99%

“…When these arrays are formatted in a matrix-addressable configuration, they may serve as efficient micro-displays or pattern-programmable illumination sources with a high degree of scalability. We have recently demonstrated high-resolution gallium nitride based micro-displays, with up to 128 x 96 pixels emitting at the wavelengths of 470 nm (blue) and 510 nm (green) [3], and having individual element sizes of 12 x 12 µm square on a pitch of 22 µm. Further scaling of the devices will depend on further reduction of element dimension and pitch.…”

Section: Introductionmentioning

confidence: 99%

Nitride micro‐display with integrated micro‐lenses

Choi

Girkin

et al. 2005

phys. stat. sol. (c)

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We report progress in control of the emission from both parallel-addressed and matrix-addressed micro-array light-emitting diodes (micro-LEDs), using integrated micro-lenses. The integrated matrix-addressed device consists of a 128 × 96 element array with 470 nm emission, aligned to a 128 × 96 element sapphire micro-lens array. The lenses have a diameter of 12 µm, a centre height of 1.8 µm and a measured focal length of 8 µm. The root-mean-square (r.m.s.) roughness of the lenses, as measured by atomic force microscopy (AFM), is better than 3 nm, ensuring high optical quality. The integrated array enables the light emitted from the individual elements to be well-resolved

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“…With the development of advanced device processing techniques, there has been much progress in gallium nitride based microdisplay devices [1][2][3]. Our aim in contributing to such device technology is to provide compact, portable means of projecting spatiotemporal patterned photoexcitation for biomedical applications at short visbible wavelengths and the UV.…”

Section: Introductionmentioning

confidence: 99%

Integration of a matrix addressable blue/green LED array with multicore imaging fiber for spatiotemporal excitation in endoscopic biomedical applications

Xu¹,

Davitt

Dong

et al. 2008

Phys. Status Solidi (c)

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We have developed a micro‐scale endoscopic optical image projection device, integrating an InGaN MQW blue/green two‐dimensional (2D) LED array to a multicore imaging fiber. A scalable matrix addressing scheme was used for the electrical access to individual elements in the densely packed 2D‐LED array. A prototype 10×10 element array was fabricated by specialized device process flow, using deep reactive ion etching and polyimide etch‐back processes for device isolation and planarization. Individual elements of the array have been operated under cw current injection up to 3 kA/cm2, suggesting uncompromised performance and robustness of the planarized device structure. The device was butt‐coupled to a 30,000 pixel multicore image fiber to generate a spatiotemporal pattern of light at the output end of the fiber. As application demonstration, selected illumination patterns have been projected to the eye of Xenopus laevis tadpoles in studies of their developing visual system, as well as optically excitable neural cells in the brain. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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High-Resolution 128<tex>$times$</tex>96 Nitride Microdisplay

Cited by 76 publications

References 15 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

Nitride micro‐display with integrated micro‐lenses

Integration of a matrix addressable blue/green LED array with multicore imaging fiber for spatiotemporal excitation in endoscopic biomedical applications

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