Light Extraction Efficiency Part A. Ray Tracing for Light Extraction Efficiency (LEE) Modeling in Nitride LEDs

Keraly, Christopher Lalau; Kuritzky, Leah Y.; Cochet, M.; Weisbuch, C.

doi:10.1007/978-94-007-5863-6_9

Cited by 14 publications

(8 citation statements)

References 32 publications

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“…The roughening improves LEE by reducing the effective refractive index of AlN 79 and results in favorable scattering geometries for light extraction. 80 Figure 3a compares the EQE as a function of current density between a UV LED on SiC substrate, as a reference (Figure 3b); a smooth TFFC UV LED before roughening (Figure 3c); and a KOH-roughened TFFC LED (Figure 3d). Direct estimate of the LEE in smooth and submicron roughened thin-film LEDs is challenging due to the wave nature of light, subwavelength structures, and coherence effects, such as interference and diffraction.…”

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confidence: 99%

“…KOH roughening of nitrogen-polar AlN exposes facets defined by {101̅1̅}, forming random hexagonal pyramids (SEM of submicron roughening is shown in the inset in Figure ; AlN pyramids diagonal length was ∼190–160 nm). The roughening improves LEE by reducing the effective refractive index of AlN and results in favorable scattering geometries for light extraction …”

mentioning

confidence: 99%

“…From photoluminescent (PL) measurements of AlGaN n-i-n structures, we estimate that removing the p-GaN layer, from the AlGaN LED structure, will increase the LEE by to 43%. To increase the LEE further, researchers might wish to find innovative ways to increase the effective contact reflectivities , in the desired UV range.…”

mentioning

confidence: 99%

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AlGaN Deep-Ultraviolet Light-Emitting Diodes Grown on SiC Substrates

SaifAddin¹,

Almogbel

Zollner³

et al. 2020

ACS Photonics

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The disinfection industry would greatly benefit from efficient, robust, high-power deep-ultraviolet light-emitting diodes (UV–C LEDs). However, the performance of UV–C AlGaN LEDs is limited by poor light-extraction efficiency (LEE) and the presence of a large density of threading dislocations. We demonstrate high power AlGaN LEDs grown on SiC with high LEE and low threading dislocation density. We employ a crack-free AlN buffer layer with low threading dislocation density and a technique to fabricate thin-film UV LEDs by removing the SiC substrate, with a highly selective SF6 etch. The LEDs (278 nm) have a turn-on voltage of 4.3 V and a CW power of 8 mW (82 mW/mm2) and external quantum efficiency (EQE) of 1.8% at 95 mA. KOH submicron roughening of the AlN surface (nitrogen-polar) and improved p-contact reflectivity are found to be effective in improving the LEE of UV light. We estimate the improved LEE by semiempirical calculations to be 33% (without encapsulation). This work establishes UV LEDs grown on SiC substrates as a viable architecture to large-area, high-brightness, and high-power UV LEDs.

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confidence: 99%

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confidence: 99%

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AlGaN Deep-Ultraviolet Light-Emitting Diodes Grown on SiC Substrates

SaifAddin¹,

Almogbel

Zollner³

et al. 2020

ACS Photonics

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“…The proposed solution is to use ray tracing method. This method is well known and used, including the bulk optics systems (Horiuchi et al 2010) and for analysis the light extraction efficiency of LEDs (Borbely and Johnson 2004;Lalau Keraly et al 2013;Zang et al 2016). The ray tracing method based on the geometrical optics allows to determine of the route travelled by the ray from the moment of launch, by using the Snell's law.…”

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confidence: 99%

Ray tracing methods in numerical analysis of double-clad microstructured optical fibre coupler

2017

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The article presents the analysis of a double-clad microstructured optical fibre (DC MOF) couplers based on the ray tracing technique. The calculations were done for couplers made of well-defined fibre structures. Such couplers can be employed in laser systems using a DC MOF as a gain medium and a side pumping method which will allow to build fully-fiberized laser systems based on active microstructured fibres.

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“…Standard raytracing is often employed to model C ex . [6][7][8][9][10][11] In our case, however, this is not fully warranted: we employ small-scale ($1 lm) surface roughness (SR) to randomize photon trajectories, [12][13][14] and ray optics do not necessarily apply in such a regime. 4,15,16 Rather, as discussed in Ref.…”

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confidence: 97%

High light extraction efficiency in bulk-GaN based volumetric violet light-emitting diodes

David

Hurni

Aldaz

et al. 2014

Applied Physics Letters

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We report on the light extraction efficiency of III-Nitride violet light-emitting diodes with a volumetric flip-chip architecture. We introduce an accurate optical model to account for light extraction. We fabricate a series of devices with varying optical configurations and fit their measured performance with our model. We show the importance of second-order optical effects like photon recycling and residual surface roughness to account for data. We conclude that our devices reach an extraction efficiency of 89%.

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Light Extraction Efficiency Part A. Ray Tracing for Light Extraction Efficiency (LEE) Modeling in Nitride LEDs

Cited by 14 publications

References 32 publications

AlGaN Deep-Ultraviolet Light-Emitting Diodes Grown on SiC Substrates

AlGaN Deep-Ultraviolet Light-Emitting Diodes Grown on SiC Substrates

Ray tracing methods in numerical analysis of double-clad microstructured optical fibre coupler

High light extraction efficiency in bulk-GaN based volumetric violet light-emitting diodes

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