Overcoming the 'green gap'

Pleasants, Simon

doi:10.1038/nphoton.2013.202

Cited by 27 publications

(13 citation statements)

References 1 publication

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“…However, a 70% light output power increase is observed in the L–I curve of the green LED with PHP. Different absolute values of the light output power as a function of the emission wavelength are a typical feature of InGaN-based LEDs 3738Figure 3(d) and (f) respectively show the I–V curves of the blue and green LEDs, in which the hollowed red and black squares indicate the data points for the LEDs with and without PHPs, respectively.…”

Section: Resultsmentioning

confidence: 99%

Indium gallium nitride-based ultraviolet, blue, and green light-emitting diodes functionalized with shallow periodic hole patterns

Jeong

Salas‐Montiel

Lerondel

et al. 2017

Sci Rep

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In this study, we investigated the improvement in the light output power of indium gallium nitride (InGaN)-based ultraviolet (UV), blue, and green light-emitting diodes (LEDs) by fabricating shallow periodic hole patterns (PHPs) on the LED surface through laser interference lithography and inductively coupled plasma etching. Noticeably, different enhancements were observed in the light output powers of the UV, blue, and green LEDs with negligible changes in the electrical properties in the light output power versus current and current versus voltage curves. In addition, confocal scanning electroluminescence microscopy is employed to verify the correlation between the enhancement in the light output power of the LEDs with PHPs and carrier localization of InGaN/GaN multiple quantum wells. Light propagation through the PHPs on the UV, blue, and green LEDs is simulated using a three-dimensional finite-difference time-domain method to confirm the experimental results. Finally, we suggest optimal conditions of PHPs for improving the light output power of InGaN LEDs based on the experimental and theoretical results.

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Section: Resultsmentioning

confidence: 99%

Indium gallium nitride-based ultraviolet, blue, and green light-emitting diodes functionalized with shallow periodic hole patterns

Jeong

Salas‐Montiel

Lerondel

et al. 2017

Sci Rep

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“…Various methods, including using nonpolar and semipolar orientations of III‐nitrides were proposed as solutions to these polarization‐related challenges . Removal of polarization was expected to improve the radiative efficiency, optical gain, charge transport, and potentially offer solutions to the challenging problems in III‐nitride light‐emitting diodes (LEDs) known as efficiency droop and the green gap . Nonpolar and semipolar orientations were expected to boost LED efficiency in the green spectral region by reducing the QCSE and increasing the indium incorporation efficiency .…”

Section: Introductionmentioning

confidence: 99%

“…Removal of polarization was expected to improve the radiative efficiency, optical gain, charge transport, and potentially offer solutions to the challenging problems in III‐nitride light‐emitting diodes (LEDs) known as efficiency droop and the green gap . Nonpolar and semipolar orientations were expected to boost LED efficiency in the green spectral region by reducing the QCSE and increasing the indium incorporation efficiency . In addition, anisotropic in‐plane biaxial strain in nonpolar and semipolar orientations lifts the valence band degeneracy and enables polarized light emission and anisotropic optical gain .…”

Section: Introductionmentioning

confidence: 99%

A Decade of Nonpolar and Semipolar III-Nitrides: A Review of Successes and Challenges

Monavarian

Rashidi

Feezell

2018

Phys. Status Solidi A

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The performance of III-nitride devices is degraded by polarization in a wurtzite crystal structure. Nonpolar and semipolar III-nitrides have been extensively studied since the early 2000s as a solution to the polarizationrelated issues. Removal of polarization is expected to improve the radiative efficiency, optical gain, charge transport, and potentially offer solutions to the challenging problems in III-nitride light-emitting diodes (LEDs) known as efficiency droop and the green gap. In addition, use of nonpolar and semipolar orientations is also predicted to offer polarization pinning in some devices due to anisotropic in-plane strain. Despite the many potential advantages over c-plane, nonpolar and semipolar optoelectronic devices have not successfully replaced conventional c-plane devices in the commercial sector. Here, nonpolar and semipolar III-nitrides are reviewed after more than a decade of development. The successes and challenges of nonpolar and semipolar orientations for applications such as LEDs, laser diodes, superluminescent diodes, and vertical-cavity surface emitting lasers are discussed. New potential avenues for nonpolar and semipolar III-nitrides are also highlighted, including visible-light communication and power electronics. The availability of low-cost, high-crystal-quality substrates with nonpolar or semipolar orientation is discussed and alternative approaches for realizing these orientations are presented, including selective-area bottom-up nanostructures.

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“…3,4 This efficiency drop of the green LEDs, as known as the "green gap", limits the development of LEDs. 5,6 Moreover, many advanced LED applications such as vehicle head lamps and LED projectors are obstructed by a broad emission pattern of conventional LEDs. Therefore, it is important to develop high-efficiency green LEDs with directional radiation patterns for next-generation lighting sources.…”

Section: Introductionmentioning

confidence: 99%

Bridging the “green gap” of LEDs: giant light output enhancement and directional control of LEDs via embedded nano-void photonic crystals

et al. 2016

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Green LEDs do not show the same level of performance as their blue and red cousins, greatly hindering the solid-state lighting development, which is so-called "green gap". In this work, nano-void photonic crystals (NVPCs) were fabricated to embed within the GaN/InGaN green LEDs by using epitaxial lateral overgrowth (ELO) and nano-sphere lithography techniques. The NVPCs act as an efficient scattering back-reflector to outcouple the guided and downward photons, which not only boosting light extraction efficiency of LEDs with an enhancement of 78% but also collimating the view angle of LEDs from 131.5゜to 114.0゜. This could be because the highly scattering nature of NVPCs which reduce the interference giving rise to Fabry-Perot resonance. Moreover, due to the threading dislocation suppression and strain relief by the NVPCs, the internal quantum efficiency was increased by 25% and droop behavior was reduced from 37.4% to 25.9%. The enhancement of light output power can be achieved as high as 151% at a driving current of 350 mA. Giant light output enhancement and directional control via NVPCs points the way towards a promising avenue of solid-state lighting.

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Overcoming the 'green gap'

Cited by 27 publications

References 1 publication

Indium gallium nitride-based ultraviolet, blue, and green light-emitting diodes functionalized with shallow periodic hole patterns

Indium gallium nitride-based ultraviolet, blue, and green light-emitting diodes functionalized with shallow periodic hole patterns

A Decade of Nonpolar and Semipolar III-Nitrides: A Review of Successes and Challenges

Bridging the “green gap” of LEDs: giant light output enhancement and directional control of LEDs via embedded nano-void photonic crystals

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