Polarization ratio enhancement of a-plane GaN light emitting diodes by asymmetric two-dimensional photonic crystals

Chou, Yen I.; Li, Hsiang-Wei; Yin, Yu-Feng; Wang, Yuting; Lin, Yu-Ju; Lin, Da-Wei; Wu, Yuh‐Renn; Kuo, Hao‐Chung; Huang, Jian

doi:10.1063/1.4876655

Cited by 9 publications

(10 citation statements)

References 13 publications

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“…At 100 meV, Δ E of peak 1 and peak 2 are 28 meV and 16 meV, respectively. It means that Δ E increases with the driving current for both emissions, which is consistent with other reports on m -plane InGaN MQW LEDs 8,28 . It was explained by the anti-crossing of | Z > and | Y > subbands, or crystal momentum conservation.…”

Section: Resultssupporting

confidence: 92%

“…At 30 mA current, ρ is 0.34 and 0.49 for peak1 and peak 2, respectively, which confirms that higher indium composition leads to larger polarization degree. The ρ values obtained are comparable with other reports for nonpolar blue LEDs 24,26–28 . Actual polarization degrees for the nonpolar LED should be larger than the values obtained, because no special processing, such as using a confocal microscope or black absorber applied to bottom and side surfaces of devices 8 , were performed in our measurements to reduce light scattering which severely affects the polarization.…”

Section: Resultssupporting

confidence: 91%

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Optical and polarization properties of nonpolar InGaN-based light-emitting diodes grown on micro-rod templates

Bai¹,

Jiu²,

Poyiatzis³

et al. 2019

Sci Rep

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We have demonstrated non-polar a -plane InGaN multiple-quantum-well (MQW) light-emitting diodes (LEDs) on sapphire, achieved by overgrowing on a micro-rod template with substantially improved crystal quality. Photoluminescence measurements show one main emission peak at 418 nm along with another weak peak at 448 nm. Wavelength mapping measurements carried out by using a high spatial-resolution confocal PL system indicate that the two emissions origin from different areas associated with the underlying micro-rod patterns. Electroluminescence measurements exhibit a negligible blue-shift of 1.6 nm in the peak wavelength of the main emission when the driving current increases from 10 to 100 mA, indicating that the quantum confined Stark effect is effectively suppressed in in the nonpolar LED. A polarization ratio of 0.49 is obtained for the low-energy emission (~448 nm), while the main emission (~418 nm) shows a polarization ratio of 0.34. Furthermore, the polarization ratios are independent of injection current, while the energy separation between m-polarized and c-polarized lights increases with the injection current for both emissions.

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 91%

Optical and polarization properties of nonpolar InGaN-based light-emitting diodes grown on micro-rod templates

Bai¹,

Jiu²,

Poyiatzis³

et al. 2019

Sci Rep

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“…The light output intensity at 465.5 nm and full width at half maximum of the emission spectrum for the InGaN/GaN LEDs with the optimal periodic PS NS array window layers were stronger and narrower than those of the conventional InGaN/GaN LEDs. The guided light that is emitted from the InGaN/GaN active region underwent TIR and could not phase match to the radiation modes when the amplitude of the in-plane wave vector in the semiconductor was higher than that in the air [ 9 , 32 ]. The periodic PS NS array window layers could modulate the amplitude of the in-plane wave vector in the semiconductor to less than that in air, and therefore, the light was emitted from the semiconductor with the periodic PS NS array because the phase of the guided modes matched the radiation modes, resulting in a high light output intensity and a narrow emission spectrum.…”

Section: Resultsmentioning

confidence: 99%

“…When the periodicity is chosen correctly, the modified in-plane wave vector falls within the escape corn, resulting in extraction to air at an angle dependent on the specific lattice constant within this range. Several methods exist to define the periodic PC structures on indium-tin-oxide (ITO) or p-GaN, including electron beam lithography [ 6 – 9 ], laser holographic lithography [ 10 ], focused ion beam technology [ 11 ], nanoimprint lithography [ 12 ], and self-assembled colloidal polystyrene nanosphere (PS NS) coating [ 13 , 14 ]. The self-assembled PS NS coating method has advantages such as a large area arrangement with a gradually changing fill factor, simple process, sophisticated equipment, and etching damage.…”

Section: Introductionmentioning

confidence: 99%

Preparation of a Periodic Polystyrene Nanosphere Array Using the Dip-Drop Method with Post-deposition Etching and Its Application of Improving Light Extraction Efficiency of InGaN/GaN LEDs

Lei

Yang

et al. 2018

Nanoscale Res Lett

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In this study, we synthesized a periodic polystyrene nanosphere (PS NS) array using the dip-drop method with post-deposition etching to improve the light extraction efficiency (LEE) of InGaN/GaN light-emitting diodes (LEDs). The dip-drop method has advantages such as simple procedure, inexpensive equipment, room temperature deposition, and easy implementation in LEDs. The arrangement of PS NSs on an indium-tin-oxide (ITO)-coated glass substrate depends on the average dip-drop speed and the concentration of the PS NS suspension. The periodic PS NS array can modulate the in-plane wave vector of emission light from a semiconductor to free space and thus increase the escape probability. The calculated and experimental results indicated that the light output intensity of the InGaN/GaN LEDs can be improved by using the periodic PS NS array as a window layer; this array comprises PS NSs with a diameter of 100 nm separated with periods of 100 and 100 nm in the x and y directions. Because of the improved LEE, the InGaN/GaN LEDs with the optimal PS NS array window layers exhibited a 38% increase in light output intensity compared with the conventional InGaN/GaN LEDs under 20-mA driving current.

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“…Chou et al studied and designed a method using asymmetric PC growth on GaN-based LEDs to enhance LEE. 95 The structure schematic is shown in Figure 24C. From Figure 24D, the PC LED's LOP rose by 44.87% compared to the planar device's at 20 mA.…”

Section: Surface (Top Bottom) 2d Photonic Crystal Ledsmentioning

confidence: 99%

Design of photonic crystals for light‐emitting diodes

Wang,

Dong,

et al. 2023

J Am Ceram Soc.

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Photonic crystals (PC) can greatly enhance the optoelectronic performance of LEDs, due to their distinctive color and photonic band gap, etc. Therefore, many scholars have conducted extensive research based on the high light extraction efficiency, good monochromaticity, and other excellent optoelectronic properties of PC LEDs. This review discusses the main principles of photonic crystals to improve the optoelectronic performance of LEDs and summarizes 12 structural applications of photonic crystal LEDs, such as PC slabs, Bragg grating, Backside reflectors, Surface PC, Embedded PC, Dual PC, PC beads, CPC, PC thin films, LIPC, defective PC, composite architectures with other materials that boost LED optoelectronic qualities. In summary, it is found that photonic crystals can not only greatly improve the light extraction efficiency of LEDs but also improve other optoelectronic properties such as luminescent color, and directional radiation angle, and reduce the manufacturing cost of LEDs. Photonic crystal LEDs are expected to be a strong candidate for future lighting technology Finally, the prospects and challenges of PC LEDs are summarized.This article is protected by copyright. All rights reserved

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Polarization ratio enhancement of a-plane GaN light emitting diodes by asymmetric two-dimensional photonic crystals

Abstract: Articles you may be interested in Polarized light extraction in m-plane GaN light-emitting diodes by embedded photonic-crystals Appl.

Cited by 9 publications

References 13 publications

Optical and polarization properties of nonpolar InGaN-based light-emitting diodes grown on micro-rod templates

Optical and polarization properties of nonpolar InGaN-based light-emitting diodes grown on micro-rod templates

Preparation of a Periodic Polystyrene Nanosphere Array Using the Dip-Drop Method with Post-deposition Etching and Its Application of Improving Light Extraction Efficiency of InGaN/GaN LEDs

Design of photonic crystals for light‐emitting diodes

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