Structural Effects on Highly Directional Far-Field Emission Patterns of GaN-Based Micro-Cavity Light-Emitting Diodes With Photonic Crystals

Lai, Chun‐Feng; Kuo, Hao‐Chung; Chao, Chia-Hsin; Yu, Peichen; Yeh, Wen-Yung

doi:10.1109/jlt.2010.2061836

Cited by 20 publications

(16 citation statements)

References 20 publications

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“…Since the same phosphor rubber and configuration is used for all three scenarios and there is no diffusing element presented in the setup, the difference of the far field emission pattern is solely attributed to the effect of the beam angle of the light emitters, which refer to the LED, SLD or LD. For instance, LED, as a surface emitter, exhibits a Lambertian emission pattern, where the intensity profile is proportional to the cosine of the emission angle [33]. Both SLD and LD are edge emitter, and narrower beam angles are expected compared to that of the LED.…”

Section: Sld Based Phosphor Converted White Lightmentioning

confidence: 99%

Semipolar InGaN-based superluminescent diodes for solid-state lighting and visible light communications

Shen

Lee

et al. 2017

SPIE Proceedings

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III-nitride light emitters, such as light-emitting diodes (LEDs) and laser diodes (LDs), have been demonstrated and studied for solid-state lighting (SSL) and visible-light communication (VLC) applications. However, for III-nitride LEDbased SSL-VLC system, its efficiency is limited by the "efficiency droop" effect and the high-speed performance is limited by a relatively small -3 dB modulation bandwidth (<100 MHz). InGaN-based LDs were recently studied as a droop-free, high-speed emitter; yet it is associated with speckle-noise and safety concerns. In this paper, we presented the semipolar InGaN-based violet-blue emitting superluminescent diodes (SLDs) as a high-brightness and high-speed light source, combining the advantages of LEDs and LDs. Utilizing the integrated passive absorber configuration, an InGaN/GaN quantum well (QW) based SLD was fabricated on semipolar GaN substrate. Using SLD to excite a YAG:Ce phosphor, white light can be generated, exhibiting a color rendering index of 68.9 and a color temperature of 4340 K. Besides, the opto-electrical properties of the SLD, the emission pattern of the phosphor-converted white light, and the high-speed (Gb/s) visible light communication link using SLD as the transmitter have been presented and discussed in this paper.

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Section: Sld Based Phosphor Converted White Lightmentioning

confidence: 99%

Semipolar InGaN-based superluminescent diodes for solid-state lighting and visible light communications

Shen

Lee

et al. 2017

SPIE Proceedings

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“…LEE is thus enhanced by destructing TIR and converting the waveguide modes into air modes. Although diffractive gratings work well to solve the problem of poor LEE [30], it is still very challenging to determine the various optimization parameters due to its heavy computational burden [31]- [33]. These parameters, such as the thickness of GaN, the position of source (quantum wells), filling factor, lattice constant and hole depth, all play important roles in the LEE of GaN-based LED.…”

Section: Introductionmentioning

confidence: 99%

Enhancing LED Light Extraction by Optimizing Cavity and Waveguide Modes in Grating Structures

Yeh

Fang

Chiou

2013

J. Display Technol.

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An optimization of light extraction efficiency (LEE) from light-emitting diodes (LEDs) is provided. The optimization is achieved when both the cavity and waveguide modes are in their best conditions and their emitted waves interfere constructively in the grating-assisted structures. In other words, high LEE appears when the structural parameters results in good cavity modes in both planar and grating structures, and also when the propagation direction of the fundamental waveguide mode is significantly converted to the direction normal to the grating surface by the gratings. In this paper, we use two simple equations, one for cavity modes and the other for waveguide modes, to predict the loci of the optimal structural parameters of gratings. The prediction is verified with the rigorous coupled wave analysis (RCWA). We systematically present an investigation of the various structural effects of gratings on the LEE of the thin film vertical gallium-nitride (GaN) based LEDs. The results show that ultra-high LEE can be achieved when the equivalent cavity thickness is good for fundamental cavity mode, the source is positioned around antinodes for both cavity and waveguide modes, there is significant diffraction, and the fundamental waveguide mode is largely converted to the normal direction to the air, and the emitted waves from fundamental cavity and waveguide modes interfere constructively.

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“…Dry etching of GaN, on the contrary, is not impacted by those characteristics and, in addition, shows a fairly good anisotropy when covered by a hard etch mask such as SiO 2 , SiN x or Ni. Thus, several techniques such as inductively coupled plasma (ICP) etching have been employed, together with etch masks, to create nanoporous GaN films 29 , but mainly to achieve 2D PhC on the surface of a LED structure [20][21][22][23] . In that case, the configuration of the nanoholes can be accurately tuned and controlled by various nanopatterning techniques, such as electron beam lithography, interference lithography or nanoimprint lithography.…”

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confidence: 99%

Influence of the reactor environment on the selective area thermal etching of GaN nanohole arrays

Coulon

Feng

Damilano

et al. 2020

Sci Rep

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Selective area thermal etching (SATE) of gallium nitride is a simple subtractive process for creating novel device architectures and improving the structural and optical quality of III-nitride-based devices. In contrast to plasma etching, it allows, for example, the creation of enclosed features with extremely high aspect ratios without introducing ion-related etch damage. We report how SATE can create uniform and organized GaN nanohole arrays from c-plane and (11-22) semi-polar GaN in a conventional MOVPE reactor. The morphology, etching anisotropy and etch depth of the nanoholes were investigated by scanning electron microscopy for a broad range of etching parameters, including the temperature, the pressure, the NH 3 flow rate and the carrier gas mixture. The supply of NH 3 during SATE plays a crucial role in obtaining a highly anisotropic thermal etching process with the formation of hexagonal non-polar-faceted nanoholes. Changing other parameters affects the formation, or not, of non-polar sidewalls, the uniformity of the nanohole diameter, and the etch rate, which reaches 6 µm per hour. Finally, the paper discusses the SATE mechanism within a MOVPE environment, which can be applied to other mask configurations, such as dots, rings or lines, along with other crystallographic orientations. Nanostructures are continuously drawing the attention of the III-nitride community for their success in improving light emitting devices 1-4 and their use for emerging applications such as water splitting 5 , single photon sources 6 , piezoelectric nanogenerators 7 or solar light harvesting 8. Among the different geometries available, arrays of nanoholes, in the form of a porous or two-dimensional photonic crystal (2D PhC) layer, have been widely investigated. On one side, a porous layer can provide a change in refractive index 9,10 , an increased surface area resulting in both higher sensitivity 11 and larger photocurrent 12,13 , a more efficient light extraction due to enhanced scattering 14,15 , and improved crystal quality by reducing strain and dislocation density 16-19. On the other side, a 2D PhC layer allows one to enhance the IQE thanks to the Purcell effect, increase the light extraction efficiency and improve/control the directionality of III-nitride based light emitting diodes (LED) 20-23. As such, networks of nanoholes have been used in several applications such as distributed Bragg reflectors 10 , sensors 11 , hydrogen generation 12,13 , LEDs 14,22,23 , free-standing GaN films 17 , and energy storage 18,19. The fabrication of nanohole arrays is usually achieved from a III-nitride layer or an LED structure via a subtractive process or what is called a top-down approach. Porous layers are generally obtained from GaN layers by various techniques, such as electrochemical etching 9,11,14,16 , photo-electrochemical etching 12,13 , metal assisted chemical etching 24,25 , and high temperature annealing with 26 , or without, a catalyst 15,17-19,27,28. Although the depth of the pores can reach a few microns 13,17-19,24,2...

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Structural Effects on Highly Directional Far-Field Emission Patterns of GaN-Based Micro-Cavity Light-Emitting Diodes With Photonic Crystals

Cited by 20 publications

References 20 publications

Semipolar InGaN-based superluminescent diodes for solid-state lighting and visible light communications

Semipolar InGaN-based superluminescent diodes for solid-state lighting and visible light communications

Enhancing LED Light Extraction by Optimizing Cavity and Waveguide Modes in Grating Structures

Influence of the reactor environment on the selective area thermal etching of GaN nanohole arrays

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