Extraction Efficiency of GaN-Based LEDs

Schad, Sven‐Silvius; Scherer, M.; Seyboth, M.; Schwegler, V.

doi:10.1002/1521-396x(200111)188:1<127::aid-pssa127>3.0.co;2-t

Cited by 24 publications

(10 citation statements)

References 6 publications

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“…In addition, research efforts have integrated ZnO nanostructures on GaN light-emitting diodes for enhanced emission efficiency. [12][13][14] Both AlInGaP-based LEDs with truncated inverted pyramid (TIP) structures and GaN-based LEDs on SiC substrates 15 for the substrate shaping process can enhance light extraction efficiency. The processes included with selective PEC etching process, 16 the controlled wet chemical etching on the AlInN layer, 17 and the oxidizing process 18,19 on the GaN materials can also affect the optical properties of nitride-based devices.…”

Section: Introductionsupporting

confidence: 69%

Fabrication of Mesa Shaped InGaN-Based Light-Emitting Diodes Through a Photoelectrochemical Process

Yang

Lin

Chiang

et al. 2008

Journal of Elec Materi

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InGaN-based light-emitting diodes (LEDs) were fabricated to have a higher light extraction through the photoelectrochemical (PEC) mesa shaping process. After the PEC selective wet oxidation and wet etching processes, stable and controllable crystallographic etching planes were formed as p-type GaN {1011} planes and n-type GaN {1010} planes included at an angle of 27 deg. The ever-present cone-shaped structure of a PEC-treated LED has a larger light scattering area and higher light extraction cones on the mesa sidewall, as analyzed by microphotoluminescence and light output power measurement. This cone-shaped-sidewall LED has a higher light output power and a larger divergence angle compared with a conventional LED measured in an LED chip form

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Section: Introductionsupporting

confidence: 69%

Fabrication of Mesa Shaped InGaN-Based Light-Emitting Diodes Through a Photoelectrochemical Process

Yang

Lin

Chiang

et al. 2008

Journal of Elec Materi

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“…[3,4] Further simulation work was carried out by Schad et al, and a sidewall angle of 64 • was optimal for a truncated pyramid GaN-based LED on SiC substrate. [6] For the model, the bottom and top sizes are 200 µm × 200 µm and 300 µm × 300 µm, with a total thickness of 100 µm. By means of simulation, we found that as the chip size increases the enhancement of LEE by chip shaping decreases dramatically.…”

Section: Led Chip Designmentioning

confidence: 99%

“…For GaN-based LED chips on SiC substrate, a significant amount of light emission from the active layer is trapped inside the semiconductor structure because of total internal reflection (TIR). The extraction efficiency could be improved using a shaped SiC substrate, [1,2,6] but improvement is relatively small when the chip size exceeds 1 mm × 1 mm.…”

Section: Introductionmentioning

confidence: 99%

Progress in research of GaN-based LEDs fabricated on SiC substrate

Chen

Yan

et al. 2015

Chinese Phys. B

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The influence of buffer layer growth conditions on the crystal quality and residual stress of GaN film grown on silicon carbide substrate is investigated. It is found that the AlGaN nucleation layer with high growth temperature can efficiently decrease the dislocation density and stress of the GaN film compared with AlN buffer layer. To increase the light extraction efficiency of GaN-based LEDs on SiC substrate, flip-chip structure and thin film flip-chip structure were designed and optimized. The fabricated blue LED had a maximum wall-plug efficiency of 72% at 80 mA. At 350 mA, the output power, the Vf, the dominant wavelength, and the wall-plug efficiency of the blue LED were 644 mW, 2.95 V, 460 nm, and 63%, respectively.

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“…Maximizing the fraction of photons generated within the semiconductor quantum wells that actually escapes out of the device structure is a major challenge for any LED design [4]. Even supposing 100% internal quantum efficiency is achieved, the overall wall plug efficiency of the LED will still be poor if the light extraction efficiency is low.…”

Section: Improving Light Extraction Efficiency From Gan-based Led Strmentioning

confidence: 99%

Improving the Efficiency of Solid State Light Sources

McKittrick¹

2003

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This proposal addresses the national need to develop a high efficiency light source for general illumination applications. The goal is to perform research that would lead to the fabrication of a unique solid state, white-emitting light source. This source is based on an InGaN/GaN UV-emitting chip that activates a luminescent material (phosphor) to produce white light.White-light LEDs are commercially available which use UV from a GaN chip to excite a phosphor suspended in epoxy around the chip. Currently, these devices are relatively inefficient. This research will target one technical barrier that presently limits the efficiency of GaN based devices. Improvements in efficiencies will be achieved by improving the internal conversion efficiency of the LED die, by improving the coupling between the die and phosphor(s) to reduce losses at the surfaces, and by selecting phosphors to maximize the emissions from the LEDs in conversion to white light. The UCSD research team proposes for this project to develop new phosphors that have high quantum efficiencies that can be activated by the UV-blue (360-410 nm) light emitted by the GaN device. SCIENTIFIC ACHIEVEMENTS: DEVELOPMENT OF NEW PHOSPHORS Objective:The main goal for the UCSD team was to develop new phosphor materials with a very specific property: phosphors that could be excited at long . The photoluminescence of these new phosphors must be activated with photons emitted from GaN based dies. The GaN diodes can be designed to emit UV-light in the same range (λ=350-410 nm). A second objective, which is also very important, is to search for alternate methods to fabricate these phosphors with special emphasis in saving energy and time and reduce pollution. Achievements:The UCSD group has pioneered a method, combustion synthesis, to rapidly produce multicomponent oxides. The combustion synthesis method is based in the use of metal nitrates (oxidizers) and a fuel (urea, carbohydrazide or hydrazine) that initiates a highly exothermic reaction, as described in more detail in [1,2]. As an example of this process, EuAlO 3 :Eu 3+ is synthesized by reacting two precursors, Eu(NO 3 ) 3 and 3 Al(NO 3 ) 3 using hydrazine as a fuel in a controlled atmosphere which is heated below <200ºC to produce the combustion reaction. The powder obtained is red-emitting (λ=610 nm) with strong absorption in the UV (λ= 365 nm). The product is then exposed to a heated ammonia flow which yields EuAlO 3 :Eu 2+ green luminescent powders. Thus, a new phosphor material that absorbs efficiently photons in the range λ=250-400 nm and with a broad emission peak centered at λ=525 nm is synthesized.In this work we also found that combustion synthesis is a powerful technique to develop With the same method is possible to produce Y 2 SiO 5 :Ce 3+ a blue-emitting oxide phosphor that is efficiently excited at λ=365 nm. Figure 1 shows these three phosphors excited by UV at a wavelength of 365 nm and the corresponding luminescence spectrum of the blend of these three colors producing a white-emitting phosphor.An...

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Extraction Efficiency of GaN-Based LEDs

Cited by 24 publications

References 6 publications

Fabrication of Mesa Shaped InGaN-Based Light-Emitting Diodes Through a Photoelectrochemical Process

Fabrication of Mesa Shaped InGaN-Based Light-Emitting Diodes Through a Photoelectrochemical Process

Progress in research of GaN-based LEDs fabricated on SiC substrate

Improving the Efficiency of Solid State Light Sources

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