scholarly journals Optical polarization characteristics and light extraction behavior of deep-ultraviolet LED flip-chip with full-spatial omnidirectional reflector system

2019 ◽  
Vol 27 (20) ◽  
pp. A1601 ◽  
Author(s):  
Shuang Zhang ◽  
Yuan Liu ◽  
Jun Zhang ◽  
Yi Zhang ◽  
Linlin Xu ◽  
...  
Keyword(s):  
Flip Chip ◽  
Light Extraction ◽  
Optical Polarization ◽  
Extraction Behavior ◽  
Polarization Characteristics ◽  
Reflector System ◽  
Deep Ultraviolet

scholarly journals Investigation on Light Extraction Behavior of Surface Plasmon-Coupled Deep-Ultraviolet LED in Different Emission Directions

Crystals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 82
Author(s):  
Mei Ge ◽  
Yi Li ◽  
Youhua Zhu ◽  
Meiyu Wang
Keyword(s):  
Surface Plasmon ◽  
Three Dimensional ◽  
Strong Absorption ◽  
Light Extraction ◽  
Light Extraction Efficiency ◽  
Time Domain Simulation ◽  
Al Nanoparticles ◽  
Extraction Behavior ◽  
Deep Ultraviolet ◽  
Difference Time

The light extraction behavior of an AlGaN-based deep-ultraviolet LED covered with Al nanoparticles (NPs) is investigated by three-dimensional finite-difference time-domain simulation. For the transmission spectra of s- and p-polarizations in different emission directions, the position of maximum transmittance can be changed from (θ = 0°, λ = 273 nm) to (θ = 0°, λ = 286 nm) by increasing the diameter of Al NPs from 40 nm to 80 nm. In the direction that is greater than the critical angle, the transmittance of s-polarization is very small due to the strong absorption of Al NPs, while the transmittance spectrum of p-polarization can be observed obviously for the 80 nm Al NPs structure. For a ~284 nm AlGaN-based LED with surface plasmon (SP) coupling, although the luminous efficiency is significantly improved due to the improvement of the radiation recombination rate as compared with the conventional LED, the light extraction efficiency (LEE) is lower than 2.61% of the conventional LED without considering the lateral surface extraction and bottom reflection. The LEE is not greater than ~0.98% (~2.12%) for an SP coupling LED with 40 nm (80 nm) Al NPs. The lower LEE can be attributed to the strong absorption of Al NPs.

Demonstration of enhanced optical polarization for improved deep ultraviolet light extraction in coherently grown semipolar Al0.83Ga0.17N/AlN on ZnO substrates

2011 ◽  
Vol 99 (12) ◽  
pp. 121906 ◽  
Author(s):  
Kohei Ueno ◽  
Atsushi Kobayashi ◽  
Jitsuo Ohta ◽  
Masaharu Oshima ◽  
Hiroshi Fujioka
Keyword(s):  
Ultraviolet Light ◽  
Light Extraction ◽  
Optical Polarization ◽  
Deep Ultraviolet

Analysis of the Light-Extraction Efficiency of Flip-Chip Deep-Ultraviolet Light-Emitting Diodes with Embedded Photonic Crystals

2021 ◽  
Vol 16 (4) ◽  
pp. 591-596
Author(s):  
Meng Liu ◽  
Xuan Zheng ◽  
Wenfei Liu ◽  
Juan Li ◽  
Wenjing Wang ◽  
...  
Keyword(s):  
Photonic Crystals ◽  
Ultraviolet Light ◽  
Flip Chip ◽  
Light Emitting Diodes ◽  
Extraction Efficiency ◽  
Light Extraction ◽  
Light Extraction Efficiency ◽  
Light Emitting ◽  
Deep Ultraviolet ◽  
Ultraviolet Light Emitting Diodes

In the present study, embedded photonic crystals were introduced into the p-GaN contact layer of light-emitting diodes to increase the light-extraction efficiency of flip-chip deep-ultraviolet light-emitting diodes. As demonstrated by performing three-dimensional finite-difference time domain simulation, the embedded photonic crystals could be designed to increase the total reflectivity on the p-GaN contact layer, thereby increasing the light-extraction efficiency. In addition, the effects of the embedded photonic crystals configurations on the light-extraction efficiency of deep-ultraviolet light-emitting diodes were examined. Light-extraction efficiency over 21% for transverse magnetic polarized emission could be generally expected by rigorously optimizing the active layer position, as well as the depth, period, and filling factor of photonic crystals. Moreover, an investigation was conducted on the light-extraction efficiency over the whole ultraviolet spectrum, and more light-extraction efficiency harvest on a broadband ultraviolet spectrum has been achieved as compared with flip-chip planar deep-ultraviolet light-emitting diodes. The optimized structure will be promising for increasing the light-extraction efficiency of AlGaN-based flip-chip deep-ultraviolet light-emitting diodes.

scholarly journals Perspectives on UVC LED: Its Progress and Application

Photonics ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 196
Author(s):  
Tsung-Chi Hsu ◽  
Yu-Tsai Teng ◽  
Yen-Wei Yeh ◽  
Xiaotong Fan ◽  
Kuo-Hsiung Chu ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Flip Chip ◽  
Layer Structure ◽  
Light Emitting Diode ◽  
Internal Quantum Efficiency ◽  
Reverse Current ◽  
Light Extraction ◽  
Epitaxial Layers ◽  
High Electron ◽  
Recombination Rates

High-quality epitaxial layers are directly related to internal quantum efficiency. The methods used to design such epitaxial layers are reviewed in this article. The ultraviolet C (UVC) light-emitting diode (LED) epitaxial layer structure exhibits electron leakage; therefore, many research groups have proposed the design of blocking layers and carrier transportation to generate high electron–hole recombination rates. This also aids in increasing the internal quantum efficiency. The cap layer, p-GaN, exhibits high absorption in deep UV radiation; thus, a small thickness is usually chosen. Flip chip design is more popular for such devices in the UV band, and the main factors for consideration are light extraction and heat transportation. However, the choice of encapsulation materials is important, because unsuitable encapsulation materials will be degraded by ultraviolet light irradiation. A suitable package design can account for light extraction and heat transportation. Finally, an atomic layer deposition Al2O3 film has been proposed as a mesa passivation layer. It can provide a low reverse current leakage. Moreover, it can help increase the quantum efficiency, enhance the moisture resistance, and improve reliability. UVC LED applications can be used in sterilization, water purification, air purification, and medical and military fields.

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