scholarly journals Improving the External Quantum Efficiency of High-Power GaN-Based Flip-Chip LEDs by Using Sidewall Composite Reflective Micro Structure

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1073
Author(s):  
Liang Xu ◽  
Kaiping Fan ◽  
Huiqing Sun ◽  
Zhiyou Guo
Keyword(s):  
Quantum Efficiency ◽  
High Power ◽  
External Quantum Efficiency ◽  
Flip Chip ◽  
Light Emission ◽  
Light Output ◽  
Vertical Direction ◽  
Bragg Reflector ◽  
Light Extraction Efficiency ◽  
Micro Structure

For high-power applications, it is important to improve the light extraction efficiency and light output of the vertical direction of LEDs. Flip-chip LEDs (FCLEDs) with an Ag/SiO2/distributed Bragg reflector/SiO2 composite reflection micro structure (CRS) were fabricated. Compared with the normal Ag-based FCLEDs, the light output power of the CRS-FCLEDs was increased by 6.3% at an operational current of 1500 mA, with the corresponding external quantum efficiency improved by 6.0%. Further investigation proved that the CRS structure exhibited higher reflectance compared with the commonly used Ag-mirror reflective structure, which originates from the increased reflective area in the sidewall and partial area of the n-GaN contact orifices. It exhibited markedly smaller optical degradation and thus higher device reliability as compared to normal Ag-based FCLED. Moreover, the light emission intensity distributions and far-field angular light emission measurements show that the CRS-FCLED has a strengthened light output in the vertical direction, which shows great potential for applications in high-power fields, such as headlamps for automobiles.

scholarly journals Improving the External Quantum Efficiency of High Power GaN Based Flip-Chip LEDs using Ag/SiO2/DBR/SiO2 Composite ReflectiveStructure

2021 ◽  
Author(s):  
Liang Xu ◽  
Jinglin Zhan ◽  
Huiqing Sun ◽  
Zhizhong Chen ◽  
Zhiyou Guo
Keyword(s):  
Quantum Efficiency ◽  
High Power ◽  
External Quantum Efficiency ◽  
Flip Chip ◽  
Light Emission ◽  
Light Output ◽  
Vertical Direction ◽  
Bragg Reflector ◽  
Light Extraction Efficiency ◽  
Distributed Bragg Reflector

Abstract Improve the light extraction efficiency and light output in the vertical direction of LEDs for high-power applications, flip-chip LEDs (FCLEDs) with an Ag/SiO2/distributed Bragg reflector/SiO2 composite reflection structure (CRS) were fabricated. The enhanced opto-electrical properties were thoroughly investigated. Compared with the normal Ag-based FCLEDs, the light output power of the CRS-FCLEDs is increased by 6.3% at an operational current of 1500 mA, with the corresponding external quantum efficiency improved by 6.0%. Further investigation proved that the CRS structure exhibited higher reflectance compared with the commonly used Ag-mirror reflective structure, which originates from the increased reflective area in the sidewall and partial area of the n-GaN contact holes. Moreover, the light emission intensity distributions and far-field angular light emission measurements show that the CRS-FCLED has a strengthened light output in the vertical direction, which shows great potential for applications in high-power fields, such as headlamps for automobiles.

scholarly journals High-Power GaN-Based Vertical Light-Emitting Diodes on 4-Inch Silicon Substrate

Nanomaterials ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 1178 ◽  
Author(s):  
Qiang Zhao ◽  
Jiahao Miao ◽  
Shengjun Zhou ◽  
Chengqun Gui ◽  
Bin Tang ◽  
...  
Keyword(s):  
High Power ◽  
Silicon Substrate ◽  
Flip Chip ◽  
Heat Dissipation ◽  
Light Emitting Diodes ◽  
Light Output ◽  
Current Spreading ◽  
Light Emitting ◽  
Fabry Perot ◽  
Lift Off

We demonstrate high-power GaN-based vertical light-emitting diodes (LEDs) (VLEDs) on a 4-inch silicon substrate and flip-chip LEDs on a sapphire substrate. The GaN-based VLEDs were transferred onto the silicon substrate by using the Au–In eutectic bonding technique in combination with the laser lift-off (LLO) process. The silicon substrate with high thermal conductivity can provide a satisfactory path for heat dissipation of VLEDs. The nitrogen polar n-GaN surface was textured by KOH solution, which not only improved light extract efficiency (LEE) but also broke down Fabry–Pérot interference in VLEDs. As a result, a near Lambertian emission pattern was obtained in a VLED. To improve current spreading, the ring-shaped n-electrode was uniformly distributed over the entire VLED. Our combined numerical and experimental results revealed that the VLED exhibited superior heat dissipation and current spreading performance over a flip-chip LED (FCLED). As a result, under 350 mA injection current, the forward voltage of the VLED was 0.36 V lower than that of the FCLED, while the light output power (LOP) of the VLED was 3.7% higher than that of the FCLED. The LOP of the FCLED saturated at 1280 mA, but the light output saturation did not appear in the VLED.

Effect of Interdigitated SiO2 Current Blocking Layer on External Quantum Efficiency of High Power LEDs

2017 ◽  
Vol 38 (6) ◽  
pp. 786-792 ◽  
Author(s):  
刘梦玲 LIU Meng-ling ◽  
高艺霖 GAO Yi-lin ◽  
胡红坡 HU Hong-po ◽  
刘星童 LIU Xing-tong ◽  
吕家将 LYU Jia-jiang ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
High Power ◽  
External Quantum Efficiency ◽  
Blocking Layer ◽  
Current Blocking Layer ◽  
Current Blocking

scholarly journals Enhanced Light Extraction of Flip-Chip Mini-LEDs with Prism-Structured Sidewall

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 319 ◽  
Author(s):  
Bin Tang ◽  
Jia Miao ◽  
Yingce Liu ◽  
Hui Wan ◽  
Ning Li ◽  
...  
Keyword(s):  
Total Internal Reflection ◽  
Flip Chip ◽  
Extraction Efficiency ◽  
Light Output ◽  
Cost Effective ◽  
Light Extraction ◽  
Light Extraction Efficiency ◽  
Light Output Power ◽  
Light Emitting ◽  
Air Interface

Current solutions for improving the light extraction efficiency of flip-chip light-emitting diodes (LEDs) mainly focus on relieving the total internal reflection at sapphire/air interface, but such methods hardly affect the epilayer mode photons. We demonstrated that the prism-structured sidewall based on tetramethylammonium hydroxide (TMAH) etching is a cost-effective solution for promoting light extraction efficiency of flip-chip mini-LEDs. The anisotropic TMAH etching created hierarchical prism structure on sidewall of mini-LEDs for coupling out photons into air without deteriorating the electrical property. Prism-structured sidewall effectively improved light output power of mini-LEDs by 10.3%, owing to the scattering out of waveguided light trapped in the gallium nitride (GaN) epilayer.

Uniformity of Light Emission in Micro-area on Mesa of High-power Flip-chip LED Devices with Ceramic Packaging

2021 ◽  
Vol 42 (09) ◽  
pp. 1436-1445
Author(s):  
Xiao-zhen LI ◽  
◽  
Chuan-bing XIONG ◽  
Ying-wen TANG ◽  
Dong-hui HAO
Keyword(s):  
High Power ◽  
Flip Chip ◽  
Light Emission

scholarly journals Nanoscale Characterization of V-defect in InGaN/GaN QWs LEDs using Near-Field Scanning Optical Microscopy

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 633 ◽  
Author(s):  
Li ◽  
Tang ◽  
Zhang ◽  
Guo ◽  
Li ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Optical Microscopy ◽  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
Near Field ◽  
Light Output ◽  
Current Injection ◽  
Light Output Power ◽  
Scanning Optical Microscopy ◽  
Near Field Scanning

The size of the V-defects in the GaN/InGaN-based quantum wells blue light-emitting diode (LED) was intentionally modified from 50 nm to 300 nm. High resolution photoluminescence and electroluminescence of a single large V-defect were investigated by near-field scanning optical microscopy. The current distribution along the {10-11} facets of the large defect was measured by conductive atomic force microscopy. Nearly 20 times the current injection and dominant emission from bottom quantum wells were found in the V-defect compared to its vicinity. Such enhanced current injection into the bottom part of quantum wells through V-defect results in higher light output power. Reduced external quantum efficiency droops were achieved due to more uniform carrier distribution. The un-encapsulated fabricated chip shows light output power of 172.5 mW and 201.7 mW at 400 mA, and external quantum efficiency drop of 22.3% and 15.4% for the sample without and with large V-defects, respectively. Modified V-defects provide a simple and effective approach to suppress the efficiency droop problem that occurs at high current injection, while improving overall quantum efficiency.

scholarly journals Light-Output Enhancement of GaN-Based Light-Emitting Diodes with Three-Dimensional Backside Reflectors Patterned by Microscale Cone Array

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
Huamao Huang ◽  
Jinyong Hu ◽  
Hong Wang
Keyword(s):  
Light Emitting Diode ◽  
Three Dimensional ◽  
Light Output ◽  
Bragg Reflector ◽  
Light Extraction Efficiency ◽  
Distributed Bragg Reflector ◽  
Etching Technique ◽  
Light Emitting ◽  
Triangle Lattice ◽  
Wall Plug Efficiency

Three-dimensional (3D) backside reflector, compared with flat reflectors, can improve the probability of finding the escape cone for reflecting lights and thus enhance the light-extraction efficiency (LEE) for GaN-based light-emitting diode (LED) chips. A triangle-lattice of microscale SiO2cone array followed by a 16-pair Ti3O5/SiO2distributed Bragg reflector (16-DBR) was proposed to be attached on the backside of sapphire substrate, and the light-output enhancement was demonstrated by numerical simulation and experiments. The LED chips with flat reflectors or 3D reflectors were simulated using Monte Carlo ray tracing method. It is shown that the LEE increases as the reflectivity of backside reflector increases, and the light-output can be significantly improved by 3D reflectors compared to flat counterparts. It can also be observed that the LEE decreases as the refractive index of the cone material increases. The 3D 16-DBR patterned by microscale SiO2cone array benefits large enhancement of LEE. This microscale pattern was prepared by standard photolithography and wet-etching technique. Measurement results show that the 3D 16-DBR can provide 12.1% enhancement of wall-plug efficiency, which is consistent with the simulated value of 11.73% for the enhancement of LEE.

Sign in / Sign up

Export Citation Format

Share Document