scholarly journals Effect of Dielectric Distributed Bragg Reflector on Electrical and Optical Properties of GaN-Based Flip-Chip Light-Emitting Diodes

Micromachines ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 650 ◽  
Author(s):  
Shengjun Zhou ◽  
Haohao Xu ◽  
Mengling Liu ◽  
Xingtong Liu ◽  
Jie Zhao ◽  
...  
Keyword(s):  
Flip Chip ◽  
Heat Dissipation ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Incident Angle ◽  
Light Output ◽  
Bragg Reflector ◽  
Distributed Bragg Reflector ◽  
Light Emitting ◽  
Via Hole

We demonstrated two types of GaN-based flip-chip light-emitting diodes (FCLEDs) with distributed Bragg reflector (DBR) and without DBR to investigate the effect of dielectric TiO2/SiO2 DBR on optical and electrical characteristics of FCLEDs. The reflector consisting of two single TiO2/SiO2 DBR stacks optimized for different central wavelengths demonstrates a broader reflectance bandwidth and a less dependence of reflectance on the incident angle of light. As a result, the light output power (LOP) of FCLED with DBR shows 25.3% higher than that of FCLED without DBR at 150 mA. However, due to the better heat dissipation of FCLED without DBR, it was found that the light output saturation current shifted from 268 A/cm2 for FCLED with DBR to 296 A/cm2 for FCLED without DBR. We found that the use of via-hole-based n-type contacts can spread injection current uniformly over the entire active emitting region. Our study paves the way for application of DBR and via-hole-based n-type contact in high-efficiency FCLEDs.

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.

Light Output Enhancement of UV Light-Emitting Diodes With Embedded Distributed Bragg Reflector

2011 ◽  
Vol 23 (10) ◽  
pp. 642-644 ◽  
Author(s):  
Bo-Siao Cheng ◽  
Ching-Hsueh Chiu ◽  
Ming-Hua Lo ◽  
Yun-Lin Wu ◽  
Hao-Chung Kuo ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Uv Light ◽  
Light Output ◽  
Bragg Reflector ◽  
Distributed Bragg Reflector ◽  
Light Emitting

Ni–Cu Nanoparticles-Embedded Ag-Based Reflector for High-Efficiency Light-Emitting Diodes

2020 ◽  
Vol 20 (11) ◽  
pp. 6732-6737
Author(s):  
Eun-Kyung Chu ◽  
Kab Ha ◽  
Beom-Rae Noh ◽  
Young-Ju Kwon ◽  
Semi Oh ◽  
...  
Keyword(s):  
Flip Chip ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Forward Bias ◽  
Light Output ◽  
Single Layer ◽  
Cu Nanoparticles ◽  
Light Emitting ◽  
Forward Bias Voltage ◽  
Ag Reflector

We investigated the use of a silver reflector embedded with Ni–Cu nanoparticles to achieve low resistance and high reflectivity in GaN-based flip-chip light-emitting diodes. Compared to a single layer of Ag, the NC-NPs/Ag reflector exhibits a higher light reflectance of ~90% at a wavelength of 450 nm, a lower contact resistance of 4.75 × 10−5 II cm2, and improved thermal stability after annealing at 400°C. The NC-NPs formed after the annealing process prevents agglomeration of the Ag layer, while also reducing the Schottky barrier height between the p-GaN layer and metal reflector. The LED fabricated with a NC-NPs/Ag reflector exhibited a forward-bias voltage of 3.13 V and an improvement in light output power of 36.6% (at 20 mA), when compared with the LED composed of a Ag SL. This result indicates that the NC-NPs/Ag reflector is a promising p-type reflector for high-intensity light-emitting diodes.

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