Efficiency droop in 245–247 nm AlGaN light-emitting diodes with continuous wave 2 mW output power

2010 ◽  
Vol 96 (6) ◽  
pp. 061102 ◽  
Author(s):  
W. Sun ◽  
M. Shatalov ◽  
J. Deng ◽  
X. Hu ◽  
J. Yang ◽  
...  
Keyword(s):  
Output Power ◽  
Light Emitting Diodes ◽  
Continuous Wave ◽  
Efficiency Droop ◽  
Light Emitting

Approaches Towards the Ultimate Luminous Output Power of Light-Emitting Diodes: Bottlenecks and Remedies

2015 ◽  
Author(s):  
Xiaokun Zhang ◽  
Xiao-Dong Xiang ◽  
Yong Xiang
Keyword(s):  
Output Power ◽  
Light Emitting Diodes ◽  
Thermal Runaway ◽  
Efficiency Droop ◽  
Injection Current ◽  
Light Emitting ◽  
Excessive Heat ◽  
High Injection ◽  
Current Densities ◽  
The Cost

Although light-emitting diodes (LEDs) hold great promises for high-efficiency lighting applications, the cost per lumen still poses a challenge for LEDs to fast penetrate into the markets. Increasing the output power per LED chip reduces the number of chips required for a specific luminous flux, thus reducing the cost of LED luminaires. However, it is well known that the luminous output power of LEDs (Pout) cannot be enhanced simply by increasing the injection current density (Jinj) due to efficiency droop. Extensive efforts have been made towards avoiding efficiency droop at high injection current densities (e.g., Jinj > 50 A/cm2). Gardner et al. reported a double-heterostructure LED with an external quantum efficiency (EQE) of 40% at 200 A/cm2. Xie et al. introduced an electron-blocking layer into the LED devices and the EQE peak occurred at 900 A/cm2 approximately. Nevertheless, the EQE is always lower than 100%, excessive heat will accumulate in LEDs at high current densities and increase the junction temperatures, which will damage the device and limit its luminous output power and lifetime. In this paper, the recombination mechanism in the LED active area is analyzed and an analytic relationship between Pout and Jinj is proposed. The calculated results show that the best Pout currently achieved is far lower than its potential value. The temperature dependence of the Pout-Jinj relationship is also calculated and the thermal state of LEDs at high injection current densities predicted. The results demonstrate that LED luminaires with thermal management based on conventional fin-shaped heat sinks suffer from thermal runaway due to excessive heat accumulation before reaching their ultimate output power. The gap between the existing and predicted Pout is mainly due to thermal runaway of LED devices at high injection current densities, instead of efficiency droop. Therefore, the short-term solution of LED luminous output power enhancement should be better cooling of LED modules, such as jet/spray cooling, heat pipe cooling, or 3D embedded two-phase cooling. Long-term solutions continue to focus on reducing the efficiency droop with improved LED device structures and advanced materials.

scholarly journals High-brightness lasing at submicrometer enabled by droop-free fin light-emitting diodes (LEDs)

2020 ◽  
Vol 6 (33) ◽  
pp. eaba4346
Author(s):  
Babak Nikoobakht ◽  
Robin P. Hansen ◽  
Yuqin Zong ◽  
Amit Agrawal ◽  
Michael Shur ◽  
...  
Keyword(s):  
Output Power ◽  
Light Emitting Diodes ◽  
Efficiency Droop ◽  
Light Extraction Efficiency ◽  
Electrical Currents ◽  
High Brightness ◽  
Light Emitting ◽  
Recombination Processes ◽  
Current Densities ◽  
New Generation

“Efficiency droop,” i.e., a decline in brightness of light-emitting diodes (LEDs) at high electrical currents, limits the performance of all commercial LEDs and has limited the output power of submicrometer LEDs and lasers to nanowatts. We present a fin p-n junction LED pixel that eliminates efficiency droop, allowing LED brightness to increase linearly with current. With record current densities of 1000 kA/cm2, the LEDs transition to lasing, with brightness over 20 μW. Despite a light extraction efficiency of only 15%, these devices exceed the output power of any previous electrically driven submicrometer LED or laser pixel by 100 to 1000 times while showing comparable external quantum efficiencies. Modeling suggests that spreading of the electron-hole recombination region in fin LEDs at high injection levels suppresses the nonradiative Auger recombination processes. Further refinement of this design is expected to enable a new generation of high-brightness LED and laser pixels for macro- and microscale applications.

270 nm Pseudomorphic Ultraviolet Light-Emitting Diodes with Over 60 mW Continuous Wave Output Power

2013 ◽  
Vol 6 (3) ◽  
pp. 032101 ◽  
Author(s):  
James R. Grandusky ◽  
Jianfeng Chen ◽  
Shawn R. Gibb ◽  
Mark C. Mendrick ◽  
Craig G. Moe ◽  
...  
Keyword(s):  
Ultraviolet Light ◽  
Output Power ◽  
Light Emitting Diodes ◽  
Continuous Wave ◽  
Continuous Wave Output Power ◽  
Light Emitting ◽  
Ultraviolet Light Emitting Diodes

Improved Light Output Power of GaN-Based Light-Emitting Diodes Using Double Photonic Quasi-Crystal Patterns

2009 ◽  
Vol 30 (11) ◽  
pp. 1152-1154 ◽  
Author(s):  
Hung-Wen Huang ◽  
Chung-Hsiang Lin ◽  
Zhi-Kai Huang ◽  
Kang-Yuan Lee ◽  
Chang-Chin Yu ◽  
...  
Keyword(s):  
Output Power ◽  
Light Emitting Diodes ◽  
Light Output ◽  
Light Output Power ◽  
Light Emitting

Asymmetry of carrier transport leading to efficiency droop in GaInN based light-emitting diodes

2011 ◽  
Vol 99 (25) ◽  
pp. 251115 ◽  
Author(s):  
David S. Meyaard ◽  
Guan-Bo Lin ◽  
Qifeng Shan ◽  
Jaehee Cho ◽  
E. Fred Schubert ◽  
...  
Keyword(s):  
Carrier Transport ◽  
Light Emitting Diodes ◽  
Efficiency Droop ◽  
Light Emitting

Improvement of efficiency droop in InGaN/GaN multiple quantum well light-emitting diodes with trapezoidal wells

2010 ◽  
Vol 43 (35) ◽  
pp. 354004 ◽  
Author(s):  
Sang-Heon Han ◽  
Dong-Yul Lee ◽  
Hyun-Wook Shim ◽  
Gwon-Chul Kim ◽  
Young Sun Kim ◽  
...  
Keyword(s):  
Quantum Well ◽  
Light Emitting Diodes ◽  
Multiple Quantum Well ◽  
Efficiency Droop ◽  
Multiple Quantum ◽  
Light Emitting
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