Recombination lifetime in InGaN/GaN based light emitting diodes at low current densities by differential carrier lifetime analysis

2013 ◽  
Vol 10 (3) ◽  
pp. 327-331 ◽  
Author(s):  
Lauri Riuttanen ◽  
Pyry Kivisaari ◽  
Nikolai Mäntyoja ◽  
Jani Oksanen ◽  
Muhammad Ali ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Carrier Lifetime ◽  
Recombination Lifetime ◽  
Light Emitting ◽  
Lifetime Analysis ◽  
Current Densities

scholarly journals Study on efficiency droop in InGaN/GaN light-emitting diodes based on differential carrier lifetime analysis

2016 ◽  
Vol 108 (1) ◽  
pp. 013501 ◽  
Author(s):  
Xiao Meng ◽  
Lai Wang ◽  
Zhibiao Hao ◽  
Yi Luo ◽  
Changzheng Sun ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Carrier Lifetime ◽  
Efficiency Droop ◽  
Light Emitting ◽  
Lifetime Analysis

Electrical Measurement of Recombination Lifetime in Blue Light Emitting Diodes

2004 ◽  
Vol 829 ◽  
Author(s):  
M. A. Awaah ◽  
R. Nana ◽  
K. Das
Keyword(s):  
Blue Light ◽  
Light Emitting Diodes ◽  
Deep Level ◽  
Electrical Measurement ◽  
High Concentration ◽  
Recombination Lifetime ◽  
Light Emitting ◽  
Radiative Processes ◽  
Current Voltage ◽  
Capacitance Voltage

ABSTRACTA recombination lifetime of approximately 25 ns was extracted from measured reverse recovery storage times in AlGaN/GaN/AlGaN double heterojunction blue light emitting diodes. This experimentally determined lifetime is expected to arise from a combination of radiative and non-radiative processes occurring in the diodes. The non-radiative processes are likely to be due the presence of a high concentration deep-states as identified from the current-voltage and capacitance-voltage measurements. Current-voltage characteristics of these diodes were highly non-ideal as indicated by high values of the ideality factor ranging from 3.0 – 7.0. Logarithmic plots of the forward characteristics indicated a space-charge-limited-current (SCLC) conduction in presence of a high density of “deep-level states” in the active region of the diodes. An analysis of these characteristics yielded an approximate density of these deep-level states as 2 × 1017/cm3. The density of deep-states extracted from capacitance-voltage measurements were in good agreement with that obtained from current-voltage measurements.

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.

scholarly journals Controlling the dopant profile for SRH suppression at low current densities in λ ≈ 1330 nm GaInAsP light-emitting diodes

2020 ◽  
Vol 116 (20) ◽  
pp. 203503
Author(s):  
Parthiban Santhanam ◽  
Wei Li ◽  
Bo Zhao ◽  
Chris Rogers ◽  
Dodd Joseph Gray ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Light Emitting ◽  
Dopant Profile ◽  
Current Densities

Current Density Dependence of Transient Electroluminescence in Phosphorescent Organic Light-Emitting Diodes

2011 ◽  
Vol 1286 ◽  
Author(s):  
Hirotake Kajii ◽  
Noriyoshi Takahota ◽  
Yadong Wang ◽  
Yutaka Ohmori
Keyword(s):  
Current Density ◽  
Light Emitting Diodes ◽  
High Current Density ◽  
Organic Light Emitting Diodes ◽  
Recombination Lifetime ◽  
Light Emitting ◽  
Organic Light ◽  
Decay Times ◽  
Transient Electroluminescence ◽  
Triplet Triplet Annihilation

ABSTRACTThe transient electroluminescence (EL) of phosphorescent organic light-emitting diodes (OLEDs) was investigated. The behaviors of the transient characteristics are analyzed using the triplet-triplet annihilation model. The device exhibited a gradual decrease in quantum current efficiency owing to the triplet-triplet annihilation at a high current density. At a higher current density, the reduced rise and decay times are due to high-density triplet excitons related to the enhanced triplet-triplet annihilation and the increase of the nonradiative process. The modulation speed of the devices is mainly limited by the phosphorescent recombination lifetime.

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