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

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 Temperature dependent efficiency droop in GaInN light-emitting diodes with different current densities

2012 ◽  
Vol 100 (8) ◽  
pp. 081106 ◽  
Author(s):  
David S. Meyaard ◽  
Qifeng Shan ◽  
Jaehee Cho ◽  
E. Fred Schubert ◽  
Sang-Heon Han ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Efficiency Droop ◽  
Temperature Dependent ◽  
Light Emitting ◽  
Current Densities

scholarly journals Electroluminescence and current–voltage measurements of single-(In,Ga)N/GaN-nanowire light-emitting diodes in a nanowire ensemble

2019 ◽  
Vol 10 ◽  
pp. 1177-1187 ◽  
Author(s):  
David van Treeck ◽  
Johannes Ledig ◽  
Gregor Scholz ◽  
Jonas Lähnemann ◽  
Mattia Musolino ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Light Emitting Diodes ◽  
Detection System ◽  
Accurate Determination ◽  
Analysis Tool ◽  
Light Emitting ◽  
Current Voltage ◽  
Current Densities ◽  
Gan Nanowire ◽  
Measurement Approach

We present the combined analysis of electroluminescence (EL) and current–voltage (I–V) behavior of single, freestanding (In,Ga)N/GaN nanowire (NW) light-emitting diodes (LEDs) in an unprocessed, self-assembled ensemble grown by molecular beam epitaxy. The data were acquired in a scanning electron microscope equipped with a micromanipulator and a luminescence detection system. Single NW spectra consist of emission lines originating from different quantum wells, and the width of the spectra increases with decreasing peak emission energy. The corresponding I–V characteristics are described well by a modified Shockley equation. The key advantage of this measurement approach is the possibility to correlate the EL intensity of a single-NW LED with the actual current density in this NW. This way, the external quantum efficiency (EQE) can be investigated as a function of the current in a single-NW LED. The comparison of the EQE characteristic of single NWs and the ensemble device allows for a quite accurate determination of the actual number of emitting NWs in the working ensemble LED and the respective current densities in its individual NWs. This information is decisive for a meaningful and comprehensive characterization of a NW ensemble device, rendering the measurement approach employed here a very powerful analysis tool.

Suppression of external quantum efficiency roll-off of nanopatterned organic-light emitting diodes at high current densities

2015 ◽  
Vol 118 (15) ◽  
pp. 155501 ◽  
Author(s):  
Hiroyuki Kuwae ◽  
Atsushi Nitta ◽  
Kou Yoshida ◽  
Takashi Kasahara ◽  
Toshinori Matsushima ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
Light Emitting Diodes ◽  
Organic Light Emitting Diodes ◽  
High Current ◽  
Light Emitting ◽  
Organic Light ◽  
Current Densities

Efficiency Re-Climbing in High-Current Droop Regime for Gallium-Nitride-based Light-Emitting Diodes

2015 ◽  
Vol 24 (03n04) ◽  
pp. 1520008
Author(s):  
Guan-Bo Lin ◽  
E. Fred Schubert
Keyword(s):  
Light Emitting Diodes ◽  
Efficiency Droop ◽  
Hole Injection ◽  
Field Ionization ◽  
Cryogenic Temperatures ◽  
Light Emitting ◽  
Operating Current ◽  
Current Densities ◽  
P Type ◽  
Distinct Increase

The efficiency droop in GaInN/GaN blue light-emitting diodes (LEDs) usually commences at current density around 10 A/cm2 and the efficiency decreases monotonically after the droop onset. GaN-based LEDs suffer seriously, at typical operating current densities (10–100 A/cm2), by the efficiency droop. Efficiency re-climbing is observed in the typical droop regime at cryogenic temperatures below 125K. The “efficiency re-climbing” coincides with a distinct increase in device conductivity, which is mainly attributed to an enhancement in p-type conductivity due to field ionization of acceptors. The “efficiency re-climbing” phenomenon implies an approach of solving efficiency droop by enhancing hole injection by external electric field.

scholarly journals Высокоэффективные (EQE=37.5%) инфракрасные (850 нм) светодиоды с брэгговским и зеркальным отражателями

2021 ◽  
Vol 55 (12) ◽  
pp. 1218
Author(s):  
А.В. Малевская ◽  
Н.А. Калюжный ◽  
С.А. Минтаиров ◽  
Р.А. Салий ◽  
Д.А. Малевский ◽  
...  
Keyword(s):  
Active Region ◽  
Quantum Wells ◽  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
Light Emitting Diodes ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Light Emitting ◽  
Current Densities ◽  
Hydride Epitaxy

Developed and investigated are IR (850nm) light-emitting diodes based on AlGaAs/Ga(In)As heterostructures grown by the MOC-hydride epitaxy technique with multiple quantum wells in the active region and with a double optical reflector consisted of a multilayer Al0.9Ga0.1As/Al0.1Ga0.9As Bragg heterostructure and an Ag mirror layer. Light-emitting diodes with the external quantum efficiency (EQE) of 37.5% at current densities greater than 10A/cm2 have been fabricated.

Highly efficient organic electrophosphorescent light-emitting diodes with a reduced quantum efficiency roll off at large current densities

2004 ◽  
Vol 84 (7) ◽  
pp. 1052-1054 ◽  
Author(s):  
M. Cocchi ◽  
V. Fattori ◽  
D. Virgili ◽  
C. Sabatini ◽  
P. Di Marco ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Light Emitting Diodes ◽  
Light Emitting ◽  
Highly Efficient ◽  
Large Current ◽  
Current Densities
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