scholarly journals Enhancement in external quantum efficiency of AlGaInP red μ-LED using chemical solution treatment process

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Byung Oh Jung ◽  
Wonyong Lee ◽  
Jeomoh Kim ◽  
Myungshin Choi ◽  
Hui-Youn Shin ◽  
...  
Keyword(s):  
Chemical Treatment ◽  
Solution Treatment ◽  
Surface Recombination ◽  
Injection Current ◽  
Plasma Damage ◽  
Light Emitting ◽  
Chemical Surface ◽  
High Injection ◽  
Transmission Electron ◽  
Sidewall Surface

AbstractTo investigate the effects of their surface recovery and optical properties, extremely small sized (12 µm × 12 µm mesa area) red AlGaInP micro light emitting diodes ($$\upmu$$ μ LED) were fabricated using a diluted hydrofluoric acid (HF) surface etch treatment. After the chemical treatment, the external quantum efficiencies (EQEs) of $$\upmu$$ μ -LED at low and high injection current regions have been improved by 35.48% and 12.86%, respectively. The different phenomena of EQEs have a complex relationship between the suppression of non-radiative recombination originating from the etching damage of the surface and the improvement of light extraction of the sidewalls. The constant enhancement of EQE at a high injection current it is attributed to the expansion of the active region’s sidewall surface area by the selective etching of AlInP layers. The improved EQE at a low injection current is related to the minimization of the surface recombination caused by plasma damage from the surface. High-resolution transmission electron microscopy (HR-TEM) revealed physical defects on the sidewall surface, such as plasma-induced lattice disorder and impurity contamination damage, were eliminated using chemical treatment. This study suggests that chemical surface treatment using diluted HF acid can be an effective method for enhancing the $$\upmu$$ μ -LED performance.

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.

TiN Enhancement of Output Performance for Light-Emitting Diodes under High Injection Current

2004 ◽  
Vol 43 (2) ◽  
pp. 594-597 ◽  
Author(s):  
Chien-Chih Liu ◽  
Wei-Ting Wang ◽  
Mau-Phon Houng ◽  
Yeong-Her Wang
Keyword(s):  
Light Emitting Diodes ◽  
Injection Current ◽  
Light Emitting ◽  
Output Performance ◽  
High Injection

IR and MW Absorption Techniques for Bulk and Surface Recombination Control in High-Quaiity Silicon

1995 ◽  
Vol 386 ◽  
Author(s):  
A. Kaniava ◽  
U. Menczigar ◽  
J. Vanhellemont ◽  
J. Poortmans ◽  
A. L. P. Rotondaro ◽  
...  
Keyword(s):  
Surface Recombination ◽  
Surface Recombination Velocity ◽  
Silicon Substrates ◽  
Injection Level ◽  
Effective Lifetime ◽  
Carrier Recombination ◽  
High Injection Level ◽  
High Injection ◽  
Wide Range ◽  
Recombination Velocity

ABSTRACTThe carrier recombination rate in high-quality FZ and Cz silicon substrates is studied by contactless infrared and microwave absorption techniques. Different surface treatments covering a wide range of surface recombination velocity have been used for the separation of bulk and surface recombination components and evaluating of the efficiency of passivation. Limitations of effective lifetime approach are analyzed specific for low and high injection level. Sensitivity limits of the techniques for iron contamination are discussed

Plasma damage-free sputtering of indium tin oxide cathode layers for top-emitting organic light-emitting diodes

2005 ◽  
Vol 86 (18) ◽  
pp. 183503 ◽  
Author(s):  
Han-Ki Kim ◽  
D.-G. Kim ◽  
K.-S. Lee ◽  
M.-S. Huh ◽  
S. H. Jeong ◽  
...  
Keyword(s):  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Light Emitting Diodes ◽  
Organic Light Emitting Diodes ◽  
Plasma Damage ◽  
Light Emitting ◽  
Organic Light ◽  
Oxide Cathode

Recombination of Localized Excitons in InGaN Single- and Multiquantum-Well Structures

1996 ◽  
Vol 449 ◽  
Author(s):  
S. Chichibu ◽  
T. Azuhata ◽  
T. Sota ◽  
S. Nakamura
Keyword(s):  
Quantum Well ◽  
Stark Effect ◽  
Molar Fraction ◽  
Green Light ◽  
Localized States ◽  
Single Quantum Well ◽  
Light Emitting ◽  
Transmission Electron ◽  
Localized Excitons ◽  
Multiquantum Well

ABSTRACTSpontaneous emission mechanisms of InGaN single quantum well (SQW) blue and green light emitting diodes (LEDs) and multiquantum well (MQW) laser diode (LD) structures were investigated. Their static electroluminescence (EL) peak was assigned to the recombination of excitons localized at certain potential minima in the quantum well (QW). The transmission electron micrographs (TEM) indicated fluctuation of In molar fraction in the QWs. The blueshift of the EL peak caused by the increase of the driving current was explained by combined effects of the quantum-confinement Stark effect and band filling of the localized states by excitons.

scholarly journals Saga of efficiency degradation at high injection in InGaN light emitting diodes

2014 ◽  
Vol 38 ◽  
pp. 269-313 ◽  
Author(s):  
Vitaliy AVRUTIN ◽  
Shopan A. HAFIZ ◽  
Fan ZHANG ◽  
Ümit ÖZGÜR ◽  
Enrico BELLOTTI ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Light Emitting ◽  
High Injection
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