Comparison of the Electroluminescence of Blue and Deep-UV Light-Emitting Diodes at Elevated Temperatures

AbstractThe performance of InGaN and AlGaN-based blue (465nm) and deep ultraviolet (UV) (280 nm) light-emitting diodes (LEDs) at elevated temperatures (25-175 °C) were investigated. As a result of uniform high-Al content AlGaN alloys yielded by migration-enhanced metalorganic chemical vapor deposition, the deep-UV LED showed dominant band-edge emission, much smaller alloy broadening and weaker localization effects as compared to the InGaN LED. Strong carrier localization was retained in the blue LED up to 175 °C, leading to temperature-independent emission intensity at low-energy tails. The UV LED, however, showed a much more rapid decrease in light output with increasing temperature. The characteristic temperature was 37 K, compared to 270 K for the blue LED. These findings implicate the lack of localization effects in AlGaN alloys as one of the causal factors in the poor thermal performance of the deep UV LED and suggest that increasing carrier confining potentials will provide a critical means to improve its thermal stability.

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Efficient photochemical generation of peroxycarboxylic nitric anhydrides with ultraviolet light emitting diodes

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-8-905-2015 ◽

2015 ◽

Vol 8 (1) ◽

pp. 905-934

Author(s):

N. D. Rider ◽

Y. M. Taha ◽

C. A. Odame-Ankrah ◽

J. A. Huo ◽

T. W. Tokarek ◽

...

Keyword(s):

Ultraviolet Light ◽

Light Emitting Diodes ◽

Thermal Dissociation ◽

Measurement Techniques ◽

Light Output ◽

Internal Standard ◽

Chemical Mechanism ◽

Light Emitting ◽

Uv Led ◽

Ultraviolet Light Emitting Diodes

Abstract. Photochemical sources of peroxycarboxylic nitric anhydrides (PANs) are utilized in many atmospheric measurement techniques for calibration or to deliver an internal standard. Conventionally, such sources rely on phosphor-coated low-pressure mercury (Hg) lamps to generate the UV light necessary to photo-dissociate a dialkyl ketone (usually acetone) in the presence of a calibrated amount of nitric oxide (NO) and oxygen (O2). In this manuscript, a photochemical PAN source in which the Hg lamp has been replaced by arrays of ultraviolet light-emitting diodes (UV-LEDs) is described. The output of the UV-LED source was analyzed by gas chromatography (PAN-GC) and thermal dissociation cavity ring-down spectroscopy (TD-CRDS). Using acetone, diethyl ketone (DIEK), diisopropyl ketone (DIPK), or di-n-propyl ketone (DNPK), respectively, the source produces peroxyacetic (PAN), peroxypropionic (PPN), peroxyisobutanoic (PiBN), or peroxy-n-butanoic nitric anhydride (PnBN) from NO in high yield (> 90%). Box model simulations with a subset of the Master Chemical Mechanism (MCM) were carried out to rationalize products yields and to identify side products. The use of UV-LED arrays offers many advantages over conventional Hg lamp setups, including greater light output over a narrower wavelength range, lower power consumption, and minimal generation of heat.

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Improvement in Light Output of Ultraviolet Light-Emitting Diodes with Patterned Double-Layer ITO by Laser Direct Writing

Nanomaterials ◽

10.3390/nano9020203 ◽

2019 ◽

Vol 9 (2) ◽

pp. 203 ◽

Cited By ~ 10

Author(s):

Jie Zhao ◽

Xinghuo Ding ◽

Jiahao Miao ◽

Jinfeng Hu ◽

Hui Wan ◽

...

Keyword(s):

Double Layer ◽

Indium Tin Oxide ◽

Light Emitting Diodes ◽

Light Output ◽

Light Extraction Efficiency ◽

Direct Writing ◽

Laser Direct Writing ◽

Current Spreading ◽

Light Emitting ◽

Uv Led

A patterned double-layer indium-tin oxide (ITO), including the first unpatterned ITO layer serving as current spreading and the second patterned ITO layer serving as light extracting, was applied to obtain uniform current spreading and high light extraction efficiency (LEE) of GaN-based ultraviolet (UV) light-emitting diodes (LEDs). Periodic pinhole patterns were formed on the second ITO layer by laser direct writing to increase the LEE of UV LED. Effects of interval of pinhole patterns on optical and electrical properties of UV LED with patterned double-layer ITO were studied by numerical simulations and experimental investigations. Due to scattering out of waveguided light trapped inside the GaN film, LEE of UV LED with patterned double-layer ITO was improved as compared to UV LED with planar double-layer ITO. As interval of pinhole patterns decreased, the light output power (LOP) of UV LED with patterned double-layer ITO increased. In addition, UV LED with patterned double-layer ITO exhibited a slight degradation of current spreading as compared to the UV LED with a planar double-layer ITO. The forward voltage of UV LED with patterned double-layer ITO increased as the interval of pinhole patterns decreased.

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Low-Temperature Operation of Green, Blue and UV InGaN/GaN Multiple-Quantum-Well Light-Emitting Diodes

MRS Proceedings ◽

10.1557/proc-764-c5.5 ◽

2003 ◽

Vol 764 ◽

Author(s):

X. A. Cao ◽

S. F. LeBoeuf ◽

J. L. Garrett ◽

A. Ebong ◽

L. B. Rowland ◽

...

Keyword(s):

Quantum Well ◽

Light Emitting Diodes ◽

Multiple Quantum Well ◽

Light Output ◽

Localized States ◽

Multiple Quantum ◽

Nonradiative Recombination ◽

Light Emitting ◽

Temperature Range ◽

Green Leds

Absract:Temperature-dependent electroluminescence (EL) of InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with peak emission energies ranging from 2.3 eV (green) to 3.3 eV (UV) has been studied over a wide temperature range (5-300 K). As the temperature is decreased from 300 K to 150 K, the EL intensity increases in all devices due to reduced nonradiative recombination and improved carrier confinement. However, LED operation at lower temperatures (150-5 K) is a strong function of In ratio in the active layer. For the green LEDs, emission intensity increases monotonically in the whole temperature range, while for the blue and UV LEDs, a remarkable decrease of the light output was observed, accompanied by a large redshift of the peak energy. The discrepancy can be attributed to various amounts of localization states caused by In composition fluctuation in the QW active regions. Based on a rate equation analysis, we find that the densities of the localized states in the green LEDs are more than two orders of magnitude higher than that in the UV LED. The large number of localized states in the green LEDs are crucial to maintain high-efficiency carrier capture at low temperatures.

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Performance of vertical type deep UV light-emitting diodes depending on the Ga-face n-contact hole density

Applied Physics Letters ◽

10.1063/5.0052416 ◽

2021 ◽

Vol 118 (23) ◽

pp. 231102

Author(s):

Youn Joon Sung ◽

Dong-Woo Kim ◽

Geun Young Yeom ◽

Kyu Sang Kim

Keyword(s):

Light Emitting Diodes ◽

Uv Light ◽

Hole Density ◽

Light Emitting ◽

Deep Uv

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Improved Performance of GaN-Based Light-Emitting Diodes Grown on Si (111) Substrates with NH3 Growth Interruption

Micromachines ◽

10.3390/mi12040399 ◽

2021 ◽

Vol 12 (4) ◽

pp. 399

Author(s):

Sang-Jo Kim ◽

Semi Oh ◽

Kwang-Jae Lee ◽

Sohyeon Kim ◽

Kyoung-Kook Kim

Keyword(s):

Buffer Layer ◽

Light Emitting Diodes ◽

Defect Density ◽

Strain Relaxation ◽

Multiple Quantum Well ◽

Light Output ◽

Multiple Quantum ◽

Light Emitting ◽

Growth Interruption ◽

Aln Buffer

We demonstrate the highly efficient, GaN-based, multiple-quantum-well light-emitting diodes (LEDs) grown on Si (111) substrates embedded with the AlN buffer layer using NH3 growth interruption. Analysis of the materials by the X-ray diffraction omega scan and transmission electron microscopy revealed a remarkable improvement in the crystalline quality of the GaN layer with the AlN buffer layer using NH3 growth interruption. This improvement originated from the decreased dislocation densities and coalescence-related defects of the GaN layer that arose from the increased Al migration time. The photoluminescence peak positions and Raman spectra indicate that the internal tensile strain of the GaN layer is effectively relaxed without generating cracks. The LEDs embedded with an AlN buffer layer using NH3 growth interruption at 300 mA exhibited 40.9% higher light output power than that of the reference LED embedded with the AlN buffer layer without NH3 growth interruption. These high performances are attributed to an increased radiative recombination rate owing to the low defect density and strain relaxation in the GaN epilayer.

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Air stable and highly efficient Bi3+-doped Cs2SnCl6 for blue light-emitting diodes

RSC Advances ◽

10.1039/d1ra03622j ◽

2021 ◽

Vol 11 (42) ◽

pp. 26415-26420

Author(s):

Yue Yao ◽

Si-Wei Zhang ◽

Zijian Liu ◽

Chun-Yun Wang ◽

Ping Liu ◽

...

Keyword(s):

Quantum Yield ◽

Blue Light ◽

Light Emitting Diodes ◽

Light Emitting ◽

Color Coordinates ◽

Blue Led ◽

Highly Efficient ◽

Photoluminescence Quantum Yield ◽

Long Life

A Bi3+-doped Cs2SnCl6 exhibits photoluminescence at around 456 nm and a photoluminescence quantum yield of 31%. The blue LED based on the Bi3+-doped Cs2SnCl6 phosphor exhibits a long life of 120 hours and a CIE color coordinates of (0.14, 0.11).

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

IEEE Electron Device Letters ◽

10.1109/led.2009.2029985 ◽

2009 ◽

Vol 30 (11) ◽

pp. 1152-1154 ◽

Cited By ~ 16

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

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Robust 285 nm Deep UV Light Emitting Diodes over Metal Organic Hydride Vapor Phase Epitaxially Grown AlN/Sapphire Templates

Japanese Journal of Applied Physics ◽

10.1143/jjap.46.l537 ◽

2007 ◽

Vol 46 (No. 23) ◽

pp. L537-L539 ◽

Cited By ~ 26

Author(s):

Vinod Adivarahan ◽

Qhalid Fareed ◽

Surendra Srivastava ◽

Thomas Katona ◽

Mikhail Gaevski ◽

...

Keyword(s):

Vapor Phase ◽

Light Emitting Diodes ◽

Uv Light ◽

Light Emitting ◽

Organic Hydride ◽

Metal Organic ◽

Deep Uv

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High-Power GaN-Based Vertical Light-Emitting Diodes on 4-Inch Silicon Substrate

Nanomaterials ◽

10.3390/nano9081178 ◽

2019 ◽

Vol 9 (8) ◽

pp. 1178 ◽

Cited By ~ 2

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.

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