Liquid Phase Homoepitaxial Growth of 4H-SiC Crystals and Fabrication Techniques of Bluish-Purple Light-Emitting Diodes

1989 ◽  
Vol 162 ◽  
Author(s):  
Y. Ueda ◽  
T. Nakata ◽  
K. Koga ◽  
Y. Matsushita ◽  
Y. Fujikawa ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Light Output ◽  
Argon Atmosphere ◽  
Color Purity ◽  
Peak Wavelength ◽  
Vacuum Sublimation ◽  
High Brightness ◽  
Light Emitting ◽  
Homoepitaxial Growth ◽  
Forward Current

ABSTRACT4H-SiC single crystals have been fabricated on the seeds of 6H-type crystals by the vacuum-sublimation (modified Lely) method at a temperature of 2400 °C and under a pressure of 2–60 mbar in an argon atmosphere. Liquid phase epitaxy was attempted by using a dipping method with a 4H-SiC off-orientation substrate whose {0001} C-face varied toward the <1120> direction by 5 degrees. The polytype of the grown crystals was found to be the 4H-type through measurements of Raman scattering and photoluminescence. P-n junction diodes were epitaxially obtained on 4H-SiC substrates. Aluminum and nitrogen were doped as acceptors and donors, respectively. The LED emitted bluish-purple light with a high brightness of 2.2 mcd at a forward current of 20 mA. Other characteristics were as follows : 420–425 nm peak wavelength, 90 % color purity, and a light output of 4 μW.

Effects of V/III ratio of InGaN quantum well at high growth temperature for near ultraviolet light emitting diodes

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohd Ann Amirul Zulffiqal Md Sahar ◽  
Zainuriah Hassan ◽  
Sha Shiong Ng ◽  
Way Foong Lim ◽  
Khai Shenn Lau ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Quantum Wells ◽  
Ultraviolet Light ◽  
Light Output ◽  
Emission Peak ◽  
Organic Chemical ◽  
Peak Wavelength ◽  
Content Type ◽  
Light Emitting ◽  
Near Ultraviolet

Purpose The aims of this paper is to study the effects of the V/III ratio of indium gallium nitride (InGaN) quantum wells (QWs) on the structural, optical and electrical properties of near-ultraviolet light-emitting diode (NUV-LED). Design/methodology/approach InGaN-based NUV-LED is successfully grown on the c-plane patterned sapphire substrate at atmospheric pressure using metal organic chemical vapor deposition. Findings The indium composition and thickness of InGaN QWs increased as the V/III ratio increased from 20871 to 11824, according to high-resolution X-ray diffraction. The V/III ratio was also found to have an important effect on the surface morphology of the InGaN QWs and thus the surface morphology of the subsequent layers. Apart from that, the electroluminescence measurement revealed that the V/III ratio had a major impact on the light output power (LOP) and the emission peak wavelength of the NUV-LED. The LOP increased by up to 53% at 100 mA, and the emission peak wavelength of the NUV-LED changed to a longer wavelength as the V/III ratio decreased from 20871 to 11824. Originality/value This study discovered a relation between the V/III ratio and the properties of QWs, which resulted in the LOP enhancement of the NUV-LED. High TMIn flow rates, which produced a low V/III ratio, contribute to the increased LOP of NUV-LED.

InGaN/AlGaN Double-Heterostructure Blue Leds

1994 ◽  
Vol 339 ◽  
Author(s):  
Shuji Nakamura
Keyword(s):  
Blue Light ◽  
Full Width ◽  
Half Maximum ◽  
Ingan Layer ◽  
Peak Wavelength ◽  
Forward Voltage ◽  
High Brightness ◽  
Light Emitting ◽  
Double Heterostructure ◽  
First Time

ABSTRACTHigh-brightness InGaN/AlGaN double-heterostructure (DH) blue-light-emitting diodes (LEDs) with a luminous intensity of 1.2 cd were fabricated successfully for the first time. As an active layer, a Zn-doped InGaN layer was used. The peak wavelength and the full width at half-maximum of the electroluminescence were 450 nm and 70 nm, respectively. The forward voltage was as low as 3.6V at 20 mA.

Light-Emitting Diodes with a Peak Wavelength of 5.38 µm from Liquid-Phase Epitaxial Ga0.1In0.9Sb/InSb Heterostructures

2002 ◽  
Vol 41 (Part 1, No. 6A) ◽  
pp. 3669-3670
Author(s):  
Xiu Ying Gong ◽  
Hirofumi Kan ◽  
Takamitsu Makino ◽  
Takefumi Iida ◽  
Mitsuru Aoyama ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Light Emitting Diodes ◽  
Peak Wavelength ◽  
Light Emitting ◽  
Liquid Phase Epitaxial

HOW DO WE LOSE EXCITATION IN THE GREEN?

2011 ◽  
Vol 20 (01) ◽  
pp. 13-25 ◽  
Author(s):  
CHRISTIAN WETZEL ◽  
YONG XIA ◽  
WEI ZHAO ◽  
YUFENG LI ◽  
MINGWEI ZHU ◽  
...  
Keyword(s):  
Structural Defects ◽  
Excitation Density ◽  
Acceptor Pair ◽  
Time Resolved ◽  
High Brightness ◽  
Light Emitting ◽  
Homoepitaxial Growth ◽  
Bulk Gan ◽  
Donor Acceptor ◽  
Crystallographic Axes

Efficiency droop and green gap are terms that summarize performance limitations in GaInN / GaN high brightness light emitting diodes (LEDs). Here we summarize progress in the development of green LEDs and report on time resolved luminescence data of polar c -plane and non-polar m -plane material. We find that by rigorous reduction of structural defects in homoepitaxy on bulk GaN and V -defect suppression, higher efficiency at longer wavelengths becomes possible. We observe that the presence of donor acceptor pair recombination within the active region correlates with lower device performance. To evaluate the aspects of piezoelectric polarization we compare LED structures grown along polar and non-polar crystallographic axes. In contrast to the polar material we find single exponential luminescence decay and emission wavelengths that remain stable irrespective of the excitation density. Those findings render high prospects for overcoming green gap and droop in non-polar homoepitaxial growth.

Effects of Localized Heat Generations Due to the Color Conversion in Phosphor Particles and Layers of High Brightness Light Emitting Diodes

2003 ◽  
Author(s):  
Mehmet Arik ◽  
Stanton Weaver ◽  
Charles Becker ◽  
Michael Hsing ◽  
Alok Srivastava
Keyword(s):  
Light Emitting Diodes ◽  
Uv Light ◽  
Numerical Models ◽  
Light Output ◽  
High Brightness ◽  
Light Emitting ◽  
White Leds ◽  
Strong Candidate ◽  
Short Wavelength Light ◽  
Element Technique

The efficiency and reliability of the solid-state lighting devices strongly depend on successful thermal management. Light emitting diodes, LEDs, a strong candidate for the next generation general illumination applications are of interest. Typical white LEDs start with either blue or near UV light generated by the active quantum layers. The light is guided through a transparent encapsulant filled with micron sized phosphor particles. The phosphor particles up-convert the short wavelength light to desired colors, producing white light. Due to low quantum efficiency, during the conversion, localized heating of small particles occurs. Experimental results with high brightness LED packages showed that there is significant light output reduction. Idealized numerical models through Finite element technique were created to evaluate the effects of localized heat generations at particles and layers. Results showed that as small as a 3 mW heat generation on a 20 μm diameter spherical phosphor particle might lead to excessive temperatures which can be a major source of light output degradation and reliability concern for high brightness LEDs.

POLARIZATION PROPERTIES OF LARGE-AREA GaN-BASED LIGHT-EMITTING DIODES WITH AN OMNIDIRECTIONAL NANOSTRUCTURE

NANO ◽  
2012 ◽  
Vol 07 (05) ◽  
pp. 1250035
Author(s):  
WAN-WEI WANG ◽  
LUNG-CHIEN CHEN ◽  
YA-HSIN WANG
Keyword(s):  
Blue Light ◽  
Ag Nanoparticles ◽  
Light Emitting Diodes ◽  
Bragg Reflector ◽  
Large Area ◽  
Peak Wavelength ◽  
Light Emitting ◽  
Sapphire Substrates ◽  
Forward Current

Large-area GaN -based blue light-emitting diodes (LEDs) on sapphire substrates with an omnidirectional nanostructure consisted of Ag nanoparticles and TiO2/SiO2 Bragg reflector were fabricated. For the LEDs without the omnidirectional nanostructure, the spectra of the P- and S-polarization light are lightly different and the peak wavelength of P- and S-polarization light was estimated to be 464 nm and 463 nm, respectively at forward current of 20 mA. In contrast, for the LEDs with the omnidirectional nanostructure, the spectra of the P- and S-polarization light are nearly the same at forward current of 20 mA and 100 mA.

Comparison between the Photoluminescence Mappings Under Selective and Non-selective Excitation and the Electroluminescence Mappings of the Epitaxial Wafers with InGaN-LED Structure

2006 ◽  
Vol 955 ◽  
Author(s):  
Kazuyuki Tadatomo ◽  
Osamu Shimoike ◽  
Hiromichi Noda ◽  
Masahiro Hiraoka ◽  
Kazumasa Yoshimura ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Room Temperature ◽  
Selective Excitation ◽  
Excitation Power ◽  
Excitation Power Density ◽  
Peak Wavelength ◽  
Light Emitting ◽  
Forward Current ◽  
Pl Mapping ◽  
P Type

ABSTRACTWe compared the photoluminescence (PL) mappings of epitaxial wafers for light emitting diodes (LEDs) by using a He-Cd laser (325 nm line) and a laser diode (LD) with peak wavelength of 405 nm as excitation sources and the electroluminescence (EL) mappings of the same wafers. The samples were epitaxial wafers for blue and green InGaN-LEDs obtained in commercial. The wafers were fabricated into LEDs with a Ni/Au transparent p-type electrode and a Ti/Ni n-type electrode after the PL mapping measurements. The He-Cd laser performed the band to band excitation of (Al)GaN cladding and contact layers (non-selective excitation). Because the photo-excited carriers at the cladding and contact layers diffused into the multi-quantum wells (MQWs) and contributed the PL emission by radiative recombination in the MQWs, the PL mapping under the influence of the (Al)GaN cladding and contact layers was obtained. On the other hand, the LD (405 nm) enable us to obtain the PL mapping under selective excitation of the MQWs without the influence of the cladding and contact layers. The PL mapping measurements were carried out at room temperature (RT) at the excitation power density of 310 W/cm2 under non-selective excitation (by the He-Cd laser) and at that of 11.5 W/cm2 under selective excitation (by the LD). The EL mapping was measured at a forward current of 20 mA at RT. The area of the wafer with high EL intensity was coincident with the area with the high PL intensity under selective excitation. Therefore, the PL mapping measurement under selective excitation of MQWs is recommended to characterize the epitaxial wafers and to estimate the device performance of InGaN-LEDs.

InGaN Light-Emitting Diodes with Quantum-Well Structures

1995 ◽  
Vol 395 ◽  
Author(s):  
Shuji Nakamura
Keyword(s):  
Quantum Well ◽  
Light Emitting Diodes ◽  
Single Quantum ◽  
Peak Wavelength ◽  
Single Quantum Well ◽  
Light Emitting ◽  
Quantum Well Structures ◽  
Forward Current ◽  
20 Nm ◽  
Green Leds

ABSTRACTInGaN single-quantum-well-structure (SQW) light-emitting diodes (LEDs) with an emission wavelength between violet and orange were fabricated. The maximum on-axis luminous intensity of green LEDs was 12 cd and the external quantum efficiency was as high as 6.3 % at a forward current of 20 mA, while those of blue LEDs were 2 cd and 9.1 %, respectively. The peak wavelength and the full width at half-maximum of the green LEDs were 520 nm and 30 nm, respectively, while those of blue LEDs were 450 nm and 20 nm, respectively. The color of green InGaN SQW LEDs was greener than those of conventional GaP and AlInGaP LEDs.

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