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Applied Sciences
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GaN-Based Light-Emitting Diodes
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GaN-Based Light-Emitting Diodes

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Applied Physics General".

Deadline for manuscript submissions: closed (31 March 2020) | Viewed by 30896

Special Issue Editor

Prof. Dr. Jinsub Park

E-Mail Website
Guest Editor
Department of Electronic Engineering, Hanyang University, Seoul 04763, Korea
Interests: metal-oxide nanomaterials; compound semiconductors; optoelectronic devices; optical sensor; energy harvesting; 2D/spheres nanomaterials and applications
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Recent dramatic improvements of III-Nitride (GaN) light-emitting diodes with enhanced quantum efficiency can make it possible to expand their applications to versatile fields, such as display, solid-state lighting, and environmental, agricultural, and medical applications. In the several decades since mass production of blue LEDs began, we have caught sight of a revolution in solid-state lighting replacing transitional incandescent and fluorescent lamps. Moreover, in the recent display field, micro-LEDs can be considered as an advanced lighting source for VR/AR and TV due to their high energy efficiency and flexibility. The Journal of Applied Sciences will publish a Special Issue providing an overview of GaN-based LEDs and related cutting-edge technologies. Topics of interest include but are not limited to: epitaxy; micro-LEDs; defect engineering and characterization; electrical and optical properties; light extraction improvement methods; phosphors for III-nitride UV and visible LEDs; and theory and simulation, emerging materials; nanostructures; applications of III-nitride LEDs.

Prof. Dr. Jinsub Park
Guest Editor

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Keywords

  • Epitaxy
  • Fabrication
  • Package
  • Light extraction efficiency
  • Micro-LEDs
  • Application of LEDs

Published Papers (7 papers)

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Research

Jump to: Review

7 pages, 1570 KiB  
Article
High-Performance Color-Converted Full-Color Micro-LED Arrays
by Won Hee Kim, Young Jae Jang, Ja-Yeon Kim, Myungsoo Han, MinJae Kang, Kiyong Yang, Jae-Hyun Ryou and Min-Ki Kwon
Appl. Sci. 2020, 10(6), 2112; https://doi.org/10.3390/app10062112 - 20 Mar 2020
Cited by 19 | Viewed by 5848
Abstract
Color-converted micro-LED displays consisting of mono-blue-colored micro LED arrays and color-conversion materials have been used to achieve full color while reliving the transfer and epitaxial growth of three different-colored micro LEDs. An efficient technique is suggested to deposit the color-conversion layers on the [...] Read more.
Color-converted micro-LED displays consisting of mono-blue-colored micro LED arrays and color-conversion materials have been used to achieve full color while reliving the transfer and epitaxial growth of three different-colored micro LEDs. An efficient technique is suggested to deposit the color-conversion layers on the blue micro LEDs by using a mixture of photo-curable acrylic and nano-organic color-conversion materials through the conventional lithography technique. This study attempts to provide a solution to fabricate full-color micro-LED displays. Full article
(This article belongs to the Special Issue GaN-Based Light-Emitting Diodes)
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10 pages, 3646 KiB  
Article
Effects of Different InGaN/GaN Electron Emission Layers/Interlayers on Performance of a UV-A LED
by Dohyun Kim, Keun Man Song, UiJin Jung, Subin Kim, Dong Su Shin and Jinsub Park
Appl. Sci. 2020, 10(4), 1514; https://doi.org/10.3390/app10041514 - 23 Feb 2020
Cited by 8 | Viewed by 3018
Abstract
In this study, we investigated the effects of InGaN/GaN-based interlayer (IL) and electron emitting layer (EEL) consisting of a GaN barrier layer grown with different metal-organic (MO) precursors of gallium (Ga), which were grown underneath the active layer. The growth behavior of GaN [...] Read more.
In this study, we investigated the effects of InGaN/GaN-based interlayer (IL) and electron emitting layer (EEL) consisting of a GaN barrier layer grown with different metal-organic (MO) precursors of gallium (Ga), which were grown underneath the active layer. The growth behavior of GaN with triethyl Ga (TEGa) showed an increasing growth time due to a lower growth rate compared with GaN grown with trimethyl Ga (TMGa), resulting in the formation of columnar domains and grain boundary with reduced defect. UV-A light emitting diode (LED) chips with three types of ILs and EELs, grown with different MO sources, were fabricated and evaluated by light output power (LOP) measurements. The LOP intensity of UVLED-III with the GaN barrier layer-based IL and EEL grown by TEGa was enhanced by 1.5 times compared to that of the IL and EEL grown with TMGa at 300 mA current injection. Use of the GaN barrier layer in ILs and EELs grown by TEGa improved the crystal quality of the post grown InGaN/GaN multiple quantum well, which reduces leakage current. Therefore, for the UV-A LED with ILs and EELs grown with TEGa MO precursors, electrical and optical properties were improved significantly. Full article
(This article belongs to the Special Issue GaN-Based Light-Emitting Diodes)
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8 pages, 2918 KiB  
Article
High-Speed Light Signal Transmitters for Optical Communication Based on Ultraviolet Radiation
by Xin Li, Yue Wu, Jialei Yuan, Shuyu Ni, Chuan Qin, Yan Jiang, Jie Li and Yongjin Wang
Appl. Sci. 2020, 10(2), 693; https://doi.org/10.3390/app10020693 - 19 Jan 2020
Cited by 4 | Viewed by 2429
Abstract
A light signal transmitter based on ultraviolet radiation is realized on GaN-on-silicon platform. The light signal transmitter with ultra-small active area is fabricated by a double-etching process. The absolute value of negative junction capacitance of transmitter is as low as the pF (picofarads) [...] Read more.
A light signal transmitter based on ultraviolet radiation is realized on GaN-on-silicon platform. The light signal transmitter with ultra-small active area is fabricated by a double-etching process. The absolute value of negative junction capacitance of transmitter is as low as the pF (picofarads) scale in positive bias voltage. Small capacitance is beneficial to improve the communication performance of a transmitter. The dominant EL (electroluminescence) peak of transmitter is located at about 380 nm in the ultraviolet range. With the increase of the current, the dominant peak of transmitter remains stable and the light output power is lineally modulated. A free-space data transmission test in the ultraviolet range with 250 Mbps was conducted to indicate a promising high-speed optical communication capability of a light signal transmitter in the ultraviolet range. Full article
(This article belongs to the Special Issue GaN-Based Light-Emitting Diodes)
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14 pages, 8278 KiB  
Article
Amplification of Radiation-Induced Signal of LED Strip by Increasing Number of LED Chips and Using Amplifier Board
by Edrine Damulira, Muhammad Nur Salihin Yusoff, Ahmad Fairuz Omar and Nur Hartini Mohd Taib
Appl. Sci. 2020, 10(2), 651; https://doi.org/10.3390/app10020651 - 16 Jan 2020
Cited by 2 | Viewed by 2860
Abstract
Transducers, such as photodiodes, phototransistors, and photovoltaic cells are promising radiation detectors. However, for accurate radiation detection and dosimetry, signals that emanate from these devices have to be sufficient to facilitate accurate calibrations, i.e., assigning a quantity of radiation dose to a specific [...] Read more.
Transducers, such as photodiodes, phototransistors, and photovoltaic cells are promising radiation detectors. However, for accurate radiation detection and dosimetry, signals that emanate from these devices have to be sufficient to facilitate accurate calibrations, i.e., assigning a quantity of radiation dose to a specific magnitude of the signal. More so, purposely fabricated for luminescence, LEDs produce significantly low signals during radiation detection applications. Therefore, this paper investigates the enhancement and augmentation of photovoltaic signals that were generated when LED strips were being exposed to diagnostic X-rays. Initially, signal amplification was achieved through increasing the effective LED active area (from 60 to 120 chips); by successively connecting LED strips. Further, signal amplification was undertaken by injecting the raw LED strip signal into an amplifier board with adjustable gains. In both the signal amplification techniques, the tube voltage (kVp), tube current-time product (mAs), and source-to-detector distance (SDD) were varied. The principal findings show that effective active area-based signal amplifications produced an overall average of 91.16% signal enhancement throughout all of the X-ray parameter variations. On the other hand, the amplifier board produced an average of 36.48% signal enhancement for the signals that were injected into it. Chip number increment-based signal amplifications had a 0.687% less coefficient of variation than amplifier board signal amplifications. The amplifier board signal amplifications were impaired by factors, such as dark currents, amplifier board maximum operational output voltage, and saturation. Therefore, future electronic signal amplification could use amplifier boards having low dark currents and high operational voltage headroom. The low-cost and simplicity that are associated with active-area amplification could be further exploited in a hybrid amplification technique with electronic amplification and scintillators. Full article
(This article belongs to the Special Issue GaN-Based Light-Emitting Diodes)
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18 pages, 3311 KiB  
Article
Comparison of Current–Voltage Response to Diagnostic X-rays of Five Light-Emitting Diode Strips
by Edrine Damulira, Muhammad Nur Salihin Yusoff, Suharti Sulaiman, Nur Farah Huda Zulkafli, Nur Amiela Zulkifli, Nur Shahirah Ahmad Shakir, Mohamad Azlan Zainun, Ahmad Fairuz Omar, Nur Hartini Mohd Taib and Nik kamarullah Ya Ali
Appl. Sci. 2020, 10(1), 200; https://doi.org/10.3390/app10010200 - 26 Dec 2019
Cited by 4 | Viewed by 3425
Abstract
Light-emitting diodes (LEDs) have miscellaneous applications owing to their low cost, small size, flexibility, and commercial availability. Furthermore, LEDs have dual applicability as light emitters and detectors. This study explores the current–voltage (C–V) response of LED strips exposed to diagnostic x-rays. Cold white, [...] Read more.
Light-emitting diodes (LEDs) have miscellaneous applications owing to their low cost, small size, flexibility, and commercial availability. Furthermore, LEDs have dual applicability as light emitters and detectors. This study explores the current–voltage (C–V) response of LED strips exposed to diagnostic x-rays. Cold white, warm white, red, green, and blue LED strip colors were tested. Each strip consisted of 12 LED chips and was connected to a multimeter. The variable diagnostic x-ray parameters evaluated were kilovoltage peak (kVp), milliampere-seconds (mAs), and source-to-image distance (SID). The radiation dose was also measured using a dosimeter simultaneously exposed to x-rays perpendicularly incident on the strips. Lastly, the consistency of C–V responses, and any possible degradation after 1–2 months was also analyzed. Each LED strip color was ranked according to its C–V response in each of the investigated parameters. The LED strip color with the best cumulative rank across all the tested parameters was then examined for reproducibility. Our findings revealed that the C–V responses of LED strips are (a) generally low but measurable, (b) inconsistent and fluctuating as a consequence of kVp variations, (c) positively correlated to mAs, (d) negatively correlated to SID, and (e) positively correlated to dose. Overall results suggested cold white LED strip as most feasible for x-ray detection—in comparison to examined colors. Additionally, the reproducibility study using the cold white LED strip found a similar trend of C–V response to all variables except kVp. Outcomes indicate that LED strips have the potential to be exploited for detecting low dose (~0–100 mGy) diagnostic x-rays. However, future studies should be carried out to increase the low C–V signal. Full article
(This article belongs to the Special Issue GaN-Based Light-Emitting Diodes)
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8 pages, 3118 KiB  
Article
Mass Transfer of Microscale Light-Emitting Diodes to Unusual Substrates by Spontaneously Formed Vertical Tethers During Chemical Lift-Off
by Ja-Yeon Kim, Yoo-Hyun Cho, Hyun-Sun Park, Jae-Hyun Ryou and Min-Ki Kwon
Appl. Sci. 2019, 9(20), 4243; https://doi.org/10.3390/app9204243 - 11 Oct 2019
Cited by 7 | Viewed by 3191
Abstract
A much simplified method for transferring Gallium nitride (GaN) light emitting didoes (LEDs) to an unusual substrate, such as glass, Si, polyethylene terephthalate, or polyurethane, was demonstrated with spontaneously formed vertical tethers during chemical lift-off (CLO), without requiring a sacrificial layer or extra [...] Read more.
A much simplified method for transferring Gallium nitride (GaN) light emitting didoes (LEDs) to an unusual substrate, such as glass, Si, polyethylene terephthalate, or polyurethane, was demonstrated with spontaneously formed vertical tethers during chemical lift-off (CLO), without requiring a sacrificial layer or extra process steps. The LED arrays resided on a stamp that was coated with an adhesive layer. After the layer with the LEDs was transferred to the new substrates, the stamp was removed by acetone to complete the preparation. Over 3 × 3 cm2 LED arrays transferred to various substrates without any damage and misorientation. We also found that the optical and electrical characteristics improved after transfer due to decease in built-in stress. This simple and practical method is expected to greatly facilitate the development of transferrable full color GaN microLEDs on various substrates with either greatly reduced or no damage. Full article
(This article belongs to the Special Issue GaN-Based Light-Emitting Diodes)
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Review

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26 pages, 6313 KiB  
Review
Review of GaN Thin Film and Nanorod Growth Using Magnetron Sputter Epitaxy
by Aditya Prabaswara, Jens Birch, Muhammad Junaid, Elena Alexandra Serban, Lars Hultman and Ching-Lien Hsiao
Appl. Sci. 2020, 10(9), 3050; https://doi.org/10.3390/app10093050 - 27 Apr 2020
Cited by 33 | Viewed by 9291
Abstract
Magnetron sputter epitaxy (MSE) offers several advantages compared to alternative GaN epitaxy growth methods, including mature sputtering technology, the possibility for very large area deposition, and low-temperature growth of high-quality electronic-grade GaN. In this article, we review the basics of reactive sputtering for [...] Read more.
Magnetron sputter epitaxy (MSE) offers several advantages compared to alternative GaN epitaxy growth methods, including mature sputtering technology, the possibility for very large area deposition, and low-temperature growth of high-quality electronic-grade GaN. In this article, we review the basics of reactive sputtering for MSE growth of GaN using a liquid Ga target. Various target biasing schemes are discussed, including direct current (DC), radio frequency (RF), pulsed DC, and high-power impulse magnetron sputtering (HiPIMS). Examples are given for MSE-grown GaN thin films with material quality comparable to those grown using alternative methods such as molecular-beam epitaxy (MBE), metal–organic chemical vapor deposition (MOCVD), and hydride vapor phase epitaxy (HVPE). In addition, successful GaN doping and the fabrication of practical devices have been demonstrated. Beyond the planar thin film form, MSE-grown GaN nanorods have also been demonstrated through self-assembled and selective area growth (SAG) method. With better understanding in process physics and improvements in material quality, MSE is expected to become an important technology for the growth of GaN. Full article
(This article belongs to the Special Issue GaN-Based Light-Emitting Diodes)
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