Special Issue "GaN-Based Optoelectronic Materials and Light Emitting Devices"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Materials".

Deadline for manuscript submissions: 31 December 2019.

Special Issue Editors

Prof. Hao-chung Kuo
E-Mail Website
Guest Editor
Department of Photonics & Institute of Electro-Optical Engineering, National Chiao Tung University, Taiwan
Interests: Nanostructured optoelectronic materials and devices; III-V(Nitride) high speed semiconductor laser technology and related research
Special Issues and Collections in MDPI journals
Prof. Dr. Ke Xu
E-Mail Website
Guest Editor
Chinese Academy of Sciences, Suzhou Institute of Nano-Tech and Nano-Bionics, Beijing, China
Interests: GaN free standing substrate
Prof. Dr. Zhaojun Liu
E-Mail Website
Guest Editor
Southern University of Science and Technology, Department of Electrical and Electronic Engineering, Qingshuihe, Shenzhen, China

Special Issue Information

Dear Colleagues,

GaN is an excellent material for making optoelectronic devices. Global sales of GaN-based blue, green and white LEDs are netting billions of dollars every year, and there is also a substantial market for in-plane lasers emitting in the blue, blue-violet and green. Vertical-cavity surface-emitting lasers (VCSELs) have many advantages such as small footprint, circular symmetry of output beam, two-dimensional scalability and/or addressability, surface-mount packaging, good price-performance ratio, and simple optics/alignment for output coupling. In this Special Issue, we would like to invite all papers related light sources in many applications, including optical storage, laser printers, projectors, displays, solid-state lighting, optical communications and biosensors. Especially, in the following fields:

  • Novel LED or laser material and device from UV to green emission
  • Green laser or VCSEL for micro-projector
  • Micro-LED for micro-display application and other potential application like LiFi, Bio-application, etc.
  • Microcavity and nanolaser based on GaN material

Prof. Dr. Hao-chung Kuo
Prof. Dr. Ke Xu
Prof. Dr. Zhaojun Liu
Guest Editors

Manuscript Submission Information

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Keywords

  • LED
  • microdisplay
  • UV
  • Green
  • Laser
  • Light source
  • LiFi
  • Free standing substarte

Published Papers (11 papers)

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Research

Open AccessArticle
A Novel Liquid Packaging Structure of Deep-Ultraviolet Light-Emitting Diodes to Enhance the Light-Extraction Efficiency
Crystals 2019, 9(4), 203; https://doi.org/10.3390/cryst9040203 - 12 Apr 2019
Abstract
To realize high-efficiency, AlGaN-based, deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency and reducing thermal resistance is very crucial. We proposed a liquid packaging structure that could enhance optical power by 27.2% and 70.7% for flat type and lens type 281-nm DUV-LEDs, respectively. [...] Read more.
To realize high-efficiency, AlGaN-based, deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency and reducing thermal resistance is very crucial. We proposed a liquid packaging structure that could enhance optical power by 27.2% and 70.7% for flat type and lens type 281-nm DUV-LEDs, respectively. A significant improvement effect at different wavelengths, such as 268 nm and 310 nm, was also observed. Furthermore, using the liquid packaging structure, the thermal resistance was reduced by 30.3% compared to the conventional structure. Finally, the reliability of liquid packaging DUV-LEDs was tested. The light output maintenance of liquid packaging DUV-LEDs was compared to the conventional structure. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
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Open AccessArticle
Ultra-High Light Extraction Efficiency and Ultra-Thin Mini-LED Solution by Freeform Surface Chip Scale Package Array
Crystals 2019, 9(4), 202; https://doi.org/10.3390/cryst9040202 - 11 Apr 2019
Cited by 1
Abstract
In this study, we present a novel type of package, freeform-designed chip scale package (FDCSP), which has ultra-high light extraction efficiency and bat-wing light field. For the backlight application, mainstream solutions are chip-scale package (CSP) and surface-mount device package (SMD). Comparing with these [...] Read more.
In this study, we present a novel type of package, freeform-designed chip scale package (FDCSP), which has ultra-high light extraction efficiency and bat-wing light field. For the backlight application, mainstream solutions are chip-scale package (CSP) and surface-mount device package (SMD). Comparing with these two mainstream types of package, the light extraction efficiency of CSP, SMD, and FDCSP are 88%, 60%, and 96%, respectively. In addition to ultra-high light extraction efficiency, because of the 160-degree bat-wing light field, FDCSP could provide a thinner and low power consumption mini-LED solution with a smaller number of LEDs than CSP and SMD light source array. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
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Open AccessArticle
Design and Fabrication of the Reliable GaN Based Vertical-Cavity Surface-Emitting Laser via Tunnel Junction
Crystals 2019, 9(4), 187; https://doi.org/10.3390/cryst9040187 - 01 Apr 2019
Cited by 1
Abstract
In this study, we theoretically designed and experimentally fabricated an InGaN vertical-cavity surface-emitting laser (VCSEL) with a tunnel junction (TJ) structure. From numerical simulation results, the optical loss of the device can be reduced by a TJ structure. Additionally, the leakage current of [...] Read more.
In this study, we theoretically designed and experimentally fabricated an InGaN vertical-cavity surface-emitting laser (VCSEL) with a tunnel junction (TJ) structure. From numerical simulation results, the optical loss of the device can be reduced by a TJ structure. Additionally, the leakage current of the VCSEL with TJ structure was much smaller than that of the VCSEL with an Indium-Tin-Oxide (ITO) layer. We have been demonstrated that laser output performance is improved by using the TJ structure when compared to the typical VCSEL structure of the ITO layer. The output power obtained at 2.1 mW was enhanced by a factor of 3.5 by the successful reduction of threshold current density (Jth) from 12 to 8.5 kA/cm2, and the enlarged slope efficiency was due to less absorption in VCSEL with a TJ structure. Finally, the samples passed the high temperature (70 °C) and high operation current (1.5 × Jth) test for over 500 h. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
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Open AccessArticle
Deep Etched Gallium Nitride Waveguide for Raman Spectroscopic Applications
Crystals 2019, 9(3), 176; https://doi.org/10.3390/cryst9030176 - 26 Mar 2019
Abstract
Gallium nitride (GaN) materials with a high chemical stability and biocompatibility are well suited for bio-sensing applications and evanescent wave spectroscopy. However, GaN poses challenges for processing, especially for deep etching using conventional etching techniques. Here, we present a dry-etching technique using tetraethyl [...] Read more.
Gallium nitride (GaN) materials with a high chemical stability and biocompatibility are well suited for bio-sensing applications and evanescent wave spectroscopy. However, GaN poses challenges for processing, especially for deep etching using conventional etching techniques. Here, we present a dry-etching technique using tetraethyl orthosilicate (TEOS) oxide as an etching barrier. We demonstrate that a sharp, vertically-etched waveguide pattern can be obtained with low surface roughness. The fabricated GaN waveguide structure is further characterized using field-emission scanning electron microscopy, Raman spectroscopy, and a stylus profilometer. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
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Open AccessArticle
A Light Guide Plate That Uses Asymmetric Intensity Distribution of Mini-LEDs for the Planar Illuminator
Crystals 2019, 9(3), 141; https://doi.org/10.3390/cryst9030141 - 08 Mar 2019
Cited by 1
Abstract
Traditional backlights are designed with new dot patterns, and then injection molding, laser beam fabrication, or UV (Ultraviolet) roll-to-plate imprinting is used to apply dot patterns to a light guide plate—the process consumes considerable time and resources. Therefore, we propose a novel light [...] Read more.
Traditional backlights are designed with new dot patterns, and then injection molding, laser beam fabrication, or UV (Ultraviolet) roll-to-plate imprinting is used to apply dot patterns to a light guide plate—the process consumes considerable time and resources. Therefore, we propose a novel light guide design that does not use a dot pattern. We designed an asymmetric intensity distribution of mini-LEDs (Light Emitting Diode) and a light guide plate with a fully printed diffusion reflection on the bottom surface for a planar illuminator. The design rules for the proposed architecture are described in this paper. The archetype design with a 152.4 mm circular down-light has a diameter of 143 mm for the planar light source module. The experiment achieved a total efficiency of 85% and uniformity of 92.6%. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
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Open AccessArticle
Bird-Wing Optical-Reflector Design with Photocatalyst for Low-Glare Mosquito Trapping System with Light-Emitting Diodes
Crystals 2019, 9(3), 139; https://doi.org/10.3390/cryst9030139 - 07 Mar 2019
Cited by 1
Abstract
Dengue fever is the most serious vector-borne disease in Asia. There are still no dengue vaccines or therapeutic drugs, and vector-mosquito control is the main prevention and treatment method. The prevention and control of dengue-fever vector mosquitoes in Taiwan is still dominated by [...] Read more.
Dengue fever is the most serious vector-borne disease in Asia. There are still no dengue vaccines or therapeutic drugs, and vector-mosquito control is the main prevention and treatment method. The prevention and control of dengue-fever vector mosquitoes in Taiwan is still dominated by larval control. However, the removal of the source of mosquito-borne diseases has not been fully implemented, and the removal process of vector-borne mosquitoes cannot keep up with their breeding rate. In addition, chemical agents used in the elimination of pathogenic mosquitoes may cause mosquito resistance and environmental pollution. Therefore, it is important to develop new prevention and control technologies. This study is dedicated to the development of a mosquito trapping optical system with high efficiency and low glare that is safe for humans. The system is mainly equipped with ultraviolet light-emitting diodes (UV-LED), a freeform-surfaced optical reflector, and a photocatalyst. The reflector can lead light downward for the protection of user eyes, and expand the range of trapping mosquitoes to 225 π m2. Based on practical experiments, captured mosquitoes increased by about 450% through the proposed system compared to conventional traps using UV LED. In addition, the proposed system is shown to be 45% more enhanced in trapping capability after a photocatalyst (titanium dioxide) coating is applied to its reflector. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
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Open AccessArticle
Square Column Structure of High Efficiency, Reliable, Uniformly Flexible LED Devices
Crystals 2018, 8(12), 472; https://doi.org/10.3390/cryst8120472 - 16 Dec 2018
Cited by 3
Abstract
This study demonstrates that flexible white LEDs, doped with diffusion particles and with a square column structure, have excellent luminosity, uniformity, and bending reliability. This large area (5 cm × 5 cm) square column flexible device had a smaller thickness (2 mm), and [...] Read more.
This study demonstrates that flexible white LEDs, doped with diffusion particles and with a square column structure, have excellent luminosity, uniformity, and bending reliability. This large area (5 cm × 5 cm) square column flexible device had a smaller thickness (2 mm), and enhancements in both luminous efficiency (29.5%) and uniformity (44.6%) compared to the characteristics of the 6 mm reference sample. Optimization of the reflective layer coating for the square column, flexible white LED was achieved with a higher luminous efficiency (171 lm/w) and uniformity (92%). We designed a novel lightning bolt electrode to improve reliability and bendability. After the bending test, the blue flexible LED had a lower bending diameter (10 mm) but more bending circles (increased to 2000 times. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
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Open AccessArticle
Novel Method for Estimating Phosphor Conversion Efficiency of Light-Emitting Diodes
Crystals 2018, 8(12), 442; https://doi.org/10.3390/cryst8120442 - 27 Nov 2018
Cited by 3
Abstract
This study presents a novel method for estimating the phosphor conversion efficiency of white light-emitting diodes (WLEDs) with different ratios of phosphors. Numerous attempts have been made for predicting the phosphor conversion efficiency of WLEDs using Monte Carlo ray tracing and the Mie [...] Read more.
This study presents a novel method for estimating the phosphor conversion efficiency of white light-emitting diodes (WLEDs) with different ratios of phosphors. Numerous attempts have been made for predicting the phosphor conversion efficiency of WLEDs using Monte Carlo ray tracing and the Mie scattering theory. However, because efficiency depends on the phosphor concentration, obtaining a tight match between this model and the experimental results remains a major challenge. An accurate prediction depends on various parameters, including particle size, morphology, and packaging process criteria. Therefore, we developed an efficient model that can successfully correlate the total absorption ratio to the phosphor concentration using a simple equation for estimating the spectra and lumen output. The novel and efficient method proposed here can accelerate WLED development by reducing costs and saving fabrication time. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
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Open AccessArticle
Enhancing the Light-Extraction Efficiency of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes by Optimizing the Diameter and Tilt of the Aluminum Sidewall
Crystals 2018, 8(11), 420; https://doi.org/10.3390/cryst8110420 - 08 Nov 2018
Cited by 3
Abstract
To realize high-efficiency AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency (LEE) is crucial. This paper proposes an aluminum-based sidewall reflector structure that could replace the conventional ceramic-based packaging method. We design optimization simulations and experimental results demonstrated the light power output [...] Read more.
To realize high-efficiency AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency (LEE) is crucial. This paper proposes an aluminum-based sidewall reflector structure that could replace the conventional ceramic-based packaging method. We design optimization simulations and experimental results demonstrated the light power output could be enhanced 18.38% of DUV-LEDs packaged with the aluminum-based sidewall. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
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Open AccessArticle
Observation of Hybrid MAPbBr3 Perovskite Bulk Crystals Grown by Repeated Crystallizations
Crystals 2018, 8(7), 260; https://doi.org/10.3390/cryst8070260 - 25 Jun 2018
Cited by 1
Abstract
In this study, the inverse temperature crystallization method was used to produce bulk crystal CH3NH3PbBr3 (MAPbBr3) perovskite, and repeated crystallization processes were carried out to obtain a larger crystal size and develop a bulk material for [...] Read more.
In this study, the inverse temperature crystallization method was used to produce bulk crystal CH3NH3PbBr3 (MAPbBr3) perovskite, and repeated crystallization processes were carried out to obtain a larger crystal size and develop a bulk material for application in semiconductor devices. The material and optoelectronic properties of the MAPbBr3 perovskite crystals after the repeated processes were characterized. The X-ray diffraction (XRD) patterns of all samples demonstrated a pure perovskite phase. One strong diffraction peak located at 29.4°, which corresponds to the (200) perovskite plane, was observed after the first growth cycle. The mobilities for the samples after the first, second, and third growth cycles were calculated and resulted to be 0.9, 5.6, and 54.7 cm2/Vs, respectively, according to Mott–Gurney law. A higher mobility after the multiple crystallization processes indicated that the surface states caused by voids in the crystals favored electron transition in the perovskite material. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
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Open AccessArticle
Manipulation of Si Doping Concentration for Modification of the Electric Field and Carrier Injection for AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes
Crystals 2018, 8(6), 258; https://doi.org/10.3390/cryst8060258 - 20 Jun 2018
Cited by 3
Abstract
Electron overflow is one of the key factors that limit the quantum efficiency for AlGaN-based deep-ultraviolet light-emitting diodes. In this work, we report a numerical study to improve the electron injection efficiency by manipulating the electric field profiles via doping the n-Al0.60 [...] Read more.
Electron overflow is one of the key factors that limit the quantum efficiency for AlGaN-based deep-ultraviolet light-emitting diodes. In this work, we report a numerical study to improve the electron injection efficiency by manipulating the electric field profiles via doping the n-Al0.60Ga0.40N electron source layer with different concentrations and reveal the physical mechanism of the Si doping effect on the electron and the hole injection. By utilizing the appropriate doping concentration, the electric field will reduce the electron drift velocity and, thus, the mean free path. Therefore, a higher electron capture efficiency by the multiple quantum wells (MQWs) and an increase of the hole concentration in the active region can be realized, resulting in an improved radiative recombination rate and an optical output power. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
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