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Crystals
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Nitride Compound Light Emitting Diodes
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Nitride Compound Light Emitting Diodes

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

Deadline for manuscript submissions: closed (28 February 2021) | Viewed by 18283

Special Issue Editors

Dr. Julien Brault

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Guest Editor
Centre de Recherche sur l'Hetero-Epitaxie et ses Applications, 06560 Valbonne, France
Interests: optoelectronics; LEDs; quantum dots; epitaxy; semi-conductors
Dr. Wang Lai

E-Mail Website
Guest Editor
Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
Interests: wide bandgap semiconductors materials and devices
Dr. M. Ajmal Khan

E-Mail Website
Guest Editor
1. RIKEN Cluster for Pioneering Research (CPR), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
2. Farmroid Co., Ltd., 3-22-4 Funado, Itabashi-ku, Tokyo 174-0041, Japan
Interests: semiconductor materials for solar cells (Group II-IV materials, BaSi2); III-V materials and Nano scale materials (Si NWs, In- NPs, QDs) for efficient photovoltaic devices (solar cells); III-Nitride based UV-LEDs (280-320 nm) and UV Laser Diodes; Renewable energy resources management and climatic change; internal quantum efficiency (IQE) and external quantum efficiency (EQE)
Dr. Mohamed Al Khalfioui

E-Mail Website
Guest Editor
Centre de Recherche sur l’hétéro-Epitaxie et ses Applications, Université côte D’azur, Valbonne, France
Interests: molecular beam epitaxy; semiconductors; electronic transport in GaN; component fabrication; electrical characterization; LED; rare earth nitride

Special Issue Information

Dear Colleagues,

In the last two decades, nitride materials have reached an outstanding stage of development, and they now represent the second largest semiconductor market behind silicon. In particular, blue light emitting diodes (LEDs) are now widely used in a broad range of applications (e.g., domestic lighting, backlit smartphones, liquid crystal display screens, etc.). To further increase the application potential of nitride LEDs, the use of other regions of the electromagnetic spectrum is highly desirable, and current research activity is particularly focused on two topics: (1) green and red LEDs in the visible range and (2) UVB and UVC LEDs in the ultra-violet (UV) range. In both cases, the improvement of LED efficiency is based on the development of innovative routes from material growth to the device fabrication process. Indeed, LEDs with high external quantum and wall plug efficiencies require epitaxial layers with low defect densities (dislocations, point defects, unintentional impurities, etc.), a highly radiative active region, doped layers with high carrier concentrations and low resistivities for efficient carrier injection and low power consumption, and a high extraction efficiency. Optimizing all these parameters via epitaxial techniques involves structural, optical, and electrical engineering in terms of strain management (implying alloying control and defect control), quantum confinement (implying localization effect and wavelength emission), polarization discontinuity (implying radiative efficiency and doping efficiency), device design (implying injection, extraction, and wall plug efficiency), etc. Combining these approaches, which have been pushed forward by disruptive technologies, will then lead to the emergence of high-efficiency green–red and ultra-violet LEDs and enable new applications and key technologies to be developed.

Dr. Julien Brault
Dr. Wang Lai
Dr. M. Ajmal Khan
Dr. Mohamed Al Khalfioui
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Green
  • Red
  • Ultra-violet
  • AlGaN
  • InGaN
  • Doping
  • Strain
  • Epitaxy
  • Confinement
  • Wall plug efficiency

Published Papers (6 papers)

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Research

9 pages, 2788 KiB  
Article
Investigations of Sidewall Passivation Technology on the Optical Performance for Smaller Size GaN-Based Micro-LEDs
by Junchi Yu, Tao Tao, Bin Liu, Feifan Xu, Yao Zheng, Xuan Wang, Yimeng Sang, Yu Yan, Zili Xie, Shihao Liang, Dunjun Chen, Peng Chen, Xiangqian Xiu, Youdou Zheng and Rong Zhang
Crystals 2021, 11(4), 403; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11040403 - 10 Apr 2021
Cited by 20 | Viewed by 4487
Abstract
Micro-light emitting diodes (Micro-LEDs) based on III-nitride semiconductors have become a research hotspot in the field of high-resolution display due to its unique advantages. However, the edge effect caused by inductively coupled plasma (ICP) dry etching in Micro-LEDs become significant with respect to [...] Read more.
Micro-light emitting diodes (Micro-LEDs) based on III-nitride semiconductors have become a research hotspot in the field of high-resolution display due to its unique advantages. However, the edge effect caused by inductively coupled plasma (ICP) dry etching in Micro-LEDs become significant with respect to the decreased chip size, resulting in a great reduction in device performance. In this article, sector-shaped GaN-based blue Micro-LEDs are designed and fabricated. Additionally, the device performance of different size Micro-LEDs with passivation are investigated with respect to those without passivation. Several methods have been applied to minimize the etching damage near the edge, including acid-base wet etching and SiO2 passivation layer growth. The room temperature photoluminescence (PL) results demonstrate that the light emission intensity of Micro-LEDs can be significantly enhanced by optimized passivation process. PL mapping images show that the overall luminescence of properly passivated Micro-LEDs is enhanced, the uniformity is improved, and the effective luminescence area is increased. The recombination lifetime of carriers in Micro-LEDs are increased by the usage of passivation process, which proves the reduction in non-radiative recombination centers in Micro-LEDs and improved luminescence efficiency. As a result, the internal quantum efficiency (IQE) is improved from 14.9% to 37.6% for 10 μm Micro-LEDs, and from 18.3% to 26.9% for 5 μm Micro-LEDs. Full article
(This article belongs to the Special Issue Nitride Compound Light Emitting Diodes)
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14 pages, 4217 KiB  
Article
Band-Engineered Structural Design of High-Performance Deep-Ultraviolet Light-Emitting Diodes
by Jih-Yuan Chang, Man-Fang Huang, Chih-Yung Huang, Shih-Chin Lin, Ching-Chiun Wang and Yen-Kuang Kuo
Crystals 2021, 11(3), 271; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11030271 - 10 Mar 2021
Viewed by 1731
Abstract
In this study, systematic structural design was investigated numerically to probe into the cross-relating influences of n-AlGaN layer, quantum barrier (QB), and electron-blocking layer (EBL) on the output performance of AlGaN deep-ultraviolet (DUV) light-emitting diodes (LEDs) with various Al compositions in quantum wells. [...] Read more.
In this study, systematic structural design was investigated numerically to probe into the cross-relating influences of n-AlGaN layer, quantum barrier (QB), and electron-blocking layer (EBL) on the output performance of AlGaN deep-ultraviolet (DUV) light-emitting diodes (LEDs) with various Al compositions in quantum wells. Simulation results show that high-Al-composition QB and high-Al-composition EBL utilized separately are beneficial for the enhancement of carrier confinement, while the wall-plug efficiency (WPE) degrades dramatically if both high-Al-composition QB and EBL are existing in a DUV LED structure simultaneously. DUV LEDs may be of great optical performance with appropriate structural design by fine-tuning the material parameters in n-AlGaN layer, QB, and EBL. The design curves provided in this paper can be very useful for the researchers in developing the DUV LEDs with a peak emission wavelength ranging from 255 nm to 285 nm. Full article
(This article belongs to the Special Issue Nitride Compound Light Emitting Diodes)
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14 pages, 2701 KiB  
Article
UVB LEDs Grown by Molecular Beam Epitaxy Using AlGaN Quantum Dots
by Julien Brault, Mohamed Al Khalfioui, Samuel Matta, Thi Huong Ngo, Sébastien Chenot, Mathieu Leroux, Pierre Valvin and Bernard Gil
Crystals 2020, 10(12), 1097; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10121097 - 30 Nov 2020
Cited by 8 | Viewed by 2583
Abstract
AlGaN based light emitting diodes (LEDs) will play a key role for the development of applications in the ultra-violet (UV). In the UVB region (280–320 nm), phototherapy and plant lighting are among the targeted uses. However, UVB LED performances still need to be [...] Read more.
AlGaN based light emitting diodes (LEDs) will play a key role for the development of applications in the ultra-violet (UV). In the UVB region (280–320 nm), phototherapy and plant lighting are among the targeted uses. However, UVB LED performances still need to be improved to reach commercial markets. In particular, the design and the fabrication process of the active region are central elements that affect the LED internal quantum efficiency (IQE). We propose the use of nanometer-sized epitaxial islands (i.e., so called quantum dots (QDs)) to enhance the carrier localization and improve the IQE of molecular beam epitaxy (MBE) grown UVB LEDs using sapphire substrates with thin sub-µm AlN templates. Taking advantage of the epitaxial stress, AlGaN QDs with nanometer-sized (≤10 nm) lateral and vertical dimensions have been grown by MBE. The IQE of the QDs has been deduced from temperature dependent and time resolved photoluminescence measurements. Room temperature IQE values around 5 to 10% have been found in the 290–320 nm range. QD-based UVB LEDs were then fabricated and characterized by electrical and electroluminescence measurements. On-wafer measurements showed optical powers up to 0.25 mW with external quantum efficiency (EQE) values around 0.1% in the 305–320 nm range. Full article
(This article belongs to the Special Issue Nitride Compound Light Emitting Diodes)
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18 pages, 4854 KiB  
Article
Lifetime Analysis of Commercial 3 W UV-A LED
by F. Jose Arques-Orobon, Manuel Vazquez and Neftali Nuñez
Crystals 2020, 10(12), 1083; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10121083 - 27 Nov 2020
Cited by 6 | Viewed by 2898
Abstract
The lifetime of ultraviolet high-power light-emitting diodes (UV HP-LEDs) is an open issue due to their high current density, high temperature, and UV radiation. This work presents a reliability study and failure analysis of three high-temperature accelerated life tests (ALTs) for 13,500 h [...] Read more.
The lifetime of ultraviolet high-power light-emitting diodes (UV HP-LEDs) is an open issue due to their high current density, high temperature, and UV radiation. This work presents a reliability study and failure analysis of three high-temperature accelerated life tests (ALTs) for 13,500 h with 3 W commercial UV LEDs of 365 nm at a nominal current in two working conditions: continuous mode and cycled mode (30 s on/30 s off). Arrhenius–Weibull parameters were evaluated, and an equation to evaluate the lifetime (B50) at any junction temperature and other relevant lifetime functions is presented. The Arrhenius activation energy was 0.13 eV for the continuous mode and 0.20 eV for the cycled mode. The lifetime at 50% survival and 30% loss of optical power as a failure definition, working at Ta = 40 °C with a multi-fin heat sink in natural convection, was over 4480 h for the continuous mode and 19,814 h for the cycled mode. The need to add forced convection for HP-LED arrays to achieve these high-reliability values is evidenced. The main source of degradation is the semiconductor device, and the second is the encapsulation silicone break. Full article
(This article belongs to the Special Issue Nitride Compound Light Emitting Diodes)
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11 pages, 3425 KiB  
Article
GaN-Based LEDs Grown on Graphene-Covered SiO2/Si (100) Substrate
by Wurui Song, Fang Ren, Yunyu Wang, Yue Yin, Shuo Zhang, Bo Shi, Tao Feng, Jianwei Wang, Meng Liang, Yiyun Zhang, Tongbo Wei, Jianchang Yan, Junxi Wang, Jinmin Li, Xiaoyan Yi and Zhiqiang Liu
Crystals 2020, 10(9), 787; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10090787 - 05 Sep 2020
Cited by 4 | Viewed by 3339
Abstract
The growth of nitride on large-size and low-cost amorphous substrates has attracted considerable attention for applications in large-scale optoelectronic devices. In this paper, we reported the growth of GaN-based light-emitting diodes (LEDs) on amorphous SiO2 substrate with the use of nanorods and [...] Read more.
The growth of nitride on large-size and low-cost amorphous substrates has attracted considerable attention for applications in large-scale optoelectronic devices. In this paper, we reported the growth of GaN-based light-emitting diodes (LEDs) on amorphous SiO2 substrate with the use of nanorods and graphene buffer layers by metal organic chemical vapor deposition (MOCVD). The effect of different growth parameters on the morphology and vertical-to-lateral aspect ratio of nanorods was discussed by analyzing growth kinetics. Furthermore, we tuned nanorod coalescence to obtain continuous GaN films with a blue-LED structure by adjusting growth conditions. The GaN films exhibited a hexagonal wurtzite structure and aligned c-axis orientation demonstrated by X-ray diffractometer (XRD), Raman, and transmission electron microscopy (TEM) results. Finally, five-pair InGaN/GaN multi-quantum-wells (MQWs) were grown. The photoluminescence (PL) showed an intense emission peak at 475 nm, and the current–voltage (I-V) curve shows a rectifying behavior with a turn-on voltage of 5.7 V. This work provides a promising fabrication method for the large-area and low-cost GaN-based devices on amorphous substrates and opens up the further possibility of nitride integration with Si (100) complementary metal oxide semiconductor (CMOS) electronics. Full article
(This article belongs to the Special Issue Nitride Compound Light Emitting Diodes)
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8 pages, 2190 KiB  
Article
Light Output Enhancement of GaN-Based Light-Emitting Diodes Based on AlN/GaN Distributed Bragg Reflectors Grown on Si (111) Substrates
by Yibin Yang, Lingxia Zhang and Yu Zhao
Crystals 2020, 10(9), 772; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10090772 - 01 Sep 2020
Cited by 5 | Viewed by 2206
Abstract
Due to the absorption of opaque Si substrates, the luminous efficiency of GaN-based light-emitting diodes (LEDs) on Si substrates is not high. So, in this work, we insert AlN/GaN distributed Bragg reflectors (DBRs) to improve the light output of GaN-based LEDs on Si [...] Read more.
Due to the absorption of opaque Si substrates, the luminous efficiency of GaN-based light-emitting diodes (LEDs) on Si substrates is not high. So, in this work, we insert AlN/GaN distributed Bragg reflectors (DBRs) to improve the light output of GaN-based LEDs on Si (111) substrates grown via metal organic chemical vapor deposition (MOCVD). In order to obtain the highest reflectivity of the AlN/GaN DBR stop band, the growth parameters of AlN/GaN DBRs are optimized, including the growth temperature, the V/III ratio and the growth pressure. As a consequence, the interfaces of the optimal 9-pair AlN/GaN DBRs become abrupt, and the reflectivity of the DBR stop band is as high as 85.2%, near to the calculated value (92.5%). Finally, crack-free GaN-based LEDs with 5-pair AlN/GaN DBRs are grown on Si (111) substrates. The light output of the DBR-based LED is evidently enhanced by 41.8% at the injection current of 350 mA, compared with the conventional DBR-based LED without DBRs. These results pave the way for the luminous efficiency improvement of future green and red GaN-based LEDs grown on Si substrates. Full article
(This article belongs to the Special Issue Nitride Compound Light Emitting Diodes)
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