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2019 | Buch

Light-Emitting Diodes

Materials, Processes, Devices and Applications

herausgegeben von: Jinmin Li, G. Q. Zhang

Verlag: Springer International Publishing

Buchreihe : Solid State Lighting Technology and Application Series

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Über dieses Buch

Comprehensive in scope, this book covers the latest progresses of theories, technologies and applications of LEDs based on III-V semiconductor materials, such as basic material physics, key device issues (homoepitaxy and heteroepitaxy of the materials on different substrates, quantum efficiency and novel structures, and more), packaging, and system integration. The authors describe the latest developments of LEDs with spectra coverage from ultra-violet (UV) to the entire visible light wavelength. The major aspects of LEDs, such as material growth, chip structure, packaging, and reliability are covered, as well as emerging and novel applications beyond the general and conventional lightings. This book, written by leading authorities in the field, is indispensable reading for researchers and students working with semiconductors, optoelectronics, and optics.

Addresses novel LED applications such as LEDs for healthcare and wellbeing, horticulture, and animal breeding;

Editor and chapter authors are global leading experts from the scientific and industry communities, and their latest research findings and achievements are included;

Foreword by Hiroshi Amano, one of the 2014 winners of the Nobel Prize in Physics for his work on light-emitting diodes.

Inhaltsverzeichnis

Frontmatter
Chapter 1. GaN Substrate Material for III–V Semiconductor Epitaxy Growth
Abstract
The rapid commercialization of III-nitride semiconductor devices for applications in visible and ultraviolet optoelectronics and in high-power and high-frequency electronics accelerates the research, development, and commercial production of GaN substrate materials. GaN substrate with low defect density will be conducive to improve the performance and lifetime of the devices, leading to significant progress in the development of several optoelectronic and high-power devices. In this paper, various fabrication techniques and their corresponding development, considered with high potential to deliver high-quality and/or cost-effective and scalable GaN crystals, are reviewed, including liquid-phase methods and gas-phase methods. Among these growth methods, hydride vapor-phase epitaxy (HVPE) is well known as the major substrate technology with high growth rate, high crystal quality, and low cost, which attracts more attention. So, we have a special discussion on the detailed technological aspects of HVPE for the production of GaN substrate materials.
Rong Zhang, Xiangqian Xiu
Chapter 2. SiC Single Crystal Growth and Substrate Processing
Abstract
Silicon carbide (SiC) is the typical representative of the third-generation semiconductor materials. Due to the wide bandgap, high thermal conductivity, high saturated carrier mobility, high threshold breakdown electric field strength, and high chemical stability, it is an ideal substrate for the fabrication of power electronics and radio frequency devices operating at extreme environments, such as high temperature, high frequency, high power, and strong radiation. Therefore, SiC has extensive applications in white-light illumination, automobile electronic, radar communication, aeronautic and aerospace, and nuclear radiation. Since the 1990s, SiC has attracted much attention due to the breakthrough in SiC single crystal growth technology. Up to now, 6” SiC substrates are commercially available. In this chapter, we mainly introduce the SiC single crystal growth and substrate processing technologies. In Sect. 2.1, SiC material development history and single crystal growth method were described. In Sect. 2.2, the structure and properties of SiC were given. In Sect. 2.3, we focus on the SiC single crystal growth by PVT method. In Sect. 2.4, the formation mechanism of structural defects in SiC and how to control these defects were presented. In Sect. 2.5, the control of electrical behavior of SiC was discussed. In Sect. 2.6, the SiC substrate processing technology was introduced. We wish this chapter has the reference value for SiC crystal grower and substrate processing technician.
Xiangang Xu, Xiaobo Hu, Xiufang Chen
Chapter 3. Homoepitaxy of GaN Light-Emitting Diodes
Abstract
Light-emitting diodes (LEDs) employing heterostructures of group-III nitrides are a prime contender for the realization of energy-efficient solid-state lighting (US Department of Energy, Solid-State Lighting Program, http://​www.​netl.​doe.​gov/​ssl; Basic Research Needs or Solid-State Lighting, Report of the Basic Energy Sciences Workshop on Solid-State Lighting, May 22–24, 2006. www.​sc.​doe.​gov/​bes/​reports/​files/​SSL_​rpt.​Pdf). As a direct bandgap material, alloys of GaxInxN can be tuned to emit light covering every portion of the visible spectrum. White light of good color-rendering quality (additive white) requires a more or less continuous spectrum and can be obtained by the combination of various such light sources. On the other hand, image information encoded in red-green-blue (RGB) colors can be reproduced by three highly monochromatic light sources of red, green, and blue. Current best practices in LED lighting employ blue or near-UV LEDs to excite a phosphor that downconverts those photons into longer wavelength light dependent on the phosphor chemistry and composition. The more efficient approach employs LEDs that emit directly at the target wavelength and thereby bypass the energy loss of downconversion. Even in the ideal case of 100% quantum efficiency, this downconversion from the blue to the green amounts to a 20% energy loss. Of particular interest therefore are high efficiency LEDs in the green (525 nm) and deep green (555 nm) spectral region.
Current technology primarily employs heteroepitaxial metalorganic vapor phase epitaxy (MOVPE) of AlGaInN alloys on dissimilar substrates like sapphire or SiC resulting in high densities of threading dislocations. In heteroepitaxial GaN, threading dislocations as high as 109–1011 cm2 are commonplace (Ponce et al., Appl Phys Lett 69:770, 1996) unless specialized multistep regrowth methods are being applied (Usui et al., Jpn J Appl Phys 36: L899, 1997; Nam et al., Appl Phys Lett 71:2638, 1997; Iwaya et al., Jpn J Appl Phys 37:L316, 1998). This typically results in high densities of threading dislocations that are extremely difficult to prevent from penetrating the active quantum well (QW) region. The considered roles of those defects range from electrically active donor centers (Leung et al., Appl Phys Lett 74:2495, 1999), highly active non-radiative recombination centers (Rosner et al., Appl Phys Lett 70:420, 1997), over mid-gap trap states assisting charge tunneling (Monemar and Sernelius, Appl Phys Lett 91:181103, 2007), and seeds for V-defects (Wu et al., Appl Phys Lett 72:692, 1998; Wetzel et al., Appl Phys Lett 85:866, 2004), to pathways of metal impurity electromigration and acceptor diffusion.
Promising therefore are freestanding GaN templates or bulk wafers that can be grown by hydride vapor phase epitaxy with a low threading-dislocation densities typically in the mid 106 cm2 (Hanser et al., Proceedings of the CS MANTECH Conference, April 24–27, Vancouver, British Columbia,Canada, 2006) or lower. Large area substrates for homoepitaxial growth of GaN layers have recently become available as a result of recent progress in production of thick freestanding GaN (FS-GaN) layers grown by hydride vapor-phase epitaxy (HVPE) (Kelly et al., Jpn J Appl Phys 38:L217–L219, 1999; Jasinski et al., Appl Phys Lett 78:2297–2299, 2001; Chao et al., Appl Phys Lett 95:051905–051905-3, 2009). Such substrates have been successfully applied to grow LED structures using metal-organic chemical vapor deposition (MOCVD) (Miskys et al., Appl Phys Lett 77:1858–1860, 2000), resulting in high-quality films, as demonstrated by their superior optical and electrical characteristics.
In this chapter, we discuss the progress in growth of bulk GaN by HVPE; the main challenges and solutions of HVPE growth method, including dislocation reduction, strain control, and doping of GaN; structural characterization, electrical characterization, and optical characterization of homoepitaxial InGaN/GaN light-emitting diodes; efficiency droop and efficiency enhancement; and light efficiency extraction of homoepitaxial InGaN/GaN light-emitting diodes. Meanwhile, nonpolar and semipolar orientations GaN LED grown on bulk GaN substrates also have been investigated.
Ke Xu, Miao Wang, Taofei Zhou, Jianfeng Wang
Chapter 4. GaN LEDs on Si Substrate
Abstract
Fabrication of GaN LEDs on Si is an attractive work but also with great challenge. One needs to overcome the huge difference in lattice parameter and thermal expansion coefficient between GaN and Si. With the help of substrate patterning and AlN/AlGaN buffer layer technologies, stress can be well controlled and high-quality crack-free GaN with low dislocation density are successfully grown. By strain engineering and utilizing V-defect in the active region, high-efficiency LED structure is developed. The chip fabrication process of LED on Si substrate is totally different from that on sapphire substrate that yields a vertical thin film device structure which has many unique features.
Fengyi Jiang, Jianli Zhang, Qian Sun, Zhijue Quan
Chapter 5. The AlGaInP/AlGaAs Material System and Red/Yellow LED
Abstract
In this chapter, AlGaInP and AlGaAs alloy compound semiconductor system was reviewed for solid-state lighting application, including their lattice and bandgap structure, heterojunction, and quantum well properties. LEDs based on AlGaInP quantum well and GaAs substrate operating in the red, orange, and yellow visible spectrum were discussed including the major classes of AlGaInP device structures, such as GaP-absorbing substrate LEDs enhanced by distributed Bragg reflectors (DBRs), transparent-substrate LEDs (TS-LEDs), thin-film LEDs (TF-LEDs), and GaP window/current-spreading layer. AlGaInP/AlGaAs material MOCVD epitaxy and LED chip processing technology were introduced briefly.
Guohong Wang, Xiaoyan Yi, Teng Zhan, Yang Huang
Chapter 6. The InGaN Material System and Blue/Green Emitters
Abstract
Due to the advantage of low-power consumption, long lifetime, and high efficiency, nitride-based light-emitting diodes (LEDs) have long been considered to be a promising technology for next-generation illumination. The efforts on this topic could be tracked back to the 1950s. The possibility of a new lighting technology using GaN was considered by Philips Research Laboratories in the 1950s, and the photoluminescence of GaN power was obtained by H.G. Grimmeiss and H. Koelmans. The first single-crystal film of GaN was prepared by Maruska and Tietjenusing, the HVPE technique in 1969. At the end of the 1980s, the breakthrough of Amano, Akasaki, and Nakamura on p doping opened the way to p-n junctions in GaN. Another crucial step in developing efficient blue LEDs was the growth of alloys (AlGaN, InGaN), which are necessary to produce heterojunctions. In 1994, Nakamura and co-workers achieved a quantum efficiency of 2.7% using a double heterojunction InGaN/AlGaN. It was the first step toward the commercial development of efficient nitride LEDs, and their tremendous application was open. Today’s efficient of LEDs is the result of a long series of breakthroughs in fundamental materials physics and high-quality crystal growth, in device physics with advanced heterostructure design, and in optical physics for light extraction. And the application will continue to expand to many novel fields. At the same time, the efficiency, which relates to fundamental physics, growth, and fabrication, still needs to be further improved. In this chapter, some pioneering and significant experiment results.
In this work, we will focus on two important wavelength range of nitride LEDs, namely, blue and green one. We describe a number of factors that affect the efficiency of LEDs and analyze the effects of polarization, carrier transport, carrier localization, current expansion, epitaxial structure design, Auger recombination, and light extraction. Some pioneering and significant experiment results will be presented. We hope it can provide some meaningful information for the development of high-efficiency GaN-based blue and green LEDs.
Ning Zhang, Zhiqiang Liu
Chapter 7. Al-Rich III-Nitride Materials and Ultraviolet Light-Emitting Diodes
Abstract
Aluminum nitride (AlN) material is commonly used as a crucial template for the growth of high-quality Al-rich III-nitride materials and high-performance deep-ultraviolet light-emitting diodes (DUV LEDs). In this chapter, the heteroepitaxy of AlN film by MOVPE and the development of AlN epitaxy techniques on sapphire substrates are discussed. The structural design for efficient DUV LEDs is then introduced. Since bulk AlN substrates are a perfect candidate for AlGaN-based DUV LEDs due to similar thermal expansion coefficients and relatively small lattice mismatches, we also discussed AlN homoepitaxy, pseudomorphic AlGaN, and DUV LEDs on AlN substrates. The limited light extraction efficiency (LEE) is another obstacle for power DUV LEDs and their applications. The intrinsic Al-rich-induced optical polarization effect and related methods for improving the LEE are presented.
Jianchang Yan, Junxi Wang, Yuhuai Liu, Jinmin Li
Chapter 8. Technology and Droop Study for High Internal Quantum Efficiency
Abstract
Although the high efficiency above 300 lm/W is achieved for white LED in laboratory, the commercial LED approaches half of the maximum. Efficiency droop (ED) is still a serious problem for high-power applications. In this chapter, some techniques to achieve high internal quantum efficiency (IQE) for GaN-based LEDs are presented. The effects of defects and polarization are discussed in detail. The IQE of green and deep ultraviolet-LEDs are particularly concerned. In the IQE measurement, the general temperature-dependent photoluminescence method is analyzed, and some significant developments are introduced to obtain a more accurate value. The exact origins of ED are still on debates. We tend to attribute the droop to various origins for different situations. At last, we give some remedies to alleviate the droop. Radiative recombination rate enhancement may be more important for low-droop LEDs. Localized surface plasmon and nanocavity may be the potential candidates for novel low-droop devices.
Bo Shen, Zhizhong Chen
Chapter 9. On the Light Extraction Efficiency for III-Nitride-Based Light-Emitting Diodes
Abstract
Considering the large contrast of the refractive index between the air and the III-nitride semiconductor layer, the external quantum efficiency for III-nitride-based light-emitting diodes is strongly influenced by the light extraction efficiency. This chapter reviews the current status for the technologies that have been adopted thus far to improve the light extraction for III-nitride-based light-emitting diodes. Meanwhile, in-depth physical interpretations are also presented and discussed.
Zi-Hui Zhang, Yonghui Zhang, Sung-Wen Huang Chen, Wengang Bi, Hao-Chung Kuo
Chapter 10. Enhancing Wall-Plug Efficiency for Deep-UV Light-Emitting Diodes: From Crystal Growth to Devices
Abstract
Deep ultraviolet light-emitting diodes (200–280 nm) have many potential applications in diagnostics, therapeutics, security, and tanning. But, the state-of-the-art LEDs suffer from low external quantum efficiency (< 20%). The external quantum efficiency is composed of internal quantum efficiency, injection efficiency, and the light extraction efficiency. These components are limited due to fundamental material and physics-based challenges. In this chapter, a set of novel heterostructure designs are presented to improve the individual efficiency components that compose the external quantum efficiency. Theoretical analysis followed by crystal growth and experimental data are presented showing enhancement of each efficiency components. Inclusion of such new design techniques will enhance the external quantum efficiency of deep-UV light emitters.
SM Islam, Vladimir Protasenko, Shyam Bharadwaj, Jai Verma, Kevin Lee, Huili (Grace) Xing, Debdeep Jena
Chapter 11. Reliability of Ultraviolet Light-Emitting Diodes
Abstract
This chapter presents an extensive review of the literature on the degradation processes of GaN-based UV-A, UV-B, and UV-C LEDs. For the state-of-the-art devices, the main open issue is the increase in Shockley–Read–Hall non-radiative recombination inside the quantum well, originating from local generation of defects or from diffusion processes of dopant atoms or foreign impurities. Temperature acts as a significant acceleration factor, especially in lower wavelength devices, affected by a higher turn-on voltage. Changes in the chemical structure of the package and of the encapsulant, induced by the high energy of the photons, may lead to a lower reflectivity and transmittance, thus limiting the overall reliability of the devices.
Carlo De Santi, Desiree Monti, Pradip Dalapati, Matteo Meneghini, Gaudenzio Meneghesso, Enrico Zanoni
Chapter 12. Nitride Nanowires for Light Emitting Diodes
Abstract
This chapter describes the present status of nitride nanowire (NW) light emitting diodes (LEDs). The main focus is on the NW synthesized by a bottom-up approach. NW growth methods are described and the device processing is presented. Different realizations of NW LEDs are reviewed, grouped by their spectral domain and the targeted applications. Existing challenges of NW technology for LEDs are analyzed. New functionalities offered by the NW geometry are described, namely the use of NWs to create mechanically flexible light sources.
Nan Guan, Xing Dai, François H. Julien, Joël Eymery, Christophe Durant, Maria Tchernycheva
Chapter 13. Light-Emitting Diodes for Healthcare and Well-being
Abstract
With the rapid development of semiconductors both in materials and technologies in recent years, LED has taken on a new look: higher luminous intensity, more stable peak wavelength, narrower half-wave bandwidth, better monochromaticity and orientation, and a nearly full coverage of the whole spectrum. In addition, LED devices are small in size, easy to operate and carry, and low in cost. They can be used to form complicated geometric figures so as to form point, line, and surface light sources and even flexible soft light source adaptable to the shape of a treatment area to realize evener illumination. For these reasons, LED light sources are now more and more popular in clinical practice. In this chapter, the mechanisms and indications of LED phototherapy and the status quo of the research on and development of LED phototherapy devices are introduced.
Ying Gu, Haixia Qiu, Ying Wang, Naiyan Huang, Timon Cheng-Yi Liu
Chapter 14. Light-Emitting Diodes for Horticulture
Abstract
This chapter firstly describes the fundamental concepts of photosynthesis of plants and LEDs for applications in the plant factory with artificial lighting (PFAL). The complexity of light environment control to maximize the cost performance of the PFAL is discussed for getting an idea of smart LED lighting system related to phenotyping, information and communication technology, and artificial intelligence. Secondly, influences of LED lighting environment at seedling stage on lettuce transplant growth and its subsequent growth and nutritional values were discussed as a case study for supporting a good system impact. Therefrom, effects of light intensity, photoperiod and LED quality on growth and quality of hydroponic lettuce were introduced for suitable light environment control in the PFAL.
Dongxian He, Toyoki Kozai, Genhua Niu, Xin Zhang
Chapter 15. The Effect and Mechanism of Light on the Growth, Food Intake, and Gonad Development of Atlantic Salmon (Salmo salar) Reared in RAS
Abstract
Atlantic salmon exhibit seasonal reproduction. However, the mechanisms governing this are still unclear. Generally speaking, kisspeptin has been recognized as a regulator of reproduction. Here, we report a relationship between kisspeptin, GnRH, and photoperiod in Atlantic salmon. The results demonstrated that the expression of the Atlantic salmon kisspeptinreceptor (skissr) was not always consistent with the expression pattern of Atlantic salmon GnRH3 (sGnRH3) during all developmental processes. Kisspeptin may exert its influence primarily in the early and later stages of gonad development by promoting the secretion of sGnRH3. Meanwhile, the expression levels of kissr were higher in fish with gonads at stage II and stage V under the long-day photoperiod regime than under the short-day regime. In addition, both skissr and sGnRH3 were also expressed in the saccus vasculosus (SV), an organ only found in fish. The SV might be a seasonal sensor regulating reproduction in addition to the hypothalamus (Hyp).
Ying Liu, Xiaolong Gao, Liang Chi
Backmatter
Metadaten
Titel
Light-Emitting Diodes
herausgegeben von
Jinmin Li
G. Q. Zhang
Copyright-Jahr
2019
Verlag
Springer International Publishing
Electronic ISBN
978-3-319-99211-2
Print ISBN
978-3-319-99210-5
DOI
https://doi.org/10.1007/978-3-319-99211-2

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