Light-emitting Diode Industry Research Articles

Light-emitting diode technology and applications: introduction

Spurred on by the invention of the blue light-emitting diode (LED) a quarter of a century ago, the LED industry has advanced dramatically and has revolutionized the signaling/signage, mobile and flat panel display, and more recently, general lighting markets. Indeed, LEDs now out-surpass in performance all conventional (e.g., incandescent, fluorescent, high-intensity discharge) light sources in general illumination applications. The question arises: what more is to be done? Thus comes the thesis for this special issue on LEDs and applications. From the contributed articles, we learn that LED technology continues to evolve and transform itself not only within the existing applications but is also positioning for brand new applications to come, both of which are highlighted here.

R&D planning of manufacturing industry: a systematic method based on SITRM

Industrial technology roadmapping (ITRM) offers an important tool for technology R&D planning in manufacturing industry. However, previous studies cannot support the R&D planning and management in practical applications since they remain conceptual and lack of robustness in a volatile environment. In response, this research uses scenario planning and Bayesian network to support R&D planning for developing an ITRM. The first step is to construct the scenarios which are used as inputs for the scenario-based technology roadmapping (SITRM). Second, a Bayesian network topology model of SITRM is developed, in order to display various states of random variables and the uncertainty in relationships between nodes uncertainty of SITRM. Finally, based on probability deduction methods of Bayesian network, a quantitative analysis process and calculation model in supporting technology R&D planning was performed. As an illustrative example, light emitting diode industry in Guangdong is presented to show the feasibility of this method.

R&D planning of manufacturing industry: a systematic method based on SITRM

Industrial technology roadmapping (ITRM) offers an important tool for technology R&D planning in manufacturing industry. However, previous studies cannot support the R&D planning and management in practical applications since they remain conceptual and lack of robustness in a volatile environment. In response, this research uses scenario planning and Bayesian network to support R&D planning for developing an ITRM. The first step is to construct the scenarios which are used as inputs for the scenario-based technology roadmapping (SITRM). Second, a Bayesian network topology model of SITRM is developed, in order to display various states of random variables and the uncertainty in relationships between nodes uncertainty of SITRM. Finally, based on probability deduction methods of Bayesian network, a quantitative analysis process and calculation model in supporting technology R&D planning was performed. As an illustrative example, light emitting diode industry in Guangdong is presented to show the feasibility of this method.

Laser-Scanned Programmable Color Temperature of Electroluminescence from White Light-Emitting Electrochemical Cells.

Recently, the control of correlated color temperature (CCT) of artificial solid-state white-light sources starts to attract more attention since CTs affect human physiology and health profoundly. In this work, we proposed and demonstrated a method that can widely tune the CCTs of electroluminescence (EL) from white-light-emitting electrochemical cells (LECs) by employing plasmonic filters. These integrated on-chip plasmonic filters are composed of semicontinuous thin Ag film or Ag nanoparticles (NPs) both included in the indium tin oxide anode contact, which have different characteristics of plasmonic resonant absorptions that can tune the EL spectra of white LECs. The CCTs of EL from white LECs integrated with semicontinuous thin Ag film and randomly distributed Ag NPs are 5778 and 2350 K, respectively. A commercially available laser scanning system was used to locally thermal anneal the semicontinuous thin Ag film to form the randomly distributed Ag NPs on the scanned areas. Hence, these two kinds of filters can be integrated on the same chip of white LEC, giving more freedom to control the CCTs of white EL and more potential applications. In addition, the laser scanning system used here is quite often used in display manufactures so that our proposed method can be immediately adopted by the light-emitting diode industry.

Modeling of the rapid lifetime assessment system with multiple stresses for LED devices using adaptive genetic algorithm

The light-emitting diode (LED) is a promising candidate for the lighting, instrument reading, etc., due to its features of high efficiency, long lifetime, small size, fast response, anti vibration, low-voltage operation, and environmental protection, which is an emerging cold light source. This paper proposes a novel model of the rapid lifetime assessment system with multiple stresses for LED devices, to solve the problems of the complex environmental stresses imposed on the lifetime of LED devices, the model of accelerated life testing without consideration of multiple stresses, and the low-precision lifetime assessment model. This model is suitable for all types of LED devices. Taking the operating time to 30% of lumen depreciation as the lifetime of LED devices, the environmental temperature and humidity, and input current are the inputs of this model, and the lifetime of the LED device is the output of this model. The parameters of this model are determinated by using the designed adaptive genetic algorithm. A several number of sample data is first obtained through accelerated life testing under the condition of high temperature, humidity, and current. The parameters of this model are then identified with the obtained sample data. This model is further built by applying the identified parameters. Additionally, the lifetime evaluation is carried out via this model under the condition of normal temperature, humidity, and current. Research results demonstrate that the proposed model can evaluate the lifetime of LED devices fast with a comparatively high accuracy; the evaluated lifetime of the proposed model is close to the realizable life expectancy of the LED industry under the condition of normal temperature, humidity, and current; the practicability of the proposed model for lifetime reliability evaluation of LED devices is verified; the proposed model can be further developed with much more stresses.

Red-Phosphor-Dot-Doped Array in Mirror-Surface Substrate Light-Emitting Diodes

Micro-patterned red-phosphor-dot-doped array in mirror-surface substrate light-emitting diodes (LEDs), which are primarily characterized with imbedded red phosphor dots in yellow phosphor slurry and an installed mirror on the substrate surface, are investigated. These dots scatter lights in different colors, compensate the long waveband in LED spectra, and allow exiting blue rays to escape in large angles. This mirror surface reflects downward blue lights emitted by chips, blends various-wavelengthed light beams, and enhances the cooling effect on the entire module. With the aid of these two modifications, the quantum efficiency (QE) and the luminous efficacy of radiation (LER) have been typically elevated by 16.6% and 38.8%, respectively. Proposed modules can be used in the LED industry for guiding improvements of QE, LER, and yellow–blue ratio uniformity.

Toward sustainability: using big data to explore the decisive attributes of supply chain risks and uncertainties

Rapid market changes aimed at sustainability have led to supply chain risks and uncertainties in the Taiwanese light-emitting diode industry. These risks and uncertainties can be captured by social media, quantitative and qualitative data (referred to herein as big data), but the industry has been unable to manage this information boom to respond to customer needs. These various types of data have their own characteristics that affect decision making about developing firm capabilities. This study aggregates the various data to undertake an extensive investigation of supply chain risks and uncertainties. Specifically, this study proposes using the fuzzy and grey Delphi methods to identify a set of reliable attributes and, based on these attributes, transforming big data to a manageable scale to consider their impacts. Subsequently, both the fuzzy and grey Decision Making Trial and Evaluation Laboratories applied to determine the causal relationships for supply chain risks and uncertainties. The results reveal that capacity and operations have greater influence than other supply chain attributes and that risks stemming from triggering events are difficult to diagnose and control. The implications, conclusions and findings are addressed.

Contact photolithography using a carbon-black embedded soft photomask and ultraviolet light emitting diodes with application on patterned sapphire substrates.

This paper presents a contact photolithography method for large-area ultraviolet (UV) patterning using a soft polydimethylsiloxane (PDMS) photomask and a planar light source consisting of arrayed light-emitting diodes (LEDs). With simple design and construction, the UV light source can achieve uniformly distributed UV light intensity over an area of 4" in diameter but its divergent angle is 15°. To overcome this large divergent angle, a PDMS soft mold embedded with carbon-black inserts as the UV light blocking materials is applied. It is demonstrated that, when increasing the aspect ratio of the carbon-black inserts, one can achieve excellent UV patterning results. Both experimental data and simulation results are presented. This contact photolithography system has been successfully used for manufacturing patterned sapphire substrates (PSSs) in LED industry. The advantages and potential applications of the proposed method will be addresses.

X-ray photoemission spectroscopy investigation of CaTiO3:Eu for luminescence property: effect of Eu3+ ion

Charge compensation of on-site Eu 4f–5d transition that determines the luminescent performance was confirmed with valance band spectrum. Influence of photoelectrons from CaTiO3: Eu to the corresponding luminescent performance was discussed based on the crystal structure, doping level and the relations to their luminescent property. This paper is important to further optimize the luminescent performance for improving the efficiency and reducing the cost in light emitting diode industry.

Effects of the surface area of phosphor powders on colour coordinate variance

In this study, the colour coordinate behaviours according to the surface area of phosphors were investigated to implement the colour coordinate of the desired zone in a random colour coordinate. For this purpose, the mixing ratio and dispensing amount of a green phosphor (Ce:YAG) and three red phosphors (CaAlSiN3:Eu2+) with different specific surface areas were adjusted, and the corresponding colour coordinate behaviour was examined. As a result, the colour coordinate behaviour was found to be considerably influenced by the mixing ratio of red and green phosphors and the surface area of the phosphor powder particles. In conclusion, the colour coordinate of the desired zone can be more efficiently implemented by predicting the characteristics of different types of phosphors and their colour coordinate behaviours. The findings of this study are expected to greatly increase the yield of the light-emitting diode industry.

Government policy change and evolution of regional innovation systems in China: evidence from strategic emerging industries in Shenzhen

The mid-2000s witnessed a paradigm shift of technological innovation in China, characterized by a policy change from expectation of technological spillover from transnational corporations to an emphasis on indigenous innovation and domestic firms. Notably, seven strategic emerging industries (SEIs) have been designated by the central government to foster technological upgrading in the wake of the 2008 global financial crisis. While increasing attention has been paid to these policy changes, the practice of developing SEIs and subsequent impacts on innovation dynamisms remain understudied. Drawing upon an institutional evolution perspective on the regional innovation systems (RIS) approach, I examine how foreign-invested and domestic firms have adjusted their innovation strategies in the changing institutional environment, through examining the light-emitting diode (LED) industry, one of the state-designated SEIs in Shenzhen. This study was conducted primarily from on-site field investigation, firm-level surveys, and in-depth interviews during the period of 2008 and early 2013. It sheds light on the adaptation of the local state, reflected by the Shenzhen municipal government's recent abolishment of the LED industry development plan after four years of implementation. I urge more studies to examine other SEIs designated by various governments in different cities and regions in China to better understand policy change and effects on national innovation systems and RISs in the contemporary global economy.

The influence of the technological regime on the global light-emitting diode industry: lessons from innovative leaders and latecomers

The light-emitting diode (LED) sources have become the first efficiency recommendation and one of the top sustainability measures in building a sustainable economy and eco-friendly society. The emergence and rapid development of latecomers to low-carbon LED technology in Asia has shifted the oligopolistic structure that had been appropriated by the first-movers in the US, Europe and Japan. It is thus critical to understand the innovation trajectories and influential factors for reinforcing the development of the global LED industry. This study highlights the variations of technological regime in dominant firms, demonstrating that the eco-innovations in the global LED technological regime is built sequentially, by product innovation of international leaders through technological appropriation (i.e. intellectual property rights), process innovation of Korean and Taiwanese latecomers through production capability, followed by various diffusion modes integrating with Chinese and other latecomers through market and production competition in the global LED industry. Three policy imperatives are then elaborated.

Fabrication of three-dimensional and submicrometer-scaled microstructures based on metal contact printing and silicon bulk machining

This paper describes a method that contains a series of processes for producing three-dimensional (3-D) microstructures with a feature size in the submicrometer scale. It starts from using a metal contact printing lithography to pattern a thin metal film on the surface of a (100) silicon substrate. The metal film has a hole-array pattern with a hole diameter ranging from 300 nm to 800 nm and is used as an etching mask for silicon bulk machining to create concave pyramid-shaped surface microstructures. Using this bulk-machined silicon substrate as a template, polymer 3-D microstructures are replicated on top of a silicon dioxide (SiO2) layer. Finally, through a dry etching process, 3-D microstructures with a profile similar to the replicated polymer microstructures are formed on the SiO2 layer. Potential applications of these fabricated SiO2 microstructures in the light-emitting diode industry will be addressed.

(Invited) High Brightness, Large Scale GaN Based Light-Emitting Diode Grown on 8-Inch Si Substrate

GaN based light-emitting diodes(LEDs) grown on a Si substrate is one of promising future technologies in LED industry due to its scalability and costeffectiveness compare to the conventional sapphire based LEDs.One of major technical issues in GaN/Si LED is the severemismatch oflattice and thermal expansion coefficientsbetween GaNand Si, which induces significant tensile strain in the GaNepilayer that often leads to wafer cracking. Optical loss by the absorbing Si substrate is another barrier to overcome for realizing high-brightness LEDs competitive to those on sapphire or SiC substrates.In this study, we demonstrated blue LEDs grown on 8-inch diameter Si substrate and fabricated high brightness devicesutilizing vertical chip process Thecrack-free InGaN/GaN LED waferswith strain-engineered buffer structure were grown on 8-inch diameter Si(111) substrates by metalorganic chemical vapor deposition (MOCVD) system (Veeco TurboDisk k465i).The optimized growth conditions of AlN buffer layer improved the crystalline quality of GaNepilayers. The FWHM of (002) and (102) ω-scan is 280 and 420 arcsec, respectively. These values are comparable to the best reported so far for GaN on silicon. The surface morphology of GaN layer investigated using atomic force microscopy (AFM) exhibits very smooth surface and clear atomic step flow patterns. The root-mean-square (RMS) roughness is 0.15 nm in a 5x5 μm2 scan area.For LED on 8-inch Si, MQW PL wavelength uniformity of ~0.5% (2.4 nm) has been achieved using the proper strain/curvature engineering with optimized wafer carrier designs. These are among the lowest values reported to date.After the epitaxial growth with silicon substrate, a 1mm × 1mm sized vertical type LED(VLED) was fabricated using both wafer bonding process and Si removing process. While the GaN on sapphire employs a laser lift-off technique to remove the substrate, we developed the wet etching process in order to remove the silicon substrate without any damageon the surface of LED structure. The electro-optical characteristics of the fabricated VLED in this work shows good efficiency(almost 1W light power at 1A inject current) with operating voltage of 4.0V.

Dual beam organic depth profiling using large argon cluster ion beams.

Argon cluster sputtering of an organic multilayer reference material consisting of two organic components, 4,4′-bis[N-(1-naphthyl-1-)-N-phenyl- amino]-biphenyl (NPB) and aluminium tris-(8-hydroxyquinolate) (Alq3), materials commonly used in organic light-emitting diodes industry, was carried out using time-of-flight SIMS in dual beam mode. The sample used in this study consists of a ∽400-nm-thick NPB matrix with 3-nm marker layers of Alq3 at depth of ∽50, 100, 200 and 300 nm. Argon cluster sputtering provides a constant sputter yield throughout the depth profiles, and the sputter yield volumes and depth resolution are presented for Ar-cluster sizes of 630, 820, 1000, 1250 and 1660 atoms at a kinetic energy of 2.5 keV. The effect of cluster size in this material and over this range is shown to be negligible. © 2014 The Authors. Surface and Interface Analysis published by John Wiley & Sons Ltd.

Saga of efficiency degradation at high injection in InGaN light emitting diodes

Saga of efficiency degradation at high injection in InGaN light emitting diodes

Competing in the Global LED Industry: The Case of Taiwan

Light-emitting diode (LED) is a very essential application for energy-savings nowadays. The revenue of the Taiwan LED components industry is ranked top one in the world, followed by that of Japan and South Korea. Based on the advantage of their electronics industry, Taiwanese LED companies create a unique model to compete with the international firms. Large international LED companies achieve economies of scale by vertically integrating their operations. Taiwanese LED companies specialize and achieve an optimal efficiency by vertically disintegrating across the upstream, midstream, and downstream sectors in the value chains. Taiwanese LED companies create economies of scale and economies of scope through a complete industrial value chain.

Advanced Analyses of Technology Innovations, Patents, and Intellectual Property

A good indicator of the technical competitiveness of a country or an enterprise is the number of high quality international patents it owns. The latest statistics from the World Intellectual Property Organization (WIPO) showed that USA, Japan, Germany, China, and South Korea are among the top patent filing countries [1] . WIPO data indicate that these countries and their global companies are directing significant resources toward engineering innovations, design inventions, and technology R&D. The end result will be to capitalize their intellectual assets for competitive advantage. The huge and ever growing data and knowledge content of international patent (cyber-) depositories creates great challenges for engineers, researchers, and technology strategists to fully utilize the wealth of knowledge [2] . Most critically, engineers must make correct R&D decisions based on the complex sets of patent information. This special issue features research papers focusing on the advances of representing, modeling, reasoning, analyzing, and synthesizing knowledge related to innovations, intellectual property (IP), patents, and technology adoptions. For industries with short life cycles and technical products (e.g., semiconductor, LED, and consumer electronics), state-of-the-art knowledge engineering approaches for IP and patent analysis are essential for sustaining competitive advantage. We have accepted five articles in this special issue and each has developed methodologies using industrial cases for verification. The papers are highlighted briefly as follows. The article “ Applying Hybrid-Quantity Analysis in the Asia Semiconductor Industry ,” co-authored by Chin-yuan Fan, Ming-Fong Lai, and Shu-Hao Chang, provides an integrated approach to explore competing technological and strategic-group relationships within the semiconductor industry in the Asia-Pacific region. They use a combination of patents, multidimensional scaling, and K-means clustering to conduct their hybrid analyses. Their findings provide recommendations for technology development strategies. The paper, entitled “ Ontology-based Patent Licensing and Litigation Strategic Knowledge System for the Light Emitting Diode Industry ” co-authored by Amy J.C. Trappey, Yu-Hui Wang, Charles V. Trappey, Chun-Yi Wu, and Tzu-Hsuan Lin, develops a scientific and analytical approach for strategic cross-licensing decision support, particularly for the extremely competitive global companies in LED industry. Yu-Hui Wang and Benjamin Liu present their research in the paper entitled “ Innovation Effect on Patent Pool Formation: Empirical Case of Philips’ Patents in Digital Versatile Disc 3C . ” The paper evaluates both the quantity and quality of Philips’ patents in a leading DVD patent pool. The legitimacy of patent pools and their strategic value are discussed and investigated using the DVD 3C patent pool as the case example. In the paper “ Application of the Honeybee Mating Optimization Algorithm to Patent Document Classification in Combination with the Support Vector Machine (SVM), ” co-authors Chui-Yu Chiu and Pei-Ting Huang combine the honeybee mating optimization algorithm with SVM as a novel patent categorization approach with accurate results. The paper, entitled “ Exploring the Innovative Value of the RFID Industry ” co-authored by Pei-Shu Fan, Cheng-Chin Tsao and Yi-Ching Liaw, examines a number of patent indicators to predict and explain future technological developments in the RFID industry. The research identifies the relative regional technological advantages in RFID development using relevant patent indicators and clustering analysis.

Ontology-based Patent Licensing and Litigation Strategic Knowledge System for the Light Emitting Diode Industry

This research studies the patents, intellectual properties and licensing landscape of the Light Emitting Diode (LED) industry. The ontology of LED technology is described and defined as four major sub-technology domains. The finding provides LED companies with consistent knowledge of their own and their competitors’ patents and intellectual property rights (IPR) ownership. Major LED companies often use their IPRs to gain and protect their market competitiveness, to form alliances, and to create patent licensing or cross-licensing strategies. Newly established LED technology companies competing with global industry leaders face many challenges unaddressed in the research literature. This research focuses on the empirical and quantitative analysis of historical IP and patent related conduct in relation to corporate strategy. Based on the heuristic rules derived from historical conduct, the research establishes a standardized analytical procedure to use in the evaluation of patent licensing and litigation. The results help researchers effectively and consistently analyze their technical capabilities, evaluate their patent licensing strategies, and review litigation in view of the LED-related IP and patent marketplace.

Metal contact printing photolithography for fabrication of submicrometer patterned sapphire substrates for light-emitting diodes

This paper reports an improved method that combines a metal film contact printing method with traditional photolithography for fabrication of submicrometer-scale patterned sapphire substrates (PSSs) used for high-brightness light-emitting diodes (LEDs). First, a patterned metal thin film is transferred from the surface of a mold onto a photoresist (PR) layer deposited on top of the sapphire substrate. The transferred metal pattern acts as a photomask for subsequent photolithographic processes. PR structures with a high aspect ratio of 5 and a small line width of 500 nm are fabricated on 2 and 4 in. sapphire wafers. Finally, inductively coupled plasma etching is performed on the sapphire substrates to obtain PSSs by using the patterned PR microstructures as an etching mask. Experiments have been performed and both 2 and 4 in. PSSs with submicrometer-scaled and cone-shaped surface features were successfully obtained. These PSSs can be used in the LED industry to obtain high-brightness LEDs.