Author: Engineering LED network editor
On July 31, 2009, the “China-US LED Technology and Cooperation Forum†aimed at promoting academic exchanges and corporate cooperation between the Chinese and American LED industry was held in Shenzhen University City. The forum was organized by Gaogong LED Network and California Lighting. Co-hosted by the Technology Center and the Lighting Energy Conservation Center. The guest lineup of this conference is very strong, including Professor Michael Siminovitch, Director of the California Lighting Technology Center, Dr. Paul Phillips, Vice President of LSI Product Development, and Dr. Shao Jiaping, Cree China CTO. The forum has achieved great success, and Shenzhen TV, China Business News, EDN, etc. have all reported.
   Cree is the only company in the world's top five LED chip companies to set up FAB in China, and its every move has attracted the attention of domestic counterparts. Gaogong LED Editor is honored to interview Dr. Shao Jiaping, Cree China CTO after the meeting. He shared his insights on technology and industry.
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Cree China CTO Shao Jiaping delivered a speech at the "China-US LED Technology and Cooperation Forum" Source: Gaogong LED Network
   Adhere to the use of silicon carbide substrates to create a competitive advantage that cannot be replicated
   As everyone knows, Cree is the only company in the industry to insist on the use of silicon carbide substrates. At present, most domestic enterprises adopt sapphire substrates, because silicon carbide is expensive, and related patents are basically in the hands of Cree. In this regard, Dr. Shao said: “Cree is a highly vertically integrated company in the LED semiconductor lighting industry. Cree's co-founder is a material expert himself, before mass production of SiC substrate blue LED chips in the early 1990s. There are SiC materials and devices for RF power generation. Currently, Cree's high-power and high-brightness LED chips are based on SiC substrates. Cree also has 4-inch zero-defect SiC wafer materials and related RF and power. Electronic and switching devices are available.
   When asked if other substrates would be used in the future, Dr. Shao said Cree had no plans to use sapphire or silicon substrates for the time being.
   The main reason is that the heteroepitaxial technology of blue-green InGaN/GaN-based materials is limited by itself, such as the lattice mismatch between sapphire substrates, silicon substrates and InGaN/GaN-based materials based on MOCVD epitaxial technology (Lattice Mis╉) The atch is larger, and the defect density in the corresponding epitaxial layer is higher, resulting in a relatively low quantum efficiency of the epitaxial wafer and the chip.
   He believes that although the current Strain Management and other technical routes have been used to make InGaN/GaN blue-green LED epitaxy and chips on large-size sapphire and silicon substrates, it has made some progress from the mature large-scale, large-scale Production still requires considerable effort. Cree's 3-inch and 4-inch silicon carbide substrates are currently in use at about half each, and all are ready to transition to four inches in the future.
   Product advantages, chip performance is significantly ahead of domestic counterparts
   Cree's products have always been ahead of the world in performance. What strategy does it use to achieve this? Dr. Shao said that Cree's continuous efforts, continuous investment, and high vertical integration from SiC materials, substrates, GaN-based epitaxy and chip, package and application enable its chip technology and lighting-grade XLamp® components to perform. Lead the industry.
   He cited the electro-optical conversion efficiency of the 450-465 nm band blue power chip as an example. The 40 mil square power chip, with a typical Vf forward voltage of about 3.2 V -3.3 V at 350 mA drive current, integrated radiation With a power rating of 450mW (even up to 500 mW), the chip's electro-optic conversion efficiency can be as high as 40% -50% or even higher. To put it another way, for every 1 W of electrical power consumed, a radiated optical power of 0.4 W-0.5 W or higher can be obtained. This high efficiency ensures that Cree's chips and devices truly deliver outstanding energy savings, longevity, and low carbon emissions in real-world semiconductor lighting applications.
   He gave another example. Cree's lighting-grade XLamp® components, such as the mainstream XR┡, XP┡, MC┡, etc., have the following main features:
1. Have a LMâ””0 life test report passed by the US Department of Energy ENERGY STAR;
2. The color temperature bin is fully aligned to the ANSI C78.377A standard recommended by the Energy Department ENERGY STAR;
3. Green and environmentally friendly, fully meet the requirements of RoHS and REACH standards;
4. The color point is stable, such as long time (nearly 10,000 hours), high temperature and high humidity (such as 85oC / 85% RH), high current (such as 700 mA), the color coordinate drift Δu', v' < 0.004 ( 4?stepMacAdam Ellipse Range);
5. Under certain operating conditions (such as junction temperature not exceeding 135 degrees Celsius, ambient temperature not exceeding 25 degrees Celsius, driving current 700 mA), the L70 life can reach more than 50,000 hours.
   Chip costs will fall further as capacity increases
   The cost issue has always been a key obstacle to the popularity of LED Lighting. Which technologies currently limit the cost reduction? How will the future develop? In this regard, Dr. Shao said that in general, it is mainly the scale of LED epitaxy and chip production. As the cost of materials, equipment depreciation/maintenance, and advanced R&D will decrease rapidly as the capacity scale increases, the price of LED chips will further decline in the foreseeable future.
   He also stressed that with the further improvement and improvement of epitaxial (quantum well) structure design, epitaxial growth process, chip manufacturing processing technology, the subsequent production and application maturity, the overall production yield will continue to increase, which will also be LED chips. Another drive for price declines.
   Continue to increase research and development to ensure a competitive advantage
   It is understood that Cree and Nichia, PHILIPS Lumileds, Osram Opto, and Toyoda Gosei are also known as the “Big Five†on the global patent map of LED semiconductor lighting. They have the core original patented technology in different aspects such as materials, epitaxy, chip, package and application. As shown below:
World LED chip patent map source ledsmagazine
   Dr. Shao said that in the future, Cree will further increase investment in research and development and maintain its leading position in the field of LED semiconductor lighting. For the domestic LED standard, he suggested to refer to the work of the US Department of Energy, the International Lighting Institute IES and other institutions to learn from each other's strengths, both to adapt to the national conditions and to synchronize with the international.
Attachment: Cree's main patents are as follows (provided by Dr. Cree Shao):
Mini Screwdriver,Small Screwdriver,Mini Tool Flashlight
Asia Leader Import & Export Co., Ltd. , http://www.nbflashlight.com