Chip is the core component of LED. At present, there are many LED chip manufacturers at home and abroad, including LED lighting manufacturer Danfeng Lighting Co., Ltd., but there is no unified standard for chip classification. If it is classified by power, it can be divided into high power and small and medium power; If classified by color, they are mainly red, green and blue; If classified by shape, it is generally divided into square piece and round piece; If classified by voltage, it can be divided into low-voltage DC chip and high-voltage DC chip. In terms of comparison between domestic and foreign chip technologies, foreign chip technologies are new, and domestic chips focus on production rather than technology.
Substrate material and wafer growth technology become the key
At present, the key to the development of LED chip technology lies in the substrate material and wafer growth technology. In addition to traditional sapphire, silicon (SI) and silicon carbide (SIC) substrate materials, zinc oxide (ZnO) and gallium nitride (GAN) are also the focus of current LED chip research. At present, sapphire or silicon carbide substrates are mostly used in the market to epitaxial grow broadband gap semiconductor gallium nitride. These two materials are very expensive and are monopolized by large foreign enterprises. The price of silicon substrates is much cheaper than sapphire and silicon carbide substrates, which can produce larger substrates, improve the utilization of MOCVD, and improve the yield of die. Therefore, in order to break through the international patent barrier, Chinese research institutions and led enterprises began to study silicon substrate materials.
However, the problem is that the high-quality combination of silicon and gallium nitride is the technical difficulty of LED chips. The technical problems such as high defect density and cracks caused by the huge mismatch between their lattice constants and thermal expansion coefficients have hindered the development of the chip field for a long time.
Undoubtedly, from the perspective of substrates, the mainstream substrates are still sapphire and silicon carbide, but silicon has become the future development trend in the chip field. For China, where the price war is relatively serious, the silicon substrate has more cost and price advantages: the silicon substrate is a conductive substrate, which can not only reduce the die area, but also eliminate the dry etching steps for the gallium nitride epitaxial layer. In addition, the hardness of silicon is lower than that of Sapphire and silicon carbide, which can also save some costs in processing.
At present, the LED industry is mostly based on 2-inch or 4-inch sapphire substrates. If silicon-based gallium nitride technology can be adopted, at least 75% of the raw material cost can be saved. According to the estimation of Sanken electric company of Japan, the manufacturing cost of large-size blue GaN LED using silicon substrate will be 90% lower than that of sapphire substrate and silicon carbide substrate.
Large differences in chip technology at home and abroad
In foreign countries, first-class enterprises such as OSRAM, Purui of the United States and Sanken of Japan have made breakthroughs in the research of large-size gallium nitride based LEDs on silicon substrates. International LED giants such as Philips, Samsung of Korea, LG and Toshiba of Japan have also set off a research upsurge of gallium nitride based LEDs on silicon substrates. Among them, in 2011, Puri developed high luminous efficiency gallium nitride based LEDs on 8-inch silicon substrates, achieving a luminous efficiency of 160lm/w comparable to the performance of top-level LED devices on sapphire and silicon carbide substrates; In 2012, OSRAM successfully produced 6-inch gallium nitride based LED on silicon substrate.
In contrast, in mainland China, the technological breakthroughs of LED chip enterprises are mainly to improve production capacity and large-size sapphire crystal growth technology. In addition to the successful mass production of 2-inch gallium nitride based high-power LED chips on silicon substrate by crystal energy Optoelectronics in 2011, Chinese chip enterprises have made no major breakthrough in the research on gallium nitride based LED on silicon substrate.
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