Substrate materials and wafer growth technology into the key
At present, the development of LED chip technology is the key to the substrate material and wafer growth technology. In addition to traditional sapphire, silicon (Si), silicon carbide (SiC) substrate materials, zinc oxide (ZnO) and gallium nitride (GaN) are also the focus of current LED chip research. At present, most of the market using sapphire or silicon carbide substrate to epitaxially grow wide bandgap semiconductor gallium nitride, the two materials are very expensive, and are monopolized by large foreign companies, and the price of silicon substrate than sapphire and carbon Silicon substrate is much cheaper, can produce a larger size of the substrate, improve the utilization of MOCVD, thereby increasing the die yield. So, in order to break through the international patent barriers, Chinese research institutions and LED companies from silicon substrate materials to study.
But the problem is that the high quality of silicon and gallium nitride is the technical difficulty of LED chip, the lattice constant and the thermal expansion coefficient of the huge mismatch caused by the high defect density and crack and other technical problems have long blocked the field of chips development of.
Undoubtedly, from the substrate point of view, the mainstream substrate is still sapphire and silicon carbide, but silicon has become the future development trend of the chip field. For relatively severe price war in China, the silicon substrate is more cost and price advantage: the silicon substrate is a conductive substrate, not only can reduce the die area, but also eliminates the gallium nitride epitaxial layer of dry etching steps , In addition, the hardness of silicon than sapphire and silicon carbide in the processing can also save some of the cost.
LED industry is currently mostly 2 inches or 4 inches sapphire substrate based, such as the use of silicon-based gallium nitride technology, at least 75% of the cost of raw materials. According to Japan's Sanken Electric Corporation estimates that the use of silicon substrate production of large-size blue gallium nitride LED manufacturing costs than sapphire substrates and silicon carbide substrate 90% lower.
Domestic and foreign chip technology differences
In the foreign, Osram, the United States Puri, Japan Sanken and other first-class enterprises have large-size silicon substrate gallium nitride-based LED research breakthrough, Philips, South Korea's Samsung, LG, Toshiba and other international LED giants also set off a The research boom of gallium nitride based on silicon substrate. Among them, in 2011, the United States Puri 8-inch silicon substrate developed on the high efficiency of gallium nitride-based LED, made with sapphire and silicon carbide substrate on the top level of LED device performance comparable to the luminous efficiency of 160lm / W ; In 2012, OSRAM successfully produced 6-inch silicon substrate gallium nitride-based LED.
In contrast, China's LED chip enterprise technology breakthrough point is mainly to improve production capacity and large-size sapphire crystal growth technology, in addition to crystal photoelectric in 2011, the successful realization of 2-inch silicon substrate GaN gallium-based high-power LED chip production, China's chip companies in the silicon substrate gallium nitride-based LED research on the big breakthrough, the current mainland China LED chip business or the main production capacity, sapphire substrate materials and wafer growth technology, San An photoelectric, BDO Runda, the same side shares And other mainland chip giants are mostly in the production capacity to achieve a breakthrough.