Substrate materials and wafer growth techniques are 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), 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 commercially available sapphire or silicon carbide substrates are used to epitaxially grow wide-bandgap semiconductor gallium nitride. Both materials are very expensive and are monopolized by foreign large companies, and the price of silicon substrates is higher than that of sapphire and carbonization. Silicon substrates are much cheaper, making larger substrates and increasing the utilization of MOCVD, thereby increasing tube crystal yield. Therefore, in order to break through international patent barriers, Chinese research institutions and LED companies began research on silicon substrate materials.
However, the problem is that the high-quality combination of silicon and gallium nitride is a technical difficulty of the LED chip. The technical problems of high defect density and crack caused by the large mismatch between the lattice constant and the thermal expansion coefficient of the two have long hindered the chip field. development of.
Undoubtedly, from the perspective of the substrate, the mainstream substrate is still sapphire and silicon carbide, but silicon has become the future development trend of 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 not only reduces the tube crystal area, but also eliminates the dry etching step of the gallium nitride epitaxial layer. In addition, silicon has a lower hardness than sapphire and silicon carbide, and it can also save some costs in processing.
At present, the LED industry is mostly based on 2 or 4 inch sapphire substrates. If silicon-based GaN technology can be used, at least 75% of raw material cost can be saved. According to estimates by Japan's Sanken Electric Co., the manufacturing cost of fabricating large-size blue GaN LEDs using silicon substrates is 90% lower than that of sapphire substrates and silicon carbide substrates.
Chinese and foreign chip technology differences
Leading companies such as Osram International, BRIDGELUX, and SAMCO INC have made breakthroughs in the research of large-size silicon-based GaN-based LEDs, such as Philips, South Korea's Samsung, LG, and Toshiba. The LED giant has also set off a research boom in GaN-based LEDs on silicon substrates. Among them, in 2011, Puri developed high-efficiency GaN-based LEDs on 8-inch silicon substrates, achieving luminous efficiency comparable to that of top-level LED devices on sapphire and silicon carbide substrates of 160 lm/W. In 2012, OSRAM successfully produced a 6-inch silicon-on-silicon gallium-based LED.
In contrast, China's breakthrough in LED chip technology is mainly to increase production capacity and large-size sapphire crystal growth technology. In addition to the successful mass production of GaN-based high - power LED chips on 2-inch silicon substrate in 2011, Jingneng Optoelectronics Co., Ltd. Chip companies have no major breakthrough in the research of GaN-based LEDs on silicon substrates. At present, China's LED chip companies are still focusing on production capacity, sapphire substrate materials and wafer growth technology, Sanan Optoelectronics, Dehao Runda, Tongfang, etc. Most of the chip giants have made breakthroughs in production capacity.
At the end of the 1940s, the first semiconductor triode was born in the world. With its characteristics of small size, light weight, power saving, and long life, it was quickly used by various countries and replaced electronic tubes in a large range. In the late 1950s, the first integrated circuit appeared in the world. It integrated many electronic components such as transistors on a silicon chip, making electronic products smaller. Integrated circuits have rapidly developed from small-scale integrated circuits to large-scale integrated circuits and ultra-large-scale integrated circuits, thereby enabling electronic products to develop in the direction of high efficiency, low consumption, high accuracy, high stability, and intelligence.
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