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High brightness LED chips in the market and future trends
2013-05-25 14:28:07

High brightness LED chips in the market and future trends
 
System of high brightness LED infrared light is divided into GaAs and AlGaAs system, red, orange, yellow, green AlGaInP system, green and blue InGaN system, as well as UV GaN and AlGaN system. InGaN Blu-ray optical efficiency of the system is high, combined with quaternary red, yellow, light, has begun to be widely used in lighting, backlight, display, traffic lights and other fields. UV LED has a broad market prospect, semiconductor UV light source lighting, sterilization, medical, printing, chemical and biological detection, high-density information storage and confidentiality of communications and other fields has great application value. Infrared LED peak wavelength from 850nm to 940nm infrared LED, widely used in the field of remote control, drive, computer mouse, sensors, security devices and display backlight, infrared LED demand continues to grow, the driving force comes mainly from household appliances, security systems and wireless communications products and so on.
 
White applications is an important market of the blue LED chip, is the most important direction of development, the use of blue chip plus YAG yellow phosphor to form white light source. At present, the international LED manufacturers in power blue chip has obvious advantages, the domestic LED chip companies mainly in small and medium-power blue chip larger development, but due to over-investment in previous years caused overcapacity , leading to small and medium-sized power blue chip market to a more serious price war. For the blue LED chip, the main direction of development of silicon-based LED chips, high-voltage LED chips, flip the LED chip. For small and medium-power LED chip market, the mainstream market trends 0.2-0.5W market. Package options include 2835,5630 and COB packaging. For other segments, such as the vertical structure of the chip, package can be applied to directional lighting applications, such as flashlight, miner's lamp, flash, searchlights and other lighting products.
 
Silicon substrate LED chip is receiving attention
 
Mainstream blue chip currently on the market are generally grown on a sapphire substrate, which is represented by Nichia Corporation of Japan; addition, there is a blue chip is grown on a silicon carbide substrate, as the representative of the United States Career.
 
In recent years, the growth of blue LED chips on silicon substrate more and more people's attention. The silicon substrate due to the IC automatic production line of the factory can be used, relatively easy adoption of IC factories 6 inch and 8 inch line mature technology, coupled with the large size of the silicon substrate is relatively low cost, and thus the cost of the silicon substrate LED chip expected to be significant decline, could also contribute to the rapid penetration of the semiconductor lighting. Silicon-based LED chip when a property has the following characteristics:
 
? vertical structure, with silver mirror lens, allows more uniform current distribution, in order to achieve high current drive;
 
? Silicon substrate, good heat dissipation, is conducive to cooling of the chip;
 
? with the lambertian morphology, light uniformity, easy for secondary optics;
 
? suitable for ceramic substrate package;
 
? suitable for LED flash and strong directional lighting applications, can be used in indoor, outdoor and portable lighting market.
 
On the development of silicon-based LED chip, LatticePower in 2009 had launched a low-power silicon LED chip is widely used in the field of digital display. June 2012 LatticePower in Guangzhou released a new generation of high-power silicon-based LED chip products, has aroused great concern of the LED industry at home and abroad, launched 28mil, 35mil, 45mil and 55mil, including four silicon power LED chip, 45mil chip to achieve a luminous efficiency of 120lm / w, and at the end of the year reached 130lm / W, and good reliability. Silicon-based LED chip ceramic package with internationally renowned product has a good price, has aroused great interest in the packaging plants at home and abroad and LED lamp factory. It is reported that Sharp and Puri also announced at the end of 2012, production of the silicon substrate white chips, introduced two white chips; manufacturers including Samsung, Osram, Epistar is actively engaged in the silicon-based LED chip research.
 
The LED market is in a stage of rapid development, will promote the further decline of the cost of the LED chip semiconductor lighting into the family million. Since the silicon substrate has a low cost IC factory manufacturing processes mature, with 6-12 inch large-size silicon-based LED technology continues to evolve, silicon-based LED technology will reduce costs and improve production efficiency has a huge advantage, This LED industry will have a significant impact.
 
Facing bottlenecks in the development of high-brightness chip
 
At present, the further development of semiconductor lighting market the luminous efficiency of the blue LED chip to rising cost to be declining. Career silicon carbide-based LED chip has been achieved 200lm / W luminous efficiency of mass production, R & D level of luminous efficiency can reach 276lm / w. The decline in the cost of the LED chip and light effects enhance this race, are experiencing the following development bottleneck.
 
The first is the existence of blue chip Droop effect. In the conditions of current density, external quantum efficiency of the light emitting diode will drop tests showed Droop effect is caused by a variety of reasons, including Auger effect, this effect limits the blue chips in a large current density, thus hinder the lumen of the decrease in cost.
 
The second is and green the bandgap (Greengap) and red-bandgap (Redgap). When the wavelength from the blue into the green band, the quantum efficiency of the LED will be decreased, such as the 530nm green quantum efficiency drops quickly; magenta spectra for the red, the internal quantum efficiency can reach 100%, but the ideal red-orange light emitting white light source wavelength (614nm), its efficiency is decreased rapidly. These effects limit the green and red chip Increases efficiency, delaying the next generation of high-quality white light. In addition, the efficiency of the green and yellow LED itself, the impact of the polarization field, and this effect becomes stronger with higher concentration of indium atoms.
 
The third is the extension of the heterogeneous growth problems. Since the epitaxial growth of defects in the crystal, the formation of a large dislocation density and defect, resulting in decline in luminous efficiency and lifetime decrease. Currently whether Blu Circuit is silicon carbide, sapphire, silicon substrate technology is heteroepitaxial exist between the substrate and the epitaxial crystal lattice mismatch dislocation after the epitaxial growth, and at the same time due to the difference of the thermal expansion coefficient of the cooling process in thermal stress is generated, resulting in the epitaxial layer defects, cracks, chips, such as bending. Substrate directly affects the quality of the crystal quality of the epitaxial layer, thus affecting the efficiency and lifetime of light. If the use of the a homogeneous GaN substrate for epitaxial growth, the use of non-polar technology, can minimize the defects of the active layer, so that the current density of the LED chips 5-10 times higher than conventional chips, and significantly improve the luminous efficiency. It is reported that Seoul Semiconductor adopt the native substrate developed nPola new products, compared with the current of the LED, the brightness in the same area five times higher, but GaN homogeneous substrate for LED still too expensive.
 
Overall, the future development of the blue LED chip, flip-chip, high-voltage chips, silicon chips are the main trends. Flip-chip good heat dissipation can increase the injection current, do not fight the line can improve the reliability of the product in the application process; high-voltage LED chip can be more closely match the supply voltage can improve the power conversion efficiency, plus custom IC power, best suited for LED bulb; epitaxially grown in 6-inch or 8-inch silicon substrate, the silicon-based LED chip can significantly reduce the cost of the LED, thus speeding up the era of semiconductor lighting applications. For other colors, the red LED chip and green LED chips, light efficiency there is still much room for improvement, with the red and green LED chip light efficiency is further improved, not necessarily white is Blu-ray LED chip and yellow phosphor form, it may be RGB or other form of white package may also change a lot.

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