Silicon-based GaN research and development in high-power LED

2015-10-05 Category:Industry News

Recently, held in Guangzhou in 2013 LED epitaxial silicon technology and latest trends in special equipment and materials, the Dr. Sun Qian, vice president of research and development of silicon substrate LED LatticePower participants entitled "silicon substrate GaN High Power LED R & D and industrialization, "the report, together with their peers to share the latest advances in silicon substrate development and industrialization of high-power LED and large-size silicon substrate LED technology.
    
In his speech, Dr. Sun Qian talked about a very important now is to pursue cost-effective LED. The view from the first step epitaxial substrate, sapphire substrate accounted for 10% of the market, the technology is mature and is currently the mainstream of the market, but the sapphire substrate have heat problems, 8-12 inch size is difficult to achieve, prices are more expensive, P surface current expansion is poor, the development of China's LED industry, there are many practical problems.
    
The silicon substrate has some advantages, inexpensive materials, good heat dissipation coefficient; difficulty is that there is a high defect density, reduce LED brightness. Academia wants to integrate silicon and gallium nitride, but there are difficulties, the main difficulty is the large gallium and silicon lattice mismatch between. Due to the high defect density, 54% of the thermal expansion coefficient, the epitaxial film cracks in the cooling process. There will be a chemical reaction back to melt the metal frame directly to the end of the silicon substrate.
    
Gallium nitride and silicon together is very difficult, a lot of work in front, such as silicon substrate surface groove, GaN superlattice buffer layer, which can be achieved without cracks, which is basically feasible route. 17% lattice mismatch, this will affect the performance of the material, gallium nitride is now producing no cracks to 4 microns, pad wafer curvature of less than 10 microns epitaxial silicon on sapphire crystal quality and flat substrates.
    
The silicon substrate is a new conductor, it would absorb sunlight molecules, we can use chemical etched, if the film is only a few microns, we do reflective metal contacts.
    
Production data, which is the standard deviation of a wavelength within the standard sheet 1.3nm, the wavelength range of 4nm microns. GaN-based LED silicon substrate wafer warpage is small, the silicon substrate two inches LED most about 4-5 microns, 6 inches below 10 microns.
    
2 inches silicon substrate 4545 high power LED production silicon chip, the light intensity of die parallel 500lm/W, reverse leakage less than 0.1uA, parallel voltage 3V, most wavelength within 5nm. LED silicon substrate do cheap and poor quality, high-power LED performance silicon substrate R & D progress, in June 2012, 2-inch silicon reach 110lm/W, 2013 January reach 140lm/W.
    
The difference between silicon and sapphire, sapphire substrate is transparent, the vertical structure of the silicon substrate, the white light uniformly, easily with secondary optics. Silicon substrate GaN-based LED chip direct white light, the phosphor-coated white chips straight centralized distribution.
    
The next step how to do it? Is to improve the performance and reduce the value. Flip-wave silicon substrate LED chip, more efficient process would be better. 6 inches silicon substrate GaN-based high-power LED research and development, is expected to reduce costs by more than 50%.
    
Has developed a 6-inch silicon substrate GaN-based LED epitaxial and advanced technology, the luminous efficiency of 125lm / w, to solve crack constraints and quality issues, to ensure that no leakage problems. Vertical structure LED chip technology, at 350mA, 45 and 55mil LED chip silicon substrate reached 140lm/w and 150lm/W.