With high value in energy-saving and emission-reduction, LED lighting becomes an important strategic emerging industry all around the world. The current three LED lighting technology routes are based on GaN LEDs grown on sapphire, SiC and Si substrates respectively. Among them, the first two routes were mainly developed by Japan and US, and the relevant contributors were awarded the top level science and technology prizes in their countries, respectively. The third route, which is the achievement of this project, is developed by our country. For ten years of focus on technology breakthrough and productive practice, this project develops a third route of LED lighting with complete independent intellectual property rights and unique advantages in the market, breakthrough the restrain of foreign patents and elevates the status of LED technology of our country in the world.
It was a dream to make GaN LEDs on Si substrate in LED industry. However, as the lattice mismatches and thermal mismatch between GaN and Si substrate are both very large, the epi-film is poor in crystal quality and easily cracked. Together with the problem of light absorption by the opaque substrate, it was believed that fabrication of high efficient GaN based LEDs on Si substrate is impossible. Nevertheless, the worldwide difficulty has been resolved by this project after more than 3000 times experiments. By innovating new methods, structures and techniques to overcome the huge tensile strength during epitaxial growth and chip fabrication processes, GaN based LEDs of single face emitting with high internal quantum efficiency, high light extraction efficiency and excellent reliability are successfully developed and industrialized for the first time in the world. The relevant technologies have been granted 68 invention patents, including 19 US patents. Base on this project, enterprises of chip fabrication, device package and product application with more than 30 types of products were founded, forming a complete Si substrate LED industry chain from upstream, midstream and downstream. The products have been widely used in general lighting as well as special light all around the world.