Sapphire substrate has many advantages: First, the sapphire substrate production technology is mature, good quality components; Secondly, the stability of sapphire good to use in high-temperature growth process; Finally, the sapphire of high mechanical strength, easy to handle and cleaning. Therefore, most processes are generally on sapphire as a substrate. Figure 1 Example of the use made of sapphire LED chip. Use of sapphire as a substrate, there are some problems, such as lattice mismatch and thermal mismatch stress, which will generate a large number of defects in epitaxial layer, while the device for subsequent processing difficult. Sapphire is an insulator, the resistivity at room temperature is greater than 1011Ω?; Cm, in which case the vertical structure of the device can not be produced; usually produced in the epitaxial layer on the surface of n-and p-type electrode (as shown in Figure 1 shown). In the production of two electrodes on the surface, resulting in a reduction of the effective emitting area, while increasing the device fabrication process of photolithography and etching process, resulting in lower material utilization, the cost increase. Since P-type GaN doping difficulties,
LED billboard, the current widely used in the preparation of p-GaN metal transparent electrodes on the ways in which current spread, in order to achieve the purpose of uniform light. But the metal transparent electrode generally absorb about 30% to 40% of the light,
LED sign, while the chemical properties of GaN-based materials stability, high mechanical strength, its not easy to etch,
LED message board, so the etching process of the need for better equipment,
electric signs,
LED point light dotted facade
