 Wysłany: Pon 3:01, 07 Mar 2011 Temat postu: economic and cultural center LED |
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| These three substrates comprehensive performance comparison shown in Table 1. In addition to these three common substrate materials, there GaAS,menu board, AlN, ZnO and other materials can also be used as a substrate, usually need to choose according to the design. Evaluation of substrate 1. Substrates and epitaxial films of structural matching: epitaxial materials and substrates on the crystal structure of the same or similar, the lattice constant mismatch is small,LED billboard, crystalline properties, and defect density is low;
2. Substrates and epitaxial film coefficient of thermal expansion mismatch: coefficient of thermal expansion matching is very important, epitaxial film and substrate material in the thermal expansion coefficient of the difference is too large not only likely to epitaxial film quality drops, but also in the device operation process, because the heat caused by the device of the damage; 3. substrates and epitaxial films of the chemical stability of match: substrate materials have good chemical stability, in the epitaxial growth temperature and atmosphere, not easily broken down and corrosion, not because the chemical reaction with the epitaxial film to decline in the quality epitaxial films ; 4. materials, ease of preparation and cost of high and low: Taking into account the needs of industrial development,restaurant board, preparation of the substrate material be simple, cost should not be very high. Substrate size is generally not less than 2 inches. GaN-based LED current for more substrate materials, but can be used for commercial substrates are only two, namely sapphire and silicon carbide substrate. Others, such as GaN,LED message board, Si, ZnO substrate is still in development stage, some distance away from the industry. GaN: the best substrate for GaN growth is the GaN single crystal material, can greatly improve the crystalline quality of epitaxial films and reduce the dislocation density and improve the working life of the device to improve the luminous efficiency and device operating current density. Preparation of GaN single crystal body, but very difficult, so far there has not been an effective approach. |
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