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Chips using silicon carbide substrates for the L-type electrodes, two electrodes located in the surface and bottom of the device,[link widoczny dla zalogowanych], the heat generated can be exported through the electrode; the same time that the substrate does not require conductive layer, and therefore will not be current photo diffusion layer of material absorption,[link widoczny dla zalogowanych], which also enhance the light extraction efficiency.
But relative to the sapphire substrate, the silicon carbide manufacturing costs higher, to achieve its commercial also need to reduce the corresponding costs. Performance comparison of three kinds of substrate in front of An Introduction to the LED chip is made of three commonly used substrates.
These three substrates comprehensive performance comparison shown in Table 1. In addition to these three common substrate materials, there GaAS, AlN,[link widoczny dla zalogowanych], 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, 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,[link widoczny dla zalogowanych], 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