The quality of the LED epitaxial wafer depends on the substrate material, and the epitaxial growth technology related to the substrate material is the cornerstone of the development of the semiconductor lighting industry technology.
Different substrate materials require different epitaxial growth techniques, chip processing techniques, and device packaging techniques. Substrate materials determine the development path of semiconductor lighting technology. The choice of substrate material depends mainly on the following nine aspects:
1, good electrical conductivity, can be made up and down structure;
2, good chemical stability, not easy to decompose and corrode in the temperature and atmosphere of epitaxial growth;
3, good structural characteristics, the epitaxial material and the crystal structure of the substrate are the same or similar, the lattice constant mismatch is small, the crystallization performance is good, and the defect density is small;
4, the price is low;
5, the optical performance is good, the light emitted by the fabricated device is absorbed by the substrate is small;
6, large size, generally requires a diameter of not less than 2 inches.
7, good interface characteristics, is conducive to nucleation of the epitaxial material and strong adhesion;
8, good thermal performance, including good thermal conductivity and thermal mismatch;
9, mechanical properties are good, the device is easy to process, including thinning, polishing and cutting;
It is very difficult to select the substrate to meet the above nine aspects at the same time. Therefore, at present, the development and production of semiconductor light-emitting devices on different substrates can only be adapted by changes in epitaxial growth technology and adjustment of device processing processes. There are many substrate materials for gallium nitride research, but there are only two kinds of substrates that can be used for production, namely sapphire Al2O3 and silicon carbide SiC substrate. Table 2-4 provides a qualitative comparison of the performance of five substrate materials for gallium nitride growth.
The following factors must be considered in the evaluation of the substrate material:
1. Chemical stability matching between substrate and epitaxial film: The substrate material should have good chemical stability, and it is not easy to decompose and corrode in the temperature and atmosphere of epitaxial growth, and the quality of epitaxial film cannot be degraded due to chemical reaction with epitaxial film. ;
2. Matching the thermal expansion coefficient of the substrate and the epitaxial film: the matching of the thermal expansion coefficient is very important. The difference between the thermal expansion coefficient of the epitaxial film and the substrate material may not only reduce the quality of the epitaxial film, but also cause heat during the operation of the device. And cause damage to the device;
Carbon Fiber Rigid Felt Tube,Vacuum Furnace Insulation Cylinder,Carbon Fiber Thermal Insulation Cylinder,Heat Insulation Screen Of Vacuum Furnace
HuNan MTR New Material Technology Co.,Ltd , https://www.hnmtr.com