Patterned sapphire substrates can be used repeatedly as the main body of the substrate, so it can be used as the sacrificial substrate of LED. As a sacrificial substrate, the related patent applications mainly involve the improvement of the structure and material of the separation layer. The formation of the separation layer and semiconductor film on the sapphire substrate to form semiconductor devices can reduce the process difficulty and cost.
The crystal orientation of sapphire determines whether it can be used in LED devices on a large scale. Technicians in this field have long considered the influence of sapphire crystal orientation on device characteristics. The early patent layout direction is mainly C plane substrate. At present, C-plane patterned sapphire substrate is mature and commonly used substrate in this field, which has low manufacturing cost and stable physical and chemical properties.
Then, the direction of patent layout in this field turns to the treatment of the sapphire substrate surface, forming a rough pattern on the substrate that can improve the quality of the gallium nitride layer, so as to improve the luminous efficiency of devices. For example, patent applications CN1742381A and TW200807747A have disclosed that a concave-convex structure is formed on the surface of the sapphire substrate to improve quantum efficiency. However, arbitrary roughening of the concave-convex structure may reduce crystallinity or internal quantum efficiency. Therefore, higher requirements for the roughness of the concave-convex structure are required to ensure crystallization performance.
The lattice mismatch between the patterned sapphire substrates and the Group III compound lattice is difficult to grow a single crystal layer. Therefore, the relevant patent application discloses that porous structure or buffer layer structure can be formed between the epitaxial layer and sapphire substrate to overcome the defect, and different manufacturing technology can be selected according to different porous structure or buffer layer.
In addition, in order to provide better raw sapphire crystal materials, the inventors also focus on the research and development and patent layout of processing technology and cutting technology of raw materials. For example, relevant patents improve the processing technology to manufacture larger patterned sapphire substrates and use diamond wire technology for cutting, so as to facilitate large-scale manufacturing and production of sapphire substrates.