The composition of sapphire is alumina (Al2O3), which is composed of three oxygen atoms and two aluminum atoms in a covalent bond mode. Its crystal structure is a hexagonal lattice structure. It is often used in the facet of A-Plane. C-Plane and R-Plane. Because sapphire has a wide optical penetration band, it has excellent light transmission from near-ultraviolet light (190nm) to mid-infrared light. Therefore, it is widely used in optical components, infrared devices, and high-intensity. Laser lens material and reticle material, it has high sound speed, high temperature resistance, corrosion resistance, high hardness, high light transmission, high melting point (2045 ° C), etc. It is a very difficult material to process, so it is often Used as a material for photovoltaic elements. The quality of ultra-high brightness white/blue LEDs currently depends on the material quality of gallium nitride epitaxial (GaN), while the gallium nitride epitaxial quality is closely related to the surface quality of the sapphire substrate used, sapphire (single crystal Al2O3)C The lattice constant mismatch between the surface and the III-V and II-VI deposited films is small, and meets the high temperature requirements of the GaN epitaxial process, making the sapphire wafer a key material for white/blue/green LEDs. .

The following figure is a cutaway view of sapphire; a top view of the crystal structure; a side view of the crystal structure; a structural diagram of the Al2O3; a schematic view of the crystal surface of the sapphire: