Sapphire substrates for LED mainly used by sapphire manufacturers are divided into three types:
It is a sapphire substrate for LED commonly used by many manufacturers for GaN growth, which mainly because sapphire wafers growth along the C axis has a mature process, relatively low cost, and stable physical and chemical properties, and the technology is mature and stable when epitoxy is carried out on the C plane.
C-plane sapphire substrate is commonly used. In 1993, Professor Akasaki of Japan and Dr. Nakamura Shuji, who were in Nichia at that time, broke through the problems of lattice mismatch (buffer layer) between InGaN and sapphire substrate, p-type material activation and so on, and finally, At the end of 1993, Nichia was the first to develop blue LED.
It is mainly used to grow non-polar/semi-polar plane GaN epitaxial films to improve luminous efficiency. Generally, the GaN epitaxial film prepared on the sapphire substrate usually grows along the c-axis, and the c-axis is the polar axis of GaN, which leads to a strong built-in electric field in the active layer quantum well of GaN-based device, and the luminous efficiency will be reduced. Therefore, the development of non-polar GaN epitaxy can overcome this physical phenomenon and improve the luminescence efficiency.
By means of growth or etching, nanoscale specific regular micro-structure patterns are designed and made on sapphire substrate to control the light output form of LED, and the differential defects between GaN growing on sapphire substrate can be reduced at the same time, so as to improve the epitaxy quality, enhancing the internal quantum efficiency of LED, and increasing the efficiency of light extraction.
