The patterned sapphire substrate used by many epitaxial manufacturers can be divided into three types:
This is a sapphire substrate surface for GaN growth widely used by manufacturers, mainly because sapphire crystal growth along the C axis has a mature process, relatively low cost, and stable physical and chemical performance, and the technology of epitlite on C-plane is mature and stable.
R-plane or m-plane sapphire substrate is mainly used to grow non-polar/semi-polarity surface GaN epitaxial film, in order to improve the luminous efficiency. Usually, GaN epitaxial film in the patterned sapphire substrates preparation was grown along the C axis, and the C axis is the polar axis, which leads to a strong built-in electric field in the active layer quantum wells of GaN-based devices, which will reduce the luminous efficiency. The non-polar GaN epitaxy is developed to overcome this physical phenomenon and improve the luminous efficiency.
In the way of Growth or Etching, nanoscale specific microstructural patterns are designed and made on sapphire substrate so as to control the light output form of LED; besides, the differential defects between GaN growing on sapphire substrate can be reduced, the quality of epitlite can be improved, and the internal quantum efficiency of LED and the optical extraction efficiency can be enhanced.
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