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What is Sapphire Substrate
Al2O3 , adopted as the primary substrate materials of GaN and InGaN growth, has been esteemed as sapphire substrate.
By now sapphire substrate has been applied in most of the LED chip manufacturing techniques, which has the following advantages:
(1) Mature technology and well-performed ability
(2) High light transmittance without absorption of visible light
(3) Good stability and high temperature growth
(4) Excellent mechanical strength
However, some disadvantages also exist by selecting sapphire substrate:
Firstly, lattice mismatch and thermal stress mismatch will resort to epitaxy defects and badly impact the following manufacturing process. Sapphire substrate is one electrical-resistance substance with high electrical resistivity. So P electrode and N electrode were set up on epitaxy surface, which can lessen the lighting area and make it more difficult in photoetching and photoengraving.
Moreover, high hardness of sapphire substrate makes it difficult to carve up and cut and bad electrical conductivity has become the key point to be solved.