Investigation of GaN-Based Light-Emitting Diodes Grown on Patterned Sapphire Substrates by Contact-Transferred and Mask-Embedded Lithography

The influences of pattern size and etching depth of patterned sapphire substrates (PSSs) on crystal quality and light output power of light-emitting diodes (LEDs) were investigated by contact-transferred and mask-embedded lithography. The present results indicate that a smaller pattern size facilitates superior light extraction efficiency. However, a suitable pattern size and etching depth should be chosen to obtain the highest quality of GaN film. In comparison with the conventional sapphire substrate, the largest light output enhancement (${\sim}28.9$%) was observed when the pattern diameter and the etching depth of PSS were 400 and 400 nm, respectively.