Study of GaN-based light-emitting diodes with double roughened surfaces

In this paper, GaN-based blue light emitting diodes with double roughened surfaces were fabricated and compared with planar LEDs and these with single roughened layer. The double roughened surfaces were fulfilled by patterned sapphire substrates (PSS) and roughened p-GaN surface. Magnesium treatment during the growth process was used to produce p-GaN surface roughening. After the epitaxial growth, the four group samples were fabricated using the standard process (four mask steps) with a mesa area of 10×23 mil2. At last, 25 LED devices were packaged for each group using the same packaging material and by the same method. It was found that import of PSS and roughened p-GaN surface may lead to a little higher voltage by simply copying the epitaxial process of planar LED. However, even fabricated by the non-optimized epitaxial process, comparing with planar LEDs, the optical power of the package can be increased by 40.1% by using the patterned sapphire substrate, 10.2% by using p-GaN surface roughing, and 44.9% by using double roughing technologies.