III-Nitride-Based Light-Emitting Diodes With GaN Micropillars Around Mesa and Patterned Substrate

In this paper, the textured-sidewall mesa and GaN microsize pillars (¿-pillars) around the mesa region were fabricated on III-nitride light-emitting diodes (LEDs) with a patterned sapphire substrate (PSS). We demonstrated that the light-waveguide mode outside the mesa region of III-nitride LEDs could be disrupted by a GaN ¿-pillar around the mesa region and PSS. We found that the power enhancement of LEDs with textured sidewall, ¿-pillars around the mesa, and PSS from ray-tracing simulation was about 65% larger than that of conventional LEDs. It was found that we could achieve a high power enhancement of about 60% of LEDs with textured sidewall, ¿ -pillars around the mesa, and a patterned substrate, and it was close to the result of simulation. It was also found that the light intensity outside the mesa region with ¿ -pillars of LEDs with or without a patterned substrate would decay in proportion to the distance away from the mesa edge, by studying the light emission intensity image of the whole LEDs. The decay lengths for the textured sidewall and ¿-pillars around the mesa LEDs with or without a patterned substrate are 12 and 17 ¿m, respectively. We understand that the light outside the mesa region could be extracted earlier by introducing the GaN ¿-pillars and patterned substrate together.