GaN-Based Light-Emitting Diodes With Pillar Structures Around the Mesa Region

This study presents the numerical and experimental demonstrations for the enhancement of light extraction efficiency in nitride-based light-emitting diodes (LEDs) with textured sidewall and micro-sized pillar waveguides (TSMPW) and nano-textured sidewall and nano-pillars (NTSNP) around the mesa. Using hydrothermal ZnO nanorods as the etching hard mask, the authors successfully formed vertical GaN nano-pillars on the mesa-etched regions. It was found that electrical characteristics observed from the proposed LEDs were near the same as the control samples without the pillars. Output power enhancement of LED with TSMPW was about 11% compared with conventional LEDs, and the output power enhancement of LED was greater than 45% upon replacement of TSMPW with the NTSNP structure. The light extraction efficiency enhancement factors of the LEDs with TSMPW and NTSNP structures simulated by finite-difference time-domain analysis were 16.6% and 23%, respectively.