Optical and thermal performance of nitride-based thin-film flip-chip light-emitting diodes

Nitride-based light-emitting diodes (LEDs) were fabricated based on initial patterned sapphire substrate by thin film (TF) and flip-chip (FC) techniques. An enhancement of 7.7% in light output power was first obtained by optimizing the p-type contact layer. Then, periodic patterned surface was optimized by wet etching after removal of the sapphire substrate, and the light output power of the TFFC-LEDs was enhanced by 19.8% as compared to that of the TFFC-LEDs with original patterned surface. The device performance characteristic including illuminant pattern, emission wavelength movement and junction temperature variation of the optimized TFFC-LEDs were shown as compared with commercialized LEDs. The results indicate that the TFFC-LEDs possess uniform current distribution and lower junction temperature, thus show promising applications in various areas such as automotive lighting, illegal capture and solid-state lighting.