Efficiency enhancement of InGaN/GaN light-emitting diodes with a back-surface distributed bragg reflector

The design, fabrication, and performance characteristics of a back-surface distributed Bragg reflector (DBR) enhanced InGaN/GaN light-emitting diode (LED) are described. A wide reflectance bandwidth in the blue and green wavelength regions is obtained using a double quarter-wave stack design composed of TiO₂ and SiO₂ layers. More than 65% enhancement in extracted light intensity is demonstrated for a blue LED measured at the chip level. Similar improvement in green LED performance is discussed and achieved through simulation. Possible applications of back-surface DBR-enhanced LEDs include surface-mount packages with significantly reduced vertical profiles, resonant cavity LEDs, and superluminescent diodes.