Improved light output power of GaN-based ultraviolet light-emitting diode using a mesh-type GaN/SiO2/Al omnidirectional reflector

Abstract

We investigated the effect of a mesh-type GaN/SiO2/Al omnidirectional reflector (ODR) on the light output power of AlGaN/InGaN-based ultraviolet (365nm) LEDs and compared their performance with that of LEDs with a GaN/ITO/Al reflector. Using the scattering matrix method, the normal incidence reflectance was calculated to be 93.7% for the GaN/SiO2 (62nm)/Al ODR and 79% for the GaN/ITO (30nm)/Al reflector. The Ag/Ni/Al/Ni (52nm/10nm/200nm/20nm) contact showed a specific contact resistance of 3.2x10(-5)cm(2) after annealing at 500 degrees C for 1min. The forward-bias voltages at 20mA of LEDs with ODR were in the range of 3.49-3.54V, which were similar to that of LEDs with an ITO/Al reflector (3.51V). The LEDs with ODR had series resistances in the range of 14.8-12.5, whereas the LED with an ITO/Al reflector showed 11.7. The LEDs with ODR yielded 9.3-19.9% higher light output power at 20mA than the LED with an ITO/Al reflector. The improved light output power was attributed to the optimization of the high reflectance of the ODR (reflective area) and contact area.