Beam Divergence and Thermal Transient Characteristics of InGaN/GaN Light Emitting Diodes with Rear Side Grown ZnO Nanorods

We report the enhanced light output power of InGaN/GaN light-emitting diodes (LEDs) with ZnO nanorods grown on the polished rear side of the sapphire substrate. ZnO seeds were spin coated on the polished bottom side of the sapphire substrate and a simple solution technique was employed to grow ZnO nanorods. Results reveal that the rear side grown ZnO nanorods enhance the light output power of the GaN LEDs significantly due to the light wave guiding and reflectivity of ZnO nanorods. The light output power from the GaN LED with rear side grown ZnO nanorods was 15% higher than that of a conventional LED. Thermal conductivity characteristics showed that GaN LEDs with ZnO nanorods possess low thermal resistance (25.1 degrees C/W) compared to the conventional LEDs (40.5 degrees C/W) because of high thermal conductivity of ZnO nanorods. (C) 2012 The Japan Society of Applied Physics