GaN-Based Light-Emitting Diodes Integrated With Zinc Oxide Photonic Crystals

To improve the light output of GaN-based blue light-emitting diodes (LEDs), 2-D photonic crystals (PhCs) were integrated by selective growth of
c
-axis-oriented zinc oxide (ZnO) rods on ZnO transparent electrodes. Submicrometer-pitched periodic and vertical structures with high refractive index enable the surface diffracting grating to serve as an efficient light extractor for LEDs. A chemical bath deposition of ZnO rods below 100 °C prevented PhC fabrication from damaging the underneath layers. The fabricated ZnO PhC with a period of 0.6 μm enhanced the light output by 1.4 times. The pitch dependence of the enhancement in the experiment was consistent with the prediction by numerical calculation. The obtained results demonstrate that the solution-grown ZnO exhibits excellent optical and structural properties for PhCs.