Efficiency Enhancement and Beam Shaping of GaN-InGaN Vertical-Injection Light-Emitting Diodes via High-Aspect-Ratio Nanorod Arrays

The enhanced light extraction and collimated output beam profile from GaN-InGaN vertical-injection light-emitting diodes (VI-LEDs) are demonstrated utilizing high-aspect-ratio nanorod arrays. The nanorod arrays are patterned by self-assembled silica spheres, followed by inductively coupled-plasma reactive ion etching. The fabricated nanorod arrays not only provide an omnidirectional escaping zone for photons, but also serve as waveguiding channels for the emitted light, resulting in a relatively collimated beam profile. The light output power of the VI-LED with nanorod arrays is enhanced by 40%, compared to a conventional VI-LED. The measured far-field profiles indicate that the enhancement is mainly along the surface normal direction, within a view angle of 20deg.