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GaN-based light emitting diodes encompassed with self-aligned nanorod arrays of three distribution densities were designed and fabricated. Light diffraction behaviors are characterized by considering the radiation profiles as well as the angular spectra of those nanorod structures. We demonstrate that the device with the less regular and less dense nanorod (with a fill factor 0.19) distribution has the highest enhancement factor. As we regard the nanorod arrays as localized photonic crystals, the enhancement is due to a large varying lattice constant as well as the leaky mode operation when the emission wavelength falls within the photonic band-gap. Meanwhile the light emission directionality is more obvious when the guided modes are phase matched to the radiation modes that lie above the cut-off frequency of the Brillouin zone boundaries.

We present a practical top-down etch process to fabricate InGaN/GaN multiple quantum well nanorod structure. By using nature lithography to define nanostructure, and a space layer to prevent p-type contact from connecting n-type GaN, the nanorod light emitting diode array is realized. The quantum confine stark effect is suppressed in nanorod LEDs which is indicated by their nearly constant electroluminescence peak wavelength at the injection current range between 25mA and 100mA. Furthermore, Raman measurement confirms strain relaxation between lattice mismatch layers of such a nanostructure.