Far-Field and Near-Field Distribution of GaN-Based Photonic Crystal LEDs With Guided Mode Extraction

The near-field and far-field distribution of GaN LEDs with square photonic crystal (PhC) lattice are experimentally investigated. The optical images of the near-field pattern are obtained from the guided electroluminescent light generated at the center of a special annular structure. For increasing lattice constant, symmetric patterns with varying number of petals according to the symmetry of the PhC are observed. The far-field distribution is studied with GaN-based film-transferred PhC LEDs with the thickness about 1500 nm. Angular-resolved measurements under electrical injection revealed guided modes extraction behavior and polarization based on the Bragg's diffraction with the PhC lattice. Good agreement with the two-dimension free photon band structure is obtained.