In this work, a GaN-based quantum well LED is theoretically analyzed in a multi-layer structure composed of a quantum well embedded in a waveguide core surrounded by photonic crystal slab and a sapphire substrate. The electromagnetic eigenmodes are obtained throughout above structure via revised plane wave-scattering matrix method. The omnidirectional transmission and reflection are investigated for both TE and TM polarizations from diffraction channels in Ewald construction. Then, we introduced angular power density and calculated radiative modes extraction efficiency. All structural parameters, such as lattice geometry, lattice constant, photonic crystal thickness and filling factor, are taken into account. We also investigated the coupling efficiency between waveguide modes and Bloch modes in structure which include decomposed emission and extraction regions. In order to design a quantum well white LED, we used a MQW with adjusted material composition. The photoluminescence spectrum for both TE and TM polarizations is obtained through a combination of k.p perturbation and transfer matrix method.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.