Tailoring evanescent wave coupling in GaN/AlGaN core/cladding light-emitting diodes

We investigated GaN/AlGaN core/cladding light-emitting diodes (LEDs) that surpass the limit of light extraction that is typically exhibited by conventional GaN LED structures. Full-vectorial electromagnetic calculations confirmed that with an upper two-dimensional dielectric pattern, the extraction efficiency of the subwavelength-thick GaN/AlGaN waveguide increased by ~50% relative to that of the homogeneous GaN structure. Electric-field intensity profiles demonstrated that this significantly enhanced light extraction was a result of the thin waveguide effect in which the evanescent field of guided modes penetrates further into the upper dielectric pattern. The waveguide effect was investigated at various refractive indices and thicknesses of the cladding.