Directionality control through selective excitation of low-order guided modes in thin-film InGaN photonic crystal light-emitting diodes

This letter explores the impact of quantum well placement and photonic crystal (PhC) etch depth on the emission directionality of thin-film InGaN PhC light-emitting diodes (LEDs). The far-field pattern of 800-nm-thick PhC LEDs is tuned by varying only the etch depth of a surface-patterned hexagonal PhC from 90 to 440 nm. This dependence on etch depth is shown to arise from the preferential excitation of a subset of the allowed guided modes. Selective excitation of the TE0 and TE1 modes is utilized to achieve a vertically directional emission pattern comprised of only these two modes.