Design of an LED chip structure with an integrated two-dimensional photonic crystal to enhance the light-extraction efficiency

We numerically simulated the light-extraction efficiency of light-emitting diodes (LEDs) with an integrated two-dimensional photonic crystal (PC) structure on the top surface in order to enhance light extraction. We considered InGaN-based LED chips with a typical emission wavelength of λ o = 460 nm and an emission wavelength inside the LED chip of λ = λ o / nGaN , where nGaN is the refractive index of G a N. We used positive (relief) and negative (intaglio) patterns for the PC structures with square arrangements. The pattern period (Λ), width ( d ), and height ( h ) of the PC structure were varied systematically in the PC-LEDs; then the light-extraction efficiency of each PC-LED was simulated numerically using a three-dimensional finite-difference time-domain method to optimize the PC structure in terms of light extraction. The PC LED with a square pilla pattern with Λ ≃ 1.4λ, d ≃ 0.75Λ, and h ≃ 0.75Λ had the maximum light-extraction efficiency for positive patterns while the cylindrical hole pattern with Λ ≃ 1.2λ, d ≃ 0.5Λ, and h ≃ 0.5Λ had the maximum light-extraction efficiency for negative patterns.