Patent ID: 10056526

Abstract:
The light extraction efficiency of a deep ultraviolet LED is increased. The deep ultraviolet LED has a design wavelength λ, and includes, sequentially arranged from a side opposite to a substrate, a reflecting electrode layer, a metal layer, a p-GaN contact layer, a p-AlGaN layer that is transparent to light with the wavelength λ, one of a multi-quantum barrier layer or an electron blocking layer, a barrier layer, and a quantum well layer. A thickness of the p-AlGaN layer is less than or equal to 100 nm. A reflecting photonic crystal periodic structure having a plurality of voids is provided in a region in a thickness direction including at least an interface between the p-GaN contact layer and the p-AlGaN layer such that the reflecting photonic crystal periodic structure does not extend beyond the p-AlGaN layer in a direction of the substrate. Maximum light extraction efficiency is obtained when a distance from end faces of the voids in the direction of the substrate to the quantum well layer is greater than or equal to a total thickness of the barrier layer and the multi-quantum barrier layer (or the electron blocking layer) and less than or equal to 80 nm, and a depth h of each void is less than or equal to a total thickness of the p-AlGaN layer and the p-GaN contact layer. The reflecting photonic crystal periodic structure has a photonic band gap that opens for TE polarized components. A period a of the photonic crystal periodic structure satisfies a Bragg condition with respect to light with the design wavelength λ. An order m in a formula of the Bragg condition satisfies 1≤m≤5. Provided that a radius of each void is R, R/a with which the photonic band gap becomes maximum is satisfied.