Deep ultraviolet LED and method for manufacturing the same

A method for manufacturing a deep ultraviolet LED with a design wavelength λ (200 to 350 nm), comprising:

• preparing a stacked structure including a reflecting electrode layer, a metal layer, a p-GaN contact layer, a p-AlGaN layer, an electron blocking layer, a barrier layer, a quantum well layer, a second barrier layer, a n-AlGaN layer, an AlN buffer layer, and a sapphire substrate that are arranged in this order;
• preparing a mold for forming a reflecting photonic crystal periodic structure, wherein
• the photonic crystal periodic structure has a plurality of air holes and is adapted to be provided in a region of a thickness direction including at least an interface between the p-GaN contact layer and the p-AlGaN layer such that the photonic crystal periodic structure does not extend beyond the p-AlGaN layer toward the substrate,
• the photonic crystal periodic structure consists of air and the p-GaN contact layer and the p-AlGaN layer,
• the photonic crystal periodic structure has a photonic band gap,
• the photonic band gap is open for transverse electric polarized components,
• the wavelength λ, a period a of the photonic crystal periodic structure, and an average refractive index nav of two materials forming the photonic crystal periodic structure satisfy a Bragg condition of mλ/nav=2a,
• the average refractive index nav is obtained by two materials of the air and the p-AlGaN layer, having different refractive indices, on a bottom face of the photonic crystal structure,
• an order m of the Bragg condition is in a range of 2<m<5, and
• a depth h of the air holes is greater than or equal to ⅔ a length of the period a;
• growing crystals of the stacked structure up to the p-GaN contact layer, and imprinting a structure of the mold thereto through nanoimprinting;
• sequentially dry-etching the stacked structure using ICP plasma with the bi-layer resist layer as a mask, thereby forming the photonic crystal periodic structure;
• preparing a quartz hemispherical lens that is transparent to light with the wavelength λ, with a radius that is greater than or equal to a radius of a circumscribed circle of the substrate;
• and
• bonding the hemispherical lens to a rear surface of the sapphire substrate,
• wherein:
• a method of the bonding is selected the group consisting of surface activated bonding (SAB), atomic diffusion bonding (ADB), bonding performed after modifying a surface with atmospheric-pressure plasma or ozone gas, and bonding performed with an adhesive that is transparent to light with the design wavelength, so that scattering and absorption of light at a bonded interface are suppressed.