Deep ultraviolet LED and method for manufacturing the same

Patent metadata

Field	Value
Publication number	US-10950751-B2
Application number	US-202016860875-A
Country	US
Kind code	B2
Filing date	Apr 28, 2020
Priority date	Sep 3, 2015
Publication date	Mar 16, 2021
Grant date	Mar 16, 2021

Abstract

Provided is a deep ultraviolet LED with a design wavelength λ, including a reflecting electrode layer, an ultra-thin metal layer, and a p-type contact layer that are arranged in this order from a side opposite to a substrate; and a hemispherical lens bonded to a rear surface of the substrate on a side of the p-type contact layer, the hemispherical lens being transparent to light with the wavelength λ. The refractive index of the hemispherical lens is greater than or equal to the average value of the refractive index of the substrate and the refractive index of air and is less than or equal to the refractive index of the substrate. The hemispherical lens has a radius that is greater than or equal to the radius of an inscribed circle of the substrate and is about equal to the radius of a circumscribed circle of the substrate.

First claim

The invention claimed is:

1. 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 n av of two materials forming the photonic crystal periodic structure satisfy a Bragg condition of mλ/n av =2a,
the average refractive index n av 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.

Assignees

• Marubun Co Ltd
• Toshiba Machine Co Ltd
• Riken
• Ulvac Inc
• Tokyo Ohka Kogyo Co Ltd

Inventors

• Kashima Yukio
• Matsuura Eriko
• Kokubo Mitsunori
• Tashiro Takaharu
• Hirayama Hideki
• Kamimura Ryuichiro
• Osada Yamato
• Morita Toshiro

Classifications

• H10H20/835

  Reflective materials · CPC title

• H10H20/812

  within the light-emitting regions, e.g. having quantum confinement structures · CPC title

• H10H20/814 Primary

  having reflecting means, e.g. semiconductor Bragg reflectors · CPC title

• H10H20/0137

  the light-emitting regions comprising nitride materials · CPC title

• H10H20/81

  Bodies · CPC title