Light emitting device

Patent metadata

Field	Value
Publication number	US-2024421259-A1
Application number	US-202418742415-A
Country	US
Kind code	A1
Filing date	Jun 13, 2024
Priority date	Jun 16, 2023
Publication date	Dec 19, 2024
Grant date	—

Abstract

A light emitting device includes: a flip-chip type light emitting element; a sealing portion; and a lens as defined herein, the light emitting element includes an n-type layer, an active layer, an electron blocking layer, a composition gradient layer, a p-type contact layer, and a p-side electrode as defined herein, and a thickness of the composition gradient layer is set such that light directed from the active layer toward the n-type layer and light directed from the active layer toward a side opposite to the n-type layer and then reflected by the p-side electrode toward the n-type layer strengthen each other in a direction perpendicular to a main surface of the light emitting element due to interference.

First claim

What is claimed is:

1 . A light emitting device comprising:
a flip-chip type light emitting element configured to emit ultraviolet light; a sealing portion in contact with and covering at least an upper surface of the light emitting element and having a refractive index higher than a refractive index of air and lower than a refractive index of the light emitting element; and a lens in contact with and covering the sealing portion and having a refractive index higher than the refractive index of the sealing portion, wherein the light emitting element comprises an n-type layer comprising an n-type group III nitride semiconductor containing Al, an active layer located at a main surface of the n-type layer at a side opposite to the sealing portion, comprising a group III nitride semiconductor containing Al, and having a quantum well structure including a well layer and a barrier layer, an electron blocking layer located at a main surface of the active layer at a side opposite to the n-type layer, comprising a p-type group III nitride semiconductor containing Al, and having an Al composition higher than an Al composition of the barrier layer, a composition gradient layer located at a main surface of the electron blocking layer at a side opposite to the active layer, comprising a p-type group III nitride semiconductor containing Al, and having an Al composition which decreases as a distance from the active layer increases, a p-type contact layer located at a main surface of the composition gradient layer at a side opposite to the electron blocking layer, and comprising a p-type group III nitride semiconductor containing Al, and a p-side electrode located at a main surface of the p-type contact layer at a side opposite to the composition gradient layer, and configured to reflect ultraviolet light from the active layer, and wherein a thickness of the composition gradient layer is set such that light directed from the active layer toward the n-type layer and light directed from the active layer toward a side opposite to the n-type layer and then reflected by the p-side electrode toward the n-type layer strengthen each other in a direction perpendicular to a main surface of the light emitting element due to interference.

2 . The light emitting device according to claim 1 ,
wherein when a total thickness from an uppermost layer of the barrier layer to the p-type contact layer is d1, and the thickness of the composition gradient layer is d2, the thickness d2 is set such that the total thickness d1 satisfies n×d1=m×λ, wherein n is an average refractive index of layers from the electron blocking layer to the p-type contact layer at an emission wavelength, λ is the emission wavelength, and m is 0.55 or more and 0.9 or less.

3 . The light emitting device according to claim 1 ,
wherein the composition gradient layer has a structure in which a first composition gradient layer and a second composition gradient layer are stacked in order from a side of the electron blocking layer, the first composition gradient layer is non-doped or doped with p-type impurities, and the second composition gradient layer is doped with p-type impurities and has a p-type impurity concentration higher than the first composition gradient layer.

4 . The light emitting device according to claim 2 ,
wherein the composition gradient layer has a structure in which a first composition gradient layer and a second composition gradient layer are stacked in order from a side of the electron blocking layer, the first composition gradient layer is non-doped or doped with p-type impurities, and the second composition gradient layer is doped with p-type impurities and has a p-type impurity concentration higher than the first composition gradient layer.

5 . The light emitting device according to claim 3 ,
wherein the thickness of the composition gradient layer is set by a thickness of the first composition gradient layer.

6 . The light emitting device according to claim 4 ,
wherein the thickness of the composition gradient layer is set by a thickness of the first composition gradient layer.

7 . The light emitting device according to claim 3 ,
wherein a ratio of a thickness of the first composition gradient layer to the thickness d2 of the composition gradient layer is 0.4 to 0.7.

8 . The light emitting device according to claim 4 ,
wherein a ratio of a thickness of the first composition gradient layer to the thickness d2 of the composition gradient layer is 0.4 to 0.7.

9 . The light emitting device according to claim 1 ,
wherein the sealing portion is provided at the upper surface of the light emitting element and is not provided at a side surface of the light emitting element.

10 . The light emitting device according to claim 2 ,
wherein the sealing portion is provided at the upper surface of the light emitting element and is not provided at a side surface of the light emitting element.

11 . The light emitting device according to claim 1 ,
wherein the electron blocking layer has a structure in which a first electron blocking layer and a second electron blocking layer are stacked in order from a side of the active layer, and an Al composition of the second electron blocking layer is lower than an Al composition of the first electron blocking layer and lower than a maximum value of the Al composition of the composition gradient layer.

12 . The light emitting device according to claim 2 ,
wherein the electron blocking layer has a structure in which a first electron blocking layer and a second electron blocking layer are stacked in order from a side of the active layer, and an Al composition of the second electron blocking layer is lower than an Al composition of the first electron blocking layer and lower than a maximum value of the Al composition of the composition gradient layer.

13 . A manufacturing method for a light emitting device,
the light emitting device including a flip-chip type light emitting element configured to emit ultraviolet light, a sealing portion in contact with and covering at least an upper surface of the light emitting element and having a refractive index higher than a refractive index of air and lower than a refractive index of the light emitting element, and a lens in contact with and covering the sealing portion and having a refractive index higher than the refractive index of the sealing portion, the light emitting element including an n-type layer comprising an n-type group III nitride semiconductor containing Al, an active layer located at a main surface of the n-type layer at a side opposite to the sealing portion, comprising a group III nitride semiconductor containing Al, and having a quantum well structure including a well layer and a barrier layer, an electron blocking layer located oat a main surface of the active layer at a side opposite to the n-type layer, comprising an p-type group III nitride semiconductor containing Al, and having an Al composition higher than an Al composition of the barrier layer, a composition gradient layer located at a main surface of the electron blocking layer at a side opposite to the active layer, comprising a p-type group III nitride semiconductor containing Al, and having an Al composition which decreases as a distance from the active layer increases, a p-type contact layer located at a main surface of the composition gradient layer at a side opposite to the electron blocking layer, and comprising a p-type group III nitride semiconductor containing Al, and a p-side electrode located at a main surface of the p-type contact layer at a side opposite to the composition gradient l

Assignees

• Toyoda Gosei Kk
• Univ Meijo

Inventors

• Okuno Koji
• Saito Yoshiki
• Oya Masaki
• Nagata Kengo
• Takeuchi Tetsuya
• Kamiyama Satoshi
• Iwaya Motoaki
• Ishiguro Hisanori
• Iwatsuki RIE

Classifications

• H10H20/01335

  the light-emitting regions comprising nitride materials · CPC title

• H10H20/835

  Reflective materials · CPC title

• H10H20/812

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

• H10H20/84 Primary

  Coatings, e.g. passivation layers or antireflective coatings · CPC title

• H10H20/854

  characterised by their material, e.g. epoxy or silicone resins · CPC title