Nitride semiconductor light emitting element with bragg reflection layers and anti-reflection layers to improve light extraction efficiency

• US 8,049,235 B2
• Filed: 01/23/2007
• Issued: 11/01/2011
• Est. Priority Date: 01/24/2006
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Nakahara, Ken
• Primary Examiner(s): Nguyen; Ha Tran T
• Assistant Examiner(s): Gupta; Raj R
• Application Number:
  US12/223,172
• Publication Number:
  US 20100224892A1
• Time in Patent Office: 1,743 Days
• Field of Search: 257/98
• US Class Current: 257/98
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating

Abstract

Provided is a nitride semiconductor light emitting element that has improved light extraction efficiency and a wide irradiation angle of outgoing light irrespective of the reflectance of a metal used for an electrode. An n side anti-reflection layer 2 and a p side Bragg reflection layer 4 are formed so as to sandwich an MQW active layer 3 that serves as a light emitting region, and the nitride semiconductor light emitting element has a double hetero structure. On top of the n side anti-reflection layer 2, an n electrode 1 is formed. Meanwhile, at the lower side of the p side Bragg reflection layer 4, a p electrode 5, a reflection film 7, and a pad electrode 8 are formed, and the pad electrode is bonded to a support substrate 10 with a conductive bonding layer 9 interposed in between. Both the n side anti-reflection layer 2 and the p side Bragg reflection layer 4 also serve as contact layers. The n side anti-reflection layer 2 is disposed on the light-extracting-direction side while the p side Bragg reflection layer 4 is disposed on the opposite side to the light-extracting-direction side. Consequently, the light extraction efficiency is improved.

Claims

1. A nitride semiconductor light emitting element, comprising:

a p side electrode;

a p type nitride semiconductor layer disposed on the p side electrode;

a light emitting region disposed on the p type nitride semiconductor layer;

an n type nitride semiconductor layer disposed on the light emitting region; and

an n side electrode disposed on the n type nitride semiconductor layer, wherein

the n type nitride semiconductor layer is disposed on a light extraction side of the light emitting region and the p type nitride semiconductor layer is disposed on a side opposite to the light extraction side of the light emitting region,

the n type nitride semiconductor layer is formed to be an anti-reflection layer which is formed of a first multilayer film comprised of alternating n-InGaN semiconductor layers and n-GaN semiconductor layers, the layer of the first multilayer film closest to the light emitting region being an n-InGaN semiconductor layer and the layer of the first multilayer film furthest from the light emitting region being an n-GaN semiconductor layer, and

the p type nitride semiconductor layer is formed to be a Bragg reflection layer which is formed of a second multilayer film comprised of alternating p-AlGaN semiconductor layers and p-GaN semiconductor layers, the layer of the second multilayer film closest to the light emitting region being a p-AlGaN semiconductor layer and the layer of the second multilayer film furthest to the light emitting region being a p-GaN semiconductor layer.

2. The nitride semiconductor light emitting element according to claim 1, wherein

each of the n-InGaN semiconductor layers and the n-GaN semiconductor layers is formed to have a film thickness of an odd integer multiple of a quarter of the wavelength λ

of the emitted light in that layer, and

each of the p-AlGaN semiconductor layers and the p-GaN semiconductor layers is formed to have a film thickness of an integer multiple of a half of the wavelength λ

of the emitted light in that layer.

3. The nitride semiconductor light emitting element according to claim 1, wherein

the n side electrode is in contact with an n-GaN layer of the anti-reflection layer, and

the p side electrode is in contact with a p-GaN layer of the Bragg reflection layer.