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Highly efficient group-iii nitride based light emitting diodes via fabrication of structures on an n-face surface 実績あり

外国特許コード F110004824
整理番号 E06704WO
掲載日 2011年7月22日
出願国 大韓民国
出願番号 20067013748
公報番号 20060131799
公報番号 101156146
出願日 平成15年12月9日(2003.12.9)
公報発行日 平成18年12月20日(2006.12.20)
公報発行日 平成24年6月18日(2012.6.18)
国際出願番号 US2003039211
国際公開番号 WO2005064666
国際出願日 平成15年12月9日(2003.12.9)
国際公開日 平成17年7月14日(2005.7.14)
優先権データ
  • 2003US39211 (2003.12.9) WO
発明の名称 (英語) Highly efficient group-iii nitride based light emitting diodes via fabrication of structures on an n-face surface 実績あり
発明の概要(英語) A gallium nitride (GaN) based light emitting diode (LED), wherein light is extracted through a nitrogen face (N-face) (42) of the LED and a surface of the N-face (42) is roughened into one or more hexagonal shaped cones. The roughened surface reduces light reflections occurring repeatedly inside the LED, and thus extracts more light out of the LED. The surface of the N-face (42) is roughened by an anisotropic etching, which may comprise a dry etching or a photo- enhanced chemical (PEC) etching.
(C) KIPO WIPO 2007
従来技術、競合技術の概要(英語) BACKGROUND ART
(Main: this application is hereby incorporated in its entirety with one or more reference numbers as is displayed through a large number of other publications were incorporated herein by reference. The reference number of other publications ordered according to the following list of references named""in part can be found. Each of these publications are incorporated herein by reference. in)
(Gallium nitride) - based broadband semiconductor LED GaN (light emitting diode) is about 10 years have been used. The development of a full color development LED LED (full field color) display, traffic signalers LED, together with the realization of a technique such as white LED LED resulted in surprising changes.
The efficiency of the fluorescent lamps is LED can be replaced with a needle and therefore attention in recent years. In particular, (74 lm/W) [1] white LED the efficiency of the efficiency of a conventional fluorescent tube (75 lm/W) be closer. Nevertheless, improved efficiency is preferably used.
LED improvement of the efficiency of the two approaches to the principles of the invention. The first approach is to crystal quality and epitaxial layer structure is determined by internal quantum efficiency (ηi) increases and, on the other hand, the second approach is the light extraction efficiency (ηextraction) will increase.
The internal quantum efficiency cannot be easily increased. Unique η for blue LEDi value is 70% or more [2], the low-potential (轉 位) GaN substrate grown on the ultraviolet (UV) is about 80% η of recent LEDi[3] the present. Very little room for improvement of these values.
On the other hand, the light extraction efficiency improvement in many cases. Many of these issues, a high reflectivity mirror, such as a treated surface of a low slope, the dispersion structure and the like at a high temperature, the optical loss (internal loss of light) inside the removal can be focused.
For example, the refractive index of air (n ≒ 2.5) GaN taken into consideration [4], the light escape cone of the critical angle (light escape cone) is about 23°. Light emission from the backside of the side wall and assuming negligible, but only about 4% of the internal light to be extracted is expected to be zero. The escape cone is reflected into the substrate of the external light, does not escape through a sidewall of the case, the active layer by the electrode to repeatedly reflected or absorbed therein.
LED how much light emission depending on the structure are affected. LED structure on the light extraction efficiency through the effect of the most appropriate example to be described. The following describes some types of structure are instances LED <.
Fig. 1 is a P type pad electrode (10), translucent electrode (12), p type layer (14), active region (16), n type layer (18), n type electrode (20), and a substrate that includes (22) a typical LED sectional view of the structure. GaN is generally grown on an insulating substrate such as sapphire and therefore, P type and N type electrode (10, 20) is on the same plane must be made on, (10, 20) to obtain the element structure of an electrode due to the (device structure), current flows in from the side. Due to the high resistance of the P type GaN, so that current is spread over the P type semitransparent metal thin film as an electrode (12) GaN are adopted. The transparency of the semitransparent electrode (12) is preferably 100% or, as used in the thin metal based LED GaN transparency of the electrode 70% is maximum. Moreover, the light emitted from the inside of cover LED pad electrode (10) for wire bonding must be formed, the extraction efficiency is expected to be quite low.
Fig. 2 is a transparent sapphire substrate (24), n type layer (26), n type electrode (28), the active region (30), p type layer (32), p type electrode (34), solder (36), and a host comprising a submount (38) flip-chip type LED sectional view of the structure. In order to improve the external efficiency, light is flip-chip type of light is extracted through the transparent sapphire substrate (24) LED structure may be. The method includes the light absorption by the metal thin film and the pad electrode with regard to reduction of conventional LED more advantages. However, most of the light emitted from the active region and the N type layer (26) at the interface between the substrate (24), and reflected at the interface between the substrate (24) and air.
GaN film is separated from the sapphire substrate so that a technique (laser lift off) method is called"LLO"below. The method comprises a flip-chip type system by applying GaN LED, the sapphire substrate can be realized without GaN LED. The resulting GaN surface assumes a non planar orientation, a significantly improved extraction efficiency is expected.
Another approach is to increase the extraction efficiency, and prevents internal light reflection and light is diffused from the upper surface of the processing LED[5]. However, the conventional and durable materials GaN wet etching method is not greatly affected, the surface treatment of the material gallium phosphide (GaP) LED group have been mentioned only in the context of. Thus, the idea of a semiconductor device with a light scattering surface treatment for the first time even if the 1970's is contemplated, such as for use in preparing type LED to be used has been considered difficult and expensive.
However, as described above, a typical GaN LED is based on a sapphire or silicon carbide on the substrate (SiC) p- GaN/active layer/n - GaN constructed from a thin film.
The surface treatment layer thickness constant GaN [6] even though they require, light is extracted through the P field GaN surface on the surface of the P field GaN requesting translucent because of the high resistance of the P field GaN relatively thick P field GaN not preferable for the growth and, [7] for surface treatment such as dry etching a portion of the processing method can cause electrical damage. Damage to the active layer of magnesium memory effect [8] since (Mg) metal organic chemical vapor deposition (MOCVD, Metal Organic Chemical Vapor Deposition) structure with a p- side down (down structure) is also preferably not grown. In recent years, substrate grown on a sapphire substrate in order to detach from the membrane GaN LLO (Laser Lift Off) [9-11] has been used in the method. Moreover, the system is to prepare LLO GaN LED for [12, 13] has been used. However this technique is the surface morphology or extraction efficiency was no mention to the effect.
On the other hand, in the present invention, flip-chip technology [14] by using a method and LLO, without the substrate (substrate - free) nitrogeN (N - side - up) side rises LED GaN system structure can be made. Thereafter, the side surface of the elevated LED N GaN system for processing using the anisotropic etching may be a step. Thus, light extraction of the square 6 useful in a configuration similar to that of a cone""surface occurred. The extraction efficiency of an optimal surface treatment LED LED before the treatment was increased more as compared with Fig. 100%.
Here, it is difficult and sometimes GaN anisotropically etching the note. This can be compared to other semiconductor materials is a material that is chemically stable GaN because of the fact. (Textured) surface texture in order to make a dry etching but can be used, such as photolithography requires ancillary processes, a fine GaN on a configuration similar to that of a cone is not possible to make the surface of a lesion.
(Photo field enhanced chemical etching) for etching gallium PEC (Ga field face) GaN in use, a small pit is formed on the surface. This is similar to that of a sharp (distinct) cone feature which causes the nitrogen surface (N field face) of the contrast GaN PEC etching. LLO prepared using the techniques of dealing with the small but LED GaN based report, the present invention relates to anisotropic etching by using a method based on the surface of the nitrogen surface GaN GaN LED cone configuration similar to that used to fabricate the structure.
AMEND STATUS: Delete
特許請求の範囲(英語) [claim1]
1. (Al, Ga, In) N compound semiconductor light emitting diode (compaound semiconductor) in (LED) of,
Light from the light emitting layer (light) (emitting layer) is exposed by removal of the substrate (substrate removal) (exposed) n of the light emitting diode is (N field type layer) nitrogen surface of thyristor type (nitrogen face (N field face) ) and (extracted) extracted through,
A plurality of exposed nitrogen faces are structured in the form of a cone (cones) (structured),
At least a portion of the cone is of size, repeatedly occurs inside the light emitting diode light (light reflections) reflected by reducing the nitrogen from the emission layer to increase light extraction surface of said light into and out of order (enhancing), wherein the scattered light in a light emitting diode (scattered) dispersed (diffracted), wherein the wavelength of the light emitting diode (wavelength) (not smaller) is not smaller than the size that the light emitting diode.

[claim2]
2. AMEND STATUS: Delete

[claim3]
3. AMEND STATUS: delete

[claim4]
4. Method according to claim 1,
Wherein the structured surface of the N type layer is anisotropically etched nitrogen nitrogen (anisotropically etched) one with the light emitting diode.

[claim5]
5. Method according to claim 4,
Wherein the anisotropic etching is dry etching the surface with nitrogen and a nitrogen surface (dry etched) is a light emitting diode.

[claim6]
6. Method according to claim 4,
Wherein the anisotropic etching is a wet etched surface of the nitrogen (wet etched) has a nitrogen surface of the light emitting diode.

[claim7]
7. Method according to claim 6,
The wet etched surface is a (photo field enhanced chemical) nitrogen PEC said etched nitrogen surface of the light emitting diode.

[claim8]
8. AMEND STATUS: Delete

[claim9]
9. Method according to claim 1,
Wherein the nitrogen surface is exposed by a technique (laser lift off technique) LLO nitrogen to the surface on the light emitting diode.

[claim10]
10. Method according to claim 1,
Wherein the light emitting diode (c - plane) c- plane grown on the wafer GaN (grown) and a p type layer of gallium (Ga - face) if (p - type layer) of the front surface of the light emitting diode.

[claim11]
11. Method according to claim 1,
Wherein the light emitting diode N type electrode, n type layer, active region, P type layers and P type electrode and the light emitting diode.

[claim12]
12. Method according to claim 11,
Wherein the n type layer, active region and each of P type layer (Al, Ga, In) comprises N alloy of said light emitting diode.

[claim13]
13. Method according to claim 11,
Wherein the p type electrode is the N type layer and the surface to increase light reflection to reduce light absorption to have a reflectance ratio (property of high reflection) the light emitting diode.

[claim14]
14. Method according to claim 11,
Wherein the light emitting diode, the N type electrode below the absorption of the light emission can be avoided and extraction efficiency of light so as to be increased (efficiency of the extraction of the light), the N type electrode current concentration (below) below (concentrate) in order to prevent the N type electrode below (under) the current blocking layer are aligned comprises (current field blocking layer) of the light emitting diode.

[claim15]
15. Method according to claim 10,
Wherein the light emitting diode wherein the light emitting diode passing through the side wall of the leakage current (sidewalls) inhibit (restrain) (leakage current) for the current confining frame made of an insulator comprising (current field confining frame) of the light emitting diode.

[claim16]
16. Method according to claim 1,
Wherein the structured surface is the surface of the nitrogen of nitrogen with respect to the plane of the angle is equal or smaller angle (facets) 6 having a plurality of hexagonal cone (hexagonal shaped cones) characterized in that it comprises a light emitting diode.
2sin-1(nair/ns)
(Nairis the refractive index of air (reflective index) and, nsis (Al, Ga, In) compound semiconductor N)

[claim17]
17. Method according to claim 1,
Wherein the structured surface is nitrogen and the nitrogen of equal to or less than or equal to the angle against the surface of the small angle cone having a first surface including a plurality of 6 wherein the rectangular light emitting diode.
2sin-1(nenc/ns)
(Wherein the nitrogen surface applied to the surface of the epoxy for, nencepoxy refractive index, nsis (Al, Ga, In) compound semiconductor N)

[claim18]
18. (Al, Ga, In) N method for manufacturing a compound semiconductor light emitting diode,
The light emitting diodes by removing the substrate n type layer when the surface of the nitrogen (N field face) exposing step (exposing),
Wherein the n type layer exposed by the plurality of conical surface of the nitrogen in the step of structuring comprises (structuring) and,
The size of the at least a portion of the cone, is repeatedly generated in the light emitting diode and the internal reflection of light from the light emitting layer for reducing nitrogen to increase extraction of light out of, in the light emitting diode so that the light is scattered or dispersed, in the wavelength of the light emitting diode is formed is not smaller than the size of the light emitting diode.

[claim19]
19. N type electrode, n type layer, active region, P type layers and p type electrode on the compound semiconductor (Al, Ga, In) N method for manufacturing a light emitting diode,
N is nitrogen surface type layer by removing the exposed substrate,
A plurality of said exposed surface to nitrogen cone comprising structured and arranged,
At least a portion of the cone size, wherein the light emitting diode in light reflection occurs repeatedly within the n type layer by reducing the nitrogen through the structured surface to increase light extraction from the active region for light, the light is scattered in the light emitting diode so as to be dispersed in, wherein in the wavelength of the light emitting diode is formed is not smaller than the size of the light emitting diode.

[claim20]
20. AMEND STATUS: Delete

[claim21]
21. Method according to claim 18,
Wherein the N type layer and said surface is structured by anisotropic etching using the method for manufacturing a light emitting diode.

[claim22]
22. Method according to claim 21,
Wherein the anisotropic etching is dry etching and said light emitting diode.

[claim23]
23. Method according to claim 21,
Wherein the anisotropic etching is a wet etching method for manufacturing a light emitting diode.

[claim24]
24. Method according to claim 23,
Wherein the wet etch etches PEC characterized in that the light emitting diode.

[claim25]
25. Method according to claim 18,
Wherein the nitrogen face of the surface is roughened (roughening) by patterning or structuring (patterning) and the light emitting diode.

[claim26]
26. AMEND STATUS: Delete
  • 出願人(英語)
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
  • UNIVERSITY OF CALIFORNIA
  • 発明者(英語)
  • FUJII Tetsuo
  • GAO Yan
  • HU Evelyn L.
  • NAKAMURA Shuji
国際特許分類(IPC)
参考情報 (研究プロジェクト等) ERATO NAKAMURA Inhomogeneous Crystal AREA
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