JP2013135169A - Semiconductor light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting device which has excellent light extraction efficiency from a light-emitting surface of the semiconductor light-emitting element to the outside.SOLUTION: A semiconductor light-emitting device comprises: a semiconductor light-emitting element having a plurality of projections on a light extraction surface side; and an encapsulation material provided so as to cover the semiconductor light-emitting element and having a refraction factor at a wavelength of 408 nm of 1.50 and under.

Description

  The present invention relates to a semiconductor light emitting device formed by sealing a semiconductor light emitting element.

  The semiconductor light emitting element is sealed with a sealing material such as a transparent resin in order to protect it from moisture, dust, and the like. In order to prevent light emitted from the semiconductor light emitting element from being reflected at the interface between the semiconductor light emitting element having a high refractive index and the sealing material, it is necessary to increase the refractive index of the sealing material. For example, Patent Document 1 describes a semiconductor light emitting device using a sealing material formed from a composition containing a diphenylsiloxane-based compound having an alkenyl group at the molecular chain end. Patent Document 2 describes a semiconductor light emitting device using a sealing material formed from a composition containing metal oxide fine particles.

JP 2010-180323 A JP 2006-316264 A

  Increasing the refractive index of the sealing material improves the light extraction efficiency from the light emitting surface of the semiconductor light emitting element to the sealing material. However, if the refractive index of the sealing material increases, the sealing material and the outside (air: refraction) The refractive index difference from the light emitting surface of the semiconductor light emitting element is finally reduced, which is reflected at the interface between the sealing material and the outside.

  When high refractive index GaN, InGaN, or the like is used for the semiconductor layer of the semiconductor element, it is necessary to increase the refractive index of the sealing material in order to suppress reflection at the interface between the light emitting surface of the semiconductor light emitting element and the sealing material. In the end, there is a problem that the efficiency of extracting light from the light emitting surface of the semiconductor light emitting element to the outside is lowered.

  An object of this invention is to provide the semiconductor light-emitting device excellent in the light extraction efficiency from the light emission surface of a semiconductor light-emitting element to the exterior.

  The present inventors have intensively studied to solve the above problems. As a result, it has been found that the above problems can be solved by a semiconductor light emitting device having the following configuration, and the present invention has been completed. That is, the present invention relates to the following [1] to [3], for example.

[1] A semiconductor light emitting device having a plurality of protrusions on the light extraction surface side, and a sealing material having a refractive index of 1.50 or less at a wavelength of 408 nm provided so as to cover the semiconductor light emitting device. A semiconductor light emitting device.
[2] The semiconductor light-emitting device according to [1], wherein a refractive index of the sealing material at a wavelength of 408 nm is 1.42 or less.
[3] The semiconductor light emitting device according to any one of [1] or [2], wherein the sealing material is a sealing material containing a fluorine atom-containing polysiloxane.

  According to the present invention, light emitted from a semiconductor light emitting element can be efficiently extracted outside.

Hereinafter, embodiments of the present invention will be described.
1. Semiconductor light emitting device

  The semiconductor light emitting device in the present invention has a plurality of protrusions on the light extraction surface side.

The critical angle between a semiconductor light emitting device having a refractive index of 3.00 or more and a sealing material having a refractive index of 1.45 or less is about 29 degrees or less. Of the light traveling from the light emitting layer of the semiconductor light emitting element to the encapsulant, light having an incident angle with respect to the interface between the semiconductor light emitting element and the encapsulant is totally reflected, so that when the critical angle is 29 degrees or less, A lot of light will be reflected at the interface.

  However, since the semiconductor light emitting device of the present invention has a plurality of protrusions on the light extraction surface side, light having an incident angle larger than the critical angle is totally transmitted at the interface between the semiconductor light emitting device and the sealing material. Even if it is reflected, the reflected light is directed to another interface, and if the incident angle of the reflected light is smaller than the critical angle, the light can be extracted to the sealing material side.

  In this way, by having a plurality of protrusions on the light extraction surface side of the semiconductor light emitting element, even if it is totally reflected once at the interface, there is a possibility that the reflected light can be extracted toward another interface, As a result, the light extraction efficiency from the light emitting layer of the semiconductor light emitting element toward the sealing material can be improved.

  FIG. 1 shows the principle. When there is no protrusion on the light extraction surface side of the semiconductor light emitting element (see (a)), the light reflected at the interface between the semiconductor light emitting element and the sealing material is directed to the inside of the semiconductor light emitting element, and the sealing material side The light cannot be extracted. On the other hand, when the semiconductor light emitting device has a protrusion on the light extraction surface side (see (b)), the light reflected at the interface between the semiconductor light emitting device and the sealing material has an incident angle smaller than the critical angle at another interface. As a result, the light once totally reflected can be extracted to the sealing material side.

  The semiconductor light emitting device is not particularly limited, and for example, JP 2009-170655 A, JP 2007-173530 A, JP 2007-157778 A, JP 2005-294870 A, JP 2004-296879 A. JP, 2004-047662, JP 2003-243703, JP 2003-88641, JP 2002-329885, JP 2002-064221, JP 2001-274456, JP-A-2001-196629, JP-A-2001-177147, JP-A-2001-068786, JP-A-2000-261629, JP-A-2000-124502, JP-A-10-294531, JP-A-09 No.-312442 and JP-A-09-237 It may be a semiconductor light-emitting device of known structure and material and the procedure described for 16 JP.

  Examples of the structure of the semiconductor light emitting device include a double heterojunction type and a quantum well junction type. The semiconductor light emitting device may be provided with a current blocking layer, a passivation layer, a color filter layer, and the like.

  The material of the semiconductor layer of the semiconductor light emitting device is, for example, a gallium nitride compound such as InGaN, InGaAlN, or GaN, another inorganic compound such as SiC, InN, AlN, GaAs, GaP, GaAlAs, GaAsP, or AlGaInP, or a copper phthalocyanine compound. Examples thereof include organic compounds such as derivatives, polyphenylene vinylene derivatives, polyalkylthiophene derivatives, and polyalkylfluorene derivatives. Among these, a gallium nitride compound having a high refractive index is preferable because the effects of the present invention can be more remarkably exhibited.

  The protrusion may have any structure or number, but in order to improve the light extraction efficiency from the semiconductor light emitting element to the sealing material, the protrusion has a cone shape. It is preferable to have as many protrusions (at least 10 or more) as possible with different crossing angles between the bottom surface and the side surface.

In order to prevent damage to the semiconductor layer when forming the protrusions, the protrusions are usually formed in the passivation layer. The protrusions can be formed by photofabrication using a resist or imprinting.
2. Sealing material

The sealing material in the present invention is provided so as to cover the semiconductor light emitting element, and has a refractive index of 1.50 or less at a wavelength of 408 nm.

In order to improve the light extraction efficiency from the sealing material to the outside, the difference in refractive index between the sealing material and the outside is made as small as possible, that is, the refractive index of the outside is constant. It is preferable to make the rate as small as possible. However, if the refractive index of the encapsulant is lowered too much, the critical angle between the semiconductor light emitting element and the encapsulant becomes too low, and the semiconductor light emitting element can be obtained only with a plurality of protrusions formed on the light emitting surface of the semiconductor light emitting element. Therefore, the refractive index of the sealing material is usually 1.50 or less, preferably 1.42 or less, and the lower limit is usually 1.20 or more, preferably 1.30 or more.

If the refractive index of the encapsulant is 1.50 or less, the critical angle between the encapsulant and the outside is about 42 degrees or less, and a large amount of light can be extracted from the encapsulant. If the refractive index of the encapsulant is 1.42 or less, the critical angle between the encapsulant and the outside is about 45 degrees or less, and most of the light can be taken out from the encapsulant. it can.

  In addition, the refractive index in this invention means the absolute refractive index in 1 atmosphere, 25 degreeC, and wavelength 408nm. The refractive index can be measured with a spectroscopic ellipsometer (for example, device name “M-2000” manufactured by JA Woollam).

  The material of the sealing material may be an organic material or an inorganic material as long as it has a refractive index of 1.50 or less and is as transparent as possible in the visible light region. Among these, an inorganic material excellent in heat resistance and light resistance is preferable. Moreover, since the versatility is high among inorganic materials, a material containing polysiloxane is usually used. Among materials containing polysiloxane, a polysiloxane containing a fluorine atom is preferable because the refractive index can be easily lowered.

The sealing material in the present invention contains inorganic particles such as silica for adjusting the viscosity, a phosphor for converting the wavelength of light, and heat conductive particles such as boron nitride for releasing heat. be able to.
Further, in the same manner as the semiconductor light emitting device, a plurality of protrusions may be formed on the light extraction surface of the sealing material in order to improve the light extraction efficiency from the sealing material to the outside.
3. Semiconductor light emitting device

  The semiconductor light emitting device of the present invention comprises a semiconductor light emitting element having a plurality of protrusions on the light extraction surface side, and a sealing material having a refractive index of 1.50 or less at a wavelength of 408 nm provided so as to cover the semiconductor light emitting element. It is characterized by having.

  In the semiconductor light emitting device of the present invention, after forming a plurality of protrusions on the light extraction surface side of the semiconductor light emitting element, the semiconductor light emitting element and the external electrode are electrically connected, and then the refractive index is 1.50 or less at a wavelength of 408 nm. It can be manufactured by covering the semiconductor light emitting element with a sealing material.

  The electrical connection between the semiconductor light emitting element and the external electrode in the semiconductor light emitting device of the present invention may be a wire bonding type or a flip chip type.

FIG. 2 shows an example schematically showing a method for manufacturing a semiconductor light emitting device.
As shown in FIG. 2A, the buffer layer 201, the n-type GaN cladding layer 202, the InGaN / GaN active layer 203, and the p-type GaN are formed on the sapphire substrate 200 by metal organic chemical vapor deposition. The clad layer 204 is formed sequentially. Next, tin-doped indium oxide (ITO film 205) is formed on the clad layer 204 by sputtering.

  Next, as shown in FIG. 2B, a passivation film 206 is formed, and a plurality of protrusions 207 are formed on the passivation film 206 by an imprint method. Next, after exposing the n-type cladding layer 202 by a photofabrication method or the like, an external connection electrode 208 is formed by a sputtering method or the like. Thereafter, the elements are separated by laser dicing, and the semiconductor light emitting element 210 is formed.

Next, as shown in FIG. 2C, the semiconductor light emitting device 210 is disposed on the bottom surface of the groove of the package 211 having a mortar-shaped groove, and the external electrode 212 and the external connection electrode 206 are electrically connected by wire bonding. Connect to.

  Next, as shown in FIG. 2D, a coating material (a composition containing fluorine atom-containing polysiloxane) for forming a sealing material including the phosphor 214 and the like in the groove of the package 211 is cast and heated. The coating material can be cured by treatment to form the sealing material 213, thereby forming a semiconductor light emitting device.

  The semiconductor light-emitting device of the present invention can be used as a light source for every application. For example, the backlight of a liquid crystal display, the pixel of a display, sensor light sources, such as an infrared sensor, lamps, such as a traffic light and a vehicle, can be mentioned.

The figure which showed typically the principle which the extraction efficiency of the light which goes to the sealing material from the light emitting layer of a semiconductor light-emitting device improves. The figure which showed the manufacturing method of the semiconductor light-emitting device typically.

100 Interface between semiconductor light emitting element and sealing material.
101 Light traveling from the light emitting layer toward the sealing material (light having an incident angle larger than the critical angle).
102 101 light totally reflected at the interface between the semiconductor light emitting element and the sealing material.
103 Light toward the encapsulant.
104 Light reflected by the interface 102 between the semiconductor light emitting element and the sealing material.
200 Sapphire substrate.
201 Buffer layer.
202 Cladding layer of n-type GaN.
203 InGaN / GaN active layer.
204 p-type GaN cladding layer.
205 ITO film.
206 Passivation film.
207 Protrusion.
208 External connection electrode.
210 Semiconductor light emitting device.
211 packages.
211a Groove 212 External electrode.
213 Sealant.
214 phosphor.
215 wire

Claims (3)

A semiconductor light emitting device comprising: a semiconductor light emitting device having a plurality of protrusions on the light extraction surface side; and a sealing material having a refractive index of 1.50 or less at a wavelength of 408 nm provided so as to cover the semiconductor light emitting device. apparatus.   The semiconductor light-emitting device according to claim 1, wherein a refractive index of the sealing material at a wavelength of 408 nm is 1.42 or less.   The semiconductor light-emitting device according to claim 1, wherein the sealing material is a sealing material containing a fluorine atom-containing polysiloxane.

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