WO2016006972A1 - Nitride semiconductor light emitting device comprising nano particle layer - Google Patents

Abstract

The present invention relates to a nitride semiconductor light emitting device comprising a nano particle layer and, more particularly, to a nitride semiconductor light emitting device in which the nano particle layer is interposed between a substrate and a fluorescent layer. According to one embodiment of the present invention, nano particles contained in the nano particle layer interposed between the substrate and the fluorescent layer function as a scattering point so as to increase the quantity of light emitted from a light emitting structure, thereby improving light emitting efficiency, and heat dissipation efficiency of the light emitting device can also be improved through heat dispersion by the nano particles.

Description

Nitride semiconductor light emitting device comprising a nanoparticle layer

The present invention relates to a nitride semiconductor light emitting device including a nanoparticle layer, and more particularly to a nitride semiconductor light emitting device in which a nanoparticle layer is interposed between a substrate and a fluorescent layer.

The nitride semiconductor light emitting device has a structure in which an active layer is formed between an n-type nitride layer doped with n-type impurities such as silicon and a p-type nitride layer doped with p-type impurities such as magnesium.

In the case of such a nitride semiconductor light emitting device, electrons supplied from the n-type nitride layer and holes supplied from the p-type nitride layer recombine in the active layer to generate light.

1 schematically shows a conventional nitride semiconductor light emitting device.

Referring to FIG. 1, in the general nitride semiconductor light emitting device, the substrate 110, the undoped nitride layer 120, the first conductivity type nitride layer 130, the active layer 140, and the second conductivity type nitride layer ( 150).

In addition, the general nitride semiconductor light emitting device includes a first electrode 151 in contact with the first conductivity type nitride layer 130 and a second electrode 152 in contact with the second conductivity type nitride layer 150.

On the other hand, the light generated upon recombination of electrons and holes in the active layer 140 is emitted not only in the upper direction but also in the lower direction.

At this time, the reflective layer 180 is formed on the lower portion of the substrate to reflect the light emitted in the lower direction to improve the light extraction efficiency.

Conventionally, the reflective layer mainly uses a metallic reflective layer, but recently, in order to obtain higher reflection efficiency, dielectrics having different refractive indices (for example, TiO _{2) are used.} Alternatively, a dielectric reflective layer in which SiO ₂ ) is alternately stacked is mainly used.

However, even in the case of using the dielectric reflective layer, there is a limit in improving the reflection efficiency, and there is a problem in that heat dissipation is not properly performed due to the dielectric characteristics.

Background art related to the present invention is the Republic of Korea Patent Publication No. 10-2011-0021406 (published on March 04, 2011), the document discloses a light emitting device comprising a patterned distributed Bragg reflection layer and a manufacturing method thereof It is.

As a result of intensive efforts to develop a nitride semiconductor light emitting device capable of improving light emitting efficiency, the present inventors have developed a light emitting device having improved light emitting efficiency by interposing a nanoparticle layer between a substrate and a fluorescent layer.

Accordingly, an object of the present invention is to provide a nitride semiconductor light emitting device having improved luminous efficiency, and more particularly, to provide a nitride semiconductor light emitting device having improved luminous and heat dissipation efficiency by interposing a nanoparticle layer between a substrate and a fluorescent layer. There is.

In order to solve the above technical problem,

According to an aspect of the invention, the substrate; A first conductive nitride layer, an active layer, and a second conductive nitride layer are stacked on a first surface of the substrate, and the active layer is disposed between the first conductive nitride layer and the second conductive nitride layer. Interposed light emitting structure; And a fluorescent layer laminated on the second surface of the substrate, wherein the nitride semiconductor light emitting device may be provided with a nanoparticle layer interposed between the substrate and the fluorescent layer.

According to an embodiment of the present invention, in order to increase the amount of light emitted from the light emitting structure, the nanoparticles included in the nanoparticle layer interposed between the substrate and the fluorescent layer act as scattering points to improve luminous efficiency. The heat dissipation efficiency of the light emitting device may also be improved through heat dissipation by the nanoparticles.

Figure 1 schematically shows a nitride semiconductor light emitting device according to the prior art.

2 schematically shows a nitride semiconductor light emitting device including a nanoparticle layer according to an embodiment of the present invention.

Figure 3 shows the change in luminous efficiency with or without the nanoparticle layer.

Figure 4 shows the change in luminous efficiency according to the occupancy area ratio of the nanoparticles.

5 shows a change in luminous efficiency according to the content of nanoparticles.

Certain terms are defined herein for convenience of understanding the invention. Unless defined otherwise herein, scientific and technical terms used herein have the meanings that are commonly understood by one of ordinary skill in the art. Also, unless specifically indicated in the context, the singular forms "a", "an", and "the" are intended to include their plural forms as well.

Terms including ordinal numbers such as first and second may be used to describe various components, but the components are not limited by the terms. These terms are only used to distinguish one component from another.

Hereinafter, a nitride semiconductor light emitting device including a nanoparticle layer according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention is not limited as described below.

According to an aspect of the present invention, a substrate is stacked on a first surface of the substrate, and includes a first conductivity type nitride layer, an active layer, and a second conductivity type nitride layer, wherein the active layer is the first conductivity type nitride layer. And a light emitting structure interposed between the second conductivity type nitride layer and a fluorescent layer stacked on the second surface of the substrate, wherein the nanoparticle layer is interposed between the substrate and the fluorescent layer. A semiconductor light emitting device can be provided.

First, a structure of a nitride semiconductor light emitting device including a nanoparticle layer according to an embodiment of the present invention will be described with reference to FIG. 2.

2, the nitride semiconductor light emitting device according to the present invention includes a substrate 210, a first conductivity type nitride layer 230, an active layer 240, and a second conductivity type nitride layer 250 from below. .

Typically, the first conductivity type nitride layer 230 is formed of an n-type nitride semiconductor doped with n-type impurities such as silicon (Si), and the second conductivity-type nitride layer 250 is p such as magnesium (Mg). It is formed of a p-type nitride semiconductor doped with type impurities. Of course, the reverse is also to be understood as possible.

In addition, the active layer 240 may be formed by alternately stacking quantum barrier layers (GaN) and quantum well layers (InGaN) to form a multi-quantum well (MQW) structure.

The substrate 210 may be formed of sapphire, silicon, or the like, and has a first surface and a second surface opposite thereto. The first conductivity type nitride layer 230, the active layer 240, and the second conductivity type nitride layer 250 are sequentially formed on the first surface of the substrate 210.

In addition, the first electrode 251 is further formed to be electrically connected to the first conductivity type nitride layer 230, and the second electrode 252 is further formed to be electrically connected to the second conductivity type nitride layer 250. It may be.

In addition, on the first surface of the substrate 210, in addition to the above elements 230, 240, 250, an undoped nitride layer between the substrate 210 and the first conductivity type nitride layer 230 may be used to improve crystal quality. 120 may be further formed.

In another example, a buffer layer such as an AlN layer or a low temperature GaN may be further formed between the substrate 210 and the first conductivity type nitride layer 230 or between the substrate 210 and the undoped nitride layer 220. .

The nanoparticle layer 270 is interposed between the substrate 210 and the fluorescent layer 260 stacked on the second surface of the substrate 210. The nanoparticle layer 270 serves to adhere the fluorescent layer 260 on the second surface of the substrate 210.

In addition, the nanoparticles included in the nanoparticle layer 270 serves to improve the amount of light finally emitted from the light emitting device by scattering the light emitted upward from the active layer 240 (see FIG. 3). .

In this case, the fluorescent layer 260 may be configured to have a plurality of fluorescent layers stacked.

The nanoparticle layer 270 may be formed by curing a composition including at least one nanoparticle selected from a metal, an oxide, and carbon nanotubes and a binder resin.

That is, the nanoparticle layer 270 formed as the composition including the nanoparticles and the binder resin is cured may be present in a state in which the substrate 210 and the fluorescent layer 260 are bonded to each other.

The fluorescent layer 260 may be stacked on the second surface of the substrate 210 in the form of a film.

In one embodiment, the nanoparticle layer 270 may include metal, oxide or carbon nanotubes, but may include any mixture of metal, oxide or carbon nanotubes.

Here, the metal includes at least one selected from gold, silver, aluminum, palladium, platinum and copper. In addition, the oxide is TiO ₂ , SiO ₂ , MgF ₂ , CeO ₂ , Al ₂ O ₃ , ZrO ₂ , MgO, Ta ₂ O ₅ , SnO ₂ , ZnO, B ₂ O ₃ , Li ₂ O, SrO, HfO ₂ At least one selected from SiON _x and BaO.

Here, the carbon nanotubes may be at least one selected from single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes.

In addition, the carbon nanotubes may be manufactured through various methods such as chemical vapor deposition, arc discharge, plasma torch and ion bombardment. The carbon nanotubes manufactured by various methods may satisfy the following conditions. If present, it can be used regardless of its shape.

Additionally, the nanoparticles may have at least one shape selected from sheets, wires, disks, rods, and foils, but is not necessarily limited thereto.

It is to be understood that the type and shape of the nanoparticles can be selected within a range in which improvement of light emission and heat dissipation efficiency of the light emitting device, which is an object of the present invention, is achieved.

The nanoparticle layer 270 should be able to minimize the light emitted from the active layer 240 in the upper direction is reflected in the downward direction or the light absorbed by the nanoparticles themselves.

Therefore, the average particle diameter of the nanoparticles included in the nanoparticle layer 270 is preferably 100 nm or less. More preferably, the average particle diameter of the nanoparticles is 5 nm or more and 75 nm or less, and when the average particle diameter of the nanoparticles is 5 nm or less, it is difficult to scatter light sufficiently due to insufficient network formation between nanoparticles, and the heat radiation efficiency is also lowered. Can be.

On the other hand, when the average particle diameter of the nanoparticles exceeds 100 nm, the possibility that light emitted from the active layer 240 in the upper direction is reflected in the downward direction or absorbs the light by the nanoparticles themselves increases.

In addition, the light emission and heat radiation efficiency of the nanoparticle layer 270 is the content of the nanoparticles included in the nanoparticle layer 270 and the composition in the nanoparticle layer 270 formed by curing the composition containing the nanoparticles It is also related to the area fraction occupied by nanoparticles.

In one embodiment, the composition may include 5 to 10 parts by weight of the nanoparticles per 100 parts by weight of the composition.

Here, when the content of the nanoparticles per 100 parts by weight of the composition exceeds 10 parts by weight, the possibility that the light emitted from the active layer 240 in the upper direction is reflected in the downward direction or the light absorbs the light itself of the nanoparticles increases. can do.

On the other hand, if the content of the nanoparticles per 100 parts by weight of the composition is less than 5 parts by weight, it is difficult to scatter light sufficiently due to the insufficient formation of the network between the nanoparticles (see Fig. 5), the heat radiation efficiency may also be reduced.

In addition, in one embodiment, the occupied area ratio of the nanoparticles in the nanoparticle layer 270 may be 30% or less, preferably 5 to 25%.

The area fraction occupied by the nanoparticles in the nanoparticle layer 270 is related to the content of the nanoparticles in the composition forming the nanoparticle layer 270 by curing, and thus the nanoparticles in the composition. As the content of the particles increases, the occupied area ratio of the nanoparticles in the nanoparticle layer 270 formed by curing increases.

Here, when the occupied area ratio of the nanoparticles in the nanoparticle layer 270 exceeds 30%, the light emitted upward in the active layer 240 is reflected downward, or the nanoparticles themselves By absorbing light it is possible to increase the possibility that the amount of light emitted in the upward direction is sharply reduced.

On the other hand, when the occupied area ratio of the nanoparticles in the nanoparticle layer 270 is less than 5%, the formation of the network between the nanoparticles is insufficient and it is difficult to scatter the light sufficiently, and the heat radiation efficiency may also be reduced (FIG. 4).

In one embodiment, the binder resin is a glycidyl ether type epoxy resin, cresyl glycidyl ether type epoxy resin, phenyl glycidyl ether type epoxy resin, nonylphenyl glycidyl ether type epoxy resin, butylphenyl glyc Cidyl ether epoxy resin, 2-ethylhexyl glycidyl ether epoxy resin, bisphenol F diglycidyl ether epoxy resin, bisphenol a diglycidyl ether epoxy resin, 1,6-hexanediol digly Cedyl ether type epoxy resin, 1,4-butanediol diglycidyl ether type epoxy resin, alicyclic diglycidyl ether type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene epoxy resin, silicone modified epoxy Resin, phenol novolak-type epoxy resin, cresol novolak-type epoxy resin, bisphenol A modified phenol novolak-type epoxy resin, liquid bismaleimide addition epoxy Resin, trimethylolpropane triglycidyl ether type epoxy resin, polyvalent cycloaliphatic epoxy resin, triglycidyl isocyanurate type epoxy resin, aminophenol addition diglycidyl ether type epoxy resin, N, N, N ', N'-tetraglycidyl-4,4'-methylenebisbenzeneamine resin, polyvalent oxetane resin, resin in which two or more of the above compositions are alternately formed, and tris- (hydroxyphenyl) ethane glycy At least one selected from a dill ether type epoxy resin, a solid cresol novolak type epoxy resin, and a bismaleimide type resin.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, these Examples are only for illustrating the present invention, and the scope of the present invention will not be construed as being limited by these Examples.

Changes in Luminous Efficiency with or Without Nanoparticle Layers

In order to confirm whether the luminous efficiency is increased by the nanoparticle layer interposed between the sapphire substrate and the fluorescent layer stacked on the second surface of the sapphire substrate, the light emitting device does not include the nanoparticle layer shown in FIG. And the luminous efficiency of the light emitting device including the nanoparticle layer shown in Figure 2 was compared.

As the nanoparticles included in the nanoparticle layer included in the light emitting device according to the embodiment of the present invention, Ag powder having an average particle diameter of 50 nm and carbon nanotubes having an average particle diameter of 10 nm were used. Phenyl glycidyl ether type epoxy resin was used. The nanoparticle layer was formed by dotting and curing on a substrate.

Referring to FIG. 3 in which the experimental results are shown, all forward current values in the case of a light emitting device in which a nanoparticle layer including Ag powder or carbon nanotubes is interposed compared to a light emitting device that does not include a nanoparticle layer. As the improved light output (Pout) value was shown, it was confirmed that the luminous efficiency was increased by the nanoparticle layer interposed between the substrate and the fluorescent layer laminated on the second surface of the substrate.

This can be seen that the nanoparticles contained in the nanoparticle layer is a result of scattering the light emitted upward in the active layer.

Changes in Luminous Efficiency According to Occupancy Area Ratio of Nanoparticles

To confirm the change in luminous efficiency according to the occupied area ratio occupied by the nanoparticles in the nanoparticle layer interposed between the sapphire substrate and the fluorescent layer laminated on the second surface of the sapphire substrate, shown in FIG. 2. In the light emitting device including the nanoparticle layer, the luminous efficiency was compared while changing the occupancy area ratio of the nanoparticles from 0% to 35%.

The occupancy area ratio was calculated as the ratio of the area occupied by the nanoparticles to the total area of the nanoparticle layer.

Referring to FIG. 4, in which the experimental results are shown, as the occupied area ratio of the nanoparticles in the nanoparticle layer increases from 0% to 30%, improved light output for all forward current values ( Pout) value was confirmed. However, when the occupied area ratio is 35%, it was confirmed that the occupied area ratio of the nanoparticles was 0%, that is, the Pout value was lower than that when the nanoparticle layer containing the nanoparticles was not interposed. .

In other words, if the area area occupied by the nanoparticles in the nanoparticle layer is excessively high (e.g., greater than 30%), the light output value will decrease, as expected, rather than in the upper direction in the active layer. It can be expected that the amount of light emitted in the upper direction is rapidly decreased because the emitted light is reflected in the downward direction or the nanoparticles absorb the light by themselves.

Changes in Luminous Efficiency and Radiation Efficiency According to Nanoparticle Content

In order to confirm the change in luminous efficiency according to the content (weight ratio) of the nanoparticles in the nanoparticle layer interposed between the sapphire substrate and the fluorescent layer laminated on the second surface of the sapphire substrate, the nanoparticles shown in FIG. 2 In the light emitting device including the layer, light emission efficiency and heat radiation efficiency were compared while changing the content of nanoparticles from 0 wt% to 15 wt%.

Referring to FIG. 5, where the experimental results of the luminous efficiency are shown, when the content of the nanoparticles in the nanoparticle layer is 5 wt% and 10 wt%, all forward current values are greater than when 0 wt% is used. It can be seen that the improved light output (Pout) value for. In particular, when the content of the nanoparticles is 5 wt% showed the highest light output (Pout) value.

However, when the content of the nanoparticles in the nanoparticle layer is 15 wt%, the content of nanoparticles is 0%, that is, the Pout value is lower than that when the nanoparticle layer containing nanoparticles is not interposed. I could confirm that it came out.

In other words, if the content of the nanoparticles in the nanoparticle layer is excessively high (e.g., greater than 10 wt%), the light output value will decrease rather than expected, which is emitted upward in the active layer. It can be expected that the amount of light emitted in the upper direction is drastically reduced because the light is reflected in the downward direction or the nanoparticles absorb the light by themselves.

In addition, with respect to heat dissipation efficiency, when the nanoparticle layer including nanoparticles interposed between the sapphire substrate and the fluorescent layer laminated on the second surface of the sapphire substrate is not interposed, the temperature of the light emitting device is about 45 ° C. On the other hand, when the nanoparticle layer with the nanoparticle content of 5 wt% and 10 wt% is interposed, it was confirmed that the temperature of the light emitting device is maintained at about 35 ° C or less.

That is, it can be seen that the heat radiation efficiency of the light emitting device is improved by the nanoparticles included in the nanoparticle layer. In addition, the heat dissipation efficiency increases as the content of the nanoparticles in the nanoparticle layer increases. At this time, if the content of the nanoparticles is excessively increased to increase the heat dissipation efficiency, the light emission efficiency decreases. It is important to keep the content of particles at a level of 5 wt% to 10 wt% based on the total weight.

As mentioned above, although an embodiment of the present invention has been described, those of ordinary skill in the art may add, change, delete or add components within the scope not departing from the spirit of the present invention described in the claims. The present invention may be modified and changed in various ways, etc., which will also be included within the scope of the present invention.

Claims (11)

1. Board;

   A first conductive nitride layer, an active layer, and a second conductive nitride layer are stacked on a first surface of the substrate, and the active layer is disposed between the first conductive nitride layer and the second conductive nitride layer. Interposed light emitting structure; And

   And a fluorescent layer laminated on the second surface of the substrate,

   The nanoparticle layer is interposed between the substrate and the fluorescent layer,

   A nitride semiconductor light emitting device comprising a nanoparticle layer.
2. The method of claim 1,

   The nanoparticle layer,

   At least one nanoparticle selected from metals, oxides and carbon nanotubes; And

   Binder resin; is formed by curing the composition comprising,

   A nitride semiconductor light emitting device comprising a nanoparticle layer.
3. The method of claim 2,

   The metal is at least one selected from gold, silver, aluminum, palladium, platinum and copper,

   A nitride semiconductor light emitting device comprising a nanoparticle layer.
4. The method of claim 2,

   The oxide is TiO ₂ , SiO ₂ , MgF ₂ , CeO ₂ , Al ₂ O ₃ , ZrO ₂ , MgO, Ta ₂ O ₅ , SnO ₂ , ZnO, B ₂ O ₃ , Li ₂ O, SrO, HfO ₂ , SiON at least one selected from _x and BaO,

   A nitride semiconductor light emitting device comprising a nanoparticle layer.
5. The method of claim 2,

   The average particle diameter of the nanoparticles is 100 nm or less,

   A nitride semiconductor light emitting device comprising a nanoparticle layer.
6. The method of claim 5,

   The average particle diameter of the nanoparticles is 5 nm or more and 75 nm or less,

   A nitride semiconductor light emitting device comprising a nanoparticle layer.
7. The method of claim 2,

   The binder resin is a glycidyl ether type epoxy resin, cresyl glycidyl ether type epoxy resin, phenyl glycidyl ether type epoxy resin, nonylphenyl glycidyl ether type epoxy resin, butylphenyl glycidyl ether type epoxy resin , 2-ethylhexyl glycidyl ether type epoxy resin, bisphenol F diglycidyl ether type epoxy resin, bisphenol a diglycidyl ether type epoxy resin, 1,6-hexanediol diglycidyl ether type epoxy resin , 1,4-butanediol diglycidyl ether type epoxy resin, alicyclic diglycidyl ether type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene epoxy resin, silicone modified epoxy resin, phenol novolak type Epoxy Resin, Cresol Novolac Epoxy Resin, Bisphenol A Modified Phenol Novolac Epoxy Resin, Liquid Bismaleimide Additive Epoxy Resin, Trimethylol Ropan triglycidyl ether type epoxy resin, polyvalent cycloaliphatic epoxy resin, triglycidyl isocyanurate type epoxy resin, aminophenol addition diglycidyl ether type epoxy resin, N, N, N ', N' Tetraglycidyl-4,4'-methylenebisbenzeneamine resin, polyvalent oxetane resin, resin in which two or more of the above compositions are alternately composed, and tris- (hydroxyphenyl) ethane glycidyl ether type epoxy resin At least one selected from a solid cresol novolac epoxy resin and a bismaleimide resin,

   A nitride semiconductor light emitting device comprising a nanoparticle layer.
8. The method of claim 7, wherein

   The binder resin is a phenyl glycidyl ether type epoxy resin,

   A nitride semiconductor light emitting device comprising a nanoparticle layer.
9. The method of claim 2,

   The composition comprises 5 to 10 parts by weight of the nanoparticles per 100 parts by weight of the composition,

   A nitride semiconductor light emitting device comprising a nanoparticle layer.
10. The method of claim 2,

    Occupancy area ratio occupied by the nanoparticles in the nanoparticle layer is 30% or less,

    A nitride semiconductor light emitting device comprising a nanoparticle layer.
11. The method of claim 1,

    The fluorescent layer is configured by stacking a plurality of fluorescent layers,

    A nitride semiconductor light emitting device comprising a nanoparticle layer.

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