WO2016051857A1

WO2016051857A1 - Nitride semiconductor light emitting device

Info

Publication number: WO2016051857A1
Application number: PCT/JP2015/065079
Authority: WO
Inventors: 聡駒田
Original assignee: シャープ株式会社
Priority date: 2014-09-30
Filing date: 2015-05-26
Publication date: 2016-04-07

Abstract

A nitride semiconductor light emitting device A is provided with: an LED element 2 that emits ultraviolet light having a predetermined wavelength; a base 1 formed of a ceramic sintered body; and a resin sealing section 3 that resin-seals the LED element that is disposed such that a sapphire substrate 20 is adjacent to the base 1. The resin sealing section 3 is formed of a sealing resin having a refractive index that is close to the intermediate value between the refractive index of a nitride semiconductor layer and that of the air.

Description

Nitride semiconductor light emitting device

The present invention relates to a nitride semiconductor light emitting element (ultraviolet LED element) that emits ultraviolet light and a nitride semiconductor light emitting device that emits ultraviolet light.

Ultraviolet LED elements are promising for industrial applications such as resin curing and photolithography light sources, and in that case, use with high power of several hundred watts or more is required. In order to reduce the size of the package of the ultraviolet LED element, it is preferable that the number of chips to be mounted is small. However, in such an LED, since a high current needs to flow per chip, the chip height (thickness) The mainstream is that anodes and cathodes are formed at both ends of the) direction, and current flows in the vertical direction.

In the nitride semiconductor used for the ultraviolet LED element, sapphire is generally used as a material for the growth substrate. Sapphire is an insulator. When anodes and cathodes are formed at both ends in the height (thickness) direction as described above, a nitride semiconductor multilayer film is stacked, and then the growth substrate is peeled to form electrodes. The

A normal ultraviolet LED element is attached to a Si support substrate after crystal growth, and then the sapphire substrate (growth substrate) is peeled off using a laser or the like. Since the Si support substrate has low reflectivity for ultraviolet light, a reflective metal layer using a metal having high reflectivity for ultraviolet light is formed between the nitride semiconductor layer and the support substrate to improve light extraction efficiency. ing.

An ultraviolet LED device is formed by mounting the ultraviolet LED element thus formed on a base. In the ultraviolet LED device, a metal base having a high reflectance is used in order to increase the light extraction efficiency. Usually, a base made of aluminum having a high surface reflectance is used. For example, an LED element is mounted in a recess of a base coated with aluminum having a recess, and the surface is coated with glass and packaged.

Also, a package made of a ceramic sintered body sealed with a silicone resin with respect to an ultraviolet LED element mounted on a flip chip as in Patent Document 1 has been proposed. Patent Document 2 proposes a package in which ultraviolet light is transmitted through a sapphire substrate using a package sealed with a silicone resin for an ultraviolet LED element mounted on a flip chip. Patent Document 3 proposes a method in which an ultraviolet LED element is sealed with an addition-type thermosetting silicone resin containing dimethyl silicone resin as a main component from the viewpoint of heat resistance and light resistance.

JP2011-228411 JP2005-228996 JP2013-138216

In the ultraviolet LED element in which the reflective metal layer is formed, a barrier metal layer is further required to suppress the migration of the reflective metal material when a current is applied. Moreover, manufacture of the LED element of the sticking peeling structure mentioned above requires the sticking process which sticks the laminated | stacked LED element to a support substrate, and the peeling process which peels after sticking, and manufacturing cost becomes high.

In addition, AlGaN, which is an essential nitride semiconductor for ultraviolet LED elements, is difficult to control strain, and tends to cause warping of the substrate. When the substrate is warped, there is a problem in that the attaching and peeling processes are not performed with high accuracy. Further, when the substrate is enlarged (increased in diameter) in order to increase the number of chips that can be taken per wafer, there is a problem that the influence of the warp of the substrate is further increased.

Also, in the package coated with glass as described above, total reflection occurs in the package due to the difference in refractive index between glass and air, and the light extraction efficiency decreases.

An object of the present invention is to provide a nitride semiconductor light emitting device with high light extraction efficiency while suppressing manufacturing cost.

In order to achieve the above object, a nitride semiconductor light-emitting device according to the present invention includes a nitride semiconductor light-emitting element that emits ultraviolet light including a sapphire substrate and a nitride semiconductor layer, a base made of a ceramic sintered body, and the nitride. A sealing resin portion for sealing the semiconductor light emitting device, wherein the nitride semiconductor light emitting device is disposed on the base so that the sapphire substrate is on the lower side with respect to the nitride semiconductor layer, and the resin sealing portion Is made of a material having a refractive index between the refractive index of the nitride semiconductor layer and the refractive index of air.

According to this configuration, since the sapphire substrate as the growth substrate is left, the Si substrate sticking step and the sapphire substrate peeling step can be omitted. In addition, the negative effect on the manufacturing process due to the warpage of the nitride semiconductor layer is smaller than that including the pasting step and the peeling step, so that the yield can be increased and the manufacturing cost can be reduced.

The ceramic sintered body has a larger band gap than the nitride semiconductor layer, and therefore absorbs less light, and light is easily scattered inside the ceramic sintered body. Furthermore, the surface of the ceramic sintered body has a high reflectance in the ultraviolet region. Therefore, the light extraction efficiency is improved by attaching the ceramic sintered body to the base with the transparent sapphire substrate facing down. In addition, since the refractive index of the sealing resin used for the resin sealing part is close to the intermediate value between the refractive index of the nitride semiconductor and the refractive index of air, total reflection can be suppressed and light can be extracted compared to when sealing is not performed. Efficiency is further improved.

In the above configuration, irregularities may be formed on the surface of the sapphire substrate on which at least the nitride semiconductor layer is laminated.

In the above configuration, the unevenness of the sapphire substrate may be a dot-like unevenness in which convex portions are two-dimensionally arranged.

In the above configuration, the nitride semiconductor layer may include an AlGaN layer including an n-type AlGaN layer and an undoped AlGaN layer.

In the above configuration, the undoped AlGaN layer may be formed between the n-type AlGaN layer and the sapphire substrate.

In the above configuration, the AlGaN layer may have a total thickness of 6 μm or more.

In the above configuration, the LED element may include an oxide transparent conductive layer on the anode side.

In the above configuration, the oxide transparent conductive layer may be ITO.

In the above configuration, the oxide transparent conductive layer may have a thickness of 60 nm or less.

In the above configuration, the nitride semiconductor element may include an n-side electrode and a p-side electrode, and at least one of the n-side electrode and the p-side electrode may include a main electrode and a branch electrode extending from the main electrode.

In the above configuration, the base may be an alumina sintered body.

In the above configuration, the resin sealing portion may be formed of a silicone resin.

In the above configuration, the resin sealing portion may be formed of dimethyl silicone resin.

In the above configuration, the LED element may have an emission wavelength of 300 nm to 375 nm.

In the above configuration, the LED element may have a light extraction surface on the anode side.

According to the present invention, it is possible to provide a nitride semiconductor light emitting device with high light extraction efficiency while suppressing manufacturing cost.

1 is a perspective view of a nitride semiconductor light emitting device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II of the nitride semiconductor light emitting device shown in FIG. It is sectional drawing of the LED element of the nitride semiconductor light-emitting device shown in FIG. It is an expanded sectional view of a sapphire substrate. It is a figure which shows arrangement | positioning of the unevenness | corrugation of the growth surface of a sapphire substrate. It is a top view of the electrode of the LED element shown in FIG. It is a perspective view of the nitride semiconductor light-emitting device concerning 2nd Embodiment of this invention. FIG. 8 is a cross-sectional view taken along line VIII-VIII of the nitride semiconductor light emitting device shown in FIG.

(First embodiment)
A nitride semiconductor light emitting device according to the present invention will be described with reference to the drawings.

About Nitride Semiconductor Light-Emitting Device As shown in FIGS. 1 and 2, a nitride semiconductor light-emitting device A includes a flat base 1 and an LED element (nitride semiconductor light-emitting element) placed on the upper surface of the base. 2 and a resin sealing portion 3 that seals the LED element 2.

LED element 2 emits ultraviolet light of about 300 nm to about 375 nm. The LED element 2 includes a sapphire substrate 20, an AlN buffer layer 21, an undoped AlGaN layer 22, an n-type nitride semiconductor layer 23, an active (light emitting) layer 24, a p-type nitride semiconductor layer 25, and an ITO (Indium Tin Oxide) layer 26. , A SiO 2 cover layer 27, a p pad electrode 28 and an n pad electrode 29.

In the LED element 2, a semiconductor multilayer film is formed on one main surface (growth surface) of the sapphire substrate 20. As shown in FIG. 4, irregularities are formed on the growth surface 200 of the sapphire substrate 20. The concave and convex portions 201 of the growth surface 200 have a planar arrangement as shown in FIG. That is, the top part of the convex part 201 is arrange | positioned in the position used as the vertex of a regular hexagon on the growth surface 200. FIG. Note that the arrangement method of the convex portions 201 is not limited to this.

Since the refractive index of the sapphire substrate 20 is about 1.7 and the refractive index of the nitride semiconductor is about 2.5 and the difference in refractive index is large, the ultraviolet light generated in the nitride semiconductor layer is the boundary surface with the sapphire substrate 20. It is easy to totally reflect. However, since the concavo-convex portion is formed on the growth surface 200 of the sapphire substrate, the ultraviolet light is irregularly reflected by the concavo-convex portion at the boundary between the sapphire substrate 20 and the nitride semiconductor layer. By this irregular reflection, it becomes possible to change the light path of the reflected light to increase the amount of light in the escape cone, that is, to extract a lot of light from the LED element 2.

The unevenness of the sapphire substrate 20 may have a configuration (dot type) in which the convex portions 201 are arranged according to a certain rule as described above, or a configuration in which the concave grooves and the convex portions are arranged in stripes (stripe). Type). Both the stripe type and the dot type can obtain the effect of irregular reflection, but the dot type is more preferable because it can reduce the flat region where the effect of irregular reflection is not obtained, and thus the light extraction efficiency is improved.

The nitride semiconductor used in the LED element 2 according to the present invention is a compound of at least one of the group 3 elements aluminum (Al) and gallium (Ga) and the group 5 element nitrogen (N). In the n-type nitride semiconductor layer 23, an element such as silicon (Si) or germanium (Ge) is added (doped) as an impurity to the above-described nitride semiconductor. In the p-type nitride semiconductor layer 25, elements such as magnesium (Mg) and zinc (Zn) are added (doped) as impurities to the nitride semiconductor.

Specifically, an AlN buffer layer 21 having a layer thickness of 20 nm is formed on the growth surface 200 of the sapphire substrate 20 on which irregularities are formed. An undoped AlGaN layer 22 having a layer thickness of 3 μm is formed on the upper surface of the AlN buffer layer 21. An n-AlGaN layer 231 having a layer thickness of 3 μm and a Si concentration of 5 × 10 ¹⁸ / cm ³ is formed on the upper surface of the undoped AlGaN layer 22. In each of these layers, the band gap is adjusted by changing the Al composition ratio. In each of these layers, the Al composition ratio is adjusted to 7% to 10% in order to make the band gap larger than the emission wavelength.

AlGaN needs a certain layer thickness in order to increase the light extraction efficiency from the side. Since n-AlGaN is doped with impurities, cracks are likely to occur due to tensile strain generated in the crystal when dislocations bend in the lateral direction in accordance with the dislocation crib model. On the other hand, since the undoped AlGaN layer 22 has higher crystallinity than n-AlGaN, it is difficult to crack even if it is grown thick. Therefore, the undoped AlGaN layer 22 is formed below the n-AlGaN layer 231 in order to make the AlGaN layer thickness necessary for extracting light from the side surface. In order to efficiently extract light from the undoped AlGaN layer 22 and the n-AlGaN layer 231 described above, the thickness of both the undoped AlGaN layer 22 and the n-AlGaN layer 231 is preferably 6 μm or more.

The sapphire substrate used in the present embodiment forms irregularities in order to increase the light extraction efficiency, but the height of the irregularities is preferably 500 nm or more, and more preferably 1 μm or more in order to facilitate processing. The layer thickness of the undoped AlGaN layer 22 is preferably at least 3 μm or more in order to form an oblique facet film in order to fill the unevenness of the sapphire substrate and to planarize it. If an Si-AlGaN layer is formed directly without forming an undoped AlGaN layer, it is difficult to planarize, and therefore an n-AlGaN layer 231 must be separately formed on the undoped AlGaN layer. The thickness of the n-AlGaN layer 231 is preferably 3 μm or more because the sheet resistance is ideally set to 10 Ωsq or less from the viewpoint of current diffusion. Therefore, it is preferable that the thickness of both the undoped AlGaN layer 22 and the n-AlGaN layer 231 is 6 μm or more.

Also, one of the factors determining the crystallinity of the n-AlGaN layer 231 is threading dislocations, and the formation of threading dislocations is caused by lattice shift when crystals (layers) are associated with each other and propagates in the crystal growth direction. Further, the growth surface 200 of the sapphire substrate 20 is uneven, and a dislocation is formed in the n-AlGaN layer 231 in the vertical direction by forming a portion where the dislocation is bent in an oblique direction at the initial growth stage of the undoped AlGaN layer. It is difficult to propagate and the threading transition density decreases. From the above, the crystallinity of the n-AlGaN layer 231 can be increased by forming the undoped AlGaN layer 22 having high crystallinity in the initial stage of growth.

On the upper surface of the n-AlGaN layer 231, an n-GaN layer 232 is formed by growing n-GaN doped so that the layer thickness is 50 nm and the Si concentration is 5 × 10 ¹⁸ / cm ³ . Here, the n-AlGaN layer 231 and the n-GaN layer 232 become the n-type nitride semiconductor layer 23.

On the top surface of the n-GaN layer 232, an active (light emitting) layer 24 is formed by laminating a total of 10 layers of an InGaN layer 241 having a thickness of 6 nm and an AlGaN layer 242 having a thickness of 10 nm. The In composition ratio of the InGaN layer 241 is set to several percent or less so that the emission wavelength is 300 nm to 375 nm, and the Al composition ratio of the AlGaN layer 242 is adjusted to about 10%.

A p-AlGaN layer 251 having a layer thickness of 40 nm and an Mg concentration of 1 × 10 ¹⁹ / cm ³ is formed on the upper surface of the active layer 24. Note that the Al composition ratio of the p-AlGaN layer 251 was 30%. Then, a p-GaN layer 252 having a layer thickness of 5 nm and an Mg concentration of 1 × 10 ²⁰ / cm ³ is formed on the upper surface of the p-AlGaN layer 251. Here, the p-AlGaN layer 251 and the p-GaN layer 252 become the p-type nitride semiconductor layer 25.

Since the p-type nitride semiconductor layer 25 has high resistance, it is difficult to diffuse current in the planar direction of the semiconductor stack. Further, the p-type nitride semiconductor has a high work function, and it is necessary to provide a transparent electrode having a high work function in order to reduce the contact resistance. Therefore, an ITO layer 26 using ITO having a high work function among the transparent electrodes is formed on the upper surface of the p-GaN layer 252 as a current diffusion layer. After the ITO layer 26 is formed, it is annealed at 500 ° C. to be transparent.

The work function of the p-type nitride semiconductor layer 25 is about 7 eV, and the work function of the ITO layer 26 is about 4 eV. In an ideal junction between the p-type nitride semiconductor layer 25 and the ITO layer 26, a Schottky barrier of about 3 eV is generated, but contact is caused by diffusion at the interface, hopping conduction through defects, and a pinning effect due to the interface state. Resistance can be lowered. A SiO2 cover layer 27 is formed on the upper surface of the ITO layer 26.

A p-pad electrode 28 is formed on the ITO layer 26. Further, a part of the n-AlGaN layer 231 is exposed by etching from the upper surface by ICP (Inductively Coupled Plasma) or the like from the p-type nitride semiconductor layer 25 side. An n contact 290 made of Al, Ti or the like is formed on the exposed portion of the AlGaN layer 231, and an n pad electrode 29 is formed on the n contact 290. In the LED element 2, the p pad electrode 28 is on the anode side, and the n pad electrode 29 is on the cathode side.

Since GaN has a high absorption coefficient at an emission wavelength of 375 nm or less, the light extraction efficiency deteriorates. Therefore, in the present invention, by using AlGaN, the light extraction efficiency is improved at an emission wavelength of 375 nm or less. In addition, although the transmittance of ITO significantly decreases when the emission wavelength is 300 nm or less, in the LED element 2, the composition ratio of Al is adjusted so that the emission wavelength is 300 nm to 375 nm. I was able to use it.

Further, in the LED element 2 described above, it is necessary to diffuse the current in the planar direction of the semiconductor stack. However, since n-AlGaN has a large band gap and it is difficult to obtain a ternary mixed crystal with high electron mobility, resistance is high and current is difficult to diffuse. Moreover, since the light absorption increases exponentially as the layer thickness of ITO increases, it is not preferable to form the ITO layer 26 thick. Therefore, the layer thickness of the ITO layer 26 is thin and current is difficult to diffuse.

In the n-AlGaN layer 231 and the ITO layer 26, current is difficult to diffuse in the planar direction of the semiconductor stack, so that current concentrates directly under the electrodes when driven with a large current. For this reason, the absorption of light on the electrode surface increases, and the light extraction efficiency decreases. Therefore, the LED element 2 has an electrode configuration as shown in FIG. 6 is a top view of the electrode configuration of the LED element shown in FIG.

As shown in FIG. 6, the p-pad electrode 28 includes a circular main electrode 281 and a pair of branch electrodes 282 extending in the opposite direction with the main electrode 281 as the center. The pair of branch electrodes 282 have a curved shape and are opposed to each other with the main electrode 281 interposed therebetween. The main electrode 281 is a part for attaching a wire for supplying electric power, and the main electrode 281 and the branch electrode 282 are integrally formed.

Further, the n pad electrode 29 is provided so as to be located within a range surrounded by the main electrode 281 and the branch electrode 282 of the p pad electrode 28 in a plan view. The n-pad electrode 29 includes a circular main electrode 291 and a pair of branch electrodes 292 extending in opposite directions with the main electrode 291 as the center. The main electrode 291 is also a member for attaching a wire, and the main electrode 291 and the branch electrode 292 are integrally formed. The position of the branch electrode 292 connected to the main electrode 291 is the same position as the position of the branch electrode 282 connected to the main electrode 281. A branch electrode 292 is arranged inside a portion surrounded by the branch electrode 282 that forms a part of the circumference.

When a current is passed between the p pad electrode 28 and the n pad electrode 29, a current flows between the branch electrode 282 and the branch electrode 292. At this time, since the position of the electrode is shifted, it is possible to flow a diffused current over a wide range of the active layer 24, and the light extraction efficiency is improved. In addition, the shape of the electrode shown in FIG. 6 is an example, and is not limited to this. It is possible to widely adopt an electrode configuration capable of diffusing current over a wide range. Further, in the configuration shown in FIG. 6, both the p pad electrode 28 and the n pad electrode 29 include branch electrodes, but may be configured to be provided in at least one of them.

As a manufacturing method of the LED element 2, the above-described AlN buffer layer 21, undoped AlGaN layer 22, n-AlGaN layer 231, n-GaN layer 232, active layer ( InGaN 241, AlGaN 242) 24, p-AlGaN layer 251, p-GaN layer 252, ITO layer 26, and SiO 2 cover layer 27 are laminated. Then, after annealing, the n-AlGaN layer 231 is exposed by mesa etching, an n contact 290 is formed on the exposed portion, and then an n pad electrode 29 is formed on the upper surface of the n contact 290. Further, after the sapphire substrate is polished to a predetermined thickness, the LED element 2 is formed by being divided into regions constituting one LED element. Thus, after forming a semiconductor layer, a protective layer, and an electrode using a large substrate, it is possible to increase work efficiency by using a method in which a chip is generated by being divided.

The LED element 2 (LED chip) formed as described above is attached to the ceramic base 1. The base 1 is a sintered body of alumina and is a white ceramic plate. The material constituting the base 1 is not limited to alumina as long as the material has a high band gap and a high reflectance. A pattern wiring 11 made of a highly conductive metal (for example, copper, aluminum or the like) is formed on the surface of the base 1.

The LED element 2 is fixed to a predetermined installation position of the base 1 thus formed with a thermosetting die bond paste resin. Specifically, a die bond paste resin is applied to the installation position of the base 1 and / or the surface opposite to the growth surface 200 of the sapphire substrate 20 of the LED element 2. Then, the LED element 2 is arranged on the base 1 so that the sapphire substrate 20 faces the base 1, and the LED element 2 is mounted on the base 1 by heat curing. Thereafter, the pattern wiring 11 of the base 1 is connected to the p pad electrode 28 and the n pad electrode 29 with a wire 12 of a metal (for example, gold) having a low resistance.

The resin sealing portion 3 is provided to suppress contact between the LED element 2 and the atmosphere, and is made of a resin that is transparent to the LED emission wavelength. The resin sealing portion 3 flows into the upper surface of the base 1 on which the LED element 2 is mounted so as to completely surround the LED element 2.

The base 1 is a plate-like member, and if the resin sealing part 3 that is a fluid is allowed to flow as it is, the resin flows and the LED element 2 may be exposed from the resin sealing part 3. is there. Therefore, in the nitride semiconductor light emitting device A, the periphery of the LED element 2 of the ceramic base 1 is subjected to water repellent processing in a circumferential shape, and the fluid resin sealing portion 3 is poured into the water repellent processed inside. Since the water-repellent processing is performed in a circumferential shape, the resin sealing portion 3 rises like a dome due to surface tension. The resin sealing portion 3 is heated and cured to form a cap of the dome-shaped resin sealing portion 3. The water repellent finish is obtained by depositing a water repellent resin in a circular shape on the outer edge forming the dome.

In the nitride semiconductor light emitting device A, it is preferable that the resin sealing portion 3 is made of a material that blocks outside air and hardly deteriorates due to ultraviolet rays. Examples include thermosetting silicone (Si) resin and dimethyl silicone resin. Since the methyl group contained in the dimethyl silicone resin has a property stable to ultraviolet rays, the dimethyl silicone resin is more preferable because it is less deteriorated by ultraviolet rays than the silicone resin.

In the LED element 2 of the nitride semiconductor light emitting device A according to the present invention, since a sapphire substrate that is less expensive than another substrate used as a growth substrate is used, the cost of the component members of the element can be reduced. Further, since the sapphire substrate 20 is left, a peeling process is not necessary. As a result, the manufacturing cost of the LED element 2 can be reduced.

Further, the nitride semiconductor light emitting device A according to the present invention is arranged such that the sapphire substrate 20 is on the base 1 side with respect to the light emitting layer. Ceramic (alumina) has a high surface reflectivity, a large band gap, and is a sintered body. Therefore, it has a high light scattering effect, so it is difficult to absorb LED light emission. Moreover, since the sapphire substrate 20 and the ceramic base 1 are arranged so as to be adjacent to each other, the light extraction efficiency of the nitride semiconductor light emitting device A of the present invention is improved.

Furthermore, the refractive index of the nitride semiconductor layer (LED element 2) is about 2.5, and the refractive index of the sealing resin (silicone resin, dimethyl silicone resin) is about 1.4. The difference in refractive index between the nitride semiconductor layer and the sealing resin is smaller than the difference in refractive index between the nitride semiconductor layer and air. Therefore, total reflection of LED light emission is less likely to occur at the interface between the nitride semiconductor layer and the sealing resin than when it is in contact with air. Since the difference in refractive index between the nitride semiconductor layer and the sealing resin and the difference in refractive index between the sealing resin and air are close to each other, the nitride semiconductor layer is sealed by sealing with the sealing resin. The light extraction efficiency is improved compared to the case where it does not stop.

In the nitride semiconductor light emitting device A according to the present invention, the LED element 2 is arranged on the ceramic base 1 so that the sapphire substrate 20 is on the base 1 side with respect to the light emitting layer, and the LED element 2 is sealed with resin By sealing with the portion 3, it is possible to reduce the manufacturing cost and increase the light extraction efficiency, that is, increase the intensity of the emitted light.

(Second Embodiment)
A nitride semiconductor light emitting device according to the present invention will be described with reference to the drawings. 7 is a perspective view of the nitride semiconductor light emitting device according to the present invention, and FIG. 8 is a cross-sectional view of the nitride semiconductor light emitting device shown in FIG. 7 cut along the line VIII-VIII. The nitride semiconductor light emitting device B has the same configuration as the nitride semiconductor light emitting device A of the first embodiment except that the base 4 is different. That is, the LED element 2 has the same configuration.

The nitride semiconductor light emitting device B uses a rectangular parallelepiped base 4 having a cylindrical recess 40 at the center. The recess 41 includes a bottom surface portion 401 having a circular shape in plan view and a peripheral wall portion 402 connected to the peripheral surface of the bottom surface portion 401. The peripheral wall 402 has a shape that widens toward the opening of the recess 40.

And, the pattern wiring 41 is formed on the base 4. The pattern wiring 41 is formed on the bottom surface portion 401 and supplies power to the LED element 2. Since the pattern wiring 41 has the same configuration as the pattern wiring 11 of the base 1, details are omitted.

The nitride semiconductor light emitting device B is manufactured as follows. A die bond paste is applied to at least one of the portion of the bottom surface portion 401 where the LED element 2 is attached or the surface of the LED device 2 opposite to the growth surface 200 of the sapphire substrate 20, and the LED device 2 is attached to the bottom surface portion 401 of the sapphire substrate 20. Install so that they are adjacent. Next, the die bond paste is cured, and the LED element 2 is fixed to the bottom surface portion 401. The pattern wiring 11 and the p pad electrode 28 are connected to the pattern wiring 11 and the n pad electrode 29 by the wire 12, respectively.

Next, the resin sealing portion 5 is formed by flowing the sealing resin into the recess 40 and curing it. Since the resin sealing part 5 is made to flow into the recessed part 40, it can suppress that resin flows widely. In addition, in order to seal LED element 2 and the wire 12 reliably with the resin sealing part 5, the depth of the recessed part 40 is formed deeper than the thickness of the LED element 2 at least.

In the nitride semiconductor light emitting device B, the light generated by the LED element 2 is emitted from the opening of the recess 40. By making the cylindrical shape such that the peripheral wall portion 402 of the recess 40 spreads toward the opening, the light incident on the peripheral wall portion 402 is reflected toward the opening side. By setting it as such a structure, the light of the LED element 2 can be condensed and the extraction efficiency of light can be improved.

Other features are the same as in the first embodiment.

In order to confirm the effect of the nitride semiconductor light emitting device according to the present invention as described above, an LED element or a nitride semiconductor light emitting device was actually manufactured. The confirmation result will be described below.

(Confirmation of the effect of ITO layer thickness)
In the first embodiment, the layer thickness of the ITO layer 26 of the LED element 2 was changed, and the emission wavelength and light output from the LED element 2 were measured.

Specifically, Sample A, Sample B, and Sample C, in which the thickness of the ITO layer 26 was 50 nm, 90 nm, and 130 nm, were prepared. Except for the thickness of the ITO layer 26, all the samples have the same configuration.

The LED element 2 formed in this manner is mounted on a silver-coated TO18 mount so that the sapphire substrate 20 faces down, and a gold wire 12 is connected to the p pad electrode 28 and the n pad electrode 29.

A current of 50 mA was applied to each sample, and LED light emission was measured with an integrating sphere for light output and emission wavelength. Sample A had a wavelength of 367.2 nm and an output of 4.57 mW. Sample B had a wavelength of 368.3 and an output of 2.29 mW. Sample C had a wavelength of 365.3 and an output of 2.28 mW.

From the above results, a remarkable improvement in output was observed when the thickness of the ITO layer 26 was 50 nm. Therefore, the thickness of the ITO layer 26 is preferably 50 nm or less. Actually, the thickness was set to 60 nm or less in consideration of the fluctuation of the layer thickness.

(Confirmation of the effect of sealing resin)
Next, an LED element was manufactured by removing the n-GaN layer 232 between the active layer 24 and the n-AlGaN layer 231 having the structure of Sample A with the ITO layer 26 having a thickness of 50 nm. Note that the n-GaN layer functions as an absorption layer, and may have lowered the light extraction efficiency, so it was removed to clarify the effect of the presence or absence of the sealing resin. Other configurations are the same as those of the first embodiment. A nitride semiconductor light emitting device in which a sample is fixed to a base 1 of an alumina sintered body and a wire 12 is wired to a p pad electrode 28 and an n pad electrode 29 and the base 1 is placed on a TO18 mount coated with silver. Two were produced.

Then, one LED element was sealed with a silicone resin to obtain a sample D. The other was used as Sample E without sealing the LED element. Then, as in the comparison of sample A, sample B, and sample C with respect to sample D and sample E, the LED elements were operated at a current of 50 mA and compared. The emission wavelengths were all 374 nm. The output of sample D was 17.2 mW, while that of sample E was 13.3 mW.

In the nitride semiconductor light emitting device according to the present invention, it was confirmed that the light output was higher and the light extraction efficiency was improved when the LED element was sealed with silicone resin.

(Confirmation of base shape effect)
Further, Sample D and Sample F were prepared by changing the shape of the base of Sample D from the flat base 1 to the base 4 that is a sintered body of alumina having a recess, and the light distribution was compared. As a result, the sample F was able to distribute light forward.

(Comparison of resin materials)
Further, Sample D and Sample G in which the sealing resin of Sample D was changed from silicone resin to dimethyl silicone resin were prepared, and the deterioration of sealing resin portion 3 due to light emission was compared. As a result, it was found that the sample G is more preferable than the sample D in the deterioration of the resin sealing portion 3 (resin cracking), and the silicone resin is preferable, but the dimethyl silicone resin is more preferable.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this content. The embodiments of the present invention can be variously modified without departing from the spirit of the invention.

DESCRIPTION OF SYMBOLS 1 Base 11 Pattern wiring 12 Wire 2 LED element 20 Sapphire substrate 200 Growth surface 201 Convex part 21 AlN buffer layer 22 Undoped AlGaN layer 23 n-type nitride semiconductor layer 231 n-AlGaN layer 232 n-GaN layer 24 Activity (light emission) Layer 241 InGaN layer 242 AlGaN layer 25 p-type nitride semiconductor layer 251 p-AlGaN layer 252 p-GaN layer 26 ITO layer 27 SiO2 cover layer 28 p-pad electrode 281 main electrode 282 branch electrode 29 n-pad electrode 291 main electrode 292 branch Electrode 290 Conductive film 3 Resin sealing part 4 Base 40 Recess 401 Bottom 402 Peripheral side wall 41 Pattern wiring 5 Resin sealing part

Claims

A nitride semiconductor light-emitting element that emits ultraviolet light comprising a sapphire substrate and a nitride semiconductor layer;
A base made of a ceramic sintered body;
A resin sealing portion for sealing the nitride semiconductor light emitting element with resin,
The nitride semiconductor light emitting device is disposed on the base such that the sapphire substrate is on the lower side with respect to the nitride semiconductor layer,
The nitride semiconductor light emitting device, wherein the resin sealing portion is made of a material having a refractive index between the refractive index of the nitride semiconductor layer and the refractive index of air.
2. The nitride semiconductor light emitting device according to claim 1, wherein irregularities are formed on a surface of the sapphire substrate on which the nitride semiconductor layer is laminated.
The nitride semiconductor light emitting device according to claim 1 or 2, wherein the nitride semiconductor layer includes an AlGaN layer including an n-type AlGaN layer and an undoped AlGaN layer.
4. The nitride semiconductor light emitting device according to claim 3, wherein the undoped AlGaN layer is formed between the n-type AlGaN layer and the sapphire substrate.
The nitride semiconductor light emitting device according to claim 3 or 4, wherein the total thickness of the AlGaN layer is 6 µm or more.
The nitride semiconductor light-emitting device according to claim 1, wherein the nitride semiconductor light-emitting element includes an oxide transparent conductive layer.
The nitride semiconductor light emitting device according to claim 6, wherein the transparent oxide conductive layer is made of ITO.
8. The nitride semiconductor light emitting device according to claim 7, wherein the oxide transparent conductive layer has a thickness of 60 nm or less.
The nitride semiconductor light emitting device includes an n-side electrode and a p-side electrode, and at least one of the n-side electrode and the p-side electrode includes a main electrode and a branch electrode extending from the main electrode. The nitride semiconductor light-emitting device according to claim 1.
The nitride semiconductor light emitting device according to any one of claims 1 to 9, wherein the base is made of an alumina sintered body.
The nitride semiconductor light emitting device according to any one of claims 1 to 10, wherein the resin sealing portion is made of a silicone resin or a dimethyl silicone resin.