JP2019129256A - Semiconductor light emitting device - Google Patents

Abstract

To provide a semiconductor light emitting device improved in light output.SOLUTION: The device comprises: a package substrate 2 integrally having an annular side wall part 21 and a bottom wall part 22 closing one opening of the side wall part 21: and a semiconductor light emitting element 4 housed in the hollow part of the side wall part 21 and mounted on the bottom wall part 21. An inner peripheral surface 22a of the side wall part 21 is formed into an inclined surface expanding outward as it is separated from the bottom wall part 22. When h represents the height of the semiconductor light emitting element 4 along the axial direction of the side wall part 21 and d represents a distance between the bottom wall part 22 side end of the semiconductor light emitting element 4 and the inclined surface with respect to a direction perpendicular to the axial direction, an inclination angle θof the inclined surface with respect to a plane perpendicular to the axial direction satisfies conditions of θ≤{(180-θ)/2}×1.32 and θ={arctan(h/d)}×180/π.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a semiconductor light emitting device.

  Conventionally, a semiconductor light emitting device in which a semiconductor light emitting element is accommodated in a recess of a package substrate is known. As such a semiconductor light emitting device, there is one in which the optical output is improved by making the inner peripheral surface of the package substrate into an inclined surface that spreads outward as it opens (see, for example, Patent Document 1).

JP, 2006-103636, A

  However, in the prior art, since the size of the semiconductor light emitting element and the distance between the semiconductor light emitting element and the package substrate are not considered, for example, the light reflected by the inclined surface reenters the semiconductor light emitting element, etc. There were times when it could not be improved enough. In particular, in the case of an ultraviolet light emitting diode that emits ultraviolet light, the element may include a layer that absorbs ultraviolet light, and in such a case, the ultraviolet light reentering the semiconductor light emitting element is absorbed, It may lead to a decrease in light output.

  SUMMARY An advantage of some aspects of the invention is that it provides a semiconductor light emitting device with improved light output.

The present invention, for the purpose of solving the above-mentioned problems, includes a package substrate integrally having an annular side wall portion and a bottom wall portion closing one opening of the side wall portion, and housed in the hollow portion of the side wall portion. A semiconductor light emitting element mounted on the bottom wall portion, the inner circumferential surface of the side wall portion being formed in an inclined surface which expands outward as the distance from the bottom wall portion increases, and the side wall portion The height of the semiconductor light emitting device along the axial direction of the semiconductor light emitting device is h, and the distance along the direction perpendicular to the axial direction between the end portion on the bottom wall side of the semiconductor When d, the inclination angle θ _{2 of the} inclined surface with respect to a plane perpendicular to the axial direction is expressed by the following equation θ ₂ ≦ {(180−θ ₁ ) / 2} × 1.32.
θ ₁ = {arctan (h / d)} × 180 / π
A semiconductor light emitting device that satisfies the above conditions is provided.

  According to the present invention, it is possible to provide a semiconductor light emitting device in which the light output is improved.

FIG. 1 is an exploded perspective view of a semiconductor light emitting device according to an embodiment of the present invention. It is sectional drawing to which the principal part of the semiconductor light-emitting device was expanded. It is a figure explaining the laminated structure of a semiconductor light-emitting device. It is a graph which shows the simulation result which calculated the optical output of the Example by this invention, and a prior art example. It is a graph which shows the result of having simulated the relationship between an inclination angle and light output, changing a reflectance. (A) is a figure which shows the path (locus) of the light from a light emission point, when the center position of the surface at the side of the nitride semiconductor layer of a transparent substrate is made into a light emission point, (b) is from a transparent substrate It is a figure explaining each area | region of the light which goes out, and the light which does not go out from a transparent substrate by total reflection. It is a graph which shows the simulation result of the change of the optical output when changing the thickness of a transparent substrate.

Embodiment
Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.

(Overall configuration of semiconductor light emitting device)
FIG. 1 is an exploded perspective view of a semiconductor light emitting device according to an embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of a main part thereof.

  The semiconductor light emitting device 1 includes a package substrate 2, a lid 3, a semiconductor light emitting element 4, and a zener diode 5.

  The package substrate 2 integrally includes an annular (short cylinder shape, frame shape) side wall portion 21 and a bottom wall portion 22 that closes one opening of the side wall portion 21. The side wall portion 21 is formed in a substantially rectangular shape (a substantially rectangular frame shape) in a plan view, and the semiconductor light emitting element 4 and the zener diode 5 are accommodated in the hollow portion of the side wall portion 21. The package substrate 2 is made of, for example, a high temperature fired ceramic multilayer substrate (HTCC, High Temperature Co-fired Ceramic). A substrate-side electrode 24 on which the semiconductor light emitting element 4 and the Zener diode 5 are mounted is provided on the bottom wall portion 22. In addition, illustration of the board | substrate side electrode 24 is abbreviate | omitted in FIG.

  The lid 3 is made of a transparent member such as quartz glass that transmits light emitted from the semiconductor light emitting element. The lid 3 is attached to the package substrate 2 so as to close the opening of the package substrate 2, that is, the other opening of the side wall portion 21 (opening opposite to the bottom wall portion 22). The lid 3 is fixed to the upper surface of the side wall portion 21 (the surface opposite to the bottom wall portion 22) in a watertight manner using a brazing material or the like.

  The semiconductor light emitting element 4 is accommodated in the hollow portion of the side wall portion 21 and is flip-chip mounted on the substrate side electrode 24 of the bottom wall portion 22. In the present embodiment, the semiconductor light emitting element 4 is composed of a light emitting diode (hereinafter referred to as an ultraviolet light LED) that emits ultraviolet light (deep ultraviolet light) having an emission wavelength (central wavelength, peak wavelength) of 360 nm or less. Details of the semiconductor light emitting element 4 will be described later.

  The Zener diode 5 is housed in the hollow portion of the side wall portion 21 together with the semiconductor light emitting element 4, and is mounted on the substrate side electrode 24 of the bottom wall portion 22. The Zener diode 5 serves to protect the semiconductor light emitting element 4 by keeping the voltage applied to the semiconductor light emitting element 4 constant and suppressing overcurrent.

(The inclination angle theta ₂ of the description of the inner circumferential surface 21a of the side wall portion 21)
In the semiconductor light emitting device 1 according to the present embodiment, the inner circumferential surface 21a of the side wall 21 is formed in an inclined surface which spreads outward (in a direction away from the central axis of the side wall 21) as being apart from the bottom wall 22. ing. Hereinafter, the inclination angle of the inclined surface with respect to the plane perpendicular to the axial direction of the side wall portion 21 (the vertical direction in FIG. 2) is referred to as the inclination angle θ ₂ . Moreover, the axial direction of the side wall part 21 may only be called axial direction.

In the semiconductor light emitting device 4, light is emitted not only from the upper surface (the surface opposite to the bottom wall portion 22) but also from the side surface. If the inclination angle θ ₂ is too large, light emitted from the side surface of the semiconductor light emitting element 4 is reflected by the inner peripheral surface 21 a of the side wall portion 21 and reenters the semiconductor light emitting element 4, thereby lowering the light output. May be mixed. Although the details will be described later, the semiconductor light emitting device 4 (ultraviolet light LED) used in the present embodiment includes a layer absorbing ultraviolet light on the bottom wall 22 side of the light emitting layer. Most of the light that re-enters is absorbed by the layer. Therefore, in order to improve the light output, the inclination angle θ ₂ is set so that the light emitted from the side surface of the semiconductor light emitting element 4 and reflected by the inner circumferential surface 21 a of the side wall 21 does not reenter the semiconductor light emitting element 4. Must be set.

Therefore, in the semiconductor light emitting device 1 according to the present embodiment, the height of the semiconductor light emitting element 4 along the axial direction of the side wall portion 21 is h, and the end portion on the bottom wall portion 22 side of the semiconductor light emitting element 4 and the inclined surface When the distance along the direction perpendicular to the axial direction with respect to (the inner peripheral surface 21a of the side wall portion 21) is d, the inclination angle θ ₂ is expressed by the following equation (1)
θ ₂ ≦ {(180−θ ₁ ) / 2} × 1.32 (1)
θ ₁ = {arctan (h / d)} × 180 / π
To meet the requirements of That is, θ ₁ in the equation (1) is an angle of incidence and an angle of emergence under which the light emitted in the direction perpendicular to the axial direction and reflected by the inner circumferential surface 21 a does not reenter the semiconductor light emitting element 4. This is the lower limit of the total value.

If the inclination angle theta ₂ is too small, in order to ensure the height of the side wall portion 21 it is necessary to increase the thickness of the side wall portion 21, may lead to enlargement of the semiconductor light-emitting device 1. Therefore, the inclination angle theta ₂ is 45 degrees or more, and more preferably 60 degrees or more.

  In the present embodiment, the side wall portion 21 is formed in a rectangular shape in a plan view, but among the four surfaces which are the inner peripheral surface 21 a of the side wall portion 21, at least the surface closest to the semiconductor light emitting element 4 It is preferable that the condition of Formula (1) is satisfied.

  In the present embodiment, since the Zener diode 5 is provided, a part of the light emitted from the side surface of the semiconductor light emitting element 4 strikes the Zener diode 5. That is, only a part of the light emitted from the side surface of the semiconductor light emitting element 4 to the Zener diode 5 side reaches the inner peripheral surface 21 a of the side wall portion 21. Therefore, it can be said that the surface on the Zener diode 5 side of the semiconductor light emitting element 4 among the four surfaces which are the inner peripheral surface 21a of the side wall portion 21 has a relatively small influence on the light output. Therefore, among the four surfaces which are the inner peripheral surface 21 a of the side wall portion 21, the three surfaces excluding the surface on the side of the zener diode 5 of the semiconductor light emitting element 4 may satisfy the condition of equation (1). The surface of the element 4 on the Zener diode 5 side may not satisfy the condition of the formula (1).

  Further, although not shown, a reflective film may be formed on the inner circumferential surface 21 a of the side wall 21. As the reflective film, for example, a film made of a metal having a high reflectivity of ultraviolet light such as aluminum may be used. The reflective film can be formed, for example, by depositing a metal such as aluminum by vapor deposition or sputtering.

(Laminated structure of semiconductor light emitting device 4)
FIG. 3 is a diagram for explaining a laminated structure of the semiconductor light emitting element 4 which is an ultraviolet LED. The semiconductor light emitting element 4 has a transparent substrate 41 and an AlGaN based nitride semiconductor layer 42 provided on the transparent substrate 41, and is mounted with the nitride semiconductor layer 42 on the bottom wall 22 side.

  In the present embodiment, the transparent substrate 41 is made of a sapphire substrate. In the present embodiment, the nitride semiconductor layer 42 is made of a buffer layer 42a made of AlN, an n-clad layer 42b made of n-type AlGaN, a light-emitting layer 42c containing AlGaN, and p-type AlGaN on the transparent substrate 41. A p-clad layer 42d and a contact layer 42e made of p-type GaN are sequentially formed. In the semiconductor light emitting device 4, a part of the light emitting layer 42c, the p cladding layer 42d, and the contact layer 42e is removed by etching or the like, and a part of the n type cladding layer 42b is exposed. An n electrode 43 is formed on the n-type cladding layer 42 b. In addition, a p electrode 44 is formed on the contact layer 42e. The n electrode 43 and the p electrode 44 are electrically connected to the substrate side electrode 24 through the bumps 46 and 47, respectively. Of the nitride semiconductor layer 42, the contact layer 42e made of p-type GaN is a layer that absorbs ultraviolet light (a layer that absorbs very much ultraviolet light).

  Strictly speaking, the height h of the semiconductor light emitting element 4 in the above formula (1) is the distance along the axial direction from the upper surface of the transparent substrate 41 to the lower surface of the p electrode 44 (surface on the bottom wall portion 22 side). It is. Strictly speaking, the distance d virtually extends the side surface of the nitride semiconductor layer 42 closest to the target sidewall 21 at the axial position of the lower surface of the p electrode 44 toward the bottom wall 22. It is the distance along the direction perpendicular to the axial direction between the virtual surface (which may coincide with the side surface of the p electrode 44) and the inner peripheral surface 21a.

(simulation result)
While using the semiconductor light emitting element 4 which is formed in a square shape having a side of 1 mm in top view and has a height h of 0.5 mm, the height of a side wall 21 is formed in a square shape having a side of 3.5 mm in top view A simulation was performed for a case where the 0.6 mm package substrate 2 was used and the distance d was 0.25 mm. The reflectance of the inner circumferential surface 21 a of the side wall portion 21 is 15%. The emission wavelength of the semiconductor light emitting element 4 was 280 nm. In this case, since h = 0.5 mm and d = 0.25 mm, the angle corresponding to (180−θ ₁ ) / 2 in the above-mentioned equation (1) is approximately 58.3 degrees.

In the simulation, the prior art was the inclination angle theta ₂ of the inner circumferential surface 21a of the side wall portions 21 and 90 degrees, the inclination angle theta ₂ of Example 1 was 58.3 degrees, and the inclination angle theta ₂ 58.3 ° The light output (radiant flux) was calculated for Example 2 in which a reflective film having an ultraviolet light reflectance of 50% was formed on the inner peripheral surface 21a. In addition, the reflectance (reflectance of ultraviolet light) of the inner peripheral surface 21a in the conventional example and Example 1 was 15%. The results are shown in FIG. As shown in FIG. 4, in Example 1, a light output about 1.2 times that of the conventional example was obtained. In Example 2 in which the reflective film was formed, a light output about 1.3 times that of the conventional example was obtained.

Furthermore, the reflectance of the inner circumferential surface 21a 70% was determined by 50%, the case of 30%, and 15%, simulating an optical output when changing the inclination angle theta ₂ (radiant flux). The results are shown in FIG. As shown in FIG. 5, when the reflectance was 15%, that the inclination angle theta ₂ to 77 degrees or more, it can be seen that the effect of more than 10% improvement in output is obtained. That is, the inclination angle theta _2, the (180-theta ₁₎ / 2, the coefficient (77 / 58.3) = above equation to 1.32 or less calculated by multiplying the (1) is satisfying the condition of An output improvement effect of 10% or more can be obtained. In order to obtain an effect even when the reflectance of the inner peripheral surface 21a is low, the inclination angle θ ₂ is expressed by the following equation θ ₂ ≦ {(180−θ ₁ ) / 2}.
It is more preferable that the relationship is satisfied.

(Description of thickness of transparent substrate 41)
As described above, since the semiconductor light emitting element 4 that is an ultraviolet light LED includes a layer that absorbs ultraviolet light (a contact layer 42e made of p-type GaN), the bottom wall portion of the light emitted by the light emitting layer 42c Most of the light traveling toward the 22 side is absorbed. Therefore, it is required to use as much light as possible toward the transparent substrate 41 side.

  FIG. 5A is a diagram showing a light path (trajectory) from the light emitting point when the light emitting point is the center position (center position in plan view) of the surface of the transparent substrate 41 on the nitride semiconductor layer 42 side. It is. As shown in FIG. 5A, light in the transparent substrate 41 spreads at a solid angle 2π and travels toward the interface of the transparent substrate 41. If the incident angle to the interface of the transparent substrate 41 is larger than the critical angle θ determined by the refractive index n2 of the transparent substrate 41 and the refractive index n1 of air, total reflection occurs at the interface of the transparent substrate 41. I will.

  As shown in FIG. 5B, of the light from the light emitting point, the light whose angle from the axial direction is smaller than the critical angle θ, that is, the light emitted to the area A shown in FIG. Since the incident angle to the surface 41a opposite to the nitride semiconductor layer 42 side is smaller than the critical angle, the light can be emitted from the upper surface 41a to the outside of the transparent substrate 41. In general, since the width L of the transparent substrate 41 is sufficiently larger than the thickness D of the transparent substrate 41, the light emitted to the region A is emitted with a minimum loss.

  Further, among the light from the light emitting point, the light having an angle from the direction perpendicular to the axial direction smaller than the critical angle θ, that is, the light emitted to the region B shown in the drawing is the incident angle to the side surface 41 b of the transparent substrate 41 Is smaller than the critical angle, so that the light can be emitted from the side surface 41 b to the outside of the transparent substrate 41. Of the light from the light emitting point, the light emitted to the area C other than the areas A and B is totally reflected by the upper surface 41a and the side surface 41b and can not be emitted from the transparent substrate 41 or the bottom wall portion of the package substrate 2 The light is emitted toward the side 22 and hardly contributes to the improvement of the light output (light emission intensity).

Here, if the thickness D of the transparent substrate 41 is made too thin, a part of the light emitted to the region B is totally reflected by the upper surface 41 a, which causes a decrease in light output. Therefore, it is desirable that the thickness D of the transparent substrate 41 be equal to or greater than the thickness (height) Dmin on the side surface 41 b of the region B in order to cause all light emitted to the region B to be emitted from the side surface 41 b. . This thickness Dmin is expressed by the following equation (2), where L is the width of the transparent substrate 41 and θ is the critical angle.
Dmin = (L / 2) tan θ (2)
Can be expressed as

Therefore, in the present embodiment, the thickness D of the transparent substrate 41 is set to the following formula (3)
D ≧ (L / 2) tan θ (3)
θ = sin ⁻¹ (n ₁ / n ₂ )
Where n _{1 is} the refractive index of air
n ₂ : The refractive index of the transparent substrate 41 is set to satisfy. As a result, all the light emitted to the region B can be emitted from the side surface 41b, the light extraction efficiency from the transparent substrate 41 can be improved, and the light output can be improved.

Here, although the light emission point is set at the center position of the transparent substrate 41 for the sake of simplicity, substantially the entire surface of the transparent substrate 41 on the nitride semiconductor layer 42 side emits light. Therefore, by setting the thickness D of the transparent substrate 41 so that the light emitted in the vicinity of one side surface 41 b of the transparent substrate 41 can be emitted from the opposite side surface 41 b, the light extraction efficiency from the transparent substrate 41 can be improved. It becomes possible to improve more. Specifically, the thickness D of the transparent substrate 41 is expressed by the following equation (4)
D ≧ L × tan θ (4)
It is more desirable to set so as to satisfy.

  The width L of the transparent substrate 41 here is the minimum value of the width of the transparent substrate 41 in plan view. In the present embodiment, the semiconductor light emitting element 4 in a square shape in plan view is used, and the transparent substrate 41 is also formed in a square shape in plan view, so the length of one side thereof is the width L. For example, when the rectangular semiconductor light emitting device 4 is used in plan view, the width in the short side direction is the width L.

(simulation result)
In the case where the width L of the transparent substrate 41 is 1 mm and the refractive index of the transparent substrate 41 is 1.81, the light output (radiant flux) at the time of changing the thickness D was calculated. The results are shown in FIG. In this case, the thickness D may be 0.33 mm or more (D / L is 0.33 or more) from the above-described formula (3).

  As shown in FIG. 6, the radiant flux is drastically decreased in the region where D / L is less than 0.33, and it was confirmed that the light output can be improved by setting D / L to 0.33 or more. .

(Operation and effect of the embodiment)
As described above, in the semiconductor light emitting device 1 according to the present embodiment, the inner peripheral surface 21a of the side wall 21 is formed into an inclined surface which expands outward as it separates from the bottom wall 22, and the inclination thereof the inclination angle theta ₂ of the surfaces, which satisfies the condition of the above formula (1),

  As a result, light emitted laterally from the semiconductor light emitting element 4 is emitted to the outside without re-entering the semiconductor light emitting element 4, and the light output can be improved.

(Summary of the embodiment)
Next, technical ideas to be understood from the embodiments described above will be described by using the reference numerals and the like in the embodiments. However, each reference numeral or the like in the following description does not limit the constituent elements in the claims to the members or the like specifically shown in the embodiments.

[1] A package substrate (2) integrally including an annular side wall portion (21) and a bottom wall portion (22) closing one opening of the side wall portion (21), and the side wall portion (21) And a semiconductor light emitting element (4) housed in the hollow portion and mounted on the bottom wall portion (22), wherein the inner circumferential surface (21a) of the side wall portion (21) is the bottom wall portion (22) And the height of the semiconductor light emitting element (4) along the axial direction of the side wall portion (21) is h, and the semiconductor light emitting element (4) of the semiconductor light emitting element (4) is Assuming that the distance between the end on the bottom wall (22) side and the inclined surface along the direction perpendicular to the axial direction is d, the inclination of the inclined surface with respect to the plane perpendicular to the axial direction The inclination angle θ ₂ is expressed by the following formula θ ₂ ≦ {(180−θ ₁ ) / 2} × 1.32.
θ ₁ = {arctan (h / d)} × 180 / π
A semiconductor light emitting device (1) that satisfies the following conditions.

[2] the inclined surface inclination angle theta ₂ is, at 45 degrees or more, the semiconductor light-emitting device according to [1] (1).

[3] The side wall portion (21) is formed in a rectangular shape in plan view, and at least the semiconductor light emitting element (4) is at least the most of the four surfaces which are the inner peripheral surface of the side wall portion (21). The semiconductor light emitting device (1) according to [1] or [2], wherein a surface close to 1 satisfies the above condition.

[4] A Zener diode (5) housed in the hollow portion of the side wall portion (21) and mounted on the bottom wall portion (22), which protects the semiconductor light emitting element (4), the side wall portion Among the four surfaces that are the inner peripheral surface (21a) of (21), the three surfaces of the semiconductor light emitting element (4) excluding the surface on the side of the zener diode (5) satisfy the above conditions [ 3] The semiconductor light-emitting device (1) according to [3].

[5] The semiconductor light-emitting device (4) is a light-emitting diode that emits ultraviolet light, and includes a layer that absorbs ultraviolet light. The semiconductor light-emitting device according to any one of [1] to [4] Device (1).

[6] The semiconductor light emitting device (4) includes a transparent substrate (41) and a nitride semiconductor layer (42) provided on the transparent substrate (41), and the nitride semiconductor layer (42) It is mounted on the bottom wall (22) side, and when the width of the transparent substrate (41) is L, the thickness D of the transparent substrate (41) is such that the following formula D ((L / 2) × tanθ
θ = sin ⁻¹ (n ₁ / n ₂ )
Where n _{1 is} the refractive index of air
n ₂ : The semiconductor light emitting device (1) according to any one of [1] to [5], which satisfies a refractive index of the transparent substrate.

  While the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. In addition, it should be noted that not all combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

The present invention can be appropriately modified and implemented without departing from the spirit of the present invention. For example, in the above embodiment, the inner circumferential surface 21a of the side wall portion 21 has been described a case where formed on a plane having a constant inclination angle theta _2, not limited thereto, the inner circumference of the side wall portion 21 surface 21a may be of a stepwise inclination angle theta ₂ is changed. Further, the inner peripheral surface 21a of the side wall portion 21 may be a curved surface curved so as to be convex downward.

DESCRIPTION OF SYMBOLS 1 ... semiconductor light emitting device 2 ... package substrate 3 ... lid 4 ... semiconductor light emitting element 5 ... Zener diode 21 ... sidewall portion 21 a ... inner circumferential surface 22 ... bottom wall portion 41 ... transparent substrate 42 ... nitride semiconductor layer

Claims (6)

A package substrate integrally having an annular side wall portion and a bottom wall portion closing one opening of the side wall portion;
A semiconductor light emitting device housed in the hollow portion of the side wall and mounted on the bottom wall;
The inner circumferential surface of the side wall portion is formed in an inclined surface which is expanded outward as it is separated from the bottom wall portion,
Let h be the height of the semiconductor light emitting device along the axial direction of the side wall portion, and be along a direction perpendicular to the axial direction of the end portion on the bottom wall portion side of the semiconductor light emitting device and the inclined surface When the distance is d, the inclination angle θ _{2 of the} inclined surface with respect to the plane perpendicular to the axial direction is: θ ₂ ≦ {(180−θ ₁ ) / 2} × 1.32
θ ₁ = {arctan (h / d)} × 180 / π
Meet the conditions of,
Semiconductor light emitting device. The inclination angle theta ₂ of the inclined surfaces is 45 degrees or more,
The semiconductor light emitting device according to claim 1. The side wall portion is formed in a rectangular shape in plan view,
Of the four surfaces that are the inner peripheral surface of the side wall portion, at least the surface closest to the semiconductor light emitting element satisfies the condition.
The semiconductor light-emitting device according to claim 1. It is housed in the hollow part of the side wall part and mounted on the bottom wall part, and comprises a Zener diode that protects the semiconductor light emitting element,
Among the four surfaces which are the inner peripheral surfaces of the side wall portion, three surfaces other than the surface on the side of the zener diode of the semiconductor light emitting element satisfy the conditions.
The semiconductor light emitting device according to claim 3. The semiconductor light emitting device is a light emitting diode that emits ultraviolet light, and includes a layer that absorbs ultraviolet light.
The semiconductor light-emitting device according to any one of claims 1 to 4. The semiconductor light emitting device has a transparent substrate and a nitride semiconductor layer provided on the transparent substrate, and is mounted with the nitride semiconductor layer on the bottom wall side,
When the width of the transparent substrate is L, the thickness D of the transparent substrate is as follows: D ≧ (L / 2) × tan θ
θ = sin ⁻¹ (n ₁ / n ₂ )
Where n _{1 is} the refractive index of air
n ₂ : satisfies the refractive index of the transparent substrate,
The semiconductor light-emitting device according to any one of claims 1 to 5.

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