JP2014027236A - Semiconductor light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting element which achieves more improved light-extraction efficiency.SOLUTION: A semiconductor light-emitting element includes an n-type nitride semiconductor layer, a luminescent layer and a p-type nitride semiconductor layer which are stacked in this order on a substrate having a plurality of salients on a surface. The n-type nitride semiconductor layer has an exposed region extending in one direction at least in a partial region. A bottom face of the salient has a shape having a plurality of apexes. The salients among the plurality of salients, which are arranged such that two adjacent apexes have minimal lengths and equal distances from an extended line extending in the one direction including the exposed region, constitute more than half of the whole.

Description

  The present invention relates to a semiconductor light emitting device.

In recent years, semiconductor light emitting devices have been widely used as light sources in devices in various fields such as displays, backlights, and lighting.
In such a widely used semiconductor light emitting device, in order to further improve the light extraction efficiency, the light emission efficiency of the device itself, such as selection of electrode material, electrode placement, reflection film placement on the bottom surface of the semiconductor light emitting device, etc. The idea which improves is made.
As an example, for example, in order to improve the light emission efficiency, it has been proposed to provide a convex portion having a predetermined shape on the surface of the substrate (Patent Document 1, etc.).

JP 2011-77562 A

However, the current situation is that further improvement in luminous efficiency is required.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a semiconductor light emitting device that further improves the light extraction efficiency.

The present application includes the following inventions.
(1) A semiconductor light emitting device configured by laminating an n-type nitride semiconductor layer, a light emitting layer, and a p type nitride semiconductor layer in this order on a substrate having a plurality of convex portions on the surface,
The n-type nitride semiconductor layer has an exposed region extending in one direction at least in a partial region,
The convex portion has a plurality of vertices in its bottom shape,
Among the convex portions, the convex portions arranged so that two adjacent vertices are the shortest and equidistant from an extension line extending in one direction including the exposed region occupy more than half of the whole. A semiconductor light emitting element characterized by the above.
(2) The semiconductor light emitting element according to the above, wherein the convex portion has a shape in which a bottom surface has three vertices.
(3) The semiconductor light emitting element according to any one of the above, wherein the convex portion has a frustum shape or a cone shape.
(4) The plurality of convex portions constitute a plurality of rows parallel to the extension line, and the convex portions of two adjacent rows among the plurality of rows are arranged with a shift of ½ pitch from each other. The semiconductor light-emitting device according to any one of the above.
(5) The plurality of convex portions constitute a plurality of rows perpendicular to the extension line, and the convex portions of two adjacent rows among the plurality of rows are arranged with a shift of ½ pitch from each other. The semiconductor light-emitting device according to any one of the above.
(6) The semiconductor light emitting element according to any one of the above, wherein the semiconductor light emitting element has a rectangular planar shape, and the one direction is a direction parallel or substantially parallel to a long side of the rectangle.
(7) An n-side pad electrode is disposed on a part of the exposed region of the n-type nitride semiconductor layer, and the n-side pad electrode is disposed in a central region in a direction orthogonal to the one direction. The semiconductor light emitting element according to any one of the above, comprising: an n-side pad portion; and an n-side extending portion extending from the n-side pad portion and extending in the one direction.
(8) An extension line extending in one direction including the exposed region coincides with an extension line extending including the n-side extension portion extending in the one direction,
Of the convex portions, two or more adjacent vertices are shortest and equidistant with respect to an extension line extending in one direction including the n-side extending portion, and more than half of the total convex portions. The semiconductor light-emitting device according to any one of the above.

  According to the semiconductor light emitting device of the present invention, it is possible to further improve the light extraction efficiency.

It is the top view which looked at the semiconductor light-emitting device of Embodiment 1 of this invention from the electrode arrangement surface side. It is the I-I 'sectional view taken on the line of FIG. It is the II-II 'sectional view taken on the line of FIG. It is an enlarged plan view which shows the direction of one convex part in the area | region Y of FIG. It is a top view which shows one arrangement | sequence of the convex part in the area | region Y of FIG. It is a top view which shows another arrangement | sequence of the convex part in the area | region Y of FIG. 2 is a graph showing directivity characteristics of the semiconductor light emitting device of FIG. 1. It is the top view which looked at the semiconductor light-emitting device of Embodiment 2 of this invention from the electrode arrangement surface side. It is an enlarged plan view which shows another direction of one convex part in a semiconductor light-emitting device. It is an enlarged plan view which shows another direction of one convex part in a semiconductor light-emitting device. It is an enlarged plan view which shows another direction of one convex part in a semiconductor light-emitting device. It is the top view which looked at the semiconductor light-emitting device of another form of this invention from the electrode arrangement | positioning surface side.

  The semiconductor light-emitting device of the present invention is mainly configured by laminating an n-type nitride semiconductor layer, a light-emitting layer, and a p-type nitride semiconductor layer in this order on a substrate having a plurality of convex portions on the surface. This semiconductor light emitting device usually includes an n-side electrode and a p-side electrode in an n-type nitride semiconductor layer and a p-type nitride semiconductor layer, respectively.

(substrate)
The substrate is not particularly limited as long as it can epitaxially grow a nitride semiconductor. The substrate is an insulating substrate such as sapphire, spinel (MgA1 ₂ O ₄ ), or AlN whose main surface is any of the C-plane, R-plane, and A-plane, silicon carbide (6H, 4H, 3C), silicon, ZnS , ZnO, GaN, GaAs, diamond, and oxide substrates such as lithium niobate and neodymium gallate that are lattice-bonded to nitride semiconductors. Among these, a sapphire substrate is preferable, and a sapphire substrate having a C-plane as one surface is preferable as the substrate before the protrusions are formed. The substrate may have an off-angle on the front surface and / or the back surface. The off-angle is, for example, about 0 to 10 °, and is about 0 to ± 5 °, about 0 to ± 2 °, about 0 to ± 1 °, about 0 to ± 0.5 °, and about 0 to ± 0. About 25 ° is preferable.
Although the thickness of the substrate is not particularly limited, it is suitable that the thickness is about 50 μm to 2 mm in consideration of the strength in the formation of convex portions and lamination of semiconductor layers.

(Convex)
The convex part which exists in the surface of a board | substrate should just be the shape in which the bottom face shape has a some vertex. That is, instead of a shape like a circle or ellipse, there are multiple points (that is, vertices) where the line forming the bottom surface suddenly changes its direction, and the shape formed by such multiple lines and vertices means. The line here does not necessarily mean only a straight line, but may be a curved line like an arc. Specifically, polygons such as triangles, pentagons, hexagons, or similar shapes, preferably, regular polygons or shapes approximated to regular polygons, more preferably approximated to triangles or regular triangles. Shape. Here, the approximate shape means a shape formed by a curved line, not a straight line connecting adjacent vertices as described above (see, for example, lines D, E, and F in FIG. 1D). ).

  The size of the bottom surface of the convex portion, for example, the distance between lines connecting adjacent vertices or the longest distance between arbitrary vertices is about 0.1 μm to 5 μm. Moreover, about 0.5-50 micrometers and about 1-20 micrometers are mentioned for the space | interval of convex parts, ie, the minimum distance of adjacent convex parts.

Examples of the shape of the convex portion include a cone shape and a frustum shape. In the case of a pyramid shape or a frustum shape, the angle formed by the bottom surface and the side surface of the convex portion is about 30 to 80 °, and preferably about 40 to 70 °.
For example, the height of the protrusion is suitably about 0.2 μm or more and not more than the total thickness of the semiconductor layers stacked on the substrate. When the emission wavelength is λ, the height is preferably λ / 4 or more. Light can be sufficiently scattered or diffracted, and the current flow in the lateral direction of the stacked semiconductor layers can be well maintained, and the light emission efficiency can be ensured.

  Among the plurality of convex portions, the specific convex portion occupies more than half of the number of convex portions on the substrate constituting one semiconductor element (for example, this may be referred to as “dominance”). In this case, it is preferable that the size (bottom area) of the plurality of convex portions arranged in one semiconductor light emitting element is the same.

For example, as shown in FIG. 1A, when the exposed region 2a of the n-type nitride semiconductor is provided at the end along the two sides of the light emitting element, the convex portion is formed on the entire surface of the substrate in FIG. 1D. Even if it is arranged in the direction shown, depending on the size of the exposed region of the n-type nitride semiconductor, a state in which specific convex portions are predominantly arranged at about 85% or more, preferably 90% or more, can do.
Further, as shown in FIG. 2, when the n-type nitride semiconductor exposed region 72a is provided near the center of the light emitting device, the entire surface of the substrate surface is arranged in the direction shown in FIG. In a certain degree, it can be set as the state by which the specific convex part was dominantly arranged. Furthermore, as shown in FIG. 2, when the exposed region is provided near the center, for example, the Wr side is the direction shown in FIG. 1D with respect to the center line W (strictly, the center line of the n-side extension portion). By arranging in the opposite direction, that is, in the direction shown in FIG. 3, the specific convex portions can be preferentially arranged at about 100%.

  A specific convex part means the convex part arrange | positioned so that it may become equidistance with respect to the line which two adjacent vertexes extend in one direction. Furthermore, it is preferable that the two vertices in the convex portion are arranged so as to be the shortest and equidistant from a line extending in one direction. Here, the line extending in one direction is, for example, an extension line in one direction in which an exposed region of an n-type nitride semiconductor layer described later extends (this extended line also includes a line extending in the exposed region), preferably It means any one of the center line of the exposed region extending in the extension direction of the exposed region and its extension line, the center line of the n-side extension portion of the n-side electrode formed on the exposed region, and its extension line. In other words, this specific convex portion is, for example, a line connecting adjacent vertices parallel to or substantially parallel to the above-described line extending in one direction, and extending in one direction within the convex portion. It means that it is arranged on the near side. Here, “parallel” or “substantially parallel” or “substantially parallel” means to allow an inclination of about ± 10 °, preferably about ± 5 °.

Such a specific convex part should just be arrange | positioned as mentioned above, may be arrange | positioned at random in the whole substrate surface, and may be arrange | positioned regularly (refer FIG. 1E and 1F).
As a regular arrangement, for example, the plurality of convex portions constitutes a plurality of columns parallel to the extension line described above, and the convex portions of two adjacent columns among the plurality of columns are ½ each other. Arrangement with a pitch deviation (FIG. 1E), the plurality of convex portions constitute a plurality of rows perpendicular to the extension line, and the convex portions of two adjacent rows out of the plurality of rows are shifted by 1/2 pitch from each other In other words, in each of the plurality of convex portions, a line connecting two vertices that are equidistant to an extension line extending in one direction including the exposed region is parallel to the extension line. And (1) are arranged so as to constitute a plurality of columns, and the convex portions of the adjacent columns are arranged shifted in the 1/2 pitch column direction, or (2) are constituted so as to constitute a plurality of rows. The convex portions of the adjacent rows are arranged in the 1/2 pitch row direction. That.

The method of forming a convex part on the substrate surface is described in, for example, JP-A-2006-310893, JP-A-2008-177528, WO2009 / 020033, JP-A-2011-77562, etc. A well-known method is mentioned.
Specifically, a method of performing etching such as dry etching or wet etching, which will be described later, using a mask pattern having an appropriate shape may be mentioned. Of these, wet etching is preferable. Examples of the etchant include a mixed acid of sulfuric acid and phosphoric acid, KOH, NaOH, phosphoric acid, potassium pyrosulfate, and the like. Further, after etching using the mask pattern, the mask pattern may be removed, and the entire surface may be etched.

The bottom surface shape of the convex portion can be controlled by appropriately adjusting the shape of the mask pattern to be used, the etching method and conditions, for example. Examples of the material and shape of the mask pattern at this time include an insulating film (resist, SiO _2, etc.). Examples of the shape include a repeating pattern of a polygonal shape such as a circle, an ellipse, a triangle, or a rectangle. Formation of such a mask pattern can be realized by a known method such as photolithography and an etching process.

  Thus, when the convex part is formed on the substrate surface, the light guided through the n-type nitride semiconductor layer is directly irradiated to the convex part surface from the active layer, and a part of the electrode arrangement surface The traveling direction is changed to the side, and the other part can be reflected in the side surface direction of the n-side exposed surface, so that the light extraction efficiency is effective.

(Semiconductor layer)
Various nitride semiconductors can be used for each semiconductor layer constituting the semiconductor light emitting element. Specifically, the organic metal chemical vapor deposition (MOCVD), or the like hydride vapor phase epitaxy (HVPE), _{an In} on the substrate _{X Al Y Ga 1-X-} Y N (0 ≦ X, 0 ≦ Y, X + Y A semiconductor in which a plurality of semiconductors such as ≦ 1) are stacked is used. Examples of the layer structure include a homo structure having a MIS junction, a PIN junction, or a PN junction, a hetero structure, or a double hetero structure. Each semiconductor layer may have a superlattice structure, a single quantum well structure or a multi-quantum well structure in which an active layer is formed as a thin film having a quantum effect.

  Specifically, the semiconductor light-emitting element includes, for example, a GaN buffer layer, a non-doped GaN layer, a Si-doped GaN layer serving as an n-type contact layer, and a Si serving as an n-type cladding layer on a sapphire substrate 1 having a plurality of protrusions. A doped GaN layer, an InGaN layer serving as an active layer, an Mg-doped AlGaN layer serving as a p-type cladding layer, and an Mg-doped GaN layer serving as a p-type contact layer can be configured by a layered structure in this order.

In such a laminated structure of nitride semiconductor layers, an exposed region where the n-type nitride semiconductor layer is exposed is formed in a partial region thereof. Normally, the exposed region includes a region surrounding the outer edge of the semiconductor light emitting element and a region for forming an n-side electrode as described later, but the exposed region in the present invention means the latter. The exposed region for forming the n-side electrode extends in one direction (for example, the arrow Z direction in FIG. 1A). The length, width, and shape of the exposed region are not particularly limited, and can be appropriately adjusted depending on the size, shape, and the like of the semiconductor light emitting element. The exposed region for forming the n-side electrode may be connected to the exposed region surrounding the outer edge of the semiconductor light emitting element, or may be arranged separately from the exposed region surrounding the outer edge. .
This exposed region is formed by removing a part of the p-type nitride semiconductor layer and the light-emitting layer, and optionally the n-type nitride semiconductor layer in the depth direction, which are present on the laminated structure of the nitride semiconductor layer. Is formed.

  In the above-described example, for example, the Mg-doped GaN layer, the Mg-doped AlGaN layer, the InGaN layer, the Si-doped GaN layer, the Si-doped GaN layer is partially removed by etching or the like, and the exposed region where the Si-doped GaN layer is exposed. Can have.

  The semiconductor light emitting device preferably has a rectangular shape when viewed from the electrode arrangement surface side. Examples of the rectangular shape include those in which two pairs of sides have a ratio of about 1: 1.5 to 8, preferably about 1: 2 to 5, more preferably 1: 2.5 to 4. Degree. Specifically, about 150 μm to 250 μm × 600 μm to 900 μm can be mentioned. In particular, when the semiconductor light emitting element is packaged in, for example, a side view type, a light emitting device that is very small in the height direction can be obtained by forming the shape elongated in the longitudinal direction.

(electrode)
The n-side electrode optionally includes a translucent conductive film connected to substantially the entire surface of the n-type nitride semiconductor layer, and an n-side pad electrode connected thereto. The p-type electrode includes a translucent conductive film connected to substantially the entire surface of the p-type nitride semiconductor layer, and a p-side pad electrode connected thereto. Note that these n-side translucent conductive film, n-side pad electrode, p-side translucent conductive film, and p-side pad electrode are used for semiconductor light emission depending on the position of the exposed region of the n-type nitride semiconductor layer described above. You may arrange | position either along the outer periphery of an element or inside.
These n-side and p-side pad electrodes are normally disposed so as to be electrically connected to the above-described translucent conductive film. That is, the pad electrode is disposed on the entire surface so as to be in contact with the translucent conductive film. As a result, the n-side and p-side pad electrodes are arranged to be electrically connected to the n-type semiconductor layer and the p-type semiconductor layer, respectively.

  In particular, in the p-type electrode, an insulating film is disposed on the p-side nitride semiconductor layer in a region surrounding the p-side pad electrode directly below and on the outer periphery with a light-transmitting conductive film interposed therebetween. It is preferable (see the insulating film 5 in FIGS. 1B and 1C). Here, examples of the insulating film include those usually used in the field, for example, a single layer or a laminated film of oxides or nitrides such as Si, Al, Zr, Ti, and Nb. Of these, silicon dioxide is preferable. The thickness of the insulating film is preferably about 50 nm to 2 μm, for example. As a result, the supply of the direct current from the p-side pad electrode to which the current is directly applied to the p-type nitride semiconductor layer directly below is relaxed, and the current is more uniformly distributed over the entire surface of the semiconductor light emitting device. It is possible to distribute.

The translucent conductive film on the n side and the p side can be formed of a known material, for example, a transparent conductive oxide such as ITO. Moreover, you may form with the single layer or laminated film of the various metals or alloy which can comprise the pad electrode mentioned later.
The n-side and p-side pad electrodes can be formed of a known material, for example, a single layer or a laminated film of metals or alloys such as W, Al, Ti, Cr, Rh, Pt, Au, and Ni. For example, a laminated film in which Al, W, Pt and Au are laminated from the n-type nitride semiconductor layer side, a laminated film in which Ni, Au and Au are laminated from the p-type nitride semiconductor layer side, and the like can be mentioned.
These electrodes may be formed of different materials and / or laminated structures on the n-side and p-side, respectively, or considering the simplification of the manufacturing method, the same laminated structure or part of the same material. You may form with the laminated structure of the same material.

The n-side pad electrode includes an n-side pad portion and an n-side extending portion extending from the n-side pad portion. The p-side pad electrode includes a p-side pad portion and a p-side extending portion extending from the p-side pad portion.
As described above, by extending the extending portion from the pad portion, the current supplied to the pad portion can be diffused over the entire surface of the semiconductor light emitting element.

The n-side pad portion and the p-side pad portion only need to have an area that can realize bonding such as wire bonding, and the direction orthogonal to one direction in which the exposed region of the n-type nitride semiconductor extends ( For example, it is preferable that they are arranged to face each other in the central region (short direction). Here, “arranged in the central region” means that a part of each of the n-side pad portion and the p-side pad portion straddles the center (for example, X in FIG. 1) of the semiconductor light emitting element in the short direction. Means that it is arranged. Especially, it is preferable that each gravity center of n side pad part and p side pad part is arrange | positioned in the center. Moreover, it is preferable that the n side pad part and the p side pad part are arrange | positioned in the same position in what is called a transversal direction.
By arranging these pad portions in a central region in the so-called short direction, it is possible to ensure good mountability even when the housing space of the semiconductor light emitting element is very narrow when packaging or the like. Is possible.

In one direction (for example, the longitudinal direction), the n-side pad portion may be arranged so as to be biased from the n-type nitride semiconductor layer toward the center side of the semiconductor light emitting device (see 21a in FIG. 2). It may be disposed substantially adjacent to the end of the n-type nitride semiconductor layer (see 11a in FIG. 1A).
In the so-called longitudinal direction, the p-side pad portion may be disposed substantially adjacent to the end of the p-type nitride semiconductor layer (see 22a in FIG. 2), or from the p-type nitride semiconductor layer, The semiconductor light emitting element may be arranged so as to be biased toward the center side (see 12a in FIG. 1A). In other words, it may be arranged away from the short side of the p-type semiconductor.
In particular, it is preferable that the n-side pad portion is disposed adjacent to the end portion of the n-type nitride semiconductor layer, and the p-side pad portion is disposed to be biased toward the center side of the semiconductor light emitting element. With such an arrangement, current can be more uniformly diffused around the entire periphery of the p-side pad electrode, and uniform current diffusion can be realized over the entire surface of the semiconductor light emitting device. In addition, since the distance from the n-side pad portion can be optimized, Vf can be reduced.
For example, the degree of disposition to the center side is about 1 to 3 times, preferably about 1 to 2 times the diameter or length of the pad portion described later.
The distance between the n-side pad portion and the p-side pad portion is, for example, about 50 to 85%, preferably 60 to 80% of the length in the longitudinal direction of the semiconductor light emitting device. Specifically, Examples include about 500 μm to 700 μm.
The n-side pad portion and the p-side pad portion do not necessarily have the same shape and size. For example, the length of the short side of the semiconductor light emitting element is about 1/6 to 1/2, preferably 1/5. Examples include a shape close to a circle having a diameter of about １ ／ or a shape that is close to a quadrangle whose one side is such a length. Specifically, the diameter or the length of one side is about 40 to 80 μm. Can be mentioned.

The n-side stretched portion and the p-side stretched portion may have the same thickness, may have different thicknesses, may have partially different thicknesses, or may be partially wide. Thickness may be used. These extending portions may have the same length or different lengths. For example, these extending portions include those having a width of about 1/20 to 1/5 of the n-side pad portion and the p-side pad portion. Specifically, it is about 3 μm to 12 μm, preferably about 5 μm to 8 μm.
The n-side stretched part and the p-side stretched part are usually arranged so that a part thereof overlaps in a part in the arrow Z direction (so-called longitudinal direction) in FIG. 1A. In such an overlap portion, the distance α (shortest distance, for example, see FIG. 1) between the end of the p-side semiconductor layer adjacent to the n-side extension and the p-side extension is the p-side extension. It is preferable to be longer than the distance β (shortest distance, for example, see FIG. 1) with respect to the end portion of the p-type semiconductor layer located on the side opposite to the n-side extending portion. The difference in length between the distance α and the distance β is, for example, about α: β = 1.5-3: 1. Specifically, α is in the range of about 100 to 150 μm, β is in the range of about 60 to 85 μm, and (α−β) is preferably about 30 to 50 μm.
Here, overlapping in one direction does not mean that it overlaps in the stacking direction of the semiconductor layers, but a line parallel to a line perpendicular to one direction is seen in one direction as viewed from the electrode arrangement surface side. When moved, it means that this parallel line intersects both the n-side stretched portion and the p-side stretched portion at any position. For example, in FIG. 1A, the area | region of the arrow M points out the area | region which overlaps in a longitudinal direction.
In the overlap region described above, the current tends to concentrate particularly. However, by making the distance α longer than the distance β, the current concentration can be effectively reduced.

  However, it is preferable that the tip of the n-side extending portion does not overlap with the p-side pad portion in one direction. Moreover, it is preferable that the tip of the p-side extending portion does not overlap the n-side pad portion in one direction. Thereby, the electric current concentration which generate | occur | produces between a pad part and an extending | stretching part can be relieve | moderated effectively.

The n-side extending portion may extend in any way as long as it extends from the n-side pad portion. For example, the whole may not necessarily extend along the side but may extend only partially toward the side (see, for example, FIG. 1A), or may extend along the center line in the short direction of the semiconductor light emitting element. Good (see, eg, FIG. 2).
Since the n-side extension portion is formed on the exposed region of the n-type nitride semiconductor layer as described above, the shape corresponds to the shape of the exposed region, and thus extends in one direction including the exposed region. The extension line to the line coincides with the extension line extending including the n-side extension part extending in one direction.

As long as the p-side extending portion extends from the p-side pad portion and further extends to the n-side pad portion side, the p-side extending portion may extend in any manner. The p-side stretched portion is at least partially stretched over a region extending from the central region of the semiconductor light emitting element to a region opposite to the region where the n-side stretched portion is disposed with respect to the central region. Is preferred. For example, it may extend linearly from the end of the p-side pad (for example, see FIG. 1A) or may have a bent portion and extend linearly (for example, see FIG. 2). When extending from the end portion of the p-side pad portion, the direction preferably extends along the long side of the semiconductor light emitting element, that is, in the direction parallel to the long side.
When the p-side extension portion extends from the center of the p-side pad portion, Vf can be further improved while improving the uniformity of the current distribution. In this case, particularly when the p-side stretched portion approaches the n-side stretched portion, current concentration is likely to occur. However, the current concentration is increased by bringing the p-side stretched portion closer to the n-side stretched portion at a place other than the overlap portion. Vf can be further improved while reducing.

(Protective film)
The upper surface of the semiconductor light emitting device of the present invention is usually formed by a protective film, and in order to secure wire bonding to the n-side pad portion and the p-side pad portion, these n-side pad portion and p-side pad portion. An opening (see protective film 6 in FIG. 1 and the like) is provided immediately above. As the protective film here, the same film as the insulating film described above can be used.

In the present invention, the light guided in the semiconductor layer, particularly in the n-type nitride semiconductor layer, is projected at the interface between the substrate and the n-side nitride semiconductor layer depending on the shape and arrangement of the protrusions on the substrate surface. The side surface of the portion can efficiently reflect toward the side surface of the semiconductor layer that defines the exposed region. Accordingly, the light efficiently reflected toward the side surface of the semiconductor layer that defines the exposed region can be directed to the light extraction surface, so that the light extraction can be improved more efficiently. In addition, the arrangement and shape of the n-side pad electrode and the p-side pad electrode in the semiconductor light-emitting element make the light emission intensity distribution uniform and reduce the forward voltage drop (Vf), thereby providing a semiconductor with excellent light-emitting characteristics and mountability. A light emitting element can be realized. In particular, by further combining both the shape and arrangement of the convex portions on the substrate surface and the arrangement and shape of the n-side pad electrode and the p-side pad electrode, it is possible to further improve the light extraction efficiency.
Embodiments of the semiconductor light emitting device of the present invention will be specifically described below.

(Embodiment 1)
As shown in FIGS. 1A to 1C, the semiconductor light emitting device 10 of this embodiment includes an n-type nitride semiconductor layer 2, a light emitting layer 3, and a p-type nitride on a substrate 1 having a plurality of convex portions 1 a. The semiconductor layers 4 are laminated in this order to form a rectangular planar shape. The semiconductor light emitting element 10 has a rectangular shape of 240 μm × 800 μm, for example, when viewed from the electrode arrangement surface side.
In a partial region of the semiconductor light emitting device 10, the n-type nitride semiconductor layer 2 is slightly removed in the depth direction together with the p-type nitride semiconductor layer 4 and the light-emitting layer 3, and the n-type nitride semiconductor layer 2 is exposed. The exposed region 2a is provided. The exposed region 2a has an extended region in one direction, for example, the arrow Z direction (so-called longitudinal direction) in FIG. 1A, and a direction perpendicular to the one direction, that is, a central region in the short direction of the semiconductor light emitting element. (A region straddling the center line X), a region disposed substantially adjacent to the short side of the semiconductor light emitting element 10 and a region including one corner portion of the semiconductor light emitting element 10 and extending in one direction And have.

The plurality of convex portions 1a on the surface of the substrate 1 are schematically shown in an enlarged manner in the Y region of FIG. 1A, and are arranged over the entire surface of the substrate 1 in the shape and orientation as shown in FIG. 1D.
That is, the convex portion 1a has a plurality of vertices, for example, three vertices A, B, and C, and the two adjacent vertices A and B extend in one direction from the exposed region 2a. It is arranged so as to be the shortest and equidistant with respect to Q. In other words, the line G connecting adjacent vertices A and B is substantially parallel to the extension line Q extending in one direction and close to the extension line Q extending in one direction within the convex portion 1a. That is, in FIG. 1A, they are arranged on the left side.
Thereby, light can be effectively diffusely reflected at the interface between the substrate 1 and the n-type nitride semiconductor layer 2, and in particular, the light irradiated on the side surface d of the convex portion 1 a is reflected by the n-type nitride semiconductor layer. Reflected by the side surface of the exposed region 2a, and due to this, reflection to the light extraction side can be further ensured.

  However, since the shape and arrangement of the convex portions 1a are arranged over the entire surface of the substrate 1 as shown in FIG. 1D, the extension lines Q of the vertices A and B described above are formed on the surface of the substrate 1 immediately below the exposed region 2a. The shortest and equidistant relationship to is not necessarily applicable.

  In this semiconductor light emitting device 10, the convex portion 1a has a shape of a bottom surface that forms a regular triangle having a side of about 2.5 μm by a line connecting vertices A, B, and C, and a taper angle of about 60 °. It has a frustum shape. The side surfaces d, e, and f arranged between the vertices A and B, the vertices B and C, and the vertices A and C each have a convex curvature toward the outside, and the upper surface j of the convex portion 1a is It has a shape close to a circle based on an equilateral triangle. In other words, the vertices of the equilateral triangle are rounded, and each side is bulged outward and rounded. The height of the convex portion 1a is, for example, about 1 μm. The distance (pitch) between adjacent vertices A is about 3.5 μm.

  The convex portion 1a has the shape and arrangement of FIG. 1D as described above on the surface of the substrate 1, and as shown in FIG. 1E, the line connecting the two vertices of each convex portion 1a is adjacent to the oblique direction. In the part 1a, it arrange | positions so that a straight line may be comprised. In other words, when the arrangement of the convex portions 1a is the first column, the second column, and the third column from the right, the second column is arranged in the column direction (vertical direction) by a half pitch of the convex portion 1a from the first column. The third row is shifted from the second row by a half pitch of the convex portion 1a in the row direction. Therefore, each convex part 1a of the third column overlaps with the convex part 1a of the first column in the row direction (lateral direction). According to such an arrangement, the convex portion 1a can effectively irradiate the side surface of the convex portion 1a with light in the lateral direction, and can surely reflect in the light extraction direction, thereby improving the light extraction effect. be able to.

  Further, as shown in FIG. 1F, the distribution of the convex portions 1a is preferably arranged so as to shift by half the width of the convex portions 1a for each row of the convex portions 1a. That is, in FIG. 1F, when the arrangement of the convex portions 1a is the first row, the second row, and the third row from the top, the second row extends in the row direction (lateral direction) from the first row by a half pitch of the convex portion 1a. The third row is shifted from the second row in the row direction by a half pitch of the convex portion 1a. Accordingly, each convex portion 1a in the third row overlaps with the convex portion 1a in the first row in the column direction (vertical direction). According to such an arrangement, in the distribution shown in FIG. 1E, the light passage L in the lateral direction can be further blocked (see arrow L in FIG. 1F). Reflection in the extraction direction can be made more reliable, and the light extraction effect can be further improved.

  The n-side electrode is formed by an n-side translucent conductive film 11n formed over most of the surface of the exposed region 2a of the n-type nitride semiconductor layer and an n-side pad electrode 11 stacked thereon. The p-side electrode is formed by a p-side translucent conductive film 12p formed on substantially the entire surface of the p-type nitride semiconductor layer and a p-side pad electrode 12 laminated thereon.

  The n-side pad electrode 11 has an n-side pad portion 11a and an n-side extending portion 11b. The n-side pad portion 11 a is disposed in the central region in the short side direction (region straddling the center line X), and is disposed substantially adjacent to the short side of the semiconductor light emitting element 10. The n-side extending portion 11b has a rounded shape at the corner portion of the semiconductor light emitting element 10 so as to extend away from the short side and extend toward the long side without extending along the short side from the n-side pad portion 11a. Has been placed. The n-side extending portion 11b has a portion that is slightly wider from the n-side extending portion 11b toward the n-side pad portion 11a.

  The p-side pad electrode 12 has a p-side pad portion 12a and a p-side extending portion 12b. The p-side pad portion 12a is disposed in a central region in the short side direction (region straddling X), and the semiconductor light emitting element 10 starts from a short side different from the short side where the n-side pad portion 11a of the semiconductor light emitting element 10 is disposed. It is biased to the center side of the child. The p-side extending portion 12b is parallel to the long side of the semiconductor light emitting element 10 from the end portion of the p-side pad portion 12a, that is, the end portion in the short direction on the side different from the side where the n-side extending portion 11b is arranged. It extends in a direction approaching the n-side pad portion 11a. In other words, the p-side extending portion 12 b extends in a region opposite to the region where the n-side extending portion 11 b is disposed with respect to the central region of the semiconductor light emitting element 10.

The p-side pad portion 12 a arranged so as to be deviated from the short side to the center side of the semiconductor light emitting element 10 is arranged, for example, about 18% of the long side length of the semiconductor light emitting element 10. Specifically, the distance from the end portion of the semiconductor light emitting element 10 to the center of the p-side pad portion 12a is about 150 μm.
As described above, since the p-side pad portion 12a is arranged so as to be biased toward the center side, it is possible to secure a region capable of emitting light on the entire circumference of the p-side pad portion 12a, and to make the light emission intensity distribution more uniform. Is possible.

The tip of the n-side extending portion 11b does not overlap with the p-side pad portion 12a in the longitudinal direction, and the tip of the p-side extending portion 12b does not overlap with the n-side pad portion 11a in the longitudinal direction. .
As a result, current concentration does not occur between the tip of the n-side extending portion 11b and the p-side pad portion 12a, and between the tip of the p-side extending portion 12b and the n-side pad portion 11a, and the semiconductor light emitting device It is possible to achieve a more uniform light intensity distribution throughout.

In addition, as shown in FIGS. 1A to 1C, this semiconductor light emitting device has a p-type nitride so as to surround directly under the p-side pad electrode 12 and its outer periphery via the p-side light-transmitting conductive film 12 p. An insulating film 5 (film thickness: 300 nm) made of SiO ₂ is disposed on the semiconductor layer 4. This relaxes the direct supply of current from the p-side pad electrode 12 to which current is directly applied to the p-type nitride semiconductor layer 4 immediately below the p-type pad semiconductor electrode 4 so as to be more uniform over the entire surface of the semiconductor light emitting device. It is possible to distribute the current.

In this way, the directivity characteristics of the semiconductor light emitting device in the case where the convex portions 1a are formed on the surface of the substrate 1 with a specific shape and arrangement were measured using a light distribution meter. The central portion of the semiconductor light emitting device 10 in the longitudinal direction is taken as line II-II ′ in FIG. 1A, the normal direction on the side surface of the exposed region 2a (left side in FIG. 1A) is 0 °, and the normal direction on the top surface of the semiconductor light emitting device 10 ( FIG. 1G shows a plot of light intensity measured with 90 ° as the front side of the paper in FIG. 1A and 180 ° as the normal direction on the side opposite to the exposed region 2a (right side in FIG. 1A).
As shown by a circle in FIG. 1G, the side surface d disposed between the vertices A and B of the convex portion 1a faces the exposed region 2a extending in the arrow Z direction (longitudinal direction) in FIG. Light can be emitted strongly to the side where the side surface d of 1a exists.

Moreover, light extraction efficiency was simulated assuming the sample which mounted the semiconductor light-emitting device 10 mentioned above on the reflecting plate (for example, silver) with die-bonding resin, and sealed the whole with the epoxy resin.
As a comparative example, in the semiconductor light emitting device 10, the shape of the convex portion 1a is the same, but the arrangement is as shown in FIG. 4A, that is, two adjacent vertices Ab and Bb, Bb and Cb, and Cb and Ab. Are arranged so as not to be the shortest and equidistant with respect to an extension line extending in one direction including the exposed region (Comparative Example 1), as shown in FIG. 4B, that is, adjacent to each other. The two apexes Ad and Bd, Bd and Cd, and Cd and Ad are arranged so as not to be the shortest and equidistant from the extension line extending in one direction including the exposed region (Comparative Example 2). Except for the above, a semiconductor light emitting device having the same configuration was fabricated, and the light extraction efficiency was simulated assuming a sample in the same manner as described above.
As a result, in the semiconductor light emitting device 10, the light extraction efficiency was improved by about 6 to 7% as compared with Comparative Examples 1 and 2. Specifically, assuming that the light extraction efficiency of the semiconductor light emitting device 10 is 100%, in Comparative Examples 1 and 2, only the light extraction efficiency of about 93 to 94% was simulated.
Thereby, in the semiconductor light emitting element 10 of this embodiment, it was confirmed that light extraction efficiency improves about 6 to 7% with respect to a comparative example.

  Further, in this semiconductor light emitting device, since the n-side pad portion 11a and the p-side pad portion 12a are disposed in the central region in the short direction, the conductive wire is bonded when the conductive wire is bonded to the pad electrode. Can be joined at an appropriate place without interfering with peripheral members and the like, so that problems such as wire breakage are not caused, and mountability can be ensured.

(Embodiment 2)
In the semiconductor light emitting device 20 of this embodiment, as shown in FIG. 2, the exposed region 72a of the n-type nitride semiconductor layer is formed inside the semiconductor light emitting device 20, and accordingly, the p-side electrode and the n-side are formed. The arrangement of the electrodes is different from that of the first embodiment.
In other words, in this semiconductor light emitting device 20, the exposed region 72a is disposed in the central region (region straddling X) in the short side direction, and a region close to a circle disposed in a biased manner inside the semiconductor light emitting device 20 and its circular shape. And a region extending from the region close to the central region of the semiconductor light emitting element 20 to the semiconductor light emitting device 20.
In the n-side electrode, a translucent conductive film 21 is formed on substantially the entire surface of the exposed region 72a, and an n-side pad electrode 21n is formed thereon. The n-side pad electrode 21n includes an n-side pad portion 21a disposed on a region close to a circle and an n-side extending portion 21b extending from the region to the central region of the semiconductor light emitting element 20.

  The p-side electrode is a central region in the short direction (a region straddling the center line X), from the region substantially adjacent to the short side of the semiconductor light emitting element 20 and its both sides, from the short side without being along the short side. A translucent conductive film 22 that is spaced apart and extends toward the long side, and is disposed on the rounded region at the corner of the semiconductor light emitting element 20, and a central region in the short direction. The p-side pad portion 22a and the p-side extending portion 22b extending from both sides thereof.

With the arrangement of the exposed region 72a of the n-type nitride semiconductor layer, an extension line (W in FIG. 2) extending including the exposed region 72a, that is, the short direction of the semiconductor light emitting element 20 2 with respect to FIG. 2 so that the two adjacent vertices of the bottom surface of the convex portion formed on the substrate 1 with the center line of On the right side with respect to the extension line W (the area indicated by the arrow Wr in FIG. 2), the area Y has the shape and orientation shown in FIG. In the area indicated by the arrow W1), the shape and orientation shown in FIG.
That is, in the region of the arrow Wr in FIG. 2, as shown in FIG. 1D, the line G connecting the adjacent vertices A and B is substantially parallel to the extension line W extending in one direction, and The line Gc connecting the adjacent vertices Ac and Bc is substantially connected to the extension line W, as shown in FIG. They are parallel and are arranged on the side close to the extension line W and on the right side in the convex portion 1ab.

The structure is substantially the same as that of the semiconductor light emitting device 10 except that the position and shape of the protruding portion 1a of the substrate and the exposed portion of the n-type nitride semiconductor layer, the n-side electrode, and the p-side electrode are different.
In this semiconductor light emitting device 20 as well, the same effect including the light extraction efficiency substantially the same as that of the semiconductor light emitting device 10 can be obtained.

(Another form)
As shown in FIG. 5, the semiconductor light emitting device 10 a of this embodiment is substantially the same except that the convex portions 1 a formed on the surface of the substrate 1 are arranged in the horizontal direction opposite to the semiconductor light emitting device 10. A configuration similar to that of the semiconductor light emitting element 10 may be employed.
In other words, as shown in FIG. 3, all the convex portions 1a are such that the line Gc connecting the adjacent vertices Ac and Bc is equidistant (that is, substantially parallel) with respect to the extension line Q. It is arranged on the side far from the extension line Q and on the right side in 1a.

Using this semiconductor light emitting element 10a, as in the first embodiment, assuming a sample mounted on a reflector (for example, silver) with a die bond resin and sealed entirely with an epoxy resin, the light extraction efficiency is improved. Simulated.
As a result, in the semiconductor light emitting device 10a, when the light extraction efficiency of the semiconductor light emitting device 10 in the first embodiment was set to 100%, a light extraction efficiency of approximately 99.5% was simulated.
Thereby, in the semiconductor light emitting element 10a of this embodiment, it was confirmed that the light extraction efficiency is improved by about 5.5 to 6% as compared with the comparative example.

(Embodiment 3)
The semiconductor light emitting device of this embodiment is substantially the same as the semiconductor light emitting device 20 except that the convex portion 1a formed on the surface of the substrate 1 is arranged over the entire surface in the shape and orientation of the convex portion shown in FIG. 1D. The same as the semiconductor light emitting device 20.
Also in this semiconductor light emitting device, substantially the same effect including the same light extraction efficiency as that of the semiconductor light emitting device 20 can be obtained.

(Embodiment 4)
The semiconductor light emitting device of this embodiment is substantially the same as the semiconductor light emitting device 20 except that the convex portion 1a formed on the surface of the substrate 1 is arranged over the entire surface in the shape and orientation of the convex portion shown in FIG. The same as the semiconductor light emitting device 20.
Also in this semiconductor light emitting device, substantially the same effect including the same light extraction efficiency as that of the semiconductor light emitting device 20 can be obtained.

  The semiconductor light emitting device of the present invention can be widely used for illumination light sources, LED displays, backlight light sources such as mobile phones, traffic lights, illumination switches, in-vehicle stop lamps, various sensors and various indicators.

DESCRIPTION OF SYMBOLS 1 Substrate 1a, 1aa, 1ab Convex part 2 N-type nitride semiconductor layer 2a, 72a Exposed region 3 Active layer 4 P-type nitride semiconductor layer 5 Insulating film 6 Protective film 10, 10a, 20 Semiconductor light emitting element 11n, 21n n side Translucent conductive film 11, 21 n-side pad electrode 11a, 21a n-side pad portion 11b, 21b n-side extending portion 12p, 22p p-side translucent conductive film 12, 22 p-side pad electrode 12a, 22a p-side pad portion 12b, 22b p-side extension A, B, C, Ab, Bb, Cb, Ac, Bc, Cc, Ad, Bd, Cd Vertex D, E, F, Dc, Ec, Fc Line forming the bottom of the convex portion G, H, K, Gc, Hc, Kc Line connecting two vertices d, e, f, dc, ec, fc Side surface of convex part j, jc Upper surface of convex part

Claims (8)

A semiconductor light emitting device configured by laminating an n-type nitride semiconductor layer, a light emitting layer, and a p type nitride semiconductor layer in this order on a substrate having a plurality of convex portions on the surface,
The n-type nitride semiconductor layer has an exposed region extending in one direction at least in a partial region,
The convex portion has a plurality of vertices in its bottom shape,
Among the convex portions, the convex portions arranged so that two adjacent vertices are the shortest and equidistant from an extension line extending in one direction including the exposed region occupy more than half of the whole. A semiconductor light emitting element characterized by the above.   The semiconductor light emitting element according to claim 1, wherein the convex portion has a shape in which a bottom surface has three vertices.   The semiconductor light emitting element according to claim 1, wherein the convex portion has a frustum shape or a cone shape.   The plurality of convex portions constitutes a plurality of rows parallel to the extension line, and the convex portions of two adjacent rows among the plurality of rows are arranged with a shift of ½ pitch. Item 4. The semiconductor light-emitting device according to any one of Items 1 to 3.   The plurality of convex portions constitutes a plurality of rows perpendicular to the extension line, and the convex portions of two adjacent rows among the plurality of rows are arranged so as to be shifted from each other by ½ pitch. Item 4. The semiconductor light-emitting device according to any one of Items 1 to 3.   The semiconductor light-emitting element according to claim 1, wherein the semiconductor light-emitting element has a rectangular planar shape, and the one direction is a direction parallel to or substantially parallel to a long side of the rectangle.   An n-side pad electrode is disposed on a part of the exposed region of the n-type nitride semiconductor layer, and the n-side pad electrode is disposed on the n-side disposed in a central region in a direction orthogonal to the one direction. The semiconductor light emitting element according to claim 1, comprising a pad portion and an n-side extending portion extending from the n-side pad portion and extending in the one direction. An extension line extending in one direction including the exposed region coincides with an extension line extending including the n-side extension portion extending in the one direction;
Of the convex portions, two or more adjacent vertices are shortest and equidistant with respect to an extension line extending in one direction including the n-side extending portion, and more than half of the total convex portions. The semiconductor light-emitting device according to claim 7, wherein:

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