JP2011082248A - Semiconductor light emitting element and method of manufacturing the same, and lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element that can have high light extraction efficiency even in a vertical direction of the semiconductor light emitting element and a method of manufacturing the same, and a lamp having excellent light emission characteristics. <P>SOLUTION: The semiconductor light emitting element includes a transparent substrate 10 having a principal surface 11 formed by providing a plurality of projections 13 on a crystal growth surface 12, and a laminated semiconductor layer formed on the principal surface 11 of the transparent substrate 10 and including at least a light emitting layer, wherein the projections 13 each comprises a multilayer laminate formed by alternately laminating a first thin film 13A and a second thin film 13B differing in refractive index from the first thin film 13A. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device having a light emitting diode (LED) structure, a method for manufacturing the same, and a lamp.

In recent years, group III nitride semiconductors have attracted attention as materials for semiconductor light emitting devices that emit light of short wavelengths. Group III nitride semiconductors are represented by the general formula Al _x Ga _y In _z N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z = 1), and include various sapphire single crystals. It is formed on a substrate made of an oxide or a group III-V compound by a metal organic chemical vapor deposition method (MOCVD method), a molecular beam epitaxy method (MBE method) or the like.

  In a general semiconductor light emitting device using the above materials, an n-type semiconductor layer made of a group III nitride semiconductor, a light emitting layer, and a p-type semiconductor layer are laminated in this order on a substrate made of a sapphire single crystal or the like. The Here, since the substrate made of a sapphire single crystal is an insulator, the element structure is generally such that the positive electrode formed on the p-type semiconductor layer and the negative electrode formed on the n-type semiconductor layer are coplanar. It becomes the structure that exists above. Such a semiconductor light emitting device has a face-up method in which light is extracted from the p-type semiconductor side using a transparent electrode for the positive electrode, and a flip in which light is extracted from the transparent substrate side using a highly reflective film such as Ag for the positive electrode. There are two types: chip type.

  External quantum efficiency is used as an index of the output of such a light emitting element. The external quantum efficiency is a product of the internal quantum efficiency and the light extraction efficiency. If this external quantum efficiency is high, it can be said to be a semiconductor light emitting device having a high light emission output. Here, the internal quantum efficiency is the rate at which the energy of the current injected into the device is converted to light in the light emitting layer, and the light extraction efficiency is the light generated in the light emitting layer outside the light emitting device. This is the ratio of light that can be extracted.

  As a method for improving the light extraction efficiency of the semiconductor light emitting device, for example, a technique for reducing light confinement inside the semiconductor light emitting device by forming irregularities on the light extraction surface of the semiconductor light emitting device on the semiconductor layer side, etc. Has been proposed (see, for example, Patent Document 1).

  For the purpose of improving crystallinity, a method has been proposed in which irregularities are formed on the surface of a substrate made of sapphire and a group III nitride semiconductor layer is grown thereon (see, for example, Patent Document 2). According to such a technique, it is possible to reduce crystal defects and improve internal quantum efficiency by utilizing the lateral growth of crystals due to the unevenness formed on the surface of the substrate.

  Here, as in the technique described in Patent Document 2, when unevenness is provided on a substrate, for example, by processing the substrate surface by an etching method or the like, a convex portion of the same material as the substrate material is formed on the substrate surface. It is common to provide it. As described above, by providing the convex portion on the transparent substrate, the light emitted from the light emitting layer is scattered by the surface of the transparent substrate having the convex portion. Thus, the effect of improving the light extraction performance can be obtained. However, such a configuration has a problem that light extraction from the semiconductor light emitting element in the vertical direction is not sufficient.

Various other proposals have been made as techniques for improving the light extraction efficiency of the semiconductor light emitting device. For example, a technique has been proposed in which a layer having a so-called DBR (Distributed Bragg Reflector) structure in which silicon oxide and titanium oxide are alternately stacked is provided on the top of a gallium nitride layer (see, for example, Patent Document 3). reference).
In addition, in order to efficiently scatter and emit light emitted from the light emitting layer from the substrate side, a technique for forming a convex portion made of silicon oxide on a semiconductor crystal growth surface of a transparent substrate made of sapphire has been proposed ( For example, see Patent Document 4).

In addition, a technique has been proposed that improves the light extraction efficiency from the surface of the semiconductor light-emitting element by providing a DBR layer having unevenness between the substrate and the semiconductor layer to diffusely reflect the light emitted from the light-emitting layer. (For example, see Patent Document 5).
In addition, by providing a DBR mirror layer in which silicon oxide and titanium oxide are alternately stacked between a substrate and a semiconductor layer, the technology for reducing light absorption by the substrate for crystal growth and improving light extraction efficiency Has been proposed (see, for example, Patent Document 6).

  In addition, by providing a DBR film in which silicon oxide and titanium oxide are alternately stacked between the buffer layer and the semiconductor layer formed on the substrate, the crystallinity of the semiconductor layer including the light-emitting layer is improved, and light emission output is achieved. Has been proposed (see, for example, Patent Document 7).

  Also proposed is a technique for improving the light extraction efficiency from the surface of a semiconductor light emitting device by providing a DBR reflection layer in which AlGaN and GaN are alternately stacked between a buffer layer and a semiconductor layer formed on a substrate. (For example, see Patent Document 8).

Japanese Patent No. 2836687 JP 2002-280611 A JP 2002-319708 A JP 2007-109793 A JP 2008-66442 A JP 2008-2111164 A JP 2009-16505 A JP 2003-309287 A

  However, any of the techniques described in any of the above-mentioned patent documents has a problem that light extraction from the semiconductor light emitting element in the vertical direction is not sufficient and the light emission intensity cannot be improved. Moreover, even when the light extraction has a sufficient structure, there is a problem that the crystallinity is lowered and the internal quantum efficiency is lowered.

The present invention has been made in view of the above problems, and provides a semiconductor light-emitting device that has high light extraction efficiency even in the vertical direction of the semiconductor light-emitting device and has excellent device characteristics such as light emission intensity, and a method for manufacturing the same. With the goal.
Furthermore, an object of the present invention is to provide a lamp that uses the semiconductor light emitting element and has excellent light emission characteristics.

As a result of intensive studies to solve the above problems, the present inventor has made the light extraction particularly in the vertical direction of the semiconductor light emitting device by optimizing the structure and material of the convex portions provided on the crystal growth surface side of the transparent substrate. The inventors have found that the efficiency can be improved, and have completed the present invention.
That is, the present invention relates to the following.

[1] A transparent substrate having a main surface on which a plurality of convex portions are provided on a crystal growth surface, and a laminated semiconductor layer including at least a light emitting layer formed on the main surface of the transparent substrate. The convex portion is composed of a multilayer laminate in which a first thin film and a second thin film having a refractive index different from the refractive index of the first thin film are alternately laminated. A semiconductor light emitting device.
[2] Multilayer lamination in which the third thin film and the fourth thin film having a refractive index different from the refractive index of the third thin film are alternately laminated on the other surface opposite to the main surface of the transparent substrate. The semiconductor light-emitting device according to the above [1], wherein a film is provided.
[3] The semiconductor light-emitting element according to the above [1] or [2], wherein an upper surface of the convex portion is a flat surface.
[4] The above-mentioned [1], wherein the first thin film and the second thin film are each made of any one of titanium oxide, silicon oxide, silicon nitride, tantalum oxide, zirconium oxide, and niobium oxide. ] The semiconductor light-emitting device according to any one of [3].
[5] The above-mentioned [2], wherein the third thin film and the fourth thin film are made of any one of a thin film material selected from titanium oxide, silicon oxide, silicon nitride, tantalum oxide, zirconium oxide, and niobium oxide. ] The semiconductor light-emitting device of any one of [4].

[6] The convex portion has a base width of 0.05 to 4 μm, a height from the crystal growth surface in a range of 0.05 to 4 μm, and a quarter or more of the base width. The semiconductor light emitting device according to any one of [1] to [5], wherein an interval between adjacent convex portions is 0.5 to 5 times the base width. .
[7] The semiconductor light-emitting element according to any one of [1] to [6], wherein the convex portion has a shape whose outer shape gradually decreases toward the top.

[8] The stacked semiconductor layer, wherein at least an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer are stacked in this order on the main surface of the transparent substrate. The semiconductor light-emitting device according to any one of [1] to [7].
[9] On the main surface of the transparent substrate, a buffer layer and an underlayer are laminated in this order so as to cover the crystal growth surface and the convex portion, and the laminated semiconductor layer is formed on the underlayer. The semiconductor light-emitting device according to [8] above, wherein

[10] By alternately laminating the first thin film and the second thin film having a refractive index different from the refractive index of the first thin film on the crystal growth surface, a plurality of convex portions made of a multilayer laminate are formed. A substrate forming step of forming a transparent substrate having a provided main surface; and a semiconductor layer forming step of forming a laminated semiconductor layer including at least a light emitting layer on the main surface of the transparent substrate. A method for producing a semiconductor light emitting device.
[11] In the substrate forming step, a third thin film and a fourth thin film having a refractive index different from the refractive index of the third thin film are further provided on the other surface opposite to the main surface of the transparent substrate. The method for producing a semiconductor light-emitting element according to the above [10], wherein a multilayer laminated film is formed by alternately laminating.
[12] In the substrate forming step, the first thin film and the second thin film are formed using any one of thin film materials of titanium oxide, silicon oxide, silicon nitride, tantalum oxide, zirconium oxide, and niobium oxide, respectively. The method for producing a semiconductor light-emitting element according to the above [10] or [11], wherein:
[13] In the substrate forming step, the third thin film and the fourth thin film are formed using any one of thin film materials of titanium oxide, silicon oxide, silicon nitride, tantalum oxide, zirconium oxide, and niobium oxide, respectively. The method for manufacturing a semiconductor light-emitting element according to any one of [10] to [12] above, wherein:
[14] In the substrate forming step, thin film materials constituting the first thin film and the second thin film are alternately and sequentially deposited on the crystal growth surface, and then a resist layer is formed on the thin film material, After patterning the resist layer, the thin film material is etched using a fluorine-based etching gas to form the convex portion formed of a multilayer laminate, wherein [10] to [13] The manufacturing method of the semiconductor light-emitting device of any one.

[15] In the semiconductor layer forming step, the stacked semiconductor layer is formed by forming at least an n-type semiconductor layer, the light emitting layer, and a p-type semiconductor layer in this order on the main surface of the transparent substrate. The method for manufacturing a semiconductor light-emitting element according to any one of [10] to [14] above, wherein:
[16] In the semiconductor layer forming step, a buffer layer and an underlayer are laminated in this order on the main surface of the transparent substrate so as to cover the crystal growth surface and the convex portion, The method for producing a semiconductor light-emitting element according to the above [15], wherein a laminated semiconductor layer is formed.

[17] A semiconductor light-emitting device obtained by the manufacturing method according to any one of [10] to [16].
[18] A lamp comprising the semiconductor light-emitting device according to any one of [1] to [9] and [17].

  According to the semiconductor light emitting device of the present invention, a laminated semiconductor layer including a transparent substrate having a main surface provided with a plurality of convex portions on a crystal growth surface, and at least a light emitting layer formed on the main surface of the transparent substrate. And a convex portion provided on the crystal growth surface is formed by alternately laminating a first thin film and a second thin film having a refractive index different from the refractive index of the first thin film. Because it is composed of a multi-layered laminate, the light emitted from the light emitting layer and directed to the convex part is totally reflected in the direction perpendicular to the convex part, while the light directed from the oblique direction to the convex part is transmitted. Or scatter. As a result, the light totally reflected by the convex portion becomes a component of light emitted in the vertical direction of the semiconductor light emitting device, so that the light extraction efficiency in the vertical direction is improved and a semiconductor light emitting device with high emission intensity is realized. it can.

  According to the method for manufacturing a semiconductor light emitting device of the present invention, the first thin film and the second thin film having a refractive index different from the refractive index of the first thin film are alternately stacked on the crystal growth surface. Then, a substrate forming step of forming a transparent substrate having a principal surface provided with a plurality of convex portions formed of a multilayer laminate, and forming a laminated semiconductor layer including at least a light emitting layer on the principal surface of the transparent substrate And a semiconductor layer forming step. Therefore, the present invention is excellent in light emission intensity by forming a laminated semiconductor layer on a transparent substrate having a convex portion made of a multilayer laminate having a DBR structure as described above. The semiconductor light emitting device can be obtained.

  Furthermore, since the lamp according to the present invention uses the semiconductor light emitting device of the present invention, the lamp has excellent light emission characteristics.

It is a figure which illustrates typically an example of the semiconductor light-emitting device concerning this invention, and is the schematic which shows the cross-section of the transparent substrate in which the convex part which consists of a multilayer laminated body was provided on the crystal growth surface. FIG. 2 is a diagram schematically illustrating an example of a semiconductor light emitting device according to the present invention, and is a cross-sectional view showing a semiconductor light emitting device in which a buffer layer, a base layer, and a laminated semiconductor layer are formed on the transparent substrate shown in FIG. 1. is there. It is a figure which illustrates typically an example of the semiconductor light-emitting device which concerns on this invention, and is a graph which shows the relationship between the reflectance of a transparent substrate, and light emission wavelength. It is a figure which illustrates typically an example of the manufacturing method of the semiconductor light-emitting device based on this invention. It is the schematic explaining typically an example of the lamp | ramp comprised using the semiconductor light-emitting device which concerns on this invention.

Hereinafter, a semiconductor light emitting device (hereinafter sometimes abbreviated as a light emitting device) according to the present invention, a manufacturing method thereof, and an embodiment of a lamp will be described with reference to the drawings as appropriate.
FIG. 1 is a view for explaining a main part of the light emitting device 1 according to the present invention, and shows a detailed cross-sectional structure of a convex portion 13 provided on a crystal growth surface 12 of a transparent substrate 10. 2 shows a light emission in which a buffer layer 2 and a base layer 3 are formed on the main surface 11 of the transparent substrate 10 shown in FIG. 1, and a laminated semiconductor layer 20 is further formed on the base layer 3. FIG. 5 is a cross-sectional view for explaining the element 1, in which a reference numeral 7 denotes a translucent positive electrode, a reference numeral 8 denotes a positive electrode, and a reference numeral 9 denotes a negative electrode. FIG. 3 is a graph showing the relationship between the light reflectance and the light emission wavelength of the transparent substrate provided in the light emitting device of the present invention. FIG. 4 is a cross-sectional view illustrating a process of the method for manufacturing the light-emitting element 1 according to the present invention, and FIG. 5 is a cross-sectional view illustrating a lamp 30 using the light-emitting element 1 of the present embodiment.

  The drawings referred to in the following description are drawings for explaining a semiconductor light emitting device, a method for manufacturing the same, and a lamp. The size, thickness, dimensions, etc. of the respective parts shown in the drawings are the dimensions of the actual semiconductor light emitting device, etc. The relationship is different.

[Semiconductor light emitting device]
The semiconductor light emitting device 1 of the present embodiment includes a transparent substrate 10 having a main surface 11 in which a plurality of convex portions 13 are provided on a crystal growth surface 12, and the transparent substrate 10 as in the example shown in FIGS. The laminated semiconductor layer 20 including at least the light emitting layer 5 formed on the main surface 11 of the substrate 10 is provided. The convex portion 13 is different from the refractive index of the first thin film 13A and the first thin film 13A. It is generally configured from a multilayer laminate in which second thin films 13B having a refractive index are alternately laminated.
In the light emitting device 1 shown in FIG. 2, the buffer layer 2 and the base layer 3 are laminated in this order on the crystal growth surface 12 of the transparent substrate 10 so as to cover the convex portion 13. A stacked semiconductor layer 20 is formed by laminating the n-type semiconductor layer 4, the light emitting layer 5, and the p-type semiconductor layer 6 in this order.

  In the example shown in FIG. 2, the third thin film 16 </ b> A and the fourth thin film 16 </ b> B having a refractive index different from the refractive index of the third thin film 16 </ b> A are provided on the other surface 15 side opposite to the main surface 11 of the transparent substrate 10. Are laminated alternately. The multilayer laminated film 16 is provided.

The light-emitting element 1 of the example described in the present embodiment is a single-sided electrode type as in the example shown in FIG. 2, and on the transparent substrate 10 as described above, the buffer layer 2 and Ga as a group III element. And a laminated semiconductor layer 20 made of a group III nitride semiconductor containing Nb.
Hereinafter, the laminated structure of the light emitting element 1 will be described in detail.

"Transparent substrate"
The transparent substrate 10 used in this embodiment has a main surface 11 provided with a convex portion 13 on the crystal growth surface 12 of the base 10A. In the example shown in FIGS. The outer shape gradually decreases toward the top. Further, in the illustrated convex portion 13, the upper surface 13c is a flat surface, and the planar shape of the base portion 13a is a circle.

"Substrate (substrate) material"
In the light emitting device 1 of the present embodiment, as a substrate material that can be used for the base 10A constituting the transparent substrate 10, a group III nitride semiconductor crystal can be epitaxially grown on the surface, and is high by a predetermined treatment. The substrate material is not particularly limited as long as transparency is obtained, and various materials can be selected and used. For example, sapphire, SiC, silicon, zinc oxide, magnesium oxide, manganese oxide, zirconium oxide, manganese zinc iron, magnesium aluminum oxide, zirconium boride, gallium oxide, indium oxide, lithium gallium oxide, lithium aluminum oxide, neodymium gallium oxide Lanthanum strontium oxide aluminum tantalum, strontium titanium oxide, titanium oxide, hafnium, tungsten, molybdenum and the like. Of the above substrate materials, sapphire is particularly preferably used, and a buffer layer 2 described later is preferably formed on the C surface of the base 10A made of sapphire.

`` Convex part ''
As described above, the convex portion 13 is formed of a multilayer laminate in which the first thin film 13A and the second thin film 13B having a refractive index different from the refractive index of the first thin film 13A are alternately laminated. The convex portion 13 is formed on the crystal growth surface 12 of the base body 10A as a layer having a so-called DBR (Distributed Bragg Reflector) structure by the laminated structure.

  The material of the convex portion 13 is not particularly limited, but the first thin film 13A and the second thin film 13B are each a thin film of titanium oxide, silicon oxide, silicon nitride, tantalum oxide, zirconium oxide, or niobium oxide. It can be set as the structure which consists of material. At this time, thin film materials having different light refractive indexes are employed for the thin film material of the first thin film 13A and the thin film material of the second thin film 13B. For example, in the case where the first thin film 13A is formed from titanium oxide and the second thin film 13B is formed from silicon oxide, five layers are alternately stacked to form a pair, and a total of 10 layers are formed. can do.

  Also, the thickness of each layer of the first thin film 13A and the second thin film 13B is not particularly limited. For example, the thickness of one layer is set to about 20 to 100 nm, and the entire protrusion 13, that is, the height of the protrusion 13 is increased. The length h is preferably about 100 to 4000 nm. By setting the film thicknesses of the entire protrusions 13 and the respective layers of the first thin film 13A and the second thin film 13B constituting the protrusions 13 within the above ranges, the light extraction efficiency, which will be described in detail later, is effectively improved.

"Main surface consisting of crystal growth surface and convex part"
The transparent substrate 10 used in the present embodiment is provided with a plurality of convex portions 13 configured as described above. And the part in which the convex part 13 is not formed in the main surface 11 of the transparent substrate 10 is made into the crystal growth surface 12 which consists of C surfaces. Therefore, as in the example shown in FIGS. 1 and 2, the main surface 11 of the transparent substrate 10 is composed of a crystal growth surface 12 formed of a C plane and a plurality of convex portions 13.

  As shown in FIGS. 1 and 2, the convex portion 13 has a shape in which the planar shape of the base portion 13a is substantially circular, the outer shape gradually decreases toward the upper portion, and the side surface 13b is inclined at the upper portion. The outer shape is gradually reduced toward the end. As shown in FIGS. 1 and 2, the planar arrangement of the convex portions 13 is arranged in a substantially grid pattern at equal intervals.

Further, the convex portion 13 in the example shown in FIGS. 1 and 2 has a base width d ₁ in the range of 0.05 to 1.5 μm, a height h in the range of 0.05 to ₁ μm and a quarter of the base width d ₁ . The distance d ₂ between the adjacent convex portions 13 is 0.5 to 5 times the base width d ₁ . Here, the base width d ₁ of the convex portion 13 refers to the length of the maximum width on the bottom side (base portion 13 a) of the convex portion 13. Further, the distance d ₂ between adjacent convex portions 13, refers to the distance between the edge of the base portion 13a of the convex portion 13 in closest proximity.

Distance _{d 2} between the adjacent protrusions 13 is preferably 0.5 to 5 times the base width _{d 1.} When the distance d ₂ between the protrusions 13 is less than 0.5 times the base width d ₁ , it is difficult to promote crystal growth from the C growth surface 12 when the underlayer 3 is epitaxially grown. In addition, it may be difficult to completely cover the convex portion 13 with the base layer 3 through the buffer layer 2, and the flatness of the surface 3 a of the base layer 3 may not be sufficiently obtained. For this reason, when the convex portion 13 is covered with the buffer layer 2 and the base layer 3 and a crystal of each semiconductor layer forming the laminated semiconductor layer is formed on the base layer 3, many pits are formed in the crystal, and the semiconductor light emitting device Output, electrical characteristics, etc. are reduced. Further, when the distance d ₂ between the convex portions 13 exceeds 5 times the base width d ₁ , when the semiconductor light emitting element is formed using the transparent substrate 10, the transparent substrate 10 and the transparent substrate 10 are formed. There is a possibility that the irregular reflection effect of light at the interface with the layer is lowered, and the light extraction efficiency cannot be sufficiently improved.

The base width d ₁ of the convex portion 13 is preferably in the range of 0.05 to 4 μm. When the base width d ₁ of the convex portion 13 is less than 0.05 μm, when the semiconductor light emitting element is formed using the transparent substrate 10, there is a possibility that the effect of irregularly reflecting light may not be obtained. If the base width d ₁ of the convex portion 13 exceeds 4 μm, it becomes difficult to epitaxially grow the base layer 3 so as to cover the convex portion 13 via the buffer layer 2. Even if an underlayer with good flatness and crystallinity can be formed, the strain between the underlayer and the light emitting layer increases, leading to a decrease in internal quantum efficiency.

  The height h of the convex portion 13 from the crystal growth surface 12 is preferably in the range of 0.05 to 4 μm. If the height h of the convex portion 13 is less than 0.05 μm, when the semiconductor light emitting element is formed using the transparent substrate 10, there is a possibility that the effect of irregularly reflecting light cannot be obtained. If the height h of the convex portion 13 exceeds 4 μm, it becomes difficult to epitaxially grow the base layer 3 so as to cover the convex portion 13 via the buffer layer 2, and the flatness of the surface 3 a of the base layer 3. May not be sufficiently obtained.

Moreover, it is preferable that the height h of the convex portion 13 from the crystal growth surface 12 is not less than 1/4 of the base width d ₁ . If it less than 1/4 the height h of the base width d ₁ of the convex portion 13, effects or to diffuse light in case of forming the semiconductor light-emitting device using a transparent substrate 10, the effect of improving the light extraction efficiency sufficient May not be obtained.

  Moreover, it is preferable that the upper limit of the ratio of the area which the convex part 13 occupies on the crystal growth surface 12 is about 60%. When the proportion of the area of the convex portion 13 on the crystal growth surface 12 exceeds 60%, the crystallinity of the buffer layer 2, the underlayer 3 and the laminated semiconductor layer 20 formed thereon is lowered, and the light emission characteristics are deteriorated. There is a risk of doing. In order to obtain the effect of improving the light extraction efficiency according to the present invention, it is preferable that the lower limit of the area ratio of the convex portion 13 on the crystal growth surface 12 is 10% or more.

  In addition, the shape of the convex part 13 is not limited to the example shown in FIG.1 and FIG.2, The effect of this invention is acquired even if it is any shape. For example, in addition to the shape in which the planar shape of the base portion 13a is circular as in the illustrated example, the base portion may be substantially polygonal, and the outer shape may be gradually reduced toward the top, or The side surface may be curved toward the outside. Moreover, the shape in which the inclination angle of the side surface changes in two steps may be used, and it may be a cylindrical shape.

  Further, the form of the planar arrangement of the convex portions 13 is not limited to the example shown in FIGS. 1 and 2. For example, the intervals between the convex portions 13 may not be equal. The form of the planar arrangement of the protrusions 13 may be a quadrangular arrangement, a triangular arrangement, or a random arrangement.

  In the semiconductor light emitting device of the present invention, by providing the transparent substrate 10 having the convex portion 13 having the DBR structure having the above configuration, the light emitted from the laminated semiconductor layer 20 (light emitting layer 5) and directed to the convex portion 13 is The light perpendicular to the convex portion 13 is totally reflected, while the light traveling in the oblique direction with respect to the convex portion 13 is transmitted or scattered. Thereby, the light totally reflected by the convex portion 13 becomes a component of light emitted toward the vertical direction of the semiconductor light emitting element 1 (up and down direction in FIG. 2), so that the light extraction efficiency in the vertical direction is improved, A semiconductor light emitting device 1 with high emission intensity can be realized.

  Further, in the semiconductor light emitting device of the present invention, the light hitting the crystal growth surface 12 of the base body 10 </ b> A made of a sapphire material or the like becomes a normal scattering form and is emitted toward the outside of the semiconductor light emitting device 1.

  Further, in the present invention, the wavelength of the light totally reflected can be adjusted by controlling the film structure of the convex portion having the DBR structure as described above. In this case, in particular, the light having a predetermined wavelength is controlled by controlling the film structure so that the convex portion 13 disposed immediately below the laminated semiconductor layer 20 (the light emitting layer 5) totally reflects the light having the predetermined wavelength. For example, it is possible to increase the emission intensity in the blue wavelength region around 450 nm.

FIG. 3A is a graph showing the relationship between the light reflectance and the wavelength of a transparent substrate having a shape equivalent to the protrusion structure described in Example 2 described later. As shown in FIG. 3 (a), the transparent substrate having the convex portion 13 having the DBR structure defined in the present invention is a transparent substrate having a conventional configuration including the convex portion having a single-layer structure of silicon oxide (described later). It can be seen that the reflectance is particularly high in the blue wavelength region around 450 nm compared to (having a structure equivalent to the protrusion structure described in Comparative Example 2).
Such a semiconductor light emitting device of the present invention including the transparent substrate 10 provided with the convex portion 13 of the DBR structure can obtain a high light emission output.

  Furthermore, according to the configuration of the semiconductor light emitting device of the present invention, the interface between the transparent substrate 10 and the base layer 3 is uneven via the buffer layer 2, so that the light is diffused into the light emitting device due to irregular reflection. Light confinement is reduced, and light extraction efficiency is further improved.

  In the present invention, the transparent substrate 10 has the main surface 10 composed of the crystal growth surface 12 and the convex portion 13 having the above-described structure, whereby the buffer layer 2 is formed on the crystal growth surface 12 composed of the C plane. A base layer 3 is formed so as to further grow laterally and cover the convex portion 13. Thereby, since the underlayer 3 becomes a layer having good crystallinity with suppressed crystal defects, the crystallinity of the laminated semiconductor layer 20 including the light-emitting layer 5 formed thereon is improved and excellent. The semiconductor light emitting device 1 having light emission characteristics can be realized.

"Multilayered film on the other side"
In the semiconductor light emitting device of the present invention, as illustrated in FIGS. 1 and 2, the third thin film 16 </ b> A and the third thin film 16 </ b> A on the other surface 15 side opposite to the main surface 11 of the transparent substrate 10. A configuration in which the multilayer laminated film 16 in which the fourth thin films 16B having a refractive index different from the refractive index are alternately laminated is provided.

  As the material of the multilayer film 16, the third thin film 16A and the fourth thin film 16B are made of titanium oxide, silicon oxide, silicon nitride, tantalum oxide, zirconium oxide, and niobium oxide, respectively, as in the case of the convex portion 13. It consists of any thin film material. Further, the multilayer laminated film 16 is different from the configuration of the convex portion 13 in that it is formed so as to cover the base body 10A on the other surface 15 side.

FIG. 3B is a graph showing the relationship between the reflectance of light and the wavelength of a transparent substrate having a structure equivalent to the backside DBR (DBR thin film laminated structure having no protrusion structure) used in Example 4 described later. It is. As shown in FIG. 3B, the transparent substrate 10 including the multilayer laminated film 16 composed of the third thin film 16A and the fourth thin film 16B having the DBR structure defined in the present invention has a single-layer structure of silicon oxide. It can be seen that the reflectance is particularly high in the wavelength region of 370 to 600 nm as compared with the transparent substrate having the structure as described above.
In the present invention, in addition to the convex portion 13 having the above-described configuration, a multilayer laminated film 16 having a similar DBR structure is provided, so that the convex portion 13 passes through the base 10A of the transparent substrate 10. The reflected light is reflected by the multilayer laminated film 16. Thereby, it becomes possible to emit light effectively to the outside of the semiconductor light emitting element 1, and the light extraction efficiency is improved.

  In addition, with the above configuration, when a wafer on which each layer is formed on the transparent substrate 10 is divided using, for example, a laser scribing method and cut out as a semiconductor light emitting device chip, laser light can easily enter the transparent substrate 10. Therefore, it becomes possible to cut into chips at a desired position with certainty.

In a conventional semiconductor element, a reflective film made of a metal film is attached to the back side of a transparent substrate, and light transmitted through the transparent substrate and directed to the other surface side is reflected. However, such a configuration has a problem that the metal film is easily peeled off from the base made of sapphire or the like.
In the present invention, since the multilayer laminated film 16 having the DBR structure having the above configuration is bonded to the base body 10A made of sapphire or the like, a high bonding force can be obtained. Further, by laminating the third thin film 16A and the fourth thin film 16B as a structure made of titanium oxide and silicon oxide, the respective layers are joined together by the oxide films, so that the effect of being difficult to peel off is obtained.

"Buffer layer"
In the present embodiment, a buffer layer 2 and a base layer 3 described later are sequentially stacked on the main surface 11 of the transparent substrate 10 so as to cover the convex portion 13.
The buffer layer 2 relaxes the difference in lattice constant between the base 10A made of sapphire and the base layer 3, and can easily form a C-axis-oriented single crystal on the main surface 11 of the transparent substrate 10 having the C-axis. can get. Therefore, by laminating a single crystal group III nitride semiconductor layer on the buffer layer 2, the underlayer 3 having excellent crystallinity can be formed. The buffer layer 2 is most preferably formed between the transparent substrate 10 and the base layer 3 as in the example shown in FIGS. 1 and 2, but the buffer layer is omitted in consideration of the element specifications. It is also possible to do.

Buffer layer _2, Al _{X Ga 1-X} N is laminated on (0 ≦ x ≦ 1) becomes the major surface 11 of the transparent substrate 10 with the composition, for example, activity and gas and metal material including a V group element in the plasma It can be formed by a reactive sputtering method in which the reaction is performed. Such a film formed by a method using a metal material that has been converted to plasma has an effect that alignment is easily obtained.
The buffer layer 2 can be made of any material as long as it is a group III nitride compound having a composition of Al _X Ga _1-X N (0 ≦ x ≦ 1). Moreover, it is preferable that the buffer layer 2 has a composition containing Al. In this case, the composition of Al is more preferably 50% or more. The buffer layer 2 is most preferably configured with AlN.

The buffer layer 2 preferably has a single crystal structure from the viewpoint of the buffer function. The group III nitride crystal forming such a buffer layer 2 has a hexagonal crystal structure, and can be formed into a single crystal film by controlling the film forming conditions, while it is an assembly based on hexagonal columns. It is also possible to form columnar crystals (polycrystals) composed of a structure.
In general, the group III nitride crystal forming the base layer 3 and the laminated semiconductor layer 20 provided in the light emitting device 1 of the present embodiment is controlled not only in the upward direction but also in the in-plane direction by controlling the film forming conditions and the like. A grown crystal can be formed. When the buffer layer 2 having the single crystal structure as described above is formed on the main surface 11 of the transparent substrate 10, the buffer function of the buffer layer 2 works effectively. The semiconductor layer 20 is a layer having good orientation and crystallinity.

"Underlayer"
The underlayer 3 described in the present embodiment is made of a group III nitride semiconductor. As described above, the crystal growth surface 12 and the convex portion 13 are formed on the main surface 11 of the transparent substrate 10 via the buffer layer 2. A group III nitride semiconductor is formed by epitaxial growth so as to cover it.

As the material of the underlayer 3, for example, a group III nitride compound having a composition of Al _x Ga _y In _z N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z = 1) is used. be able to. In addition, a material having a composition of Al _y Ga _1-y N layer (0 ≦ y ≦ 1, preferably 0 ≦ y ≦ 0.5, more preferably 0 ≦ y ≦ 0.1) is used as the underlayer 3. However, it is more preferable in that the base layer 3 having good crystallinity can be formed. For example, AlGaN or GaN can be employed. Further, the material of the underlayer 3 may be a material different from that of the buffer layer 2 as in the above composition, but the same material as that of the buffer layer 2 can also be used.

"Multilayer Semiconductor Layer"
In the example described in the present embodiment, the semiconductor light emitting device 1 having the LED structure can be configured by laminating the laminated semiconductor layer 20 on the base layer 3. Each layer constituting the stacked semiconductor layer 20 is made of a group III nitride semiconductor, and as described above, the n-type semiconductor layer 4, the light emitting layer 5, and the p-type semiconductor layer 6 are sequentially stacked. Each layer of the laminated semiconductor layer 20 is formed by MOCVD, so that a layer with higher crystallinity can be obtained.

"N-type semiconductor layer"
The n-type semiconductor layer 4 is formed by sequentially stacking an n-type contact layer 4a and an n-type cladding layer 4b. In the present embodiment, the n-type contact layer 4a may also serve as the n-type cladding layer 4b.

The n-type contact layer 4a is a layer for providing a negative electrode. The n-type contact layer 4a is made of a material having a composition of an Al _x Ga _1-x N layer (0 ≦ x <1, preferably 0 ≦ x ≦ 0.5, more preferably 0 ≦ x ≦ 0.1). It is preferable. The n-type contact layer 4a is preferably doped with an n-type impurity. The n-type impurity is preferably 1 × 10 ¹⁷ to 1 × 10 ²⁰ / cm ³ , preferably 1 × 10 ¹⁸ to 1 × 10 ^19. / Cm ³ is preferable because it can maintain good ohmic contact with the negative electrode. Further, the n-type impurity doped into the n-type contact layer 4a is not particularly limited, and examples thereof include Si, Ge, Sn, etc., and Si or Ge is preferable.

  Next, it is preferable to provide an n-type cladding layer 4 b between the n-type contact layer 4 a and the light emitting layer 5. The n-type cladding layer 4b is a layer for injecting carriers into the light emitting layer 5 and confining carriers, and can be formed of a material such as AlGaN, GaN, or GaInN. Further, the n-type cladding layer 4b may have a layered heterojunction made of the above materials or a superlattice structure in which a plurality of layers are stacked. Needless to say, when the n-type cladding layer 4b is formed of GaInN, it is preferably larger than the band gap of GaInN constituting the light emitting layer 5 described later.

Here, as an index representing the crystallinity of a semiconductor crystal, an X-ray rocking curve (XRC) half width is generally used. It can be said that the smaller the XRC half width, the more excellent the crystallinity. In the present embodiment, the XRC half-value width in a state where the base layer 3 is formed so as to cover the crystal growth surface 12 and the convex portion 13 via the buffer layer 2 and the n-type contact layer 4a is formed thereon, by the base width d ₁ of the convex portion 13 provided on the transparent substrate 10 can be properly controlled.

  On the other hand, when a buffer layer, an underlayer, and an n-type contact layer are formed on the main surface consisting only of the C-plane crystal growth surface without forming a convex portion on the substrate, the light extraction efficiency as a semiconductor light emitting device As well as it becomes difficult to suppress crystal defects in the underlying layer. For this reason, the crystallinity of the underlayer is lowered, and the crystallinity of the n-type contact layer formed thereon is also lowered, so that the above-described XRC half width is also a large numerical value.

  In this embodiment, since the crystallinity of the underlayer 3 is improved by using the transparent substrate 10 provided with the convex portion 13 having the DBR structure on the crystal growth surface 12, the n-type contact layer 4a on the base layer 3 is also formed. It becomes a layer excellent in crystallinity. As a result, the n-type cladding layer 4b, the light-emitting layer 5, and the p-type semiconductor layer 6 stacked thereon are also excellent in crystallinity, so that the semiconductor light-emitting element 1 having excellent light-emitting characteristics can be obtained. Can be realized.

"Light emitting layer"
As the light emitting layer 5 laminated on the n-type semiconductor layer 4, a structure such as a single quantum well structure or a multiple quantum well structure can be adopted. For example, the well layer (see reference numeral 5b in FIG. 2) of the quantum well structure in the light-emitting element 1 of the example illustrated in FIG. 2 is generally Ga _1-y In _y when configured to emit blue light. A group III nitride semiconductor having a composition of N (0 <y <0.4) is used. Further, in the example shown in FIG. 2, the light emitting layer 5 includes the barrier layers 5 a and the well layers 5 b alternately stacked, and the barrier layers 5 a are arranged on the n-type semiconductor layer 4 side and the p-type semiconductor layer 6 side. Is laminated.

In the case of the light emitting layer 5 having the multiple quantum well structure as in the present invention, the Ga _1-y In _y N is used as the well layer 5b, and Al _x Ga _1-x N (0 ≦≦ 5) having a larger band gap energy than the well layer 5b. z <0.3) is preferably the barrier layer 5a. The well layer 5b and the barrier layer 5a may or may not be doped with impurities by design.

  In the present invention, as described above, the transparent substrate 10 provided with the convex portion 13 having the DBR structure on the crystal growth surface 12 is used to cover the crystal growth surface 12 and the convex portion 13 with the buffer layer 2 interposed therebetween. A base layer 3 is formed so as to be embedded. Here, when a single crystal group III nitride semiconductor layer is epitaxially grown on the crystal growth surface 12 of the substrate 10A made of sapphire, a single crystal oriented in the C-axis direction is epitaxially grown from the sapphire C surface, but the protrusion 13 Does not grow epitaxially. For this reason, when the underlayer 3 grows, the crystal oriented in the C-axis direction grows epitaxially only from the crystal growth surface 12 made of the sapphire C surface. Therefore, since the underlayer 3 is epitaxially grown so as to cover the convex portion 13 on the crystal growth surface 12, it is possible to suppress the occurrence of crystal defects such as dislocations in the crystal and to improve the crystallinity. .

  Then, by forming each layer constituting the laminated semiconductor layer 20 including the n-type contact layer 4a on the base layer 3 whose crystallinity is well controlled as described above, the light emitting layer 5 A layer having excellent crystallinity with suppressed crystal defects and the like. Thereby, since the fall of internal quantum efficiency can be suppressed, it becomes possible to set it as the light emitting element 1 with high light emission output.

"P-type semiconductor layer"
The p-type semiconductor layer 6 is generally composed of a p-type cladding layer 6a and a p-type contact layer 6b. In the present embodiment, the p-type contact layer 6b can also serve as the p-type cladding layer 6a.

The p-type cladding layer 6a is a layer for confining carriers in the light emitting layer 5 and injecting carriers. The composition of the p-type cladding layer 6a is not particularly limited as long as the composition is larger than the band gap energy of the light emitting layer 5 and can confine carriers in the light emitting layer 5, but Al _x Ga _1-x N The composition is preferably (0 <x ≦ 0.4). The p-type doping concentration of the p-type cladding layer 6a is preferably in the range of 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm ³ , more preferably 1 × 10 ¹⁹ to 1 × 10 ²⁰ / cm ³ . It is a range. When the p-type dope concentration is in the above range, a good p-type crystal can be obtained without reducing the crystallinity. As the p-type impurity doped into the p-type cladding layer 6a, for example, Mg can be used. The p-type cladding layer 6a may be a layer including a superlattice structure in which a layer structure made of the above material is stacked a plurality of times.

The p-type contact layer 6b is a layer for providing a positive electrode (electrode), and is preferably formed of a material having a composition of Al _x Ga _1-x N (0 ≦ x ≦ 0.4), for example. By setting the Al composition in the p-type contact layer 6b within the above range, good crystallinity can be maintained, and good ohmic contact with the translucent positive electrode 7 formed thereon can be realized. The p-type contact layer 6b contains p-type impurities at a concentration of 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm ³ , preferably 5 × 10 ^{19 to} 5 × 10 ²⁰ / cm ³ . It is preferable from the viewpoints of maintaining good ohmic contact, preventing the generation of cracks, maintaining good crystallinity, and the like. Although it does not specifically limit as a p-type impurity doped by the p-type contact layer 6b, For example, it is preferable to use Mg.

"Translucent positive electrode"
The translucent positive electrode 7 is a translucent p-type electrode provided on the p-type contact layer 6b.
Examples of the translucent positive electrode 7 include ITO (In ₂ O ₃ —SnO ₂ ), AZO (ZnO—Al ₂ O ₃ ), IZO (In ₂ O ₃ —ZnO), and GZO (ZnO—Ga ₂ O ₃ ). The material containing at least one selected from can be provided by conventional means well known in the art. Moreover, the structure of the translucent positive electrode 7 can be used without any limitation, including a conventionally known structure. The translucent positive electrode 7 may be formed so as to cover almost the entire surface on the p-type contact layer 6b, or may be formed in a lattice shape or a tree shape with a gap. In addition, after forming the light-transmitting positive electrode 7, thermal annealing for alloying or transparency may or may not be performed.

"Positive electrode and negative electrode"
The positive electrode 8 is a p-type electrode formed on the translucent positive electrode 7 and provided for electrical connection with a circuit board, a lead frame, or the like. As the positive electrode 8, various structures using Au, Al, Ni, Cu, and the like are well known, and those of known materials and structures can be used without any limitation.

  The negative electrode 9 is an n-type electrode formed so as to be in contact with the n-type contact layer 4 b of the n-type semiconductor layer 4. When the negative electrode 9 is provided, a part of the p-type semiconductor layer 6, the light emitting layer 5, and the n-type semiconductor layer 4 is removed to form an exposed region 4c of the n-type contact layer 4b, and the negative electrode 9 is formed thereon. . As materials for the negative electrode 9, negative electrodes having various compositions and structures are well known, and these known negative electrodes can be used without any limitation.

  As described above, according to the semiconductor light emitting device 1 according to the present invention, the transparent substrate 10 having the main surface 11 provided with the plurality of convex portions 13 on the crystal growth surface 12, and the main surface of the transparent substrate 10. 11 having a laminated semiconductor layer 20 including at least the light-emitting layer 5, and a convex portion 13 provided on the crystal growth surface 12 includes a first thin film 13 </ b> A and a refractive index of the first thin film 13 </ b> A. Since the second thin film 13B having a different refractive index is alternately laminated, it is composed of a multi-layered laminate having a DBR structure, so that light emitted from the light emitting layer 5 toward the convex portion 13 is incident on the convex portion 13. On the other hand, the light traveling in the vertical direction is totally reflected, while the light traveling in the oblique direction with respect to the convex portion 13 is transmitted or scattered. Thereby, since the light totally reflected by the convex portion 13 becomes a component of light emitted toward the vertical direction of the semiconductor light emitting device 1, the light extraction efficiency in the vertical direction is improved, and the semiconductor light emitting device having high emission intensity. 1 can be realized.

[Method for Manufacturing Semiconductor Light-Emitting Element]
In the method of manufacturing a semiconductor light emitting device according to the present invention, when drawing the semiconductor light emitting device of the present invention as described above, the first thin film 13A and the refractive index of the first thin film 13A are formed on the crystal growth surface 12. A substrate forming step of forming a transparent substrate 10 having a main surface 11 provided with a plurality of convex portions 13 made of a multilayer laminate by alternately laminating second thin films 13B having different refractive indexes; And a semiconductor layer forming step of forming a laminated semiconductor layer 20 including at least the light emitting layer 5 on the main surface 11 of 10. In the present embodiment, the buffer layer 2 and the base layer 3 are stacked in this order on the main surface 11 of the transparent substrate 10 so as to cover the convex portion 13, and the stacked semiconductor layer 20 is formed on the base layer 3. An example of forming will be described.
Hereafter, each process with which the manufacturing method of this invention is equipped is demonstrated in detail.

"Substrate formation process"
4A to 4D are views for explaining an example of a process for manufacturing the transparent substrate 10 provided with the convex portion 13 having the DBR structure shown in the schematic diagram of FIG. It is sectional drawing which shows the transparent substrate 10 prepared in the manufacturing method of a form. The transparent substrate 10 has a main surface 11 composed of a crystal growth surface 12 composed of the C-plane of the substrate 10A and a plurality of convex portions 13 formed on the crystal growth surface 12.
Hereinafter, an example of a method for manufacturing the transparent substrate 10 as shown in FIG. 1 will be described.

  In the substrate forming step of the present embodiment, for example, a plurality of convex portions 13 having the above-described DBR structure are formed on the crystal growth surface 12 made of the C surface of the base 10A made of sapphire, thereby forming a crystal made of the C surface. The transparent substrate 10 is manufactured by forming the main surface 11 composed of the growth surface 12 and the convex portion 13. In such a substrate forming process, thin film materials having different refractive indexes are alternately deposited on the crystal growth surface 12 as shown in the examples shown in FIGS. After the resist layer 18 is formed and then the resist layer 18 is patterned, the thin film material is removed by etching, whereby the convex portion 13 can be formed.

  In the substrate forming process of this embodiment, first, as shown in FIG. 4A, a thin film material is deposited on the crystal growth surface 12 of the base 10A made of sapphire. Specifically, a thin film material that forms the first thin film 13A and the second thin film 13B by using any one of titanium oxide, silicon oxide, silicon nitride, tantalum oxide, zirconium oxide, and niobium oxide is conventionally used. The layers are alternately deposited by a known method. At this time, thin film materials having different light refractive indexes are selected as the thin film materials of the first thin film 13A and the second thin film 13B, and these materials are crystal grown in a total of 10 layers, for example, as a pair of 5 layers. Films are alternately formed on the entire surface 12.

  Next, as shown in FIG. 4B, a resist layer 18 is formed on the laminated structure of the thin film material deposited on the crystal growth surface 12 using a conventionally known method and material. Specifically, after depositing a resist material on a thin film material (see reference numerals 13A and 13B in FIG. 4B), it is matched with the shape and arrangement of the protrusions 13 formed on the crystal growth surface 12, Patterning is performed using a general photolithography method to form a resist layer 18.

At this time, in order to uniformly pattern the entire surface of the crystal growth surface 12, it is preferable to use the stepper exposure method among the photolithography methods. However, when forming the pattern of the convex portion 13 having the base width d ₁ of 1 μm, an expensive stepper device is required, which may increase the manufacturing cost. Therefore, when forming a mask pattern having a base width d ₁ of the convex portion 13 of 1 μm or less, in addition to a laser exposure method or a nanoimprint method used in the field of optical discs, an electron beam (EB) exposure is performed. More preferably, the method is used.

Next, as shown in FIG. 4C, the plurality of convex portions 13 having a DBR structure are formed by etching the thin film materials deposited alternately. At this time, as a method of etching the thin film material, a conventionally known dry etching method or wet etching method can be used. In the present embodiment, it is preferable to use the dry etching method among these methods because the uniform convex portion 13 can be formed and the crystal growth surface 12 formed of the C plane can be effectively exposed. As an etching gas used for dry etching, a fluorine-based etching gas such as trifluoromethane (CHF ₃ ) is preferably used.

In general, the sapphire substrate when dry etching is Cl ₂ is used as an etching gas, using Cl ₂ in the present embodiment, not only the thin film material, the base 10A is also a problem that the etching of sapphire There is. In the present embodiment, the substrate 10A functions as an etching stopper when a part of the thin film material is removed by etching using CHF ₃ as an etching gas. By adopting such a method, it is possible to reliably expose the crystal growth surface 12 composed of the C-plane even when the plurality of convex portions 13 are arranged at a narrow pitch.

  Further, in the substrate forming process, by adjusting the conditions for etching using the fluorine-based etching gas, the outer shape gradually becomes smaller toward the top as shown in FIGS. It is possible to form the convex portion 3. In the substrate forming process, it is possible to control the shape as shown in the illustrated example by appropriately adjusting each condition such as the etching processing time.

  Further, in the substrate forming step, as shown in FIG. 4D, the third thin film 16A and the refractive index of the third thin film 16A are further formed on the other surface 15 side opposite to the main surface 11 of the transparent substrate 10. By alternately laminating the fourth thin films 16B having a refractive index different from the above, the multilayer laminated film 16 can be formed so as to cover the base 10A on the other surface 15 side. At this time, the same material and method as the convex portion 13 can be adopted as the thin film material and the forming method of the third thin film 16A and the fourth thin film 16B.

Further, the film thicknesses of the third thin film 16A and the fourth thin film 16B and the entire multilayer laminated film 16 are not particularly limited. However, in consideration of productivity, light reflection performance, and the like, the third thin film 16A and the fourth thin film The film thickness of 16B is preferably 20 to 100 nm per layer, and the film thickness of the entire multilayer laminated film 16 is preferably in the range of 100 to 4000 nm.
In the case where there is a step of reducing the thickness of the substrate by grinding and polishing the back surface of the substrate before dividing into chips, it is preferable to form the multilayer film 16 after the substrate is thinned.

"Formation of buffer layer"
Next, in the buffer layer forming step, the buffer layer 2 as shown in FIG. 2 is formed on the crystal growth surface 12 forming the main surface 11 of the transparent substrate 10 prepared by the above method.

First, after performing various pretreatments on the surface of the transparent substrate 10, the transparent substrate 10 is introduced into, for example, a chamber of a sputtering apparatus, and the buffer layer 2 made of single crystal AlN is formed by sputtering. In this case, as a pretreatment method of the main surface 11 of the transparent substrate 10, for example, a wet process such as a conventionally known RCA cleaning method, a method of exposing the main surface 11 of the transparent substrate 10 in plasma, or the like is used. it can. Examples of the method for forming the buffer layer 2 on the transparent substrate 10 include a sputtering method, a MOCVD method, a pulsed laser deposition (PLD) method, a pulsed electron beam deposition (PED) method, and the like. Can be used.
In the present invention, since the buffer layer may be omitted as described above, in this case, the buffer layer forming step need not be performed.

"Underlayer formation-semiconductor layer formation process"
Next, in the step of forming the base layer 3, the wafer having the buffer layer 2 formed on the transparent substrate 10 is introduced into a reaction furnace of a MOCVD apparatus (not shown), and Al _X Ga ₁ is formed on the buffer layer 2. forming the _{-X N (0 ≦ x ≦ 1} ) formed of the underlying layer 3 of the composition.

Next, in the semiconductor layer forming step, the n-type semiconductor layer 4, the light emitting layer 5, and the p-type semiconductor layer 6 are sequentially stacked on the base layer 3. Here, the growth method of the gallium nitride-based compound semiconductor (group III nitride semiconductor) when forming the above-described underlayer 3, the n-type semiconductor layer 4, the light emitting layer 5, and the p-type semiconductor layer 6 is not particularly limited. All methods known to grow nitride semiconductors, such as reactive sputtering, MOCVD (metal organic chemical vapor deposition), HVPE (hydride vapor deposition), MBE (molecular beam epitaxy) Can be applied. Among these methods, when a gallium nitride compound semiconductor is formed by the MOCVD method, hydrogen (H ₂ ) or nitrogen (N ₂ ) as a carrier gas, trimethyl gallium (TMG) as a Ga source that is a group III source, or Triethylgallium (TEG), trimethylaluminum (TMA) or triethylaluminum (TEA) as an Al source, trimethylindium (TMI) or triethylindium (TEI) as an In source, ammonia (NH ₃ ) as an N source which is a group V material, Hydrazine (N ₂ H ₄ ) or the like is used. In addition, as a dopant, for n-type, monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is used as a Si raw material, germanium gas (GeH ₄ ) or tetramethyl germanium ((CH ₃ ) ₄ Ge) is used as a Ge raw material. And organic germanium compounds such as tetraethylgermanium ((C ₂ H ₅ ) ₄ Ge) can be used.

  Further, the gallium nitride-based compound semiconductor as described above can contain other group III elements in addition to Al, Ga, and In. If necessary, such as Ge, Si, Mg, Ca, Zn, and Be can be used. A dopant element can be contained. Furthermore, it is not limited to the element added intentionally, but may include impurities that are inevitably included depending on the film forming conditions and the like, as well as trace impurities that are included in the raw materials and reaction tube materials.

Specifically, first, by selecting and adjusting a source gas and an organic metal source to be supplied into a reaction furnace of a MOCVD apparatus (not shown), a single crystal Al _X Ga _1-X N ( An n-type contact layer 4a and an n-type cladding layer 4b of 0 ≦ x ≦ 1) are sequentially stacked. At this time, the n-type impurity (dopant) as described above is supplied into the reactor to dope the n-type contact layer 4a and the n-type cladding layer 4b with the n-type impurity.

Next, using the same MOCVD apparatus, the light emitting layer 5 is formed by alternately laminating the barrier layers 5a and the well layers 5b on the n-type cladding layer 4b. When the light emitting layer 5 illustrated in FIG. 2 is formed, six barrier layers 5a made of Si-doped GaN, five well layers 5b made of non-doped In _0.2 Ga _0.8 N, Are alternately stacked.

Next, the p-type semiconductor layer 6 including the p-type cladding layer 6a and the p-type contact layer 6b is formed on the light-emitting layer 5, that is, on the barrier layer 5a that is the uppermost layer of the light-emitting layer 5, using the same MOCVD apparatus. To do. When forming the p-type semiconductor layer 6, for example, a p-type cladding layer 6 a made of Al _0.1 Ga _0.9 N is formed on the light emitting layer 5 (the uppermost barrier layer 5 a). A p-type contact layer 6b made of Al _0.02 Ga _0.98 N is formed. At this time, by supplying a p-type impurity such as Mg into the reaction furnace, the p-type cladding layer 6a and the p-type contact layer 6b are doped with the p-type impurity.

"Formation of translucent positive electrode"
Next, the translucent positive electrode 7 made of a translucent and conductive material is formed on the p-type contact layer 6 b of the p-type semiconductor layer 6.
A method for forming the translucent positive electrode 7 is not particularly limited, and the translucent positive electrode 7 can be provided by a conventional means well known in this technical field. Also, any structure or material can be used without any limitation including conventionally known ones.

  Specifically, for example, the light-transmitting positive electrode 7 is formed by a method such as sputtering using a material such as AZO, IZO, or GZO in addition to ITO. Moreover, after forming the translucent positive electrode 7, thermal annealing for the purpose of alloying or transparency may or may not be performed.

"Formation of positive and negative electrodes"
Next, the positive electrode 8 is formed on the translucent positive electrode 7. For example, the positive electrode 8 is a three-layer electrode that is not shown in detail by laminating Ti, Al, and Au materials in order from the surface side of the translucent positive electrode 7 by a conventionally known method. be able to.

  When forming the negative electrode 9, first, a part of the semiconductor layer 20 formed of the p-type semiconductor layer 6, the light emitting layer 5, and the n-type semiconductor layer 4 formed on the transparent substrate 10 is dry-etched or the like. By removing, the exposed region 4d of the n-type contact layer 4b is formed. Then, for example, each layer of Ni, Al, Ti, and Au is laminated in this order from the n-type contact layer 4b side by a conventionally known method on the exposed region 4d, thereby omitting detailed illustration of the four layers. A negative electrode 9 having a structure can be formed.

  Then, after grinding and polishing the back surface of the transparent substrate 10 to obtain a mirror-like surface, the wafer obtained by the above steps is cut into, for example, a 350 μm square using a laser scribing method or the like. The chip-shaped semiconductor light emitting device 1 can be obtained.

  According to the method for manufacturing the semiconductor light emitting device of this embodiment as described above, the first thin film 13A on the crystal growth surface 12 and the second refractive index different from the refractive index of the first thin film 13A. By alternately laminating the thin films 13B, a substrate forming step of forming the transparent substrate 10 having the main surface 10 provided with the plurality of convex portions 13 formed of a multilayer laminate, and the main surface 11 of the transparent substrate 10 On the transparent substrate 10 having the convex portion 13 made of the multilayer laminate of the DBR structure as described above, the semiconductor layer forming step of forming the laminated semiconductor layer 20 including at least the light emitting layer 5 on the top. A semiconductor light emitting device 1 having a laminated semiconductor layer formed thereon and having excellent light emission intensity can be obtained.

[lamp]
The lamp of the present invention uses the semiconductor light emitting device of the present invention.
As a lamp | ramp of this invention, the thing formed by combining the semiconductor light-emitting device of this invention and fluorescent substance can be mentioned, for example. A lamp in which a semiconductor light emitting element and a phosphor are combined can have a known configuration by means well known to those skilled in the art. Conventionally, a technique for changing the emission color by combining a semiconductor light emitting element and a phosphor has been known, and such a technique can be employed in the lamp of the present invention without any limitation. .

  FIG. 5 is a schematic view schematically showing an example of a lamp configured using the semiconductor light emitting device according to the present invention. The lamp 30 shown in FIG. 5 is of a bullet type and uses the light emitting element 1 shown in FIG. As shown in FIG. 5, the positive electrode 8 of the semiconductor light emitting device 1 is bonded to one of the two frames 31 and 32 (the frame 31 in FIG. 5) by a wire 33, and the negative electrode 9 of the light emitting device 1 is connected to the wire 34. The light emitting element 1 is mounted by being bonded to the other frame 32. The periphery of the light emitting element 1 is sealed with a mold 35 made of a transparent resin.

Since the lamp of the present invention is formed by using the semiconductor light emitting device 1 of the present invention, it has excellent light emission characteristics.
Note that the lamp of the present invention can be used for any purpose such as a bullet type for general use, a side view type for portable backlight use, and a top view type used for a display.

  Next, although the semiconductor light-emitting device, the manufacturing method thereof, and the lamp of the present invention will be described in more detail with reference to examples and comparative examples, the present invention is not limited to these examples. In the present embodiment, description will be made with reference to FIGS.

[Examples 1 to 4]
In this example, a semiconductor light emitting device was fabricated by the procedure described below (see FIGS. 1, 2, and 5).

(Substrate formation process)
First, a plurality of convex portions 13 having the materials and structures described below were formed on the crystal growth surface 12 made of the (0001) C plane of the base 10A made of sapphire. At this time, the transparent substrates 10 of Examples 1 to 4 are formed by setting the plurality of convex portions 13 to “base width”, “height”, and “interval between adjacent convex portions” shown in Table 1 below. did.
That is, first, titanium oxide is used as the thin film material constituting the first thin film 13A on the crystal growth surface 12 of the base 10A made of C-plane sapphire having a diameter of 4 inches by using a conventionally known sputtering method. Silicon oxide was deposited as a thin film material constituting the thin film 13B. At this time, titanium oxide and silicon oxide were alternately formed on the entire crystal growth surface 12 in a total of 10 layers in pairs of 5 layers.

Next, after a resist layer 18 is laminated on the thin film material laminated on the crystal growth surface 12 using a conventionally known photolithography method, it is matched with the shape and arrangement of the protrusions 13 formed on the crystal growth surface 12. Patterning.
Next, by using the patterned resist layer 18 as a mask, the thin film material was dry-etched to form the convex portion 13, and the main surface 11 including the crystal growth surface 12 and the convex portion 13 was formed on the transparent substrate 10. At this time, trifluoromethane (CHF ₃ ), which is a fluorine-based etching gas, was used as an etching gas, and a stepper exposure method using ultraviolet light was used as an exposure method.

  In the transparent substrate 10 thus obtained, the convex portion 13 formed on the crystal growth surface 12 has a shape in which the outer diameter gradually decreases toward the upper portion, and the upper surface 13c is flat. It was.

  And the reflectance of the light of the obtained transparent substrate 10 was measured by using a reflection spectral film thickness apparatus (manufactured by Otsuka Electronics Co., Ltd.) at an emission wavelength of 450 nm, and the results are shown in Table 1 below.

(Formation of buffer layer and underlayer)
Next, the transparent substrate 10 on which the plurality of convex portions 13 were formed was introduced into the chamber of the sputter deposition apparatus and heated to 500 ° C. Then, after introducing nitrogen gas into the chamber, the internal pressure was maintained at 1 Pa, a high frequency bias of 500 W was applied to the substrate side to expose the transparent substrate 10 to nitrogen plasma, thereby cleaning the surface of the transparent substrate 10 ( Preprocessing).

  Then, a 50 nm thick buffer layer 2 made of AlN having a single crystal structure was formed on the main surface of the substrate 10 using an RF sputtering method.

  Next, the underlayer 3 was formed on the buffer layer 2 by using a low pressure MOCVD method. At this time, first, after introducing the substrate 10 on which the buffer layer 2 is formed into the reactor of the MOCVD apparatus, the temperature of the substrate 10 is raised to 1120 ° C. in a hydrogen atmosphere while continuing the circulation of the ammonia gas, Trimethylgallium (TMG) was supplied into the reactor. As a result, an underlayer 3 made of undoped GaN having a thickness of 3 μm was grown on the buffer layer 2.

(Semiconductor layer formation process)
Subsequently, the initial layer of the n-type contact layer 4a made of GaN was formed by the same MOCVD apparatus as that used for forming the base layer 3. At this time, the n-type contact layer 4a was doped with Si, and crystal growth was performed under the same conditions as the underlayer except that SiH ₄ was circulated as a Si dopant material.
Next, the n-type cladding layer 4b was laminated on the n-type contact layer 4a using the same MOCVD apparatus.

Subsequently, the light emitting layer 5 was laminated | stacked on the n-type clad layer 4b using the same MOCVD apparatus. In this example, the light emitting layer 5 having a multiple quantum well structure composed of the barrier layer 5a made of GaN and the well layer 5b made of Ga _0.85 In _0.15 N was formed. In forming the light emitting layer 5, first, a barrier layer 5a was formed on the n-type cladding layer 4b, and a well layer 5b made of Ga _0.85 In _0.15 N was formed on the barrier layer 5a. After repeating this stacking procedure five times, the sixth barrier layer 5a is formed on the fifth stacked well layer 5b, and the barrier layers 5a are arranged on both sides of the light emitting layer 5 having the multiple quantum well structure. The structure was as follows.

Next, a p-type cladding layer 6a made of GaN doped with Mg was formed on the light emitting layer 5 using the same MOCVD apparatus as in the above steps. Then, a p-type contact layer 6 b made of Mg-doped GaN was formed on the p-type cladding layer 6 a to form a p-type semiconductor layer 6.
By such a procedure, the semiconductor layer 20 in which the n-type semiconductor layer 4, the light emitting layer 5, and the p-type semiconductor layer 6 are sequentially stacked is formed on the base layer 3.

(Formation of translucent positive electrode)
Subsequently, the translucent positive electrode 7 was formed on the wafer obtained by the above procedure. At this time, a light-transmitting positive electrode 7 made of ITO was formed under a conventionally known condition so as to cover the entire upper surface of the p-type semiconductor layer 6 by using a sputtering method. Further, the translucent positive electrode 7 after film formation was subjected to annealing treatment for alloying and transparency.

(Formation of positive electrode and negative electrode)
Next, a positive electrode 8 having a three-layer structure was formed by sequentially stacking Ti, Al, and Au on the surface of the translucent positive electrode 7 by a known photolithography technique.
Further, by removing a part of the translucent positive electrode 7 and the semiconductor layer 20 by dry etching, an exposed region 4d where the n-type contact layer 4a is exposed is formed, and then Ni, Al, Ti, and Au are formed thereon. By sequentially laminating each layer, a negative electrode 9 as shown in FIG. 2 was formed.

(Division into semiconductor light emitting device chips)
Subsequently, the back side of the transparent substrate 10 of the wafer on which each electrode was formed was ground and polished to form a mirror-like surface.
Further, in Example 4, in addition to the convex portion 13 formed on the crystal growth surface 12 of the transparent substrate 10, the multilayer laminated film 16 having the same material and laminated structure as the convex portion 13 is further provided on the other surface 15 side. Formed. This wafer was cut into 240 μm × 600 μm rectangular chips by a laser scribing method to obtain LED (light emitting diode) chips (semiconductor light emitting element 1).

(Production of LED lamps with semiconductor light-emitting elements)
Then, as shown in FIG. 5, the chip (semiconductor light-emitting element 1) is placed on the lead frame 31 so that the positive electrode 8 and the negative electrode 9 are on the upper side, and is connected to the lead frame with a gold wire to thereby form a lamp. 30 was produced.

  The drive voltage Vf (mV) when a forward current of 20 mA was passed between the electrodes on the p side (positive electrode 8) and n side (negative electrode 9) of the lamp 30 produced by the above method was measured, and the light emission output was also obtained. Po (mW) was measured, and the results are shown in Table 1 below.

[Comparative Examples 1 and 2]
In Comparative Examples 1 and 2, a semiconductor light-emitting element chip having a rectangular shape of 240 μm × 600 μm square was formed in the same manner as in Example 1 except that the transparent substrate was manufactured under the conditions shown in Table 1 below. Produced. In the same manner as described above, a lamp was manufactured using this semiconductor light emitting element chip.

  Then, by the same method as described above, the driving voltage Vf (mV) when a forward current of 20 mA is passed between the p-side (positive electrode) and n-side (negative electrode) electrodes of the lamp is measured, and the light emission output Po ( mW) was measured and the results are shown in Table 1 below.

[Evaluation results]
As shown in Table 1, the semiconductor light emitting devices of Examples 1 to 4 manufactured by forming the laminated semiconductor layer 20 on the transparent substrate 10 having the convex portion 13 manufactured under the conditions specified in the present invention are in the forward direction. The drive voltage Vf at a current (I) of 20 mA was as low as 3.0 to 3.1 V, and the light emission output Po was 20.5 to 22.5 mW, so that a very high light emission output was obtained. Moreover, it turns out that the transparent substrate 10 produced in Examples 1-4 has a very high reflectance with 10-15% of the reflectance in the light emission wavelength of 450 nm which is a blue light emission area | region.
Here, in Example 4, since the multilayer laminated film 16 having the same laminated structure is formed on the other surface 15 side in addition to the convex portion 13 on the crystal growth surface 12, the light emission output Po is 22.5 mW. And very high numbers.

On the other hand, in Comparative Example 1 in which the laminated semiconductor layer is formed on the transparent substrate on which the convex portion is not provided, the drive voltage Vf is 3.1 V, which is equivalent to the above Examples 1 to 4, The light emission output Po is 18.2 mW, which is a lower output than the semiconductor elements of Examples 1 to 4.
Further, in the comparative example 2 in which the convex portion formed on the base has a single-layer structure made of conventionally known silicon oxide, and the laminated semiconductor layer is formed on the transparent substrate having such a convex portion, As in Comparative Example 1, the drive voltage Vf is 3.1 V, which is the same as in Examples 1 to 4, but the light emission output Po is 19 mW, which is a lower output than the above Examples.

In addition, the transparent substrates prepared in Comparative Examples 1 and 2 have a reflectance of 2-3% at a light emission wavelength of 450 nm which is a blue light emitting region, which is significantly lower than the transparent substrates prepared in Examples 1 to 4 above. It turns out that it is rate.
In Comparative Examples 1 and 2, the convexity is not provided on the transparent substrate, or the reflection characteristic of light at the convex part is not appropriate, and thus the reflectance is reduced. In particular, the light in the vertical direction of the semiconductor light emitting element is reduced. It is considered that the extraction efficiency is low and the light emission output is low.

  From the results of the above examples, it is clear that the semiconductor light emitting device of the present invention has a high light extraction efficiency especially in the vertical direction of the semiconductor light emitting device and is excellent in device characteristics such as light emission output.

DESCRIPTION OF SYMBOLS 1 ... Semiconductor light emitting element, 2 ... Buffer layer, 3 ... Underlayer, 4 ... N-type semiconductor layer, 5 ... Light emitting layer, 6 ... P-type semiconductor layer, 7 ... Translucent positive electrode, 10 ... Substrate, 11 ... Main surface , 12 ... Crystal growth surface, 13 ... Projection, 13A ... First thin film (thin film material), 13B ... Second thin film (thin film material), 15 ... Other surface, 16 ... Multi-layered film, 16A ... Third thin film (thin film) Material), 16B ... fourth thin film (thin film material), 18 ... resist layer, 20 ... semiconductor layer, 30 ... lamp

Claims (18)

A transparent substrate having a main surface provided with a plurality of convex portions on the crystal growth surface;
A laminated semiconductor layer including at least a light emitting layer formed on the main surface of the transparent substrate; and
The convex portion is composed of a multilayer laminate in which a first thin film and a second thin film having a refractive index different from the refractive index of the first thin film are alternately laminated. element.   Provided on the other surface opposite to the main surface of the transparent substrate is a multilayer laminated film in which third thin films and fourth thin films having a refractive index different from the refractive index of the third thin film are alternately laminated. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is provided.   The semiconductor light emitting element according to claim 1, wherein an upper surface of the convex portion is a flat surface.   The first thin film and the second thin film are each made of a thin film material selected from titanium oxide, silicon oxide, silicon nitride, tantalum oxide, zirconium oxide, and niobium oxide. 4. The semiconductor light emitting device according to any one of 3 above.   The said 3rd thin film and a 4th thin film consist of thin film materials in any one of a titanium oxide, a silicon oxide, a silicon nitride, a tantalum oxide, a zirconium oxide, and a niobium oxide, respectively. 5. The semiconductor light emitting device according to any one of 4 above.   The convex portion has a base width of 0.05 to 4 μm, a height from the crystal growth surface in a range of 0.05 to 4 μm and a quarter or more of the base width, 6. The semiconductor light emitting device according to claim 1, wherein an interval between the adjacent convex portions is 0.5 to 5 times the base width. 7.   The semiconductor light emitting element according to claim 1, wherein the convex portion has a shape in which an outer shape gradually decreases toward an upper portion.   The laminated semiconductor layer is formed by laminating at least an n-type semiconductor layer, the light emitting layer, and a p-type semiconductor layer in this order on the main surface of the transparent substrate. The semiconductor light-emitting device according to claim 7.   On the main surface of the transparent substrate, a buffer layer and an underlayer are laminated in this order so as to cover the crystal growth surface and the convex portion, and the laminated semiconductor layer is formed on the underlayer. The semiconductor light emitting device according to claim 8. On the crystal growth surface, the first thin film and the second thin film having a refractive index different from the refractive index of the first thin film are alternately laminated, thereby providing a plurality of convex portions made of a multilayer laminate. A substrate forming step of forming a transparent substrate having a main surface;
A semiconductor layer forming step of forming a laminated semiconductor layer including at least a light emitting layer on the main surface of the transparent substrate;
A method for producing a semiconductor light emitting device, comprising:   In the substrate forming step, the third thin film and the fourth thin film having a refractive index different from the refractive index of the third thin film are alternately laminated on the other surface opposite to the main surface of the transparent substrate. The method according to claim 10, wherein a multilayer laminated film is formed.   The substrate forming step includes forming the first thin film and the second thin film using any one of a thin film material selected from titanium oxide, silicon oxide, silicon nitride, tantalum oxide, zirconium oxide, and niobium oxide. 12. The method for manufacturing a semiconductor light emitting device according to claim 10, wherein the semiconductor light emitting device is manufactured.   In the substrate forming step, the third thin film and the fourth thin film are formed using any one of a thin film material selected from titanium oxide, silicon oxide, silicon nitride, tantalum oxide, zirconium oxide, and niobium oxide. The method for manufacturing a semiconductor light emitting element according to claim 10, wherein the semiconductor light emitting element is manufactured.   In the substrate forming step, thin film materials forming the first thin film and the second thin film are alternately deposited on the crystal growth surface, and then a resist layer is formed on the thin film material. The thin film material is etched using a fluorine-based etching gas after patterning, thereby forming the convex portion made of a multilayer stack. The manufacturing method of the semiconductor light emitting element of description.   The semiconductor layer forming step includes forming the laminated semiconductor layer by forming at least an n-type semiconductor layer, the light emitting layer, and a p-type semiconductor layer in this order on the main surface of the transparent substrate. The method for manufacturing a semiconductor light emitting element according to claim 10, wherein the semiconductor light emitting element is manufactured.   In the semiconductor layer forming step, a buffer layer and an underlayer are laminated in this order on the main surface of the transparent substrate so as to cover the crystal growth surface and the convex portion, and the laminated semiconductor layer is formed on the underlayer. The method of manufacturing a semiconductor light emitting element according to claim 15, wherein:   The semiconductor light-emitting device obtained by the manufacturing method of any one of Claims 10-16.   A lamp comprising the semiconductor light emitting device according to any one of claims 1 to 9 and claim 17.

Images