JP2011159801A - Semiconductor light-emitting element, method of manufacturing the same, and lamp - Google Patents

Abstract

A semiconductor light-emitting element that suppresses the refractive index between a transparent electrode layer and a protective layer, appropriately controls the refractive index of the protective layer, has excellent light extraction efficiency, and provides a high light emission output, and a method for manufacturing the same As well as a lamp.
SOLUTION: A laminated semiconductor layer 20 that is sequentially laminated on a substrate 10 and includes an n-type semiconductor layer 4, a light emitting layer 5, and a p-type semiconductor layer 6, and a p-type semiconductor layer 6 provided in the laminated semiconductor layer 20 is provided. And a protective layer 11 laminated on the transparent electrode layer 7, and the protective layer 11 is made of silicon oxide (SiO ₂ ) and titanium oxide (TiO ₂ ). At the same time, the composition ratio of silicon oxide and titanium oxide changes in the film thickness direction from the transparent electrode layer 7 side to the surface 11a side, so that the refractive index gradually decreases from the transparent electrode layer 7 side to the surface 11a side. The refractive index gradient is as follows.
[Selection] Figure 1

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 semiconductor materials for light-emitting elements 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 the above oxide or III-V group 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 sapphire single crystal is an insulator, its element structure generally includes a positive electrode (p-type electrode) formed on a p-type semiconductor layer, a p-type semiconductor layer, a light emitting layer, and A part of the n-type semiconductor layer is removed, and a negative electrode (n-type electrode) formed on a region where the part of the n-type semiconductor layer is exposed is present on the same plane.

  External quantum efficiency is used as an index of the output of such a light emitting element. If the external quantum efficiency is high, it can be said that the light-emitting element has a high output. The external quantum efficiency is expressed as a product of the internal quantum efficiency and the light extraction efficiency. The internal quantum efficiency is a rate at which the energy of current injected into the device is converted into light in the light emitting layer. On the other hand, the light extraction efficiency is a ratio of light that can be extracted outside the light emitting element in the light generated in the light emitting layer. Therefore, in order to improve the external quantum efficiency, it is necessary to improve the light extraction efficiency in addition to the light emission efficiency in the light emitting layer.

  There are mainly two methods for improving the light extraction efficiency. One is a method of reducing light absorption by an electrode or the like formed on the light extraction surface. The other is a method of reducing the confinement of light inside the light emitting element caused by the difference in refractive index between the light emitting element and its external medium.

  Here, the semiconductor element having the above composition has a characteristic that current is injected only into the semiconductor directly under the electrode because the current diffusion in the lateral direction is small, so that the light emitted from the light emitting layer is the electrode. There is a problem that it is difficult to be taken out by being blocked. Therefore, in such a semiconductor light emitting device, a transparent electrode layer is usually provided on the p-type semiconductor layer, and the current applied to the positive electrode side (p-type electrode side) by this transparent electrode layer is used for the entire p-type semiconductor layer. And light is extracted through the transparent electrode layer (see, for example, Patent Documents 1 and 2).

Further, in the semiconductor light emitting device having the above-described configuration, in order to protect the device structure from an external load in the process of electrode formation, device division (chip formation), and the like, further on the transparent electrode layer, from silicon oxide (SiO ₂ ) or the like. It has been proposed to provide a protective layer. However, when the protective layer as described above is provided, the light transmitted through the transparent electrode layer is reflected by the protective layer due to the difference in refractive index between the transparent electrode layer and the protective layer as described above, and the inside of the light emitting element The light will be trapped. For this reason, the problem that light extraction efficiency falls remarkably compared with the case where a protective layer is not provided arises.

  Here, for example, it may be possible to prevent reflection of light at these interfaces by configuring the transparent electrode layer and the protective layer with materials having a close refractive index. However, in this case, although reflection of light at the interface between the transparent electrode layer and the protective layer can be suppressed, reflection occurs at the interface between the protective layer and the sealing resin used for the package, and light is confined. was there.

  In order to solve the problem of light confinement due to the difference in refractive index between the respective films as described above, the refractive index changes in the film thickness direction by forming irregularities on the film formed on the element surface. The technique to make is proposed (for example, refer patent document 3). According to Patent Document 3, it is said that the above-described configuration increases the extraction efficiency of light transmitted through the film. However, in patent document 3, since it is the structure which changes a refractive index mechanically with the unevenness | corrugation formed in the film surface, precise processing is difficult and it is difficult to control a refractive index appropriately in a film thickness direction. There is a problem.

  Further, in a semiconductor light emitting device configured to extract light emitted from the semiconductor layer upward, the window layer for extracting light from the inside is configured by stacking oxides having different refractive indexes, It has been proposed that the refractive index be configured to gradually decrease toward the top of the element (see, for example, Patent Document 4.5). However, in the configurations described in Patent Documents 4 and 5, the refractive index difference between the window layer and the protective layer cannot be sufficiently reduced, and it is difficult to significantly increase the light extraction efficiency.

JP 2001-215523 A JP 2007-287845 A JP 2008-230114 A JP 2001-36130 A JP 2001-36131 A JP 2001-192823 A

In order to improve the light extraction efficiency of the semiconductor light emitting device, it is also conceivable to form a so-called AR coat film by depositing magnesium fluoride (MgF ₂ ) or the like on the surface of the transparent electrode layer as a protective layer. When the protective layer is composed of an AR coating film, the light reflected on the surface of the film interferes with the light transmitted through the film and reflected at the back, thereby reducing reflection in the film and reducing the light. Attenuation is reduced and light confinement can be prevented. However, since the AR coating film has a large angle dependency, when the protective layer is composed of the AR coating film, there is a serious problem that light can be extracted only from the front of the film.

The present invention has been made in view of the above problems, and while reducing the difference in refractive index between the transparent electrode layer and the protective layer, appropriately controlling the refractive index of the protective layer, excellent in light extraction efficiency, It is an object of the present invention to provide a semiconductor light emitting device capable of obtaining a high light output and a method for manufacturing the same.
Another object of the present invention is to provide a lamp that uses the semiconductor light emitting element and has excellent light emission characteristics.

The present inventor has intensively studied to solve the above problem, and as a result, the protective layer formed on the transparent electrode layer is composed of silicon oxide (SiO ₂ ) and titanium oxide (TiO ₂ ), and in the film thickness direction. Thus, it was found that the refractive index can be appropriately controlled by changing the composition ratio (or composition ratio) of silicon oxide and titanium oxide from the transparent electrode layer side to the surface side. With such a configuration, by providing a refractive index gradient in the film thickness direction of the protective layer, the refractive index difference between the transparent electrode layer and the protective layer is reduced, and reflection of light at the interface is suppressed. The present inventors have found that the light extraction efficiency is remarkably improved by appropriately controlling the refractive index gradient in the film thickness direction of the protective layer and suppressing the attenuation of light in the film of the protective layer.
That is, the present invention relates to the following.

[1] A laminated semiconductor layer that is sequentially laminated on a substrate and includes an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer, and a transparent electrode layer formed on the p-type semiconductor layer provided in the laminated semiconductor layer And a protective layer laminated on the transparent electrode layer. The protective layer is made of silicon oxide (SiO ₂ ) and titanium oxide (TiO ₂ ), and the transparent electrode in the film thickness direction. The composition ratio of the silicon oxide and the titanium oxide changes from the layer side to the surface side, so that the refractive index gradient gradually decreases from the transparent electrode layer side to the surface side. A semiconductor light emitting device.
[2] The semiconductor light-emitting element according to the above [1], wherein the protective layer has a composition ratio of the silicon oxide that increases in the film thickness direction from the transparent electrode layer side toward the surface side.
[3] The protective layer is a laminated film in which the composition ratio of the silicon oxide and the titanium oxide changes stepwise as it goes from the transparent electrode layer side to the surface side in the film thickness direction. The semiconductor light emitting device according to the above [1] or [2].
[4] The protective layer is formed of a single layer film in which the composition ratio of the silicon oxide and the titanium oxide continuously changes from the transparent electrode layer side to the surface side in the film thickness direction. The semiconductor light emitting device according to the above [1] or [2].
[5] In the protective layer, the composition ratio of the titanium oxide on the transparent electrode layer side is in the range of 30 to 100 mol%, and the composition ratio of the silicon oxide on the surface side is in the range of 70 to 100 mol%. The semiconductor light-emitting device according to any one of [1] to [4] above, wherein
[6] The protective layer has a refractive index in the range of 1.9 to 2.5 on the transparent electrode layer side and a refractive index in the range of 1.4 to 1.6 on the surface side. The semiconductor light emitting device according to any one of [1] to [5] above.
[7] The transparent electrode layer is made of any of indium zinc oxide (IZO), indium tin oxide (ITO), or titanium oxide (TiO ₂ ) -based material. The semiconductor light emitting device according to any one of [1] to [6] above.

[8] A semiconductor layer forming step of sequentially stacking an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer on a substrate to form a stacked semiconductor layer, and an upper surface of the p-type semiconductor layer provided in the stacked semiconductor layer A transparent electrode forming step of forming a transparent electrode layer, and a protective layer forming step of laminating a protective layer on the transparent electrode layer, the protective layer forming step comprising a target made of silicon oxide (SiO ₂ ) And using a sputtering method using a target made of titanium oxide (TiO ₂ ), and controlling the power applied to each of the targets, the oxidation proceeds in the film thickness direction from the transparent electrode layer side to the surface side. By changing the composition ratio between silicon and the titanium oxide, the refractive index gradient gradually decreases from the transparent electrode layer side to the surface side while providing the refractive index gradient. Method for manufacturing a semiconductor light emitting device and forming a Mamoruso.
[9] In the protective layer forming step, the protective layer is formed while increasing the composition ratio of the silicon oxide in the film thickness direction from the transparent electrode layer side toward the surface side. [8] A method for producing a semiconductor light-emitting device according to [8].
[10] In the protective layer forming step, the protective layer is formed by changing the composition ratio of the silicon oxide and the titanium oxide stepwise in the film thickness direction from the transparent electrode layer side to the surface side. The method for manufacturing a semiconductor light-emitting element according to the above [8] or [9], wherein the films are formed as a laminated film in which films having different composition ratios are laminated.
[11] In the protective layer forming step, the composition ratio of the silicon oxide and the titanium oxide is continuously changed as the protective layer is moved from the transparent electrode layer side to the surface side in the film thickness direction. It forms as a single layer film, The manufacturing method of the semiconductor light-emitting device as described in said [8] or [9] characterized by the above-mentioned.
[12] The protective layer forming step forms the protective layer while changing power applied to each of the target made of silicon oxide and the target made of titanium oxide in a range of 0 to 500 W. The method for producing a semiconductor light-emitting device according to any one of [8] to [11] above.

[13] In the transparent electrode layer forming step, the transparent electrode layer is made of an indium zinc oxide (IZO) material, an indium tin oxide (ITO) material, or a titanium oxide (TiO ₂ ) -based material. The method for manufacturing a semiconductor light-emitting element according to any one of the above [8] to [12], wherein the semiconductor light-emitting element is formed from any one of the above.
[14] The transparent electrode layer forming step includes Nb, Ta, Mo, W, Te, Sb, Fe, Ru, Ge, Sn, Bi, Al, Hf, Si, Zr, Co, Cr, Ni, V, and Mn. , Re, Ce, Y, P and B selected from the group consisting of a titanium oxide-based material containing at least one dopant element in a proportion of 30% by mass or less, and at least 0.1 to 10 volumes Characterized by annealing at a temperature of 250 ° C. or higher after sputtering film formation at a film formation rate of 0.01 to 0.2 nm / second in an atmosphere containing oxygen and a balance of an inert gas. The method for producing a semiconductor light-emitting element according to any one of [8] to [12] above.

[15] A semiconductor light-emitting device obtained by the manufacturing method according to any one of [8] to [14].
[16] A lamp comprising the semiconductor light-emitting device according to any one of [1] to [7] or [15].

According to the semiconductor light emitting device of the present invention, the protective layer laminated on the transparent electrode layer is made of silicon oxide (SiO ₂ ) and titanium oxide (TiO ₂ ), and from the transparent electrode layer side to the surface side in the film thickness direction. As the composition ratio of silicon oxide and titanium oxide changes as it goes, it has a refractive index gradient that gradually decreases from the transparent electrode layer side to the surface side, so that there is a gap between the transparent electrode layer and the protective layer. The refractive index difference between the protective layer and the sealing resin is reduced, and the reflection of light at the interface is suppressed. As a result, it is possible to provide a semiconductor light emitting device that can significantly improve the light extraction efficiency and obtain a high light emission output.

  According to the method for manufacturing a semiconductor light emitting device of the present invention, the protective layer forming step of laminating the protective layer on the transparent electrode layer uses a sputtering method using a target made of silicon oxide and a target made of titanium oxide. By controlling the power applied to each of the targets, by changing the composition ratio of silicon oxide and titanium oxide in the film thickness direction from the transparent electrode layer side to the surface side, the surface side from the transparent electrode layer side The refractive index gradient gradually decreases toward the surface, so that the protective layer is formed, so that the refractive index difference between the transparent electrode layer and the protective layer and the refractive index between the protective layer and the sealing resin Can be reduced. Thereby, since reflection of light at the interface between the transparent electrode layer and the protective layer and the interface between the protective layer and the sealing resin can be suppressed, it is possible to manufacture a semiconductor light emitting device having excellent light extraction efficiency and high light emission efficiency. It becomes possible.

  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.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which illustrates an example of the semiconductor light-emitting device based on this invention, (a) is sectional drawing which shows the laminated structure in which the laminated semiconductor layer and the transparent electrode layer were laminated | stacked on the board | substrate, and also the protective layer was formed. (B) is a plan view of (a). It is a figure which illustrates typically an example of the semiconductor light-emitting device concerning this invention, and is an enlarged view which shows the principal part of the laminated structure shown in FIG. It is a figure which illustrates typically an example of the manufacturing method of the semiconductor light-emitting device based on this invention, and is a figure which shows the example of the sputtering device used for formation of a protective layer. It is a figure which illustrates typically an example of the semiconductor light-emitting device based on this invention, and is a graph which shows the relationship between the composition ratio (in the figure,% shows mol%) of a protective film, and a refractive index. It is sectional drawing which illustrates 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 FIGS. 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 Element (Light Emitting Element)]
A semiconductor light emitting device 1 according to the present invention is sequentially stacked on a substrate 10 as shown in the examples shown in FIGS. 1A, 1B, and 2, and includes an n-type semiconductor layer 4, a light-emitting layer 5, and a p-type semiconductor. A laminated semiconductor layer 20 composed of the layer 6; a transparent electrode layer 7 formed on the p-type semiconductor layer 6 provided in the laminated semiconductor layer 20; and a protective film 11 laminated on the transparent electrode layer 7. The protective layer 11 is made of silicon oxide (SiO ₂ ) and titanium oxide (TiO ₂ ), and is formed of silicon oxide and titanium oxide as it goes from the transparent electrode layer 7 side to the surface 11a side in the film thickness t direction. The composition ratio has a refractive index gradient that gradually decreases from the transparent electrode layer 7 side to the surface 11a side (see also the graph of FIG. 4). In the illustrated light emitting device 1, the positive electrode 8 is provided at a position where the surface of the transparent electrode layer 7 is exposed from the protective layer 11, and at least a part of the protective layer 11, the transparent electrode layer 7, and the laminated semiconductor layer 20 is provided. A negative electrode 9 is formed in the exposed exposed region on the n-type semiconductor layer 4. The light emitting element 1 has an element structure in which the buffer layer 2 and the base layer 3 are stacked on the substrate 10 and the stacked semiconductor layer 20 is provided thereon.
Hereinafter, the laminated structure of the light emitting element 1 will be described in detail.

"substrate"
The substrate 10 is not particularly limited in its material, size, and the like as long as the group III nitride semiconductor crystal can be epitaxially grown on the surface. For example, sapphire, SiC, silicon, zinc oxide, magnesium oxide, manganese oxide, zirconium oxide, manganese zinc iron oxide, magnesium aluminum oxide, zirconium boride, gallium oxide, indium oxide, lithium gallium oxide, lithium aluminum oxide, neodymium gallium oxide Conventionally known materials such as lanthanum strontium oxide aluminum tantalum, strontium titanium oxide, titanium oxide, hafnium, tungsten, and molybdenum can be employed. Among these materials, it is preferable to use a material having a hexagonal crystal structure such as sapphire or SiC for the substrate 10 because a group III nitride semiconductor with good crystallinity can be stacked.

"Buffer layer"
The buffer layer 2 is provided as an intermediate layer that matches the difference in lattice constant between the substrate 10 and the layer made of a group III nitride semiconductor, and is made of, for example, a group III nitride such as single crystal AlGaN or AlN. By providing such a buffer layer 2, the group III nitride semiconductor film formed thereon becomes a crystal film having good orientation and crystallinity. In the present invention, the buffer layer 2 may be omitted.
In this specification, the composition ratio of each element in AlGaN and GaInN may be described in a omitted form.

"Underlayer and laminated semiconductor layer"
Each layer of the underlayer 3 provided on the buffer layer 2 and the laminated semiconductor layer 20 including the n-type semiconductor layer 4, the light emitting layer 5, and the p-type semiconductor layer 6 is made of a group III nitride semiconductor. In the present invention, for example, the general formula _{Al X Ga Y In Z N 1} -A M A ( and in 0 ≦ X ≦ 1,0 ≦ Y ≦ 1,0 ≦ Z ≦ 1, X + Y + Z = 1. Symbol M nitrogen A gallium nitride compound semiconductor represented by a group V element different from (N) and 0 ≦ A <1 can be used without any limitation.

"Underlayer"
The underlayer 3 is provided as a layer that serves as a base for forming the n-type semiconductor layer 4 that forms the stacked semiconductor layer 20. As such an underlayer 3, for example, a group III nitride compound containing Ga, that is, a GaN-based compound semiconductor is used, and in particular, single crystal AlGaN or GaN can be preferably used.

"Laminated semiconductor layer"
(N-type semiconductor layer)
Although the detailed illustration is omitted, the n-type semiconductor layer 4 is formed by sequentially laminating an n-type contact layer and an n-type cladding layer.

The n-type contact layer is, for example, an Al _X Ga _1-X N layer (0 ≦ x ≦ 1, preferably 0 ≦ x ≦ 0.5, more preferably 0 ≦ x ≦ 0.1, as with the base layer 3. In addition, it is preferable that an n-type impurity such as Si, Ge, or Sn is doped. The thickness of the n-type contact layer is preferably in the range of 0.5 to 5 μm, and more preferably in the range of 1 to 3 μm. When the film thickness of the n-type contact layer is within the above range, the crystallinity as a semiconductor is maintained well.

The n-type cladding layer is a layer for injecting carriers into the light emitting layer 5 described later and confining the carriers, and can be formed of a material such as AlGaN, GaN, GaInN or the like. In addition, the n-type cladding layer can have a heterojunction of these structures or a superlattice structure in which a plurality of layers are stacked. The thickness of the n-type cladding layer is not particularly limited, but is preferably in the range of 0.005 to 0.5 μm, more preferably 0.005 to 0.1 μm. Further, the n-type doping concentration of the n-type cladding layer is preferably in the range of 1.5 × 10 ^{17 to} 1.5 × 10 ²⁰ / cm ³ , more preferably 1.5 × 10 ^{18 to} 1.5 × 10 ^19. / Cm ³ . When the doping concentration of the n-type cladding layer is within this range, it is preferable from the viewpoint of maintaining good crystallinity and reducing the operating voltage of the device.

(Light emitting layer)
The light emitting layer 5 is an active layer that is stacked on the n-type semiconductor layer 4 and the p-type semiconductor layer 6 is stacked thereon. Although not shown in detail, for example, a barrier layer and a well layer are included. It can be set as the structure laminated | stacked in order in which a barrier layer is distribute | arranged by laminating | stacking alternately and the n-type semiconductor layer 4 side and the p-type semiconductor layer 6 side.
The well layer is in the case of the structure exhibited blue light emission, indium as the gallium nitride-based compound semiconductor containing, for _{example, Ga 1-s In s N} (0 <s <0.4) GaN such as indium Can be used.
As the barrier layer, for example, a gallium nitride compound semiconductor such as Al _c Ga _1-c N (0 ≦ c <0.3) having a larger band gap energy than the well layer can be preferably used.

  The well layer and the barrier layer may be doped with impurities, or may not be doped. Further, the film thickness of the well layer 5b can be set to a film thickness at which a quantum effect can be obtained, for example, 1 to 10 nm, and more preferably 2 to 6 nm in terms of light emission output.

(P-type semiconductor layer)
Although the p-type semiconductor layer 6 is formed on the light emitting layer 5 and detailed illustration is omitted, a p-type cladding layer and a p-type contact layer are usually laminated in sequence.

The p-type cladding layer is a layer for confining carriers in the light emitting layer 5 and injecting carriers. As the p-type cladding layer, it is preferable to use a material having a composition larger than the band gap energy of the light emitting layer 5 and capable of confining carriers in the light emitting layer 5, for example, Al _d Ga _1-d N (0 <d ≦ 0.4, preferably 0.1 ≦ d ≦ 0.3).

The film thickness of the p-type cladding layer is not particularly limited, but is preferably in the range of 1 to 400 nm, more preferably 5 to 100 nm. The p-type doping concentration of the p-type cladding layer 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 . When the p-type dope concentration is in the above range, a good p-type semiconductor crystal can be obtained without reducing the crystallinity.

  Note that the p-type cladding layer may have a superlattice structure in which a plurality of layers are stacked. When the p-type cladding layer has a layer structure including a superlattice structure, the light emission output is remarkably improved and the light emitting device 1 having excellent electric characteristics can be obtained.

The p-type contact layer is a layer for providing a p-type electrode (transparent electrode layer 7, positive electrode 8), and can have a composition of Al _e Ga _1-e N (0 ≦ e ≦ 0.4). When the composition of the p-type contact layer is within the above range, it is preferable from the viewpoint of maintaining good crystallinity and good ohmic contact with the transparent electrode layer 7.

Although the film thickness of a p-type contact layer is not specifically limited, The range of 10-500 nm is preferable, More preferably, it is 5-200 nm. When the thickness of the p-type contact layer is within this range, it is preferable in terms of light emission output. The p-type contact layer contains a p-type impurity (dopant) at a concentration in the range of 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm ³ , preferably 5 × 10 ^{19 to} 5 × 10 ²⁰ / cm ^3. It is preferable in terms of maintaining good ohmic contact, preventing the occurrence of cracks, and maintaining good crystallinity. Further, the p-type impurity doped in the p-type contact layer is not particularly limited, but for example, Mg or the like is suitable.

"Transparent electrode layer"
The transparent electrode layer 7 is formed on a p-type contact layer (not shown) forming the p-type semiconductor layer 6 and is a translucent electrode made of an oxide film having conductivity, and is usually used in this technical field. A translucent material can be used without any limitation. Examples of such materials include indium tin oxide (ITO: Indium Tin Oxide; In ₂ O ₃ —SnO ₂ ), indium zinc oxide (IZO: Indium Zinc Oxide; In ₂ O ₃ —ZnO), and indium gallium oxide ( IGO: Indium Gallium Oxide; In ₂ O ₃ —Ga ₂ O ₃ ), Indium Cerium Oxide (ICO: Indium Cerium Oxide; In ₂ O ₃ —Ce ₂ O ₃ ), Aluminum Zinc Oxide (AZO: Aluminum Zinc Oxide; ZnO—) al ₂ O _3), germanium oxide zinc (GZO: germanium zinc oxide; ZnO -Ga 2 O 3), and a conductive titanium oxide arbitrary impurity element is doped (TiO ₂₎ material It can be exemplified, also, the structure can also be used without any particular limitations any structure including conventionally well known structures.

In the present invention, as will be described later in the manufacturing method, when the transparent electrode layer 7 is formed from a titanium oxide (TiO ₂ ) -based material using a sputtering method, Nb, Ta, Mo, W, Te At least one selected from the group consisting of Sb, Fe, Ru, Ge, Sn, Bi, Al, Hf, Si, Zr, Co, Cr, Ni, V, Mn, Re, Ce, Y, P and B Using a target made of a titanium oxide-based material containing a dopant element of 30% by mass or less, the sputtering atmosphere is an atmosphere containing at least 0.1 to 10% by volume of oxygen and the balance being an inert gas. More preferably, after sputtering film formation at a film formation rate of 0.01 to 0.2 nm / second, annealing is performed at a temperature of 250 ° C. or higher. The transparent electrode layer 7 obtained by such a method has a significantly reduced sheet resistance as compared with a conventional titanium oxide-based transparent electrode layer and becomes a film excellent in conductivity and transparency. Current can be diffused widely. Thereby, it becomes possible to constitute the light emitting element 1 which is more excellent in light extraction efficiency.

  Further, when the transparent electrode layer 7 is made of a titanium oxide-based material by the above method, the composition ratio of the protective layer 11 on the transparent electrode layer 7 side, that is, the back surface 11b, is large in titanium oxide, as will be described in detail later. By using such a composition, the difference in refractive index between the transparent electrode layer 7 and the protective layer 11 can be almost eliminated. Therefore, reflection of light at the interface between the transparent electrode layer 7 and the protective layer 11 is further suppressed, and the light extraction efficiency can be further improved.

"Protective layer"
The light emitting device 1 of the present invention is provided with a protective layer 11 on the transparent electrode layer 7 for protecting the device structure from an external load in steps such as electrode formation and device division (chip formation). As described above, the protective layer 11 is made of silicon oxide and titanium oxide, and the composition ratio of silicon oxide and titanium oxide changes in the film thickness t direction from the transparent electrode layer 7 side to the surface 11a side. The refractive index gradient gradually decreases from the transparent electrode layer 7 side toward the surface 11a side.

  In a conventional light emitting device, the refractive index of a transparent electrode layer made of IZO, ITO or the like provided on a p-type semiconductor layer and a protective layer made of a material such as titanium oxide or silicon oxide is provided on the transparent electrode layer. The configuration was very different. For this reason, due to the difference in refractive index, there is a problem that light transmitted through the transparent electrode layer is reflected by the protective layer, the light is confined inside the light emitting element, and the light extraction efficiency is significantly reduced.

  Since the protective layer 11 provided in the light emitting element 1 of the present invention is configured to have a refractive index that decreases toward the surface 11a side in the film thickness t direction, the interface between the transparent electrode layer 7 and the protective layer 11 and protection are provided. Reflection of light at the interface between the layer 11 and the sealing resin is suppressed. Thereby, the light extraction efficiency can be improved, and the light emission efficiency of the light emitting element 1 can be significantly increased.

  In the present invention, as described above, the refractive index gradient in the film thickness t direction of the protective layer 11 is changed by changing the composition ratio of silicon oxide and titanium oxide from the transparent electrode layer 7 side toward the surface 11a side. I have control. In this case, in the film thickness t direction of the protective layer 11, the composition ratio of silicon oxide increases in the direction from the transparent electrode layer 7 side to the surface 11 a side, thereby moving toward the surface 11 a side of the protective layer 11. Accordingly, it is possible to provide a refractive index gradient in which the refractive index gradually decreases.

  As shown in the graph of FIG. 4, when the composition ratio of titanium oxide in the protective layer 11 is 100 mol%, the refractive index is 2.5, while the composition ratio of silicon oxide is 100 mol%. In that case, the refractive index is 1.4. Here, the refractive index of IZO generally used as the material of the transparent electrode layer 7 is 2.1, and the refractive index of ITO is about 2.0. For this reason, in the film thickness t direction of the protective layer 11, the transparent electrode layer 7 side has a composition ratio with a large amount of titanium oxide, and the surface 11 a side has a composition ratio with a large amount of silicon oxide. The difference between the refractive index on the side (see reference numeral 11b in FIG. 2) and the refractive index of the transparent electrode layer 7 is almost eliminated. For example, the composition ratio of titanium oxide is 63 mol% for IZO, the composition ratio of titanium oxide is 60 mol% for ITO, and the composition ratio of titanium oxide is for tin oxide (refractive index: 1.9). By making the ratio 55 mol%, the difference in refractive index can be almost eliminated. Thereby, at the interface between the transparent electrode layer 7 and the protective layer 11, the light transmitted through the transparent electrode layer 7 is suppressed from being reflected and confined inside the device, and the light extraction efficiency is prevented from being lowered. It becomes possible. When the transparent electrode layer 7 is made of a titanium oxide-based material and the composition ratio of titanium oxide on the transparent electrode layer 7 side of the protective layer 11, that is, the back surface 11 b side is 100 mol%, The difference in refractive index at the interface with the protective layer 11 can be completely eliminated. Furthermore, in this case, since the difference in refractive index at the interface between the transparent electrode layer 7 and the laminated semiconductor layer (GaN refractive index: 2.7) can be reduced, the light extraction efficiency is further improved.

  As in the example shown in FIG. 2, the protective layer 11 is formed of a laminated film in which the composition ratio of silicon oxide and titanium oxide changes stepwise from the transparent electrode layer 7 side to the surface 11a side in the film thickness t direction. It can be set as the structure which becomes. In the illustrated example, the protective layer 11 is formed by laminating 15 protective films from the protective film 11A to the protective film 11P.

  The protective layer 11 preferably has a titanium oxide composition ratio (mol%) in the range of 30 to 100 mol% on the transparent electrode layer 7 side (see the back surface 11b in FIG. 2). A range is more preferable. Moreover, it is preferable that the composition ratio of the silicon oxide in the surface 11a side is the range of 70-100 mol%. By setting the composition ratio between the front surface 11a and the back surface 11b of the protective layer 11 within the above range, the difference in refractive index between the transparent electrode layer 7 and the protective layer 11 can be reduced, or the difference in refractive index can be substantially eliminated. it can.

  Further, the protective layer 11 preferably has a refractive index in the range of 1.9 to 2.5 on the transparent electrode layer 7 side and a refractive index in the range of 1.4 to 1.6 on the surface 11a side. . By making the refractive index in the surface 11a and the back surface 11b of the protective layer 11 into the said range, as above-mentioned, the difference of the refractive index of the transparent electrode layer 7 and the protective layer 11 can be made small. Further, when the transparent electrode layer 7 is made of IZO, the refractive index on the back surface 11b side of the protective layer 11 is preferably about 2.1 which is the same as this IZO, and the transparent electrode layer 7 is made of a titanium oxide-based material. In the case of comprising, it is more preferable that the thickness is about 2.5, which is the same as titanium oxide, from the point that reflection at the interface can be prevented.

  When the protective layer 11 is composed of the laminated film as described above, the composition ratio of silicon oxide and titanium oxide in each film from the protective film 11A to the protective film 15P is appropriate as shown in Table 1 below. By adjusting the refractive index, the refractive index gradient in the film thickness t direction can be appropriately controlled. For example, in Table 1 below, in the protective film 11A on the transparent electrode layer 7 side, the composition ratio of titanium oxide is 63 mol%, the refractive index is 2.1, and the difference from the refractive index of the transparent electrode layer 7 made of IZO. Is lost. On the other hand, in the protective film 11P on the surface 11a side of the protective layer 11, the composition ratio of silicon oxide is 100 mol%, the refractive index is 1.4, and in the protective films 11B to 11N in the meantime, silicon oxide and The composition ratio of titanium oxide is gradually changed. Thereby, the protective layer 11 becomes a film having a refractive index that decreases toward the surface 11a in the film thickness t direction.

  In the present invention, the light extraction efficiency is excellent by providing the protective layer 11 that has the above-described appropriately controlled refractive index gradient and suppresses attenuation due to light interference in the film. The light emitting element 1 can be realized.

  In addition to the laminated film as shown in the example shown in FIG. 2, the protective layer 11 is not shown in detail. However, as the thickness of the protective layer 11 increases from the transparent electrode layer 7 side to the surface 11a side in the film thickness t direction, silicon oxide and oxidized It can be set as the single layer film | membrane whose composition ratio with titanium changes continuously. In such a configuration, the change in the refractive index in the film of the protective layer 11 becomes smooth, so that reflection of light in the film is suppressed and the light extraction efficiency is further improved.

Further, in the protective layer 11, the composition ratio of niobium oxide on the transparent electrode layer 7 side (see the back surface 11b in FIG. 2) is in the range of 40 to 100 mol%, and the composition ratio of silicon oxide on the surface 11a side is 60. More preferably, it is in the range of ˜100 mol%.
Further, the protective layer 11 has a composition ratio of tantalum oxide on the transparent electrode layer 7 side (see the back surface 11b in FIG. 2) in the range of 40 to 100 mol%, and a composition ratio of silicon oxide on the surface 11a side is 60. More preferably, it is in the range of ˜100 mol%.
Further, in the protective layer 11, the composition ratio of zirconium oxide on the transparent electrode layer 7 side (see the back surface 11b in FIG. 2) is in the range of 45 to 100 mol%, and the composition ratio of silicon oxide on the surface 11a side is 50. More preferably, it is in the range of ˜100 mol%.

"Positive electrode and negative electrode"
(Positive electrode)
The positive electrode 8 is a p-type electrode formed on the transparent electrode layer 7 described above, and a part of the transparent electrode layer 7 in contact with the p-type semiconductor layer 6 as shown in FIGS. Are provided for electrical connection with a circuit board, a lead frame or the like in the region where the protective layer 11 is removed.
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.

(Negative electrode)
The negative electrode 9 is an n-type electrode formed so as to be in contact with an unillustrated n-type contact layer forming the n-type semiconductor layer 4. When providing the negative electrode 9, a part of the protective layer 11, the transparent electrode layer 7, 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 of an n-type contact layer (not shown). Then, the negative electrode 9 is formed thereon.
As the negative electrode 9, various compositions and structures are well known as in the above-described positive electrode 8, and these well-known compositions and structures can be used without any limitation, and are provided by conventional means well known in this technical field. Can do.

  According to the semiconductor light emitting device 1 according to the present invention as described above, the protective layer 11 laminated on the transparent electrode layer 7 is made of at least silicon oxide and titanium oxide, and the transparent electrode layer 7 in the film thickness t direction. Since the composition ratio of silicon oxide and titanium oxide changes from the side toward the surface 11a side, the refractive index gradient gradually decreases from the transparent electrode layer 7 side toward the surface 11a side. Reflection of light at the interface is suppressed by reducing the difference in refractive index between the electrode layer 7 and the protective layer 11 and the difference in refractive index between the protective layer 11 and the sealing resin. Thereby, it becomes possible to provide the semiconductor light emitting device 1 in which the light extraction efficiency is remarkably improved and a high light emission output is obtained.

[Method for Manufacturing Semiconductor Light-Emitting Element]
The method for producing a semiconductor light emitting device of the present invention is a method for producing the light emitting device 1 as shown in FIGS. 1A, 1B and 2 described above, and the n-type semiconductor layer 4 is formed on the substrate 10. The semiconductor layer forming step of forming the laminated semiconductor layer 20 by sequentially laminating the light emitting layer 5 and the p-type semiconductor layer 6 and forming the transparent electrode layer 7 on the p-type semiconductor layer 6 provided in the laminated semiconductor layer 20. It comprises a transparent electrode forming step and a protective layer forming step of laminating a protective layer 11 on the transparent electrode layer 7, and this protective layer forming step comprises a target 47A made of silicon oxide (SiO ₂ ) and titanium oxide (TiO ₂ ). ₂ ) using a sputtering method using the target 47B (see the sputtering apparatus 40 shown in FIG. 3) and controlling the power applied to each of the targets 47A and 47B, so that the transparent By changing the composition ratio of silicon oxide and titanium oxide from the polar layer 7 side toward the surface 11a side, a refractive index gradient gradually decreases from the transparent electrode layer 7 side toward the surface 11a side. This is a step of forming the protective layer 11.
In the present embodiment, a method in which a step of forming a buffer layer, a base layer, and electrodes (a positive electrode and a negative electrode) is provided in addition to the above steps will be described as an example.

"Formation of buffer layer"
In the process of manufacturing the light emitting device 1 as shown in FIGS. 1A and 1B, first, various pretreatments are performed on the surface of the substrate 10, and then the substrate 10 is exemplified in FIG. A buffer layer 2 made of single crystal AlN is formed by sputtering into a chamber 41 of a sputter apparatus 40. As a pretreatment method for the surface of the substrate 10 at this time, for example, a wet process such as a conventionally known RCA cleaning method, a method of exposing the surface of the substrate 10 in plasma, or the like can be used. Further, as a method of forming the buffer layer 2 on the substrate 10, a conventionally known method such as a MOCVD method, a pulse laser deposition (PLD) method, a pulsed electron beam deposition (PED) method, etc., in addition to a sputtering method. Can be appropriately selected and used.

"Formation of underlayer"
"Semiconductor layer formation process"
Next, the wafer having the buffer layer 2 formed on the substrate 10 is introduced into a MOCVD apparatus (not shown), and the base layer 3 is formed on the buffer layer 2 (formation of the base layer).
Then, 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, as shown in FIGS. 1A and 1B. A laminated semiconductor layer 20 is formed.

When a gallium nitride compound semiconductor is formed by MOCVD, hydrogen (H ₂ ) or nitrogen (N ₂ ) is used as a carrier gas, trimethyl gallium (TMG) or triethyl gallium (TEG) is used as a Ga source as a group III source, an Al source As trimethylaluminum (TMA) or triethylaluminum (TEA), trimethylindium (TMI) or triethylindium (TEI) as an In source, ammonia (NH ₃ ) as an N source as a group V source, hydrazine (N ₂ H ₄ ), etc. 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.

Specifically, first, by selecting and adjusting a source gas and an organic metal source to be supplied to the inside of the MOCVD apparatus, a single crystal Al _X Ga _{1 -X} N (0 ≦ x ≦ 1) is formed on the underlayer 3. The n-type contact layer and the n-type clad layer are sequentially laminated. At this time, the n-type semiconductor layer 4 is formed by doping the n-type contact layer and the n-type cladding layer with the n-type impurity by supplying the n-type impurity (dopant) as described above into the MOCVD apparatus. .

Next, the light emitting layer 5 is formed on the n-type semiconductor layer 4 by alternately laminating barrier layers and well layers. When such a light emitting layer 5 is formed, for example, six barrier layers made of Si-doped GaN and five well layers made of non-doped In _0.2 Ga _0.8 N are alternately arranged. It can be a method of forming by stacking.

Next, the p-type semiconductor layer 6 including the p-type cladding layer and the p-type contact layer is formed on the light-emitting layer 5, that is, on the barrier layer that is the uppermost layer of the light-emitting layer 5. When forming the p-type semiconductor layer 6, for example, a p-type cladding layer made of Al _0.1 Ga _0.9 N is formed on the light emitting layer 5 (the uppermost barrier layer), and Al ₀ is formed thereon. _A p-type contact layer made of _0.02 Ga _0.98 N is formed. At this time, by supplying a p-type impurity such as Mg into the MOCVD apparatus 2, the p-type cladding layer and the p-type contact layer are doped with the p-type impurity.

  The laminated semiconductor layer 20 including the n-type semiconductor layer 4, the light-emitting layer 5, and the p-type semiconductor layer 6 is formed on the base layer 3 through the processes described above.

"Transparent electrode layer formation process"
Next, in the transparent electrode layer forming step, the transparent electrode layer 7 made of a translucent conductive material is formed on the p-type semiconductor layer 6 (p-type contact layer) constituting the laminated semiconductor layer 20.
Specifically, as shown in FIGS. 1A and 1B, ITO, IGO, ICO, AZO, GZO, or titanium oxide (TiO ₂ ) system in addition to IZO so as to cover the p-type semiconductor layer 6. A conductive material containing at least the material and the like is formed by a conventional means well known in this technical field. At this time, film formation can be performed while doping the conductive material with an arbitrary impurity element. Further, after such a transparent electrode layer 7 is formed, thermal annealing for the purpose of alloying or transparency may be further performed.

In the present invention, as described above, when the transparent electrode layer 7 is formed from a titanium oxide (TiO ₂ ) -based material using a sputtering method, Nb, Ta, Mo, W, Te, Sb, Fe At least one dopant element selected from the group consisting of Ru, Ge, Sn, Bi, Al, Hf, Si, Zr, Co, Cr, Ni, V, Mn, Re, Ce, Y, P and B Using a target made of a titanium oxide-based material that is contained in a proportion of 30% by mass or less, the sputtering atmosphere is an atmosphere containing at least 0.1 to 10% by volume of oxygen and the balance being made of an inert gas; It is more preferable to use a method of annealing at a temperature of 250 ° C. or higher after sputtering film formation at a film formation rate of 01 to 0.2 nm / second. Since the transparent electrode layer 7 obtained by such a method has a sheet resistance significantly reduced and becomes a film having excellent conductivity and transparency, the current can be diffused widely throughout the semiconductor layer, so that light extraction is possible. It becomes possible to constitute the light emitting device 1 that is more excellent in efficiency.

  Further, when the transparent electrode layer 7 is made of a titanium oxide-based material, the transparent electrode layer 7 is made by setting the composition ratio of titanium oxide on the transparent electrode layer 7 side of the protective layer 11, that is, the back surface 11 b, to 100 mol%. And the difference in refractive index between the protective layer 11 and the protective layer 11 can be eliminated. Thereby, the reflection of light at the interface between the transparent electrode layer 7 and the protective layer 11 is further suppressed, and the light extraction efficiency can be further improved.

"Protective layer formation process"
Next, in the protective layer forming step, the protective layer 11 is formed so as to cover the transparent electrode layer 7.
Specifically, as shown in FIG. 2, a sputtering method using a target 47A made of silicon oxide (SiO ₂ ) and a target 47B made of titanium oxide (TiO ₂ ) on the transparent electrode layer 7 is used (FIG. ₂ ). 3), the power applied to each of the targets 47A and 47B is controlled, and the composition of silicon oxide and titanium oxide increases from the transparent electrode layer 7 side to the surface 11a side in the film thickness t direction. By changing the ratio, the protective layer 11 is formed while providing a refractive index gradient in which the refractive index gradually decreases from the transparent electrode layer 7 side toward the surface 11a side.

"Sputtering equipment"
In the manufacturing method of the present invention, for example, a sputtering apparatus 40 as shown in FIG. In the sputtering apparatus 40 illustrated in FIG. 3, target plates 43 </ b> A and 43 </ b> B and a heater 44 are provided in a chamber 41, and a wafer (up to the transparent electrode layer 7 on the substrate 10) is formed on the heater 44. A formed wafer (see symbol A in FIG. 3) is attached. The bias current applied to the substrate is supplied to the heater 44 via the matching box 45, and the power current applied to the targets 47A and 43B via the matching box 46 is supplied to each of the target plates 43A and 43B. Is supplied. Furthermore, the inside of the chamber 41 is a sputtering atmosphere filled with a gas having a predetermined composition. Then, when the plasma is generated in the chamber 41, the silicon oxide material forming the target 47A and the titanium oxide material forming the target 47B are knocked out, and the protective layer 11 is formed on the wafer A attached to the heater 44. The

  Further, in the manufacturing method of the present invention, as described above, the target 47A made of silicon oxide and the target 47B made of titanium oxide are used as targets for forming the protective layer 11 by sputtering. In the present invention, the film forming process is performed while changing the composition ratio of the protective layer 11 by controlling the power applied to the targets 47A and 47B made of each material under the conditions described later.

`` Film formation conditions ''
In the protective layer forming step of the present invention, as described above, the film thickness t direction of the protective layer 11 is changed by changing the composition ratio of silicon oxide and titanium oxide from the transparent electrode layer 7 side toward the surface 11a side. The refractive index gradient at is properly controlled. At this time, the power applied to each of the targets 47A and 47B during film formation is controlled so that the composition ratio of silicon oxide increases in the film thickness t direction of the protective layer 11 from the back surface 11b side to the front surface 11a side. By doing so, a refractive index gradient can be provided in which the refractive index gradually decreases toward the surface 11 a side of the protective layer 11.

  Below, the procedure in the case of forming the protective layer 11 which consists of laminated films like the example shown in FIG. 2 using the sputtering device 40 illustrated in FIG. 3 is demonstrated. The protective layer 11 in the example shown in FIG. 2 is protected from the protective film 11A in which the composition ratio of silicon oxide and titanium oxide changes stepwise from the transparent electrode layer 7 side to the surface 11a side in the film thickness t direction. 15 layers of protective films up to the film 11P are laminated.

First, a wafer in which up to the transparent electrode layer 7 is laminated on the substrate 10 is introduced into the chamber 41 of the sputtering apparatus 40, and the chamber 41 is set to a sputtering atmosphere made of a predetermined gas composition. As the sputtering atmosphere at this time, it is preferable that the oxygen (O ₂ ) gas is contained in the range of 0 to 20% by volume, and the balance is an inert gas. Specifically, for example, argon (Ar) gas as an inert gas is introduced into the chamber 41 of the sputtering apparatus 40, and O ₂ gas is introduced in an amount such that the concentration in the chamber 41 is in the above range. In the present invention, by setting the sputtering atmosphere as the above condition, it is possible to provide a desired refractive index gradient while appropriately controlling the composition ratio of silicon oxide and titanium oxide in the film of the protective layer 11.

  Next, power is applied to the target 47A made of silicon oxide and the target 47B made of titanium oxide, and the composition ratio is changed stepwise in the film thickness t direction by controlling the power applied to each. Thus, the protective layer 11 is formed as a laminated film including the protective films 11A to 11P having different composition ratios.

Specifically, as in the conditions illustrated in Table 1 above, by controlling the power applied to each of the targets 47A and 47B within a range of 0 to 500 W, silicon oxide and titanium oxide are respectively controlled. A total of 15 protective films 11A to 15P having different composition ratios are stacked. At this time, in the protective film 11A on the transparent electrode layer 7 side, that is, the back surface 11b side, the power applied to the target 47B is set to 500 W, and the power applied to the target 47A is set to 64 W. Is 63% and the refractive index is 2.1. Alternatively, as in the reference example in Table 1 described above, the power applied to the target 47B is set to 500 W, and the power applied to the target 47A is set to 0 W, whereby the titanium oxide composition ratio is refracted to 100 mol%. The rate is 2.5.
Accordingly, when the transparent electrode layer 7 is made of IZO (refractive index: 2.1) or a titanium oxide-based material (refractive index: about 2.5), the refraction between the transparent electrode layer 7 and the protective layer 11 is achieved. The difference in the refractive index can be reduced or the difference in the refractive index can be almost eliminated, and it is possible to prevent the light extraction efficiency from being reduced due to the reflection of light at the interface.

  On the other hand, in the protective film 11P on the surface 11a side of the protective layer 11, the power applied to the target 47A is set to 500 W, and the power applied to the target 47B is set to 0 W, so that the composition ratio of silicon oxide is 100%. The refractive index is 1.4. Further, in the protective films 11B to 11N between the protective film 11A and the protective film 11P, as shown in Table 1 above, by changing the power applied to the targets 47A and 47B stepwise, silicon oxide and oxidized The composition ratio of titanium is changed stepwise. As a result, as shown in the graph of FIG. 4, the protective layer 11 is a film having a refractive index gradient that decreases in refractive index from the back surface 11 b side to the front surface 11 a side in the film thickness t direction. Therefore, the protective layer 11 in which reflection inside the film is suppressed can be formed, and the light emitting element 1 having excellent light extraction efficiency can be manufactured.

  The sputter deposition rate of the protective layer 11 is preferably in the range of 0.1 to 1 nm / second. By setting the deposition rate of the protective layer 11 within the above range, it is possible to provide a desired refractive index gradient while appropriately controlling the composition ratio of silicon oxide and titanium oxide in the film. When the film formation rate of the protective layer 11 is larger than the above range, it is difficult to accurately control the composition ratio (refractive index gradient), and when the film formation rate is slower than the above range, the productivity is lowered.

  In the present invention, the bias value applied to the substrate side (wafer A, substrate 10) when the protective layer 11 is formed by sputtering is not particularly limited. However, for example, in the range of 0 to 100 W, it is possible to provide a desired refractive index gradient while appropriately controlling the composition ratio of silicon oxide and titanium oxide in the film of the protective layer 11. preferable.

  In the present embodiment, the protective layer forming step is described by taking a method of forming the protective layer 11 as a laminated film as shown in FIG. 2 as an example, but the present invention is not limited to this. For example, by continuously changing the power applied to each of the targets 47A and 47B, the composition of the silicon oxide and the titanium oxide increases as the protective layer 11 moves from the back surface 11b side to the front surface 11a side in the film thickness t direction. It is also possible to form a single layer film while continuously changing the ratio. When the protective layer 11 is formed by such a method, the protective layer 11 in which the refractive index changes smoothly in the film can be obtained. Therefore, light attenuation is further suppressed, and the light-emitting element 1 that is superior in light extraction efficiency. Can be manufactured.

“Formation of electrodes”
Next, a part of the transparent electrode layer 7 is exposed by etching away a predetermined position of the protective layer 11, a positive electrode (p-type electrode) 8 is formed in this region, and a predetermined part of the laminated semiconductor layer 20 is further formed. The exposed region 4c is formed in the n-type semiconductor layer 4 by etching and removing the position, and the negative electrode (n-type electrode) 9 is formed in the exposed region 4c.

Specifically, as shown in FIGS. 1A and 1B, first, a mask pattern is formed on the surface of the protective layer 11, and a predetermined position of the protective layer 11 is removed by a method such as dry etching. Thus, the positive electrode forming region 7A of the transparent electrode layer 7 is exposed.
Next, in order from the surface 7a side of the transparent electrode layer 7, for example, each material of Ti, Al, and Au is laminated by a conventionally known method to form a positive electrode 8 having a three-layer structure that is not shown in detail. Can do.

  Next, when forming the negative electrode 9, first, a part of the protective layer 11, the transparent electrode layer 7, and the laminated semiconductor layer 20 formed on the substrate 10 is removed by a method such as dry etching, thereby obtaining an n-type. A part of an n-type contact layer (not shown) provided in the semiconductor layer 4 is exposed. Then, on the exposed region 4c, for example, four layers are omitted in detail by laminating Ni, Al, Ti, and Au materials in order from the surface side of the exposed region 4c by a conventionally known method. A negative electrode 9 having a structure can be formed.

“Division of devices (chips)”
Next, the wafer obtained by the above-described steps is ground and polished on the back surface of the substrate 10 to form a mirror-like surface, and then cut into, for example, a 350 μm square to obtain a chip-like light emitting element. 1 can be used.

  According to the manufacturing method of the semiconductor light emitting element 1 according to the present invention as described above, the protective layer forming step of laminating the protective layer 11 on the transparent electrode layer 7 includes the target 47A made of silicon oxide and titanium oxide. By using the sputtering method using the target 47B and controlling the power applied to each of the targets 47A and 47B, the silicon oxide and the silicon oxide are formed from the back surface 11b on the transparent electrode layer 7 side toward the front surface 11a side in the film thickness t direction. By changing the composition ratio with titanium oxide, the protective layer 11 is formed while the refractive index gradient gradually decreases from the back surface 11b side to the front surface 11a side. Therefore, the transparent electrode layer 7 and the protective layer are formed. 11 and the refractive index difference between the protective layer 11 and the sealing resin can be reduced. Thereby, since reflection of light at the interface between the transparent electrode layer 7 and the protective layer 11 and the interface between the protective layer 11 and the sealing resin can be suppressed, the semiconductor light emitting device 1 having excellent light extraction efficiency and high light emission efficiency. Can be manufactured.

[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 configuration well known to those skilled in the art 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. A lamp 80 shown in FIG. 5 is of a bullet type, and uses the light emitting element 1 shown in FIGS. 1A and 1B (see also FIG. 2). As shown in FIG. 5, the positive electrode 8 of the light emitting element 1 is bonded to one of the two frames 81 and 82 (the frame 81 in FIG. 5) with a wire 83, and the negative electrode 9 of the light emitting element 1 is bonded to the other with a wire 84. The light emitting element 1 is mounted by being bonded to the frame 82. Further, the periphery of the light emitting element 1 is sealed with a mold 85 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, 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, but the present invention is not limited to these examples.

[Example 1]
In this example, a sample of a semiconductor light emitting device was manufactured by the procedure described below (see FIGS. 1A, 1B, 2 and the like).
First, a substrate 10 made of sapphire and having a main surface made of a (0001) C plane was prepared. 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. At this time, a sputtering apparatus equipped with a high-frequency power source and having a mechanism capable of moving the position of the magnet in the target was used.

  Next, an underlayer 3 made of a group III nitride semiconductor was formed on the buffer layer 2 by using a low pressure MOCVD method. At this time, first, the substrate 10 on which the buffer layer 2 was formed was taken out of the sputtering apparatus and introduced into the reactor of the MOCVD apparatus. Then, while continuing the flow of ammonia gas into the reaction furnace, the temperature of the substrate 10 is raised to 1120 ° C. in a hydrogen atmosphere, and then the supply of trimethylgallium (TMG) into the reaction furnace is started, An underlayer 3 made of undoped GaN was epitaxially grown on the layer 2 until the film thickness became 3 μm.

Next, following the formation of the underlayer 3, an n-type contact layer made of GaN was formed using the same MOCVD apparatus. At this time, the n-type contact layer was doped with Si, and the crystal growth was performed under the same conditions as the underlayer 3 except that SiH ₄ was circulated as a Si dopant material. Then, an n-type semiconductor layer 4 was formed by laminating an n-type cladding layer on the n-type contact layer using the same MOCVD apparatus.

Subsequently, the light emitting layer 5 was laminated | stacked on the n-type semiconductor layer 4 produced in the said procedure using the same MOCVD apparatus. The light emitting layer 5 formed in the present example has a multiple quantum well structure including a barrier layer made of GaN and a well layer made of Ga _0.85 In _0.15 N. In forming the light emitting layer 5, first, a barrier layer is formed on the n-type cladding layer included in the n-type semiconductor layer 4, and Ga _0.85 In _0.15 N is formed on the barrier layer. A well layer was formed. After repeating such a stacking procedure five times, a sixth barrier layer is formed on the fifth stacked well layer, and the barrier layers are arranged on both sides of the light emitting layer 5 having a multiple quantum well structure. did.

Subsequently, using the same MOCVD apparatus as described above, a p-type cladding layer made of GaN doped with four layers of non-doped Al _0.06 Ga _0.94 N and three layers of Mg was formed. Further, a p-type contact layer made of Mg-doped GaN having a film thickness of 200 nm was formed thereon to form a p-type semiconductor layer 6.
In this way, the n-type semiconductor layer 4, the light emitting layer 5, and the p-type semiconductor layer 6 were laminated in this order on the base layer 3 to form a laminated semiconductor layer 20.

Next, using the wafer (semiconductor laminated substrate) obtained by the above procedure, a light emitting diode (LED), which is a kind of semiconductor light emitting device, was produced according to the following procedure.
First, a conductive material film made of an IZO material was laminated on the p-type semiconductor layer 6 by using a known sputtering method to form a transparent electrode layer 7 having a thickness of 220 nm.

Next, the protective layer 11 was formed so as to cover the transparent electrode layer 7. Specifically, first, a wafer in which up to the transparent electrode layer 7 is laminated on the substrate 10 is introduced into the chamber 41 of the sputtering apparatus 40 (see FIG. 3), and the inside of the chamber 41 is oxygen (O ₂ ). An Ar gas atmosphere containing 10% by volume of gas was used.
Next, while applying power to the target 47A made of silicon oxide and the target 47B made of titanium oxide, and controlling the power applied to each as shown in Table 1 above, the composition ratio in the film thickness t direction The protective films 11A to 11P each having a different composition ratio were sequentially stacked.

Next, a part of the protective layer 11 is removed by a known photolithography technique to expose the surface of the transparent electrode layer 7, and Ti, Pt, and Au are sequentially laminated at this position to thereby form a positive electrode 8 having a three-layer structure. Formed. At this time, the positive electrode 8 was formed in a circular shape having a diameter of 90 μm.
Then, the exposed region 4c where the n-type contact layer was exposed was provided by performing dry etching on a part of the protective layer 11, the transparent electrode layer 7, and the laminated semiconductor layer 20 to remove. Then, the positive electrode 9 as shown in FIGS. 1A and 1B was formed by sequentially laminating Ni and Au layers in the exposed region 4c.

Next, after grinding and polishing the back side of the substrate 10 of the wafer on which each electrode is formed to form a mirror-like surface, the wafer is cut into 240 μm × 600 μm square chips to form an LED (light emitting diode). A chip (semiconductor light emitting element 1) was obtained.
And as shown in FIG. 5, the said chip | tip was mounted on the lead frame 81 so that the positive electrode 8 and the negative electrode 9 might become upper side, and the lamp | ramp 80 was produced by connecting with a lead frame with a gold wire.

  Then, while measuring the light emission output Po (mW) when a forward current of 20 mA was passed between the p-side (positive electrode 8) and n-side (negative electrode 9) electrodes of the lamp 80 produced by the above method, The driving voltage (Vf) was measured, and the results are shown in Table 2 below.

[Example 2]
In this example, in the protective layer forming step, the protective layer was formed under the following conditions while the composition ratio was continuously changed in the film thickness direction, and other procedures were the same as those in Example 1 above. A light emitting element was manufactured under the same conditions.

  In this example, the power applied to each of the target 47A made of silicon oxide and the target 47B made of titanium oxide is continuously changed, so that the protective layer 11 is changed from the back surface 11b side to the front surface 11a in the film thickness t direction. A monolayer film was formed while continuously changing the composition ratio of silicon oxide and titanium oxide toward the side. And it was set as the chip-like light emitting element 1 in the procedure similar to the said Example 1, Furthermore, the lamp | ramp 80 as shown in FIG.

  Then, as in Example 1 above, the light emission output Po (mW) when a forward current of 20 mA was passed between the p-side (positive electrode 8) and n-side (negative electrode 9) electrodes of the produced lamp 80 was measured. In addition, the driving voltage (Vf) at this time was measured, and the results are shown in Table 2 below.

[Example 3]
In the present embodiment, in the transparent electrode layer forming step, the transparent electrode layer is formed from a titanium oxide-based material under the following conditions, the composition ratio of titanium oxide in the protective film 11A is 100%, and the film thickness is in the t direction. The light emitting element is manufactured under the same conditions as in Example 1 except for the point that the protective layer 11 is formed in which the composition ratio is changed stepwise and the silicon oxide composition ratio of the protective film 11P is 100%. did.

In the present embodiment, a wafer in which up to the laminated semiconductor layer 20 is laminated on the substrate 10 is introduced into the chamber of the sputtering apparatus, and the substrate 10 side is attached to the heater so that the p-type semiconductor layer 6 side is exposed in the chamber. . And the target made from a titanium oxide (made by Toshima Seisakusyo Co., Ltd.) which contains 6 mass% Nb as a dopant was mounted on the target plate. The sputtering atmosphere in the chamber was an argon gas atmosphere containing 0.8% by volume of oxygen. Further, in order to generate plasma, a power of 2000 W was applied to the target side (target plate side), and a bias of 0 W was applied to the wafer (substrate 10) side. Then, by setting various conditions based on the film formation rate data confirmed in advance, the film formation rate is set to 0.2 nm / second, and the Nb-doped film having a film thickness of 250 nm is formed on the p-type semiconductor layer 6. A titanium oxide film was formed. Next, after the inside of the chamber of the sputtering apparatus is replaced with a nitrogen atmosphere, the titanium oxide film formed by the above procedure is subjected to an annealing treatment at a temperature of 350 ° C. for 120 seconds, whereby the p-type semiconductor layer 6 is formed. A transparent electrode layer 11 made of an Nb-doped titanium oxide material was formed.
And it was set as the chip-like light emitting element 1 in the procedure similar to the said Example 1, Furthermore, the lamp | ramp 80 as shown in FIG.

  Then, as in Example 1 above, the light emission output Po (mW) when a forward current of 20 mA was passed between the p-side (positive electrode 8) and n-side (negative electrode 9) electrodes of the produced lamp 80 was measured. In addition, the driving voltage (Vf) at this time was measured, and the results are shown in Table 2 below.

[Comparative example]
In the comparative example, the chip of the semiconductor light emitting device was formed in the same manner as in Example 1 except that silicon oxide was formed as a protective film on the transparent electrode layer and the conventional configuration was provided with no refractive index gradient. A lamp was manufactured using this chip as described above.

  Then, similarly to the above, the light emission output Po (mW) when a forward current of 20 mA was passed between the p-side (positive electrode) and n-side (negative electrode) electrodes of the produced lamp was measured, and the driving voltage at this time (Vf) was measured and the results are shown in Table 2 below.

  The specifications of the protective layer and the transparent electrode layer, the light emission output (Po), and the measurement result of the drive voltage (Vf) in the above Examples and Comparative Examples are shown in Table 2 below.

[Evaluation results]
As shown in Table 2, the samples of Examples 1 to 3 having the configuration of the light emitting element according to the present invention all have a light emission output (Po) in a forward light bulb (I) of 20 mA of 19 mW or more, and a high light emission output. Obtained. From the above results, it was confirmed that the samples of Examples 1 to 3 had high light extraction efficiency and excellent light emission characteristics.
Note that Example 2 formed by continuously controlling the refractive index gradient by changing the composition ratio of silicon oxide and titanium oxide continuously in the film thickness direction in the protective layer is the same as Example 1. It was confirmed that a high light emission output was obtained. In Example 3 in which the transparent electrode layer was formed from a titanium oxide-based material using a sputtering method, the sheet resistance of the transparent electrode layer was reduced and the film was excellent in conductivity. It was confirmed that the current could be diffused widely throughout the layer, and that the light emission output was further improved.

On the other hand, in the sample of the comparative example having a conventional configuration in which the refractive index gradient is not provided in the protective layer, the light emission output (Po) is 17.5 mW, which is compared with the samples of Examples 1 to 3 above. The output is low.
In the sample of the comparative example, since the difference in refractive index between the transparent electrode layer and the protective layer is large, it is considered that light is reflected at these interfaces and the light is confined inside the device. Furthermore, since the sample of the comparative example has no refractive index gradient in the thickness direction of the protective layer, light interference occurs in the film, and the light extraction efficiency is low. It is considered inferior.

  According to the results of the above examples, the semiconductor light-emitting device of the present invention has the refractive index difference between the transparent electrode layer and the protective layer suppressed to be small, and the refractive index in the protective layer film is appropriately controlled. It is clear that the light extraction efficiency is excellent and a high light emission output can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Semiconductor light emitting element (light emitting element), 10 ... Substrate, 4 ... N type semiconductor layer, 5 ... Light emitting layer, 6 ... P type semiconductor layer, 7 ... Transparent electrode layer, 11 ... Protective layer, 11a ... Surface (Protective layer) ), 20 ... laminated semiconductor layer, 40 ... sputtering device, 47A ... target (silicon oxide: target composed of SiO _2), 47B ... target (titanium oxide: target composed of TiO _2), 80 ... lamp, t ... thickness ( Protective layer)

Claims (16)

A laminated semiconductor layer sequentially laminated on the substrate, and comprising an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer;
A transparent electrode layer formed on the p-type semiconductor layer provided in the laminated semiconductor layer;
A protective layer laminated on the transparent electrode layer,
The protective layer is made of silicon oxide (SiO ₂ ) and titanium oxide (TiO ₂ ), and the composition ratio of the silicon oxide and the titanium oxide changes in the film thickness direction from the transparent electrode layer side to the surface side. Thus, the semiconductor light emitting device has a refractive index gradient in which the refractive index gradually decreases from the transparent electrode layer side toward the surface side.   2. The semiconductor light emitting element according to claim 1, wherein the composition ratio of the silicon oxide increases as the protective layer moves from the transparent electrode layer side to the surface side in the film thickness direction.   2. The protective layer is a laminated film in which the composition ratio of the silicon oxide and the titanium oxide changes stepwise as it goes from the transparent electrode layer side to the surface side in the film thickness direction. Or the semiconductor light-emitting device of Claim 2.   The protective layer is formed of a single layer film in which a composition ratio of the silicon oxide and the titanium oxide continuously changes from the transparent electrode layer side to the surface side in the film thickness direction. The semiconductor light emitting device according to claim 1.   The protective layer has a composition ratio of the titanium oxide on the transparent electrode layer side in the range of 30 to 100 mol%, and a composition ratio of the silicon oxide on the surface side in the range of 70 to 100 mol%. The semiconductor light-emitting device according to claim 1, wherein:   The protective layer has a refractive index on the transparent electrode layer side in the range of 1.9 to 2.5, and a refractive index on the surface side in the range of 1.4 to 1.6. The semiconductor light-emitting device according to claim 1. 2. The transparent electrode layer is made of any one of indium zinc oxide (IZO), indium tin oxide (ITO), or titanium oxide (TiO ₂ ) -based material. The semiconductor light-emitting device according to claim 6. A semiconductor layer forming step of sequentially stacking an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer on a substrate to form a stacked semiconductor layer;
A transparent electrode forming step of forming a transparent electrode layer on the p-type semiconductor layer provided in the laminated semiconductor layer;
Comprising a protective layer forming step of laminating a protective layer on the transparent electrode layer;
The protective layer forming step uses a sputtering method using a target made of silicon oxide (SiO ₂ ) and a target made of titanium oxide (TiO ₂ ), and controls the power applied to each of the targets, The refractive index gradually decreases from the transparent electrode layer side to the surface side by changing the composition ratio of the silicon oxide and the titanium oxide as it goes from the transparent electrode layer side to the surface side in the thickness direction. A method for manufacturing a semiconductor light emitting device, comprising forming the protective layer while providing a gradient.   The said protective layer formation process forms the said protective layer, increasing the composition ratio of the said silicon oxide as it goes to the surface side from the said transparent electrode layer side in a film thickness direction, It is characterized by the above-mentioned. Manufacturing method of the semiconductor light-emitting device.   In the protective layer forming step, the composition of the protective layer is changed by gradually changing the composition ratio of the silicon oxide and the titanium oxide in the film thickness direction from the transparent electrode layer side to the surface side. The method of manufacturing a semiconductor light emitting element according to claim 8, wherein films having different ratios are formed as stacked films.   In the protective layer forming step, the protective layer is formed as a single layer film while continuously changing the composition ratio of the silicon oxide and the titanium oxide in the film thickness direction from the transparent electrode layer side to the surface side. The method of manufacturing a semiconductor light emitting element according to claim 8, wherein the method is formed as follows.   The protective layer forming step forms the protective layer while changing power applied to each of the target made of silicon oxide and the target made of titanium oxide in a range of 0 to 500 W, respectively. The manufacturing method of the semiconductor light-emitting device of any one of Claims 8-11. In the transparent electrode layer forming step, the transparent electrode layer is made of any one of an indium zinc oxide (IZO) material, an indium tin oxide (ITO) material, and a titanium oxide (TiO ₂ ) -based material. It forms, The manufacturing method of the semiconductor light-emitting device of any one of Claims 8-12 characterized by the above-mentioned.   The transparent electrode layer forming step includes Nb, Ta, Mo, W, Te, Sb, Fe, Ru, Ge, Sn, Bi, Al, Hf, Si, Zr, Co, Cr, Ni, V, Mn, Re, Using a target made of a titanium oxide-based material containing at least one dopant element selected from the group consisting of Ce, Y, P and B in a proportion of 30% by mass or less, at least 0.1 to 10% by volume of oxygen And sputtering at a film formation rate of 0.01 to 0.2 nm / second in an atmosphere containing an inert gas, and annealing at a temperature of 250 ° C. or higher. The manufacturing method of the semiconductor light-emitting device of any one of Claims 8-12.   The semiconductor light-emitting device obtained by the manufacturing method of any one of Claims 8-14.   A lamp comprising the semiconductor light emitting device according to any one of claims 1 to 7 or claim 15.

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