JP5388068B2 - COMPOSITE SUBSTRATE FOR LIGHT EMITTING ELEMENT FORMATION AND MANUFACTURING METHOD THEREOF - Google Patents

Description

Related Application This application is an application claiming priority based on Japanese Patent Application No. 2007-229263 filed with the Japan Patent Office on September 4, 2007, the contents of which are incorporated herein by reference.
TECHNICAL FIELD The present invention relates to a composite substrate for forming a light emitting element that can be used for a display, illumination, a backlight light source, and the like, and a method for manufacturing the same, and particularly to a composite substrate for forming a light emitting diode element using a light conversion material that emits fluorescence. It relates to a manufacturing method.

In recent years, a blue light emitting element using a nitride compound semiconductor (In _x Al _y Ga _1-xy N, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) is used as a white light source. Research and development of light-emitting diodes has been actively conducted. White light-emitting diodes are lightweight, do not use mercury, and have a long life, so that demand is expected to increase rapidly in the future. The most commonly used method for converting blue light of a blue light emitting element into white light is the front surface of a light emitting element that emits blue light, as described in, for example, Japanese Patent Application Laid-Open No. 2000-208815. In addition, a coating layer containing a phosphor that absorbs a part of blue light and emits yellow light and a mold layer for mixing the blue light of the light source and the yellow light from the coating layer are provided and have a complementary color relationship A pseudo white color is obtained by mixing blue and yellow. Conventionally, a mixture of YAG (Y ₃ Al ₅ O ₁₂ : Ce) powder activated with cerium and an epoxy resin is employed as the coating layer. However, in this method, when the coating layer is applied, uneven distribution of the phosphor powder contained therein, variation in the amount of the phosphor powder among the individual light emitting diodes, etc. are likely to occur, and the resulting color unevenness of the light emitting diodes is pointed out. Yes.
In order to avoid this, the present inventors have disclosed In _x Al _y Ga _1-xy N (0 ≦ 0) on a light conversion material substrate made of a ceramic composite oxide in PCT / JP2005 / 019739 (WO 2006/043719). a nitride semiconductor layer of x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) is formed, and blue light emitted from the light emitting layer is directly incident on the substrate to emit homogeneous yellow fluorescence from the substrate itself. Therefore, a method for obtaining a uniform white color with no color unevenness using only a light emitting chip without using a coating layer containing phosphor powder has been proposed.

However, the method using GaN as the buffer layer shown in the example of Patent Document 2 has a problem that a nitride semiconductor layer is likely to be preferentially formed in the Al ₂ O ₃ phase. Thus, preferentially formed nitride semiconductor Al ₂ O ₃ phase to isolated each other in regions other than Al ₂ O ₃ phase, excellent device formation becomes difficult. In order to avoid this and to cover the entire surface of the substrate with the nitride semiconductor layer, it is necessary to increase the film thickness. However, when the film thickness is increased, the difference between the lattice constant and the thermal expansion coefficient of the substrate and the nitride semiconductor layer will eventually cause distortion as the film thickness increases, and the device characteristics tend to be adversely affected. Become. In order to obtain a device with good characteristics, it is important to form a uniform layer over the entire surface of the substrate from the initial stage of the formation of the nitride semiconductor layer. In order to realize this, it is necessary to form a similar nitride semiconductor layer from both the Al ₂ O ₃ phase and the fluorescence emitting oxide phase having a garnet structure, and light emission is performed through the same step. By producing the element, improvement in characteristics of the obtained element is expected.
When forming the nitride semiconductor layer on the light conversion material substrate, the present inventors formed a nitride layer containing at least Al at a temperature similar to or higher than the growth temperature of the nitride semiconductor layer. , It was found that by using it as a buffer layer, it is possible to perform crystal growth of the nitride semiconductor layer from the oxide phase emitting phosphors in the substrate in the same manner as the Al ₂ O ₃ phase, and the present invention has been achieved. .
That is, the present invention relates to a composite substrate for forming a light emitting element, wherein a nitride buffer layer containing at least Al is formed on a light conversion material substrate, and the buffer layer covers the entire surface of the light conversion material substrate. .
Furthermore, as a preferable form in the present invention, the present invention relates to a composite substrate for forming a light emitting element, characterized in that the phosphor phase has a garnet structure including at least a Y element, an Al element, and a Ce element.
Further, as a preferred embodiment in the present invention, the buffer layer is formed on a light conversion material substrate having a C ₂ surface of Al ₂ O ₃ phase and a (112) surface of a phosphor phase as main surfaces at the same time. The present invention relates to a composite substrate for forming a light emitting element.
The present invention also relates to a method for manufacturing a composite substrate for forming a light emitting element, wherein a nitride buffer layer containing at least Al is formed on a light conversion material substrate, and the light conversion material substrate is entirely covered with the buffer layer.
As a more preferred embodiment, the present invention relates to a method for manufacturing a composite substrate for forming a light emitting element, wherein the nitride semiconductor layer is formed by a metal organic vapor phase reaction method.
As a more preferred embodiment, the present invention relates to a method for manufacturing a composite substrate for forming a light emitting element, wherein the Al-containing nitride buffer layer is formed at a temperature of 900 ° C. or higher and lower than 1400 ° C.
In the composite substrate for forming a light emitting element thus fabricated, a nitride semiconductor layer can be formed in the same manner from both the Al ₂ O ₃ phase and the oxide phase emitting a phosphor having a garnet structure. Thus, a high-performance white light-emitting element can be manufactured through the same process.
As a nitride semiconductor layer forming such a light emitting layer, a nitride semiconductor made of In _x Al _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) is used. A layer is preferred.

1A and 1B are schematic cross-sectional views showing an embodiment of a composite substrate for forming a light emitting device of the present invention.
FIG. 2 is an electron micrograph showing an example of the structure of the light conversion material.
FIG. 3 is a microscopic cross-sectional photograph of the GaN layer obtained in Example 1.
FIG. 4 is a microscopic cross-sectional photograph of the GaN layer obtained in Comparative Example 1.

Explanation of symbols

DESCRIPTION OF REFERENCE NUMERALS 1 Light conversion material substrate 1a Al ₂ O ₃ crystal phase of light conversion material substrate 1b Y ₃ Al ₅ O ₁₂ : Ce crystal phase 2 of light conversion material substrate 2 Buffer layer 2a Nitride layer 2b containing Al GaN layer

As a form of the composite substrate for forming a light emitting element of the present invention, for example, an intricately intertwined Al ₂ O ₃ phase 1a and an oxide phase 1b emitting phosphors are formed on the surface of the light conversion material substrate 1 as shown in FIG. 1A. Regardless of the crystal difference, the buffer layer 2 is formed on the entire surface. The buffer layer includes a nitride layer 2a containing at least Al. Further, in order to improve the uniformity of the composite substrate surface as shown in FIG. 1B, the GaN layer 2b may be formed on the nitride layer containing Al.
In the light conversion material substrate constituting the composite substrate for forming a light emitting element of the present invention, at least two oxide phases selected from a single metal oxide and a composite metal oxide are mutually and continuously three-dimensionally. It consists of a solidified body formed intertwined, at least one of the oxide phases in the solidified body is an Al ₂ O ₃ crystal phase, and at least one of the oxide phases in the solidified body is It contains a metal element oxide that emits fluorescence. The single metal oxide is an oxide of one kind of metal, and the composite metal oxide is an oxide of two or more kinds of metals. Each oxide has a single crystal state and a three-dimensionally entangled structure. Examples of such a single metal oxide include aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), magnesium oxide (MgO), silicon oxide (SiO ₂ ), titanium oxide (TiO ₂ ) and barium oxide (BaO). ), Beryllium oxide (BeO), calcium oxide (CaO), chromium oxide (Cr ₂ O ₃ ) and the like, as well as rare earth element oxides (La ₂ O ₃ , Y ₂ O ₃ , CeO ₂ , Pr ₆ O ₁₁ , Nd). ₂ O ₃ , Sm ₂ O ₃ , Gd ₂ O ₃ , Eu ₂ O ₃ , Tb ₄ O ₇ , Dy ₂ 03, Ho ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ ). As the composite metal _{oxide, LaAlO 3, CeAlO 3, PrAlO} 3, NdAlO 3, SmAlO 3, EuAlO 3, GdAlO 3, DyAlO 3, ErAlO 3, Yb 4 Al 2 O 9, Y 3 Al 5 O 12, _{Er 3 Al 5 O 12, Tb} 3 Al 5 O 12, 11Al 2 O 3 · La 2 O 3, 11Al 2 O 3 · Nd 2 O 3, 3Dy 2 O 3 · 5Al 2 O 3, 2Dy 2 O 3 · Al _{2 O 3, 11Al 2 O 3} · Pr 2 O 3, EuAl 11 O 18, 2Gd 2 O 3 · Al 2 O 3, 11Al 2 O 3 · Sm 2 O 3, Yb 3 Al 5 O 12, CeAl 11 O 18 , Er ₄ Al ₂ O _{9 and the} like.
Since the light conversion material substrate is composed of two or more kinds of oxide phases, various crystal lattice spacings can be selected depending on the combination thereof. For this reason, it is possible to match the lattice spacing of various semiconductors of the light-emitting diode, it is possible to form a good semiconductor layer with good crystal structure consistency and few defects, and the light-emitting layer formed in the semiconductor layer Therefore, efficient light emission can be obtained. Furthermore, since the light conversion material substrate is also a phosphor, it can emit uniform fluorescence by light from the light emitting layer in the semiconductor layer.
When the semiconductor layer for light emitting diodes is a nitride semiconductor layer, among the solidified bodies constituting the light conversion material substrate, a combination containing an Al ₂ O ₃ crystal that is a single metal oxide is cited as a preferable solidified body. It is done. As described above, the Al ₂ O ₃ crystal has good crystal structure matching with typical InGaN constituting the nitride semiconductor layer that emits visible light, and can form a good light emitting layer of the nitride semiconductor. is there. A combination of an Al ₂ O ₃ crystal and a garnet-type crystal single crystal that is a composite metal oxide activated with at least cerium is further preferred as a solidified body. The garnet-type crystal is represented by a structural formula of A ₃ X ₅ O ₁₂ , where A is one or more elements selected from the group of Y, Tb, Sm, Gd, La, Er, It is particularly preferable that one contains at least one element selected from Al and Ga. This is because the light conversion material composed of this particularly preferable combination absorbs part of the light conversion material while transmitting purple to blue light and emits yellow fluorescence. Among them, the combination with Y ₃ Al ₅ O ₁₂ activated with cerium is suitable because it emits strong fluorescence.
The light conversion material substrate of Al ₂ O ₃ / Y ₃ Al ₅ O ₁₂ : Ce that is one embodiment shown in FIGS. 1A and 1B is composed of an Al ₂ O ₃ single crystal and a Y ₃ Al ₅ O ₁₂ : Ce single crystal. Each oxide phase is continuously and three-dimensionally entangled with each other, and is composed of two single crystal phases as a whole. It is very important that each phase is a single crystal. If it is not a single crystal, a good quality nitride semiconductor layer cannot be formed. The light conversion material substrate can be obtained, for example, by cutting the Al ₂ O ₃ / Y ₃ Al ₅ O ₁₂ : Ce solidified body into a predetermined thickness, polishing the surface to a necessary state, and washing. As for the cutting direction of the light conversion material substrate, it is particularly preferable that the (0001) plane of Al ₂ O ₃ is the main surface. Al ₂ O ₃ has a crystal structure similar to In _x Al _y Ga _1-xy N, which is a nitride compound semiconductor, and has an Al ₂ O ₃ (0001) plane and In _x Al _y Ga _1-x-. The lattice spacing of _yN has a small difference and good matching. For this reason, by using the (0001) plane of Al ₂ O ₃ , a good quality nitride semiconductor layer can be obtained and a good light emitting layer can be formed.
The solidified body constituting the light conversion material used in the present invention is produced by solidifying the raw metal oxide after melting. For example, it is possible to obtain a solidified body by a simple method of cooling and condensing a melt charged in a crucible held at a predetermined temperature while controlling the cooling temperature, but the most preferable one is produced by a unidirectional solidification method. It is. This is because the crystal phases contained by unidirectional solidification grow continuously in a single crystal state, and each phase has a single crystal orientation.
The light-converting material used in the present invention has previously been disclosed in Japanese Patent Application Laid-Open Nos. 7-149597 and 7-187893 by the applicant of the present application, except that at least one phase contains a metal element oxide that emits fluorescence. Publication, JP-A-8-81257, JP-A-8-253389, JP-A-8-253390, JP-A-9-67194, and corresponding US applications (US Pat. No. 5,569,547). No. 5,484,752, No. 5,902,963) and the like, and can be manufactured by the manufacturing method disclosed in these applications (patents). Is. The disclosures of these applications or patents are hereby incorporated by reference.
The nitride semiconductor layer formed on the light emitting element forming composite substrate is composed of a plurality of nitride compound semiconductor layers. The plurality of nitride compound semiconductor layers are nitrided represented by the general formula, In _x Al _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), respectively. It is preferably composed of a physical compound. The nitride semiconductor layer has at least a light emitting layer that emits visible light. In order to form a good light-emitting layer, it is preferable to stack a plurality of nitride-based compound semiconductor layers adjusted to the optimum composition for each function in each layer. A plurality of nitride compound semiconductor layers and methods for forming these layers are described in, for example, Jpn. J. et al. Appl. Phys. Vol. 34 (1995), L797 and the like. Specifically, on the substrate, a GaN buffer layer (thickness 30 nm), an n-type-GaN: Si contact layer (thickness 5 μm) on which an n-electrode is formed, and n-type-Al _0.1 Ga _0.9 N: Si layer, n-type -In _0.05 Ga _0.95 N: Si layer, InGaN layer forming a single quantum well structure type light emitting layer, p-type -Al _0.1 Ga _0.9 N: Mg barrier A p-type GaN: Mg layer on which a layer and a p-electrode are formed can be obtained by laminating sequentially by a method such as MOCVD. In addition, the structure of the light emitting layer may be a multiple quantum well structure, a homo structure, a hetero structure, or a double hetero structure. However, in the present invention, since the light emitting element forming composite substrate of the present invention is used as the substrate, the nitride semiconductor layer formed on the light emitting element forming composite substrate includes Al on the surface. Since it has a nitride layer, the GaN buffer layer (thickness 30 nm) can be omitted.
The light emitting layer in the nitride semiconductor layer formed on the light emitting element forming composite substrate in the present invention is preferably visible light. When visible light passes through the light conversion material substrate constituting the composite substrate for forming a light emitting element of the present invention, the wavelength-converted fluorescence and the visible light before conversion are mixed, and depending on the wavelength of the mixed light New pseudo light can be obtained. Furthermore, it is preferable that visible light emits blue or purple. When the emission color is blue or violet, yellow fluorescence is generated from the Y ₃ Al ₅ O ₁₂ : Ce crystal when the blue or violet light from the emission layer is incident on the YAG: Ce single crystal as the substrate. In the Al ₂ O ₃ crystal, blue or violet light is transmitted as it is. Since these lights are mixed and emitted by the structure in which the light conversion material single crystal substrate is continuously and three-dimensionally entangled with each other, a uniform white color with no color unevenness can be obtained. For this reason, it is preferable that the light emitting layer in the nitride semiconductor layer is made of In _x Ga _1-x N (0 ≦ x ≦ 1). The emission wavelength can be changed by changing the molar ratio of In contained in the InGaN layer forming the light emitting layer.
By providing the buffer layer in the present invention, the nitride semiconductor layer can be preferably formed thereon. By using the composite substrate for light emitting element formation in which the nitride buffer layer in the present invention is formed, the nitride semiconductor layer can be formed without newly providing a buffer layer. In general, since the nitride semiconductor layer is formed by vapor phase growth reaction, the surface of the substrate is preferably uniform. For this reason, as with the formation of the nitride semiconductor layer, the formation of the buffer layer is preferably performed by a gas phase reaction method capable of obtaining a high-quality buffer layer. In particular, it is preferably formed by metal organic chemical vapor deposition (hereinafter referred to as MOCVD) from the viewpoint of quality and growth rate. MOCVD is a method in which an organic metal gas as a raw material is pushed onto a substrate heated with H ₂ or N ₂ to cause crystal growth on the substrate surface. The source gas related to the buffer layer includes TMA (trimethylaluminum) or TEA (triethylaluminum) as an Al source, TMG (trimethylgallium) or TEG (triethylgallium) as a Ga source, ammonia or hydrazine as an N source, In general, those used for forming a nitride semiconductor layer in MOCVD can be used.
In the present invention, the nitride buffer layer covers the entire surface of the substrate. Thus, when the nitride semiconductor layer is formed, there is no boundary between the Al ₂ O ₃ phase and the phosphor phase of the light conversion material substrate, and it is possible to stably form a laminated structure. It is also possible to grow preferentially from the Al ₂ O ₃ phase and obtain a uniform surface, but without the nitride buffer layer of the present invention, the light conversion material substrate (Al ₂ O ₃ phase and In order to obtain a uniform surface of a nitride semiconductor layer using only a composite oxide containing a phosphor phase), it is necessary to increase the film thickness, and even if a uniform surface is obtained, cracks are generated due to the distortion. In addition, the substrate may be distorted, adversely affecting device characteristics. However, by using the composite substrate on which the buffer layer is formed in the present invention, it is not necessary to increase the film thickness, it is possible to sufficiently reduce the film thickness, and there is almost no influence on the element characteristics.
The buffer layer according to the present invention includes a nitride layer containing at least Al. Specifically, it is preferable to include a nitride layer represented by Al _x Ga _1-x N (0 <x ≦ 1). More preferably, AlN is included. It is preferable to form the film under a temperature condition of 900 ° C. to 1400 ° C. so that the formation temperature is equal to or higher than that of the nitride semiconductor. More preferably, the film is formed under a temperature condition of 1150 ° C. to 1400 ° C. At 900 ° C. to 1200 ° C., it is difficult to make the nitride layer growing in the Al ₂ O ₃ phase and the phosphor phase uniform, but it is possible to form the nitride layer also in the phosphor phase. . Furthermore, it is possible to obtain a uniform surface more easily by forming the nitride layer at a higher temperature. Further, it is preferable that the buffer layer has better crystallinity because its crystallinity greatly affects the device characteristics of the nitride semiconductor layer formed on the buffer layer. A method for improving the crystallinity of Al _x Ga _1-x N (0 <x ≦ 1) as a nitride layer containing Al can be used to improve device characteristics of the nitride semiconductor layer regardless of temperature conditions. . For example, in MOCVD, when the temperature is higher, Ga inevitably decreases in the resulting Al _x Ga _1-x N (0 <x ≦ 1) composition. In view of the quality of the nitride layer formed as the buffer layer, one having a lower Ga composition is better.
Further, it is more preferable that GaN is formed on the nitride layer containing Al under the condition that the lateral crystal growth rate is increased. The formation of the nitride layer containing Al is similar to the formation of crystal nuclei in the Al ₂ O ₃ phase and the phosphor phase in the light conversion material substrate. Because of the low mobility, a slight difference between the Al ₂ O ₃ phase and the phosphor layer in the phosphor phase may appear as a difference in crystallinity and surface morphology only with the nitride layer containing Al. By growing GaN, migration is likely to occur on the nitride crystal grown in the Al ₂ O ₃ phase and the phosphor phase, and the difference between the crystal phases can be eliminated. When GaN is formed under the condition that the crystal growth rate in the lateral direction is increased, if n-type is formed by doping impurities such as Si, Ge, Se, Te, etc., the above effect is combined with the formation of the n-type-GaN contact layer. This is preferable. In order to increase the crystal growth rate in the lateral direction of GaN, it is possible to use known methods such as changing the growth conditions such as the crystal growth temperature and the V / III ratio, and the method is not selected. Further, the same effect can be obtained by using a method of performing migration preferentially by controlling the source gas supply method for the nitride layer containing Al.
By using the composite substrate for light emitting element formation according to the present invention, the nitride semiconductor layer can be formed without a buffer layer. In general, a vapor phase growth method is used to form the nitride semiconductor layer. In order to form the nitride semiconductor layer, nitrogen is easily lost during heating. By heating while flowing the group V source gas, nitrogen deficiency is reduced, and a stable nitride semiconductor layer can be formed.
Further, according to the present invention, a buffer layer having the same structure as the light emitting element forming composite substrate of the present invention is formed on the substrate using the light conversion material substrate, and a nitride semiconductor layer is formed continuously therewith. It is also possible. When forming the nitride semiconductor layer, it is possible to obtain a light-emitting element having no nitrogen deficiency due to reheating and having similar characteristics.

Hereinafter, the present invention will be described in more detail with specific examples.
Example 1
α-Al ₂ O ₃ powder (purity 99.99%) is 0.82 mol in terms of AlO _3/2 , Y ₂ O ₃ powder (purity 99.9%) is 0.175 mol in terms of YO _3/2 , CeO ₂ powder (purity 99.9%) was weighed to 0.005 mol. These powders were wet mixed in ethanol by a ball mill for 16 hours, and then ethanol was removed using an evaporator to obtain a raw material powder. The raw material powder was pre-melted in a vacuum furnace and used as a raw material for unidirectional solidification.
Next, this raw material was directly charged into a molybdenum crucible and set in a unidirectional solidification apparatus, and the raw material was melted under a pressure of 1.33 × 10 ⁻³ Pa (10 ⁻⁵ Torr). Next, the crucible was lowered at a speed of 20 mm / hour in the same atmosphere to obtain a solidified body composed of two oxide phases of Al ₂ O ₃ (sapphire) phase and (Y, Ce) ₃ Al ₅ O ₁₂ phase. .
A cross-sectional structure perpendicular to the solidification direction of the solidified body is shown in FIG. White part is _Y 3 _Al 5 _O 12: Ce crystals are black portions are _Al 2 _{O 3} crystal. It can be seen that the two crystals have a structure intertwined with each other.
The obtained solidified body was subjected to pole figure measurement by X-ray diffraction, the direction of the crystal axis was examined, and the substrate was cut out with the C plane of the Al ₂ O ₃ crystal phase as the main surface. The light conversion material cut out was polished and washed, and this was used as a light conversion material substrate. The obtained light conversion material substrate was again subjected to X-ray diffraction measurement, and it was confirmed that the error between the substrate surface and the C plane of Al ₂ O ₃ was within ± 2 °.
Formation of the buffer layer for the composite substrate for light emitting element formation was performed using a general MOCVD furnace. The source gas used was TMA as the Al source, TMG as the Ga source, and TES (tetraethylsilane) as the Si source. The source gas was introduced into the reactor by H ₂ and crystal growth was performed on the heated light conversion material substrate.
The light conversion material substrate set in the furnace was heated and heated in an H ₂ atmosphere to clean the substrate. The setting was changed to the target temperature, the raw material gas was flowed, and a nitride layer containing Al was formed. Subsequently, a GaN: Si film having a thickness of 4 μm was grown under conditions that promoted lateral growth, thereby producing a target light emitting element forming composite substrate.
As a nitride layer containing Al, AlN of 300 nm was formed at 1300 ° C. and used. As a result of observation with an electron microscope, as shown in the cross-sectional photograph of the GaN layer in FIG. 3, the boundary between the Al ₂ O ₃ phase and the phosphor phase was not observed, and a uniform GaN surface was formed. The dark part of the substrate is the Al ₂ O ₃ phase and the whitish part is the YAG phase. The GaN thin film grows in both Al ₂ O ₃ phase and YAG phase. As a result, the surface is smooth. In FIG. 3, 1a is an Al ₂ O ₃ phase of the substrate, 1b is a Y ₃ Al ₅ O ₁₂ : Ce phase, 2a is an AlN buffer layer, and 2b is a GaN: Si layer. The AlN buffer layer 2a is continuous in the lateral direction on the substrate.
(Comparative Example 1)
A light conversion material substrate prepared in the same manner as in Example 1 was used, and the article Jpn. J. et al. Appl. Phys. Vol. 34 (1995), L797, 30 nm of GaN was formed at 550 ° C. in place of the Al-containing nitride layer, and then an n-type GaN: Si layer was formed under the same conditions as in Example 1. The reason why GaN is formed to a thickness of 30 nm as the buffer layer is to improve the lattice matching with the n-type GaN: Si layer formed thereon (as described below, the thickness of the buffer GaN layer is reduced). Even if you increase it, the result is the same).
FIG. 4 shows a cross-sectional photograph of the GaN layer. The formation of GaN was clearly confirmed in the Al ₂ O ₃ phase. In the phosphor phase, a part of the surface was covered with GaN by lateral growth from the Al ₂ O ₃ phase, but the growth of GaN from the phosphor phase could not be confirmed, and the surface It can be seen that the smoothness is inferior. In FIG. 4, the GaN layer 2 grown on the Al ₂ O ₃ phase 1a is the lateral direction of the entire GaN layer 2 including the buffer GaN layer (30 nm) 2c and the n-type GaN: Si layer (4 μm) 2d. (Thus, even if the thickness of the buffer GaN layer 2c is larger than 300 nm of Example 1, for example, 4 μm, the result is the same).
(Example 2, comparative example 2)
To investigate the device characteristics, Example 1, GaN was formed in the same manner as Comparative Example 1: formation of the Si layer, followed by, n-type _-Al 0.1 _Ga 0.9 N: Si layer, n-type -In _0.05 Ga _0.95 N: Si layer, InGaN layer forming a single quantum well structure type light emitting layer, p-type-Al _0.1 Ga _0.9 N: Mg barrier layer, p on which a p electrode is formed A type-GaN: Mg layer was formed, and electrodes were formed on the n-type contact layer and the p-type contact layer to produce a light-emitting diode element.
In Example 2, similar to the production of the composite substrate for forming a light emitting element, any semiconductor layer can be formed uniformly, and light emission from the entire surface was confirmed.
In Comparative Example 2, it was difficult to form an electrode due to its form, and sufficient light emission could not be obtained.
The results of comparing the external quantum efficiencies of the manufactured light-emitting diode elements with reference to Example 1 are summarized below.
(Example 3)
As the nitride layer containing Al, 300 nm Al _0.1 Ga _0.9 N or Al _0.25 Ga _0.75 N was formed at 1150 ° C., and the same procedure as in Example 1 was used except that it was used. As a result of observation with an electron microscope, the boundary between the Al ₂ O ₃ phase and the phosphor phase was not observed as in Example 1, and a uniform GaN surface was formed on the composite substrate. This is the same as in FIG.
From the above results, it is clear that the use of the light emitting element forming composite substrate having the buffer layer according to the present invention makes it possible to more effectively utilize the light conversion material substrate and form a good white light emitting element. .

Claims (10)

A composite substrate for forming a light emitting element, comprising a light conversion material substrate and a nitride layer formed thereon, and the light conversion material substrate includes an Al ₂ O ₃ phase and at least one oxide phase emitting fluorescence. At least two or more oxide layers have a structure continuously and three-dimensionally entangled with each other, and the nitride layer has a nitride layer containing Al on the entire surface of the interface with the light conversion material substrate. The nitride layer containing Al is represented by the composition formula Al _x Ga _1-x N (0 <x ≦ 1), and has a GaN nitride layer on the nitride layer containing Al. A composite substrate for forming a light emitting element.   The nitride layer containing Al is represented by a composition formula AlN. Composite substrate for light emitting element formation. One of the oxide phases which fluoresce in the said light conversion material board | substrate has a garnet-type structure containing at least Y element, Al element, and Ce element as a composition component, The any one of Claim 1 or 2 characterized by the above-mentioned. emitting element for forming a composite substrate according to. 4. The light conversion material substrate according to claim ₃ , wherein the c-plane of the Al ₂ O ₃ phase and the (112) plane of the oxide phase emitting a phosphor having a garnet-type structure are simultaneously used as the main surface. A composite substrate for forming a light emitting device.   5. A light emitting device comprising a light emitting layer made of a nitride compound semiconductor on the nitride layer of the composite substrate for forming a light emitting device according to claim 1. The light-emitting _layer, characterized in that it consists of _{In x Al y Ga 1-x} -y N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1), light emission of claim 5 element. On a light conversion material substrate having a structure in which at least two or more oxide layers including an Al ₂ O ₃ phase and at least one fluorescent oxide phase are intertwined with each other in a continuous and three-dimensional manner. A nitride layer containing Al represented by the composition formula Al _x Ga _1-x N (0 <x ≦ 1) and GaN nitrided on the nitride layer containing Al are formed on the entire surface of the interface with the material substrate. A method for manufacturing a composite substrate for forming a light emitting element , comprising forming a nitride layer including a physical layer. The nitride layer containing Al is represented by a composition formula AlN. A method for manufacturing a composite substrate for forming a light emitting element. 9. The method for manufacturing a composite substrate for forming a light-emitting element according to claim 7, wherein at least one layer is formed by a metal organic compound vapor phase growth method in forming the nitride layer. . 10. The method according to claim 7 , wherein in the formation of the nitride layer, a nitride layer containing Al is formed at a temperature of 900 ° C. or higher and lower than 1400 ° C. using an organic metal compound vapor phase growth method. A method for producing a composite substrate for forming a light emitting element according to claim 1 .