JP2010272592A - Semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element for improving the bonding reliability between a metallic reflective layer and a dielectric layer, while taking out efficiently light generated within the light emitting element to outside of the element. <P>SOLUTION: The semiconductor light emitting element includes an n-type nitride semiconductor layer 2, a light emitting semiconductor layer 3, and a p-type nitride semiconductor layer 4, which are laminated one by one on a support substrate 1. A Pt electrode layer 5 for Ohmic contacting to the p-type nitride semiconductor layer 4 and a reflective layer C composed of light reflecting material are laminated one by one on the p-type nitride semiconductor layer 4 to form a p type electrode B. The reflective layer C includes a dielectric film 7 composed of dielectric material, a metallic reflective layer 8a composed of metal material, and a transparent adhesive layer 9 prepared between the metallic reflective layer 8a and the dielectric film 7. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device, and more particularly to an element structure of a compound semiconductor light emitting device having a light emission peak on a shorter wavelength side than red.

  Conventionally, a method of forming an electrode having a high reflectance on a compound semiconductor light-emitting element has been used as a measure for increasing the light extraction efficiency from an oxide or nitride-based compound semiconductor element. For example, in a gallium nitride compound semiconductor device, light generated in the semiconductor light emitting layer has a property of traveling in all directions, and light traveling in the direction opposite to the light extraction direction is applied to the electrode formed on the surface of the gallium nitride compound semiconductor layer. Is absorbed and cannot be taken out of the device. As a method for solving these problems, for example, Patent Literature 1, Patent Literature 2, and Patent Literature 3 are known.

Patent Document 1 discloses an example of an oxide semiconductor light emitting element having a multilayer reflective film layer. This oxide semiconductor light emitting device has a multilayer reflective film, an n-type ZnO contact layer, an n-type Mg _0.1 Zn _0.9 O cladding layer, a non-doped quantum well light-emitting layer, a p-type Mg _0.1 Zn on a sapphire substrate. _{A 0.9} O cladding layer and a p-type ZnO contact layer are stacked.

The multilayer reflective film layer is formed by alternately laminating insulator oxide LiGaO ₂ layers and oxide semiconductor ZnO layers, and is formed between the n-type ZnO clad layer and the sapphire substrate. Each of the n-type ZnO contact layer and the p-type ZnO contact layer has an electrode pad for applying a voltage.

  Patent Document 2 discloses a flip-chip group III nitride compound semiconductor light emitting device. In this light emitting device, a transparent conductive film made of ITO is formed on a p-type contact layer, an insulating protective film is formed on the transparent conductive film, and light made of silver (Ag) and aluminum (Al) is formed on the transparent conductive film. A reflective film that reflects toward the sapphire substrate is formed, and a metal layer made of gold (Au) is formed thereon.

  Between the transparent conductive film and the reflection film, there is a multiple reflection film made of a dielectric, so that light is reflected by the multiple reflection film, and light that has passed through the multiple reflection film is reflected by the reflection film. Therefore, the reflectance in consideration of the multiple reflection at the interface position between the transparent conductive film and the multiple reflection film is improved. As a result, a light emitting element with high external quantum efficiency can be obtained.

  In the light emitting device disclosed in Patent Document 3, a multilayer reflective film is disposed on a III-V group compound semiconductor substrate, and a light emitting structure including a pn junction of a III-V group compound semiconductor is further placed thereon. An ohmic electrode is provided in a part of the light emitting structure. In addition, an example in which a transparent current diffusion layer is disposed between the multilayer reflective film and the light emitting structure is shown, and the first electrode and the second electrode are provided on a part of the first conductive type semiconductor and the second conductive type semiconductor, respectively. It is the composition which provided.

  In these conventional semiconductor light emitting devices, a first conductive type semiconductor layer, a light emitting semiconductor layer having a light emitting layer (active layer) on this layer, and a second conductive type semiconductor layer are formed on a growth substrate. It has a stacked structure. In each semiconductor layer, an n-type electrode and a p-type electrode are provided so that electrical conduction is possible. Then, a forward bias is applied to the light emitting semiconductor layer (a positive voltage is applied to the electrode of the p-type contact layer) to provide the n-type nitride semiconductor layer from the electrode provided on the p-type nitride semiconductor layer. A current flows toward the electrode, holes and electrons are combined in the light emitting junction layer in the light emitting semiconductor layer to generate light of a predetermined wavelength, and the multilayer reflective film attempts to reflect in the light extraction direction It is.

JP 2004-235532 A JP 2006-120913 A JP-A-8-222761

  By the way, in the conventional semiconductor light emitting device as described above, light generated from the light emitting semiconductor layer when a forward bias is applied between the electrodes is directed in an arbitrary direction. Light that is incident on the multilayer reflection film is reflected by the multilayer reflection film, but if the incident angle of the light with respect to the multilayer reflection film increases, the reflectance of the multilayer reflection film decreases. There was a problem that strength could not be obtained.

  Therefore, in the light emitting device described in Patent Document 2, the reflectance is improved by forming a reflective film of silver or aluminum on the multiple reflective film.

  However, when a metal such as Ag is used as the material of the reflective film, the adhesion between the metal and the dielectric material is poor, so the metal reflective film (metal reflective layer) and the dielectric multilayer reflective film (dielectric layer) Does not adhere well, and there is a problem that the reflective layer and the dielectric layer may be peeled off during the manufacturing process of the light emitting element or during package mounting.

  An object of the present invention is to improve the reflectivity for light having a large incident angle with respect to a dielectric layer, reflect light generated in the light emitting layer in a desired direction, and efficiently generate light generated inside the light emitting element to the outside of the element. An object of the present invention is to provide a semiconductor light emitting device that can be taken out, reduce the possibility that the metal reflective layer and the dielectric layer are peeled off, and improve the bonding reliability between the metal reflective layer and the dielectric layer.

  The semiconductor light emitting device according to the present invention includes an n layer made of an n-type gallium nitride compound semiconductor, a light emitting layer made of a gallium nitride compound semiconductor, and a p-type nitride on a light-transmitting and conductive substrate. A semiconductor light emitting device in which a p layer made of a gallium compound semiconductor is sequentially stacked, comprising a first electrode layer made of a material capable of making ohmic contact with the p layer and a light reflecting material. A reflective layer is sequentially laminated to form one electrode. The reflective layer includes a dielectric layer made of a dielectric material, a metal reflective layer made of a metal material, and the metal reflective layer and the dielectric layer. And a first transparent adhesion layer provided therebetween.

  According to this configuration, the n layer, the light emitting layer, the p layer, the first electrode layer, and the reflective layer are sequentially stacked on the light-transmitting and conductive substrate. The reflective layer includes a dielectric layer made of a dielectric material and a metal reflective layer made of a metal material. Then, since the dielectric layer has a high reflectivity with respect to light with a small incident angle, and the metal reflective layer has a high reflectivity with respect to light with a large incident angle, the light reaching the reflective layer with an arbitrary incident angle from the light emitting layer. The reflectance that reflects the light toward the substrate can be comprehensively improved. Furthermore, since the first transparent adhesion layer is provided between the metal reflection layer and the dielectric layer, the adhesion between the metal reflection layer and the dielectric layer is improved, so that the bonding reliability between the substrate and the electrode is improved. Can be improved.

  The dielectric layer is preferably a single layer film made of a material having a refractive index lower than that of the p layer and having a thickness of 3 / 4λ or more with respect to the emission peak wavelength λ of the light emitting layer.

  The inventors of the present invention have a dielectric layer made of a material having a refractive index lower than that of the p layer, and configured by a single layer film having a thickness of 3 / 4λ or more with respect to the emission peak wavelength λ of the light emitting layer. It has been found that good reflectance can be obtained. Furthermore, by using a single layer film, the dielectric layer formation process can be simplified.

  The dielectric layer is preferably formed by alternately laminating one or more pairs of two or more different materials.

  According to this configuration, since the dielectric layer is configured by alternately stacking one or more pairs of two or more different materials, the reflectance in the dielectric layer can be improved. Also, when two or more different materials are laminated, the stress of the film cancels each other between the dielectric layers, so the stress acting between the reflective layer and the dielectric layer is relaxed, and the metal reflective layer and the dielectric As a result of improving the adhesion with the layer, the bonding reliability between the substrate and the electrode can be improved.

  Moreover, it is preferable that said 1st transparent contact | adherence layer is comprised using the Ti type oxide.

  When the first transparent adhesion layer is composed of a Ti-based oxide, it can be easily formed by EB (ion beam evaporation method or sputtering) and the adhesion between the metal reflection layer and the dielectric layer. It is possible to improve the bonding reliability between the substrate and the electrode.

  The first transparent adhesion layer is preferably doped with Nb.

  When Nb is doped into the first transparent adhesion layer composed of a Ti-based oxide, the first transparent adhesion layer becomes electrically conductive, so that the operating voltage of the semiconductor light emitting device is reduced and power consumption is reduced. As a result, the light emission efficiency of the semiconductor light emitting device can be improved.

  The concentration of Nb doped in the first transparent adhesion layer is preferably 2 to 8%.

  The inventors of the present application improve the electrical conductivity by setting the concentration of Nb doped in the first transparent adhesion layer to 2 to 8%, so that the operating voltage of the semiconductor light emitting device is reduced and the power consumption is reduced. As a result, the light emission efficiency of the semiconductor light emitting device can be improved.

The first transparent adhesion layer may be configured using any one of an oxide containing Al, Y ₂ O ₃ , and ZnS.

When the first transparent adhesion layer is configured using any one of an oxide containing Al, Y ₂ O ₃ , and ZnS, damage to the p layer made of the p-type gallium nitride compound semiconductor is reduced. In addition, the adhesion between the metal reflective layer and the dielectric layer can be improved, and the bonding reliability between the substrate and the electrode can be improved.

  Moreover, it is preferable that the thickness of said 1st transparent contact | adherence layer is 0.1-10 nm.

  The inventors of the present application have found that if the thickness of the first transparent adhesion layer is 0.1 nm to 10 nm, the adhesion strength between the metal reflection layer and the dielectric layer increases and the reflectance increases.

  The reflective layer preferably includes a second transparent adhesive layer having the same composition as the first transparent adhesive layer, formed between the first electrode layer and the dielectric layer.

  According to this configuration, the adhesion between the first electrode layer and the dielectric layer can be improved, and the bonding reliability between the substrate and the electrode can be improved.

  Further, the reflective layer is formed in a plurality of islands, the occupation ratio of the surface area of the p layer is 10 to 60%, and between the plurality of islands formed in the islands, It is preferable that the material is filled with a material that reflects light.

  The inventors of the present application form a reflective layer in a plurality of islands, and occupy 10-60% of the islands in the surface area of the p layer, and between the islands formed in the islands. It has been found that a good reflectance can be obtained by filling a material that reflects light.

  The material that reflects light is preferably a metal.

  According to this configuration, the metal filled between the plurality of islands conducts in the direction penetrating the reflective layer including the dielectric layer. As a result, the voltage required to pass the current for causing the semiconductor light emitting element to emit light can be reduced, and it becomes easy to reduce the power consumption and improve the light emission efficiency.

  The light emitting layer is preferably laminated on the surface excluding a part of the n layer, and the other electrode is preferably formed in a portion of the n layer where the light emitting layer is not laminated. .

  According to this configuration, current flows in the direction penetrating the reflective layer including the dielectric layer by the metal filled between the plurality of islands. Therefore, the light emitting layer is formed on the surface excluding a part of the n layer. By laminating and forming the other electrode in the n layer where the light emitting layer is not laminated, from the reflective layer constituting one electrode, through the first electrode layer, p layer, light emitting layer, and n layer A current path to the other electrode is obtained. In this case, since it is not necessary to remove the dielectric layer to ensure conduction, it is easy to increase the area of the dielectric layer and improve the reflectance. Further, since the two electrodes are formed avoiding the light extraction path, the light is not blocked by the electrodes, and it is easy to improve the light emission efficiency.

  Further, the other electrode may be formed on the surface of the substrate opposite to the surface on which the n layer is laminated.

  According to this configuration, current flows in the direction penetrating the reflective layer including the dielectric layer by the metal filled between the plurality of islands, so that the surface on the side opposite to the surface on which the n layer of the substrate is stacked is provided. By forming the other electrode on the surface, a current path from the reflective layer constituting one electrode to the other electrode through the first electrode layer, the p layer, the light emitting layer, the n layer, and the substrate is obtained. It is done. In this case, since it is not necessary to remove the dielectric layer to ensure conduction, it is easy to increase the area of the dielectric layer and improve the reflectance. Further, since it is not necessary to remove the n layer and the light emitting layer formed thereon in order to form the other electrode, it is easy to increase the light emission amount by increasing the area of the light emitting layer.

  In the semiconductor light emitting device having such a configuration, an n layer, a light emitting layer, a p layer, a first electrode layer, and a reflective layer are sequentially stacked on a light-transmitting and conductive substrate. The reflective layer includes a dielectric layer made of a dielectric material and a metal reflective layer made of a metal material. Then, since the dielectric layer has a high reflectivity with respect to light with a small incident angle, and the metal reflective layer has a high reflectivity with respect to light with a large incident angle, the light reaching the reflective layer with an arbitrary incident angle from the light emitting layer. It is possible to improve the reflectivity of reflecting the light toward the substrate. Furthermore, since the first transparent adhesion layer is provided between the metal reflection layer and the dielectric layer, the adhesion between the metal reflection layer and the dielectric layer is improved, so that the bonding reliability between the substrate and the electrode is improved. Can be improved.

It is sectional drawing which shows an example of a structure of the semiconductor light-emitting device concerning 1st Embodiment of this invention. FIG. 2 is a plan view of the semiconductor light emitting element shown in FIG. 1. Example of layout of transparent adhesion layer, dielectric film, and transparent adhesion layer formed in island shape with metal reflection layer, Ti layer, Ni layer, and Au layer removed from semiconductor light emitting device shown in FIG. FIG. Example of layout of transparent adhesion layer, dielectric film, and transparent adhesion layer formed in island shape with metal reflection layer, Ti layer, Ni layer, and Au layer removed from semiconductor light emitting device shown in FIG. FIG. Example of layout of transparent adhesion layer, dielectric film, and transparent adhesion layer formed in island shape with metal reflection layer, Ti layer, Ni layer, and Au layer removed from semiconductor light emitting device shown in FIG. FIG. It is a graph which shows the relationship between the incident angle of light, and the reflectance of the light of the dielectric material film 7 and the metal reflection layers 8a and 8b. It is sectional drawing which shows an example of a structure of the semiconductor light-emitting device concerning 2nd Embodiment of this invention. It is a graph which shows the result of having measured the operating voltage of a semiconductor light emitting element, and the reflectance of a p-type electrode by making into a parameter the ratio for which a dielectric film occupies the surface area of a p-type nitride semiconductor layer. It is a graph which shows the result of having comparatively measured the operating voltage of the light emitting element by the case where Nb is doped to the transparent adhesion layer, and the case where it does not dope. It is a graph which shows the result of having calculated | required the relationship between the dielectric film thickness and the omnidirectional reflectance in the reflection layer comprised by the dielectric material layer and the metal layer by simulation. When the thickness of the transparent adhesion layer (TiO ₂ ) is changed using a sample in which a dielectric layer (SiO ₂ ), a transparent adhesion layer (TiO ₂ ), and a metal layer (Ag) are laminated. It is a graph which shows the experimental result which measured the tensile force when peeling occurred. It is explanatory drawing of the sample used in FIG. It is a graph which shows the result of having measured the reflectance at the time of changing the thickness of a transparent adhesion layer.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a cross-sectional view showing an example of the configuration of the semiconductor light emitting device according to the first embodiment of the present invention. FIG. 2 is a plan view of the semiconductor light emitting device shown in FIG. 1 (surface view seen from above). FIG. 1 illustrates a cross-sectional structure of the portion indicated by the auxiliary line a in FIG.

  The semiconductor light emitting element shown in FIG. 1 uses a substrate having translucency and conductivity as the support substrate 1. On this support substrate 1, an n-type nitride semiconductor is laminated to form an n-type nitride semiconductor layer 2 (n layer). Then, a light emitting semiconductor layer 3 (light emitting layer) is stacked on most of the surface excluding a part of the n-type nitride semiconductor layer 2, and further exhibits p-type electrical conduction on the light emitting semiconductor layer 3. A p-type nitride semiconductor layer 4 (p layer) is stacked.

  An n-type electrode A is formed in a portion of the n-type nitride semiconductor layer 2 where the light emitting semiconductor layer 3 is not formed, and a p-type electrode B is formed on the p-type nitride semiconductor layer 4. FIG. 2 shows a layout of the p-type electrode B and the n-type electrode A on the surface of the semiconductor light emitting device.

  The light emitting semiconductor layer 3 is formed using a group 3 nitride semiconductor. When the light-emitting semiconductor layer 3 is formed of n-type InGaN, AlInGaN, or AlGaN, the light emission color of the light-emitting semiconductor layer 3 is adjusted by appropriately adjusting the composition ratio of In and Al, or n-type impurities such as Si, Ge, and S By appropriately doping p-type impurities such as Zn, Mg, etc., the desired color can be adjusted in the range of ultraviolet to blue.

  In FIG. 1, an n-type electrode A is formed on the n-type nitride semiconductor layer 2 exposed by removing the light-emitting semiconductor layer 3 and the p-type nitride semiconductor layer 4, and the p-type nitride semiconductor layer 4 is formed. The p-type electrode B is formed on the top.

In the p-type electrode B, a Pt electrode layer 5 (first electrode layer) having a thickness of 5 mm is formed on the p-type nitride semiconductor layer 4. Then, on the Pt electrode layer 5, a transparent adhesion layer 6 (second transparent adhesion layer) made of TiO ₂ having a thickness of 5 nm and formed in an island shape so as to cover an area of about 50% of the p-type nitride semiconductor layer 4 A dielectric film 7 (dielectric layer) made of a dielectric material in which SiO ₂ with a thickness of 31.1 nm and ZrO ₂ with a thickness of 159.1 nm are alternately laminated is formed on the transparent adhesion layer 6. ing.

Further, a transparent adhesion layer 9 (first transparent adhesion layer) made of TiO ₂ having a thickness of 5 nm is provided on the dielectric film 7.

  Then, Ag is filled so as to cover each island where the transparent adhesion layer 6, the dielectric film 7, and the transparent adhesion layer 9 are laminated and the Pt electrode layer 5, and Ag having a thickness of 300 nm is formed on the transparent adhesion layer 9. A metal reflective layer 8a made of is formed. In addition, between the islands, Ag is filled to form a metal reflection layer 8b.

  The transparent adhesive layer 6, the dielectric film 7, the transparent adhesive layer 9, and the metal reflective layers 8a and 8b form a reflective layer C, and the Pt electrode layer 5 and the reflective layer C form an electrode. .

  Further, a Ti layer 10 having a thickness of 30 nm, a Ni layer 11 having a thickness of 50 nm, and an Au layer 12 having a thickness of 1.5 μm are laminated as an electrode for package mounting on the reflective layer C, and p A mold electrode B is formed.

  The n-type electrode A is a package in which a Ti layer 10 having a thickness of 30 nm, a Ni layer 11 having a thickness of 50 nm, and an Au layer 12 having a thickness of 1.5 μm are stacked on the n-type nitride semiconductor layer 2. It is formed as an electrode for mounting.

Incidentally, as the dielectric film 7, although the case in which a laminate of SiO ₂ and ZrO _2, the thickness may be a single layer film of 380nm of SiO _2. Moreover, although the case where the transparent contact layers 6 and 9 made of TiO ₂ are formed above and below the dielectric film is shown, a configuration including only the transparent contact layer 9 may be used.

  Further, although Ag is used for the metal reflecting layers 8a and 8b, an Ag-based material or an Ag alloy may be used. Specifically, it is desirable that the material of the metal reflection layers 8a and 8b is appropriately selected with respect to the emission peak wavelength of the semiconductor light emitting element. For example, when the emission peak wavelength is 400 nm or less, Al is preferable. .

Furthermore, although TiO ₂ has been described as the material of the transparent adhesion layers 6 and 9, an oxide containing Al, Y ₂ O ₃ , ZnS, or the like may be used. Moreover, although the example which used Pt as a 1st electrode layer was described, as a rhodium (Rhodium) and Pd (palladium) with a comparatively high reflectance with a material with a favorable ohmic contact with a p-type nitride semiconductor layer, for example Good.

  Moreover, although the example which forms the transparent contact layer 6, the dielectric material film 7, and the transparent contact layer 9 in the island shape was shown, you may form not in an island shape but in a planar shape.

  When a positive voltage is applied to the p-type electrode B and a negative voltage is applied to the n-type electrode A, electrons and holes are combined in the light emitting semiconductor layer 3 to generate blue or ultraviolet light. Then, the light traveling toward the opposite side of the light extraction direction (p-type electrode B direction, upward in FIG. 1) is extracted by the dielectric film 7 and the metal reflection layers 8a and 8b (support substrate 1 direction, FIG. 1). Reflected downward (downward on the paper surface) and transmitted to the outside of the light emitting element.

  3, 4, and 5 show transparent adhesion formed in an island shape with the metal reflective layer 8 a, Ti layer 10, Ni layer 11, and Au layer 12 removed from the semiconductor light emitting device shown in FIG. 2. 4 is a plan view showing an example of a layout of a layer 6, a dielectric film 7, and a transparent adhesion layer 9. FIG.

  FIG. 3 shows that in the region of the Pt electrode layer 5 formed on the p-type nitride semiconductor layer 4, the transparent adhesion layer 6, the dielectric film 7, and the transparent adhesion layer 9 are about 40% of the p-type nitride semiconductor layer 4. An example is shown in which islands are formed so as to cover the mesh with square eyes.

  FIG. 4 shows that the transparent adhesive layer 6, the dielectric film 7, and the transparent adhesive layer 9 are about 40 of the p-type nitride semiconductor layer 4 in the region of the Pt electrode layer 5 formed on the p-type nitride semiconductor layer 4. An example in which substantially hexagonal islands are formed so as to cover%.

  FIG. 5 shows that in the region of the Pt electrode layer 5 formed on the p-type nitride semiconductor layer 4, the transparent adhesion layer 6, the dielectric film 7, and the transparent adhesion layer 9 are about 20 times the p-type nitride semiconductor layer 4. An example in which substantially hexagonal islands are formed so as to cover%.

  In the present embodiment, the island layout is shown as a mesh-shaped square or a substantially hexagonal shape, but it may be an arbitrary polygon or a substantially circular shape.

  FIG. 6 is a graph showing the relationship between the incident angle of light and the light reflectance of the dielectric film 7 and the metal reflective layers 8a and 8b. As shown in FIG. 6, as the incident angle increases, the reflectivity of the dielectric film 7 decreases, whereas the reflectivity of the metal reflective layers 8a and 8b increases.

  Accordingly, the semiconductor light emitting device shown in FIG. 1 includes the dielectric film 7 and the metal reflective layers 8a and 8b, so that the reflectance in the reflective layer C is increased as compared with the case where only the dielectric film 7 is used. It is possible to improve the efficiency of extracting the light generated in the layer 3 in the light extraction direction (the direction of the support substrate 1 and the downward direction in FIG. 1).

  In addition, since the transparent adhesion layer 9 is provided between the dielectric film 7 and the metal reflective layer 8a and the transparent adhesion layer 6 is provided between the dielectric film 7 and the Pt electrode layer 5, the dielectric layer And the metal reflective layer are improved in adhesion. Thereby, the possibility that the metal reflection layer and the dielectric layer are peeled off can be reduced, and the bonding reliability between the metal reflection layer and the dielectric layer can be improved.

  Further, since the dielectric is basically an insulator, no current flows through the dielectric multilayer reflective film described in the background art. Therefore, the light emitting element described in Patent Document 2 has an inconvenience that the area of the multilayer reflective film is reduced and the reflectance is lowered because the electrode 41 is attached to the portion where the multilayer reflective film is removed.

  Further, the light emitting elements described in Patent Documents 1 and 3 are provided with electrodes in the light extraction direction so that no current flows through the multilayer reflective film. For this reason, the light extracted from the light emitting element is shielded by the electrode portion, and there is a disadvantage that the light extraction efficiency is lowered.

  On the other hand, in the semiconductor light emitting device shown in FIG. 1, the dielectric film 7 has an island shape, and a current flows in a direction penetrating the reflective layer C through the metal reflective layer 8b. Thereby, since the p-type electrode B can be provided without removing the dielectric film 7, it is easier to improve the reflectance by increasing the area of the reflective layer C than the light emitting element described in Patent Document 2. .

  In addition, since it is not necessary to provide an electrode in the light extraction direction, it is easier to improve the light extraction efficiency than the light emitting elements described in Patent Documents 1 and 3.

(Second Embodiment)
Next, a semiconductor light emitting device according to a second embodiment of the present invention will be described. FIG. 7 is a cross-sectional view showing an example of the configuration of the semiconductor light emitting device according to the second embodiment of the present invention. The semiconductor light emitting device shown in FIG. 7 and the semiconductor light emitting device shown in FIG. 1 differ in the attachment structure of the n-type electrode A and the configuration of the reflective layer C ′.

  Since the other configuration is the same as that of the semiconductor light emitting device shown in FIG. 1, the description thereof is omitted, and the characteristic points of this embodiment will be described below.

  In the semiconductor light emitting device shown in FIG. 7, the n-type electrode A is formed on the surface of the support substrate 1 opposite to the surface on which the n-type nitride semiconductor layer 2 is laminated. The light emitting semiconductor layer 3, the p-type nitride semiconductor layer 4, and the p-type electrode B 'are formed so as to cover substantially the entire surface of the n-type nitride semiconductor layer 2.

  Thereby, since the area of the light emitting semiconductor layer 3 is larger than that of the semiconductor light emitting element shown in FIG. 1, it is easy to increase the amount of light emission.

In addition, the reflective layer C ′ does not include the transparent adhesion layer 6 and the dielectric film 7 ′ has a single layer structure of SiO ₂ having a thickness of 380 nm on the Pt electrode layer 5. Yes.

  According to this configuration, since the structure is simplified, it is easy to reduce the manufacturing cost.

  Similar to the semiconductor light emitting device shown in FIG. 1, the semiconductor light emitting device shown in FIG. 7 operates by supplying a bias voltage to each electrode from the outside.

8 shows the semiconductor light emitting device of FIG. 7 in which a dielectric film 7 ′ having a single layer structure of SiO ₂ having a thickness of 380 nm is formed on a Pt electrode layer 5 made of Pt having a thickness of 5 mm. Using the ratio of 'to the surface area of the p-type nitride semiconductor layer 4 as a parameter, the voltage applied from the outside to cause the light-emitting element to emit light by emitting a current of 40 mA and the reflectance of the p-type electrode B' were measured. It is a graph to show.

From the graph shown in FIG. 8, when the dielectric film 7 ′ made of SiO ₂ is formed in a region having an occupation ratio exceeding 60% of the Pt electrode layer 5 made of p-type Pt, the operating voltage increases rapidly. When the occupancy is 2 V or more and the occupancy is 10% or less, it is confirmed that the reflectance is lower than 95%, which is the reflectance with respect to light having a wavelength of 460 nm in Ag, and the luminous efficiency is lowered.

  In FIG. 8, when the ratio of the area of the dielectric film 7 ′ to the area of the p-type nitride semiconductor layer 4 is 10% to 60%, the reflectance of the p-type electrode B ′ is high (above Ag). This is effective because the operating voltage of the semiconductor light emitting device is low (3.2 V or less, energizing current 40 mA). On the other hand, when the ratio of the area of the dielectric film 7 ′ to the area of the p-type nitride semiconductor layer 4 is less than 10%, the reflectance of the p-type electrode B ′ is low (below Ag), and the dielectric When the ratio of the area of the body film 7 ′ to the area of the p-type nitride semiconductor layer 4 exceeds 60%, the operating voltage of the semiconductor light emitting device is high (3.4 V or more, conduction current 40 mA), which is effective. No (cannot withstand actual use).

  From this, it was confirmed that the ratio of the area of the dielectric film 7 ′ to the area of the p-type nitride semiconductor layer 4 is preferably 10% to 60%. This experimental result shows the relationship between the ratio of the area of the dielectric film to the area of the p-type nitride semiconductor layer, the reflectance, and the operating voltage, and the structure of the semiconductor light emitting device shown in FIG. The same applies to the case.

9 shows a case where the transparent light-emitting layers 6 and 9 made of TiO ₂ with a thickness of 5 nm are doped with Nb and not doped, that is, the Nb doping concentration is 0% in the semiconductor light emitting device shown in FIG. The results of comparative measurement of the operating voltage of the light emitting element are shown for the cases of 5% and 5%.

  From the experimental results shown in FIG. 9, it was confirmed that the operating voltage of the light emitting element was lower by about 0.2 V (when 40 mA was applied) when Nb was doped than when it was not doped.

  It is estimated that the same effect as in the case of 5% can be obtained when the Nb doping concentration is in the range of 2 to 8%.

  Therefore, it has been confirmed that the effect of reducing the operating voltage of the semiconductor light emitting device can be obtained when the Nb doping concentration is in the range of 2 to 8%, particularly 5%.

  FIG. 10 is a graph showing the results of a simulation of the relationship between the dielectric film thickness and the omnidirectional reflectance in a reflective layer composed of a dielectric layer and a metal layer. For the simulation, optasfilm manufactured by Opto Corporation was used.

In FIG. 10, a graph G1 is a graph in the case where the dielectric layer is a single layer film of SiO ₂ and the metal layer is Al, and a graph G2 is a single layer film of Al ₂ O _{3 in} the dielectric layer and a metal layer. FIG. Further, the reflectance indicates a case where the wavelength is λ = 470 nm.

From the graph shown in FIG. 10, regardless of whether the dielectric layer is SiO ₂ or Al ₂ O ₃ , the reflectance is almost constant at a high level of 98% or more in the range where the thickness of the dielectric is 350 nm or more. It was confirmed that 350 nm corresponds to approximately 3 / 4λ.

  Therefore, it was confirmed that when the thickness of the dielectric layer was set to 3 / 4λ or more with respect to the peak wavelength λ of the light emitting layer, good reflectance was obtained.

11, the dielectric layer shown in FIG. 12 and (SiO _2), a transparent adhesive layer and (TiO _2), using a sample formed by laminating a metal layer (Ag), a transparent adhesive layer _(TiO 2) It is a graph which shows the experimental result which measured the tension | tensile_strength when peeling generate | occur | produces when changing the thickness of.

  As shown in FIG. 11, it was confirmed that the tensile force, that is, the adhesion strength rapidly increased by setting the thickness of the transparent adhesion layer to 0.1 nm or more.

  FIG. 13 is a graph showing the result of measuring the reflectance when the thickness of the transparent adhesion layer 9 is changed in the semiconductor light emitting device shown in FIG. The reflectivity indicates a case where the wavelength λ = 470 nm.

  From FIG. 13, it was confirmed that when the thickness of the transparent adhesive layer 9 was 10 nm or less, the reflectance was 95% or more, which was more than the reflectance of the Ag single layer film.

  From the above results, by setting the thickness of the transparent adhesion layer 9 (first transparent adhesion layer) to 0.1 nm to 10 nm, the adhesion strength between the metal reflective layer and the dielectric layer is increased, and the reflectance is increased. It was confirmed that it increased.

DESCRIPTION OF SYMBOLS 1 Support substrate 2 N-type nitride semiconductor layer 3 Light emitting semiconductor layer 4 P-type nitride semiconductor layer 5 Pt electrode layer 6 Transparent adhesion layer 7 Dielectric film 8a, 8b Metal reflective layer 9 Transparent adhesion layer 10 Ti layer 11 Ni layer 12 Au layer A n-type electrode B, B 'p-type electrode C, C' reflective layer

Claims (13)

An n layer made of an n-type gallium nitride compound semiconductor, a light emitting layer made of a gallium nitride compound semiconductor, and a p layer made of a p-type gallium nitride compound semiconductor on a light-transmitting and conductive substrate Are sequentially stacked semiconductor light emitting devices,
On the p layer, a first electrode layer made of a material capable of making ohmic contact with the p layer and a reflective layer made of a material that reflects light are sequentially laminated to form one electrode,
The reflective layer is
A dielectric layer made of a dielectric material;
A metal reflective layer made of a metal material;
A semiconductor light emitting device comprising: a first transparent adhesion layer provided between the metal reflective layer and the dielectric layer. The dielectric layer is
2. The semiconductor light emitting element according to claim 1, wherein the semiconductor light emitting element is a single layer film having a refractive index lower than that of the p layer and having a thickness of 3 / 4λ or more with respect to an emission peak wavelength λ of the light emitting layer. . The dielectric layer is
The semiconductor light emitting element according to claim 1, wherein one or more pairs of two or more different materials are alternately laminated. The first transparent adhesion layer is
The semiconductor light-emitting element according to claim 1, wherein the semiconductor light-emitting element is configured using a Ti-based oxide. In the first transparent adhesion layer,
The semiconductor light emitting device according to claim 4, wherein Nb is doped. The semiconductor light emitting element according to claim 5, wherein the concentration of Nb doped in the first transparent adhesion layer is 2 to 8%. The first transparent adhesion layer is
The semiconductor light-emitting element according to claim 1, wherein the semiconductor light-emitting element is configured by using any one of an oxide containing Al, Y ₂ O ₃ , and ZnS. The thickness of said 1st transparent adhesion layer is 0.1 nm-10 nm. The semiconductor light-emitting device of any one of Claims 1-7 characterized by the above-mentioned. The reflective layer is
The second transparent adhesion layer having the same composition as the first transparent adhesion layer, which is formed between the first electrode layer and the dielectric layer, is included. The semiconductor light-emitting device described in 1. The reflective layer is
It is formed in a plurality of islands, and the occupation ratio of the surface area of the p layer is 10 to 60%, and a material that reflects light is filled between the plurality of islands formed in the islands. The semiconductor light-emitting element according to claim 1, wherein the semiconductor light-emitting element is configured as described above. The semiconductor light emitting element according to claim 10, wherein the light reflecting material is a metal. The light emitting layer is
Laminated on the surface excluding a part of the n layer,
The semiconductor light emitting element according to claim 11, wherein the other electrode is formed in a portion of the n layer where the light emitting layer is not stacked. The semiconductor light emitting element according to claim 11, wherein the other electrode is formed on a surface of the substrate opposite to the surface on which the n layer is laminated.

Images