JP5659728B2 - Light emitting element - Google Patents

Description

  The present invention relates to a light-emitting element including a reflective conductive film, which is a metal film in which semiconductor layers including a light-emitting layer are stacked and light from the light-emitting layer is reflected toward the substrate.

  As conventional light-emitting elements mounted on a mounting substrate, for example, those described in Patent Documents 1 and 2 are known. The light-emitting elements described in Patent Documents 1 and 2 will be described with reference to FIGS. 9A and 9B.

  A light-emitting element 100 (light-emitting device described in Patent Document 1) illustrated in FIG. 9A includes a light-transmitting substrate 101, an n-type nitride semiconductor layer 102, a nitride light-emitting layer 103, and a p-type nitride semiconductor. Layer 104 is laminated. Further, a transparent conductive film 105, a low refractive index dielectric layer 106, and a reflective conductive film 107 are stacked on the p-type nitride semiconductor layer 104.

The low refractive index dielectric layer 106 can be composed of a SiO ₂ layer 106a and a ZrO ₂ layer 106b, and is selected from the group of SiO ₂ , ZrO ₂ , Al ₂ O ₃ , Y ₂ O _3. It is composed of a single layer film formed of two materials. In the conventional light emitting device 100, when mounted on the mounting substrate B, the position corresponding to the bump P interposed between the conventional light emitting device 100 and the mounting substrate B is used as a formation prohibition region. The dielectric layer 106 is formed in a region other than the formation prohibition region.

  As described above, in the conventional light emitting device 100, by forming the low refractive index dielectric layer 106 away from the formation prohibition region, the transparent conductive film 105 and the low refractive index dielectric layer 106 are separated from each other by an impact during mounting. It is preventing.

  Further, in the light-emitting element 200 (semiconductor light-emitting element described in Patent Document 2) illustrated in FIG. 9B, the InGaN semiconductor light-emitting unit 202 stacked on the sapphire 201 and the P-side formed on the InGaN semiconductor light-emitting unit 202. It has a transparent electrode 203, a transparent insulating film 205 having a plurality of openings 205a, and a reflective electrode 207 bonded to the P-side transparent electrode 203 through the openings 205a. The reflective electrode 207 is mounted by a P-side pad electrode 208. Bonded to the substrate 210. In addition, an adhesive layer for improving adhesion may be provided between the transparent insulating film 205 and the reflective electrode 207.

JP 2010-199247 A International Publication No. 2006/006555

  In the light emitting element 100 described in Patent Document 1 shown in FIG. 9A, a position corresponding to the bump P is set as a formation prohibition region. From the viewpoint of heat dissipation, it is better that the number of bump bonding portions is larger. However, if the number of bump bonding portions is increased in the light emitting device described in Patent Document 1, the region where the low refractive index dielectric layer 106 is formed decreases, and light extraction is performed. Efficiency will decrease.

  In the light emitting element 200 described in Patent Document 2 shown in FIG. 9B, the InGaN semiconductor light emitting unit 202 and the mounting substrate 210 are joined by a pad electrode 208 that covers the entire surface of the reflective electrode 207, and the semiconductor. A structure in which the light emitting unit and the mounting substrate are joined via a plurality of bumps is not assumed.

  Accordingly, the present invention provides a light-emitting element that can achieve high light extraction efficiency while ensuring high impact resistance in a light-emitting element in which a semiconductor light-emitting unit and a mounting substrate are interposed via a plurality of bumps. Objective.

  As a result of repeated studies by the inventors of the present application, by providing an adhesive dielectric film made of a metal element oxide between the low refractive index dielectric layer and the reflective conductive film, a low refractive index dielectric is provided. It was found that the adhesion between the layer and the reflective conductive film was improved. As a result, it has been found that a low refractive index dielectric layer can be provided at a position corresponding to the bump P interposed between the light emitting element and the mounting substrate, and high light extraction efficiency can be obtained. Here, the “position corresponding to the bump P” means a position where the bonding surface between the bump P and the light emitting element electrode overlaps when viewed from a direction orthogonal to the formation surface of the bump P.

  Further, it has been found that when the boundary between the conductive region where the transparent conductive film and the reflective conductive film are conductive and the low refractive index dielectric film is located at a position corresponding to the bump P, the impact resistance is significantly reduced. Therefore, it has been found that high impact resistance can be secured by providing the conduction region other than the position corresponding to the bump P. Here, “providing the conduction region other than the position corresponding to the bump P” means that the conduction region and the bonding surface between the bump P and the light emitting element electrode are viewed from a direction perpendicular to the formation surface of the bump P. It means that they are formed so as not to overlap each other. In other words, the conductive region is formed outside the projection region obtained by projecting the bonding surface between the bump P and the light emitting element electrode onto the transparent conductive film.

  Therefore, the light-emitting element of the present invention includes a semiconductor layer in which an n-type layer, a light-emitting layer, and a p-type layer are laminated, a transparent electrode film that is laminated on the p-type layer, and has a refractive index smaller than that of the p-type layer, A low refractive index dielectric film formed of a silicon compound having a refractive index smaller than that of the p-type layer, laminated on the transparent electrode film so as to exclude a conductive region, and laminated on the low refractive index dielectric film. An adhesive dielectric film formed of a dielectric made of an oxide of an element, a reflective conductive film made of a metal layer bonded to the adhesive dielectric film and electrically connected to the transparent conductive film in the conductive region, and the reflective conductive film And a plurality of bumps bonded to the p electrode, and the conduction region is provided outside a projection region obtained by projecting a bonding surface of the p electrode and the bump onto the transparent conductive film. It is characterized by.

  The light emitting device of the present invention can ensure a wide range of total reflection by the low refractive index dielectric film, and since the low refractive index dielectric film is formed of a dielectric that does not absorb light, high impact resistance is ensured. However, high light extraction efficiency can be achieved.

Sectional drawing of the light emitting element which concerns on Embodiment 1 of this invention The figure which shows the transparent conductive film and low refractive index dielectric film of the light emitting element shown in FIG. The figure which shows the transparent conductive film and low refractive index dielectric film of the conventional light emitting element Sectional drawing which shows the 1st modification of the light emitting element which concerns on Embodiment 1. FIG. The figure which shows the transparent conductive film and low refractive index dielectric film of a 1st modification (A) (B) is a figure which shows the transparent conductive film and low refractive index dielectric film of a 2nd, 3rd modification. (C) (D) is a figure which shows the transparent conductive film and low refractive index dielectric film of a 4th, 5th modification. Sectional drawing of the light emitting element which concerns on Embodiment 2 of this invention. (A) And (B) is sectional drawing of the conventional light emitting element. Comparison diagram between light-emitting element according to Embodiment 1 and Modification 1 and comparative example

  A first invention of the present application includes a semiconductor layer in which an n-type layer, a light emitting layer, and a p-type layer are laminated, a transparent electrode film that is laminated on the p-type layer and has a refractive index smaller than that of the p-type layer, and a transparent electrode film A low-refractive-index dielectric film formed of a silicon compound having a refractive index lower than that of the p-type layer and a low-refractive-index dielectric film stacked on the conductive layer excluding the conductive region, and made of a metal element oxide. An adhesive dielectric film formed of a dielectric, a reflective conductive film made of a metal layer bonded to the adhesive dielectric film and electrically connected to the transparent conductive film in the conductive region, a p-electrode formed on the reflective conductive film, and a p-electrode The light emitting element is characterized in that the conductive region is provided outside the projection region obtained by projecting the joint surface between the p electrode and the bump onto the transparent conductive film.

  According to the first invention, an adhesive dielectric film formed of a dielectric made of an oxide of a metal element is provided between a low refractive index dielectric film formed of a silicon compound and a reflective conductive film formed of a metal layer. Therefore, the degree of adhesion can be improved as compared with the case where the low refractive index dielectric film is in direct contact with the reflective conductive film. Therefore, since the low refractive index dielectric film can be formed at the position corresponding to the bump, the low refractive index dielectric film can be formed in a wide range. Therefore, it is possible to secure a wide range of total reflection by the low refractive index dielectric film. In addition, since the conductive region where the reflective conductive film and the transparent conductive film are conducted is provided outside the projected region where the joint surface between the p electrode and the bump is projected onto the transparent conductive film, the conductive region and the low refractive index dielectric are provided. The boundary with the film does not overlap with the bonding surface between the p-electrode and the bump when viewed from the direction orthogonal to the bump formation surface. Therefore, high impact resistance can be ensured. Here, the oxide is a compound containing oxygen, and includes a case of containing nitrogen.

  2nd invention of this application is 1st invention WHEREIN: A conduction | electrical_connection area | region is a light emitting element provided in the peripheral part of the transparent electrode film.

  According to the second invention, since the conductive region is the peripheral portion of the transparent electrode film, a wide region inside the peripheral portion can be used as the reflective region, so that the light from the light emitting layer is totally reflected in a wide range. Therefore, the light extraction efficiency can be further improved.

  A third invention of the present application is the light-emitting element according to the first invention, wherein the conduction region is provided between the plurality of bumps and has a smaller outline than the bumps.

  According to the third invention, since the conduction region is located between the bumps, a current is also injected from between the bumps, and a good current diffusion can be obtained. In addition, by making the conduction region have an outline smaller than the bump, a wide reflection region can be secured.

  A fourth invention of the present application is the light emitting device according to claim 2 or 3, wherein in the second or third invention, the conductive regions are arranged point-symmetrically with respect to the center of the transparent conductive film.

  According to the fourth aspect of the invention, current can flow from the conductive region to the transparent conductive film in a balanced manner and can be diffused on average, so that the light extraction efficiency can be improved.

According to a fifth invention of the present application, in any one of the first to fourth inventions, the adhesive dielectric film is a dielectric of any one of Al ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ , Nb ₂ O ₅ , and TiO _2. It is a light emitting element formed from a film.

According to the fifth invention, the adhesive dielectric film is made of any one of Al ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ , Nb ₂ O _{5, and} TiO ₂ , thereby having high adhesion to the reflective conductive film. Can be planned.

  A sixth invention of the present application is the light emission according to the fifth invention, wherein an oxygen deficient film from which a part of oxygen constituting the oxide is eliminated is provided as an adhesive dielectric film between the adhesive dielectric film and the reflective conductive film. It is an element.

  According to the sixth invention, an oxygen deficient film is formed as an adhesive dielectric film between the adhesive dielectric film and the reflective conductive film, so that the dangling bond of the oxygen deficient film serves as a bond and is strongly bonded to the reflective conductive film. By doing so, adhesiveness can be improved further.

A seventh invention of the present application is the light emitting device according to the sixth invention, wherein the adhesion dielectric film is formed of Al ₂ O _3-x (where 0 <n <3).

According to the seventh invention, the adhesive dielectric film can be an oxygen deficient film with Al ₂ O _3-x (where 0 <n <3).

  An eighth invention of the present application is the light emitting device according to any one of the first to seventh inventions, wherein the adhesive dielectric film is formed thinner than the low refractive index dielectric film.

  According to the eighth aspect, the adhesive dielectric film is formed thinner than the low refractive index dielectric film, so that the light extraction efficiency can be increased.

(Embodiment 1)
A light-emitting element according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of the light-emitting element according to this embodiment. FIG. 2 is a view of the state before the light emitting element according to the present embodiment is mounted on the submount, as viewed from the electrode side. The region where the bump is formed (becomes a bonding surface between the p electrode and the bump) is a region indicated by a dotted line. The light-emitting element shown in FIG. 1 is an LED chip that is flip-chip mounted on a mounting substrate B with bumps P interposed.

  The light-emitting element includes a light-transmitting substrate 11 that is an insulating substrate, an n-type nitride semiconductor layer 121 that is an n-type layer, a nitride light-emitting layer 122 that is a light-emitting layer, and a p-type nitride that is a p-type layer. A semiconductor layer 12 in which the semiconductor layer 123 is stacked is provided. A buffer layer may be provided between the translucent substrate 11 and the n-type nitride semiconductor layer 121.

  As the translucent substrate 11, a substrate that transmits light from the nitride light emitting layer 122 can be used. As the translucent substrate 11, for example, a sapphire substrate, a SiC substrate, a ZnO substrate, or the like can be used. Note that the translucent substrate 11 may be removed after the semiconductor layer 12 is formed.

  The n-type nitride semiconductor layer 121 can be an n-type GaN layer. The n-type nitride semiconductor layer 121 is not limited to a single layer structure, and may have a multilayer structure. For example, when the translucent substrate 11 is a sapphire substrate, a buffer layer such as an AlN layer or an AlGaN layer is interposed, and the n-type nitride semiconductor layer 121 is placed on the n-type AlGaN layer and the n-type AlGaN layer. A configuration in which a type GaN layer is stacked may also be used.

  The nitride light-emitting layer 122 includes at least Ga and N, and a desired light emission wavelength can be obtained by including an appropriate amount of In as necessary. The nitride light-emitting layer 122 may have a single layer structure, but for example, may have a multiple quantum well structure in which at least a pair of InGaN layers and GaN layers are alternately stacked. In the first embodiment, the composition of the InGaN layer is set so that the emission peak wavelength of the nitride light emitting layer 122 is 450 nm. Note that the nitride light emitting layer 122 may have a single quantum well structure.

  The p-type nitride semiconductor layer 123 can be a p-type GaN layer. Further, the p-type nitride semiconductor layer 123 is not limited to a single layer structure, and may have a multilayer structure. In that case, for example, the p-type nitride semiconductor layer 123 can be a multilayer film in which a p-type AlGaN layer and a p-type GaN layer are stacked.

  Such a semiconductor layer 12 can be formed on the translucent substrate 11 by an epitaxial growth technique such as the MOVPE method. For example, a hydride vapor phase epitaxy method (HVPE method), a molecular beam epitaxy method (MBE method), or the like. Etc.).

  A transparent conductive film 13 made of a GZO (Ga-doped ZnO) film having a refractive index smaller than that of the p-type nitride semiconductor layer 123 is formed on the semiconductor layer 12. In the first embodiment, the film thickness of the transparent conductive film 13 is set to 10 nm. As the material of the transparent conductive film 13, in addition to GZO, for example, a material selected from the group of GZO, AZO (Al-doped ZnO), and ITO can be used.

By forming the transparent conductive film 13 with such a material, the contact between the transparent conductive film 13 and the p-type nitride semiconductor layer 123 can be ohmic contact. In the case where the transparent conductive film 13 is formed by GZO, AZO, ITO, etc., the film is formed by an O ₂ gas assisted electron beam evaporation method and then annealed in a mixed gas of N ₂ gas and O ₂ gas. Thus, the extinction coefficient of the transparent conductive film 13 can be set to about 0.001. Note that film formation by sputtering is preferable because a film having good flatness, low absorption, and excellent contact property can be formed.

As an example of the annealing conditions when the transparent conductive film 13 is formed by GZO, for example, the volume ratio of N ₂ gas and O ₂ gas is 95: 5, the annealing temperature is 500 ° C., and the annealing time is 5 minutes. it can. The transparent conductive film 13 may be other than the above-described film forming method and film forming conditions, but it is preferable to set the film forming method and film forming conditions so that the extinction coefficient is 0.003 or less.

  A reflective layer 14 is laminated on the transparent conductive film 13. The reflective layer 14 includes a low refractive index dielectric film 141, an adhesive dielectric film 142, and a reflective conductive film 143.

The low-refractive-index dielectric film 141 is a SiO film having a refractive index of 1.46, provided in a region excluding the peripheral portion of the transparent conductive film 13 as a conductive region C1 that establishes conduction between the transparent conductive film 13 and the reflective conductive film 143. ₂ is a dielectric film formed from ₂ . The low refractive index dielectric film 141 made of SiO ₂ is set to a film thickness of 300 nm. The low refractive index dielectric film 141 may be a silicon compound having a refractive index smaller than that of the p-type nitride semiconductor layer 123, such as SiON, in addition to the SiO ₂ film. The low refractive index dielectric film 141 can be formed by vapor deposition or sputtering.

  The conduction region C <b> 1 has a point-symmetric outline shape with the center of the transparent conductive film 13 as the center of symmetry (a point of symmetry) by ensuring a constant width of the entire peripheral edge of the transparent conductive film 13. In the first embodiment, the conductive region C1 is 16 μm as the constant width of the entire peripheral edge of the transparent conductive film 13.

The adhesive dielectric film 142 is formed of a dielectric made of an oxide with a metal element, and is formed on the low refractive index dielectric film 141. In the first embodiment, the adhesive dielectric film 142 is formed of Al ₂ O ₃ having a refractive index of about 1.6 to 1.9. The thickness of the adhesive dielectric film 142 made of an Al ₂ O ₃ film is 30 nm, which is thinner than the low refractive index dielectric film 141. The adhesive dielectric film 142 can be a Ta ₂ O ₅ film, a ZrO ₂ film, a Nb ₂ O ₅ film, or a TiO ₂ film, in addition to an Al ₂ O ₃ film. The adhesive dielectric film 142 can be formed by vapor deposition or sputtering.

  The reflective conductive film 143 is a metal film that covers the conductive region C1 that is conductive with the transparent conductive film 13 and the reflective region R1 that reflects light that has passed through the low refractive index dielectric film 141 and the adhesive dielectric film 142. The adhesive dielectric film 142 is joined. In the first embodiment, the reflective conductive film 143 is an Ag film having a high reflectance. The reflective conductive film 143 made of an Ag film can have a thickness of 100 nm. This film thickness can be set, for example, in the range of about 50 nm to 200 nm. The reflective conductive film 143 can be an Al film in addition to an Ag film. However, the reflective conductive film 143 is preferably an Ag film because the Ag film has a higher reflectance than the Al film.

  The n-electrode 15 is a cathode electrode provided in a region on the n-type nitride semiconductor layer 121 obtained by etching the p-type nitride semiconductor layer 123, the nitride light emitting layer 122, and a part of the n-type nitride semiconductor layer 121. is there. The n-electrode 15 is provided at a diagonal position of the translucent substrate 11 formed in a rectangular shape. The n electrode 15 is formed by laminating a Ti layer and an Au layer. The Ti layer of the n-electrode 15 stacked on the n-type nitride semiconductor layer 121 functions as an ohmic contact layer with respect to the n-type nitride semiconductor layer 121. The material of the ohmic contact layer may be, for example, Ti, V, Al, or an alloy containing any one of these metals. The Au layer laminated on the Ti layer functions as an n pad layer.

  The p-electrode 16 is an anode electrode laminated on the etched p-type nitride semiconductor layer 123. The p electrode 16 is provided in the remaining range where the n electrode 15 is provided. The p electrode 16 is formed by stacking an Au layer, a Ti layer, and an Au layer stacked on the reflective conductive film 143. The outermost Au layer functions as a p-pad layer. The P electrode 16 is conductively mounted on the mounting board B with the bumps P arranged in a matrix of equal intervals interposed therebetween. In the first embodiment, the light emitting element is conductively mounted on the mounting substrate B by the 5 × 5 bumps P including the bumps P for making the n-electrode 15 conductive.

  In the light emitting device configured as described above, a forward bias voltage is applied between the p electrode 16 and the n electrode 15, whereby the reflective conductive film 143, the transparent conductive film 13, and p-type nitriding are performed from the p electrode 16. A current flows to the n-electrode 15 through the metal semiconductor layer 123, the nitride light emitting layer 122, and the n-type nitride semiconductor layer 121.

  When the current flows from the reflective conductive film 143 to the transparent conductive film 13 in the conductive region C1, the transparent conductive film 13 has a high resistance to the reflective conductive film 143. Therefore, the conductive region C1 that is the peripheral portion of the transparent conductive film 13 is used. Current spreads from the transparent conductive film 13 toward the center of the transparent conductive film 13. In the first embodiment, the conduction region C1 is point-symmetric with the center of the transparent conductive film 13 as the center of symmetry (symmetry point) by ensuring a certain width of the entire peripheral edge of the transparent conductive film 13 as the conduction region C1. Since it has an outline shape, it diffuses averagely toward the center of the transparent conductive film 13 without deviation, so that the light emission efficiency of the nitride light emitting layer 122 can be improved.

In this light emitting element, the low refractive index dielectric film 141 is formed of SiO ₂ which is an example of a silicon compound. However, since the adhesive dielectric film 142 is provided, high adhesion to the reflective conductive film 143 is ensured. be able to. For example, assuming that the reflective conductive film 143 directly covers the low-refractive index dielectric film 141 without providing the adhesive dielectric film 142, the conductive film made of Ag is added to the dielectric film made of SiO _{2 formed} by the sputtering method. A film was formed and a tensile test was performed. As a result, it was 5.7 N / mm ² .

Therefore, assuming a case where the adhesive dielectric film 142 made of Al ₂ O _{3 is formed} on the low refractive index dielectric film 141 by sputtering, a tensile test of a combination of the Al ₂ O ₃ film and the Ag film was performed. As a result, the tensile strength was improved to 28.0 N / mm ² .

Table 1 shows the case where the adhesive dielectric film 142 is a Ta ₂ O ₅ film, a ZrO ₂ film, an Nb ₂ O ₅ film, or a TiO ₂ film in addition to Al ₂ O ₃ .

As can be seen from Table 1, the degree of adhesion between the low refractive index dielectric film 141 and the reflective conductive film 143 is low, and a dielectric composed of an oxide of a metal element is interposed between the low refractive index dielectric film 141 and the reflective conductive film 143. The adhesion degree is improved by providing the adhesive dielectric film 142 formed of a body. This is a material in which the bonding between Si atoms and oxygen is a covalent bond in SiO ₂ , which is a dielectric made of a non-metallic oxide, so that the bond is strong, and there are few dangling bonds necessary for adhesion, and the reflective conductive film 143 It is thought that the adhesive strength with is weak. On the other hand, since the metal-oxygen bond in the dielectric body made of an oxide of a metal element such as Al ₂ O ₃ or Ta ₂ O ₅ is ionic bond, the bond strength is weak compared to SiO ₂ and dangling bonds. Is generated and becomes a bond, so that it is considered that the adhesiveness with the reflective conductive film 142 is strong.

  As described above, by providing the adhesive dielectric film 142 on the low refractive index dielectric film 141, the adhesion between the adhesive dielectric film 142 and the reflective conductive film 143 can be improved. Even if the refractive index dielectric film 141 is provided, peeling of the reflective conductive film 143 due to impact can be prevented.

  Further, the conduction region C1 is provided outside the projection region T1 where the joint surface between the p electrode 16 and the bump P is projected onto the transparent conductive film 13 by being provided at the peripheral edge of the transparent conductive film. Become. As a result, the boundary between the conductive region and the low refractive index dielectric film does not overlap with the bonding surface between the p electrode 16 and the bump P when viewed from the direction orthogonal to the bump P forming surface. Therefore, high impact resistance can be ensured.

  FIG. 10 shows the result of verifying the effect of the present embodiment.

  As a comparative example, as shown in FIG. 3, a comparative example 1 in which the position corresponding to the bump P is a low-refractive index dielectric film formation prohibition region, and a plurality of conductive regions with small outlines are provided at the position corresponding to the bump P. Compared with Comparative Example 2 and Comparative Example 2, the contour of the conduction region is made larger and the number of the comparison example 3 is made, and the difference from the present embodiment in which the conduction region is provided at a position other than the position corresponding to the bump P is shown. Verified. Specifically, the share of the low refractive index dielectric film related to the light extraction efficiency was compared with the average value and variation of the shear strength related to the impact resistance. The results are described below.

  In Comparative Example 1 as shown in FIG. 3, since the low refractive index dielectric film 141 is not provided at the position corresponding to the bump P, the area can be secured only about 71% with respect to the transparent conductive film 13. In the present embodiment as shown in FIG. 2, the low refractive index dielectric film 141 is provided also at the position corresponding to the bump P, and only the peripheral portion is used as the conduction region C1, so that the low refractive index dielectric film 141 (reflection region) is provided. The area of R1) can be about 90% with respect to the transparent conductive film 13. Therefore, the light from the nitride light emitting layer 122 can be totally reflected in the direction of the translucent substrate 11 at the interface between the transparent conductive film 13 and the low refractive index dielectric film 141, thereby improving the light extraction efficiency. Can do.

  Further, in Comparative Example 2 and Comparative Example 3 having a conductive region with a small outline at a position corresponding to the bump P, the occupation ratio of the low refractive index dielectric film 141 is larger than that in Comparative Example 1, and the light extraction efficiency is improved. It was found that the average value and variation of the shear strength were significantly reduced, and there was a problem with impact resistance. Furthermore, from the verification results of Comparative Example 1, Comparative Example 2, and Comparative Example 3, it is found that the impact resistance decreases as the boundary between the low refractive index dielectric film 141 and the conductive region C1 increases at the position corresponding to the bump P. did.

  In contrast to these comparative examples, in the present embodiment, the low refractive index dielectric film 141 is provided at a position corresponding to the bump P, and the conductive region is provided at a position other than the position corresponding to the bump P. It was found that the light extraction efficiency and impact resistance were superior to other comparative examples.

  Further, since the low refractive index dielectric film 141 is formed of a dielectric that does not absorb light, the light extraction efficiency is improved compared to the case where a metal film (for example, a Pt film) is provided instead of the low refractive index dielectric film 141. Can be made.

Further, since the low refractive index dielectric film 141 is formed of SiO ₂ which is a silicon compound having a lower refractive index than other dielectrics, nitride light emission is caused at the interface between the low refractive index dielectric film 141 and the transparent conductive film 13. Since the light from the layer 122 can be easily totally reflected, the light extraction efficiency can be further improved.

(First Modification of Embodiment 1)
A first modification of the light-emitting element according to Embodiment 1 of the present invention will be described with reference to the drawings. In FIG. 4, the same components (materials) as in FIG.

  As shown in FIG. 4, a small-diameter through-hole 145 (see FIG. 5) smaller than the contour of the bump P is formed in the low refractive index dielectric film 141 and the adhesive dielectric film 142 so that the bonding surface between the p electrode 16 and the bump P is transparent. Outside the projection region T2 projected onto the conductive film 13, a conductive region C2 for conducting the transparent conductive film 13 and the reflective conductive film 143 is provided. The conduction region C <b> 2 is also provided at a position that becomes the peripheral portion of the transparent conductive film 13. Therefore, the reflection region R2 that reflects the light that has passed through the low refractive index dielectric film 141 and the adhesive dielectric film 142 is a remaining region excluding the conduction region C2.

  More specifically, the through holes 145 are arranged between the vertical and horizontal bumps P arranged in a matrix, so that virtual lines connecting the through holes 145 have a lattice shape, and the transparent conductive film 13 It is arranged at the position of the symmetry center with the center of.

  The through hole 145 is provided with a mask pattern in advance at a position where the through hole 145 is formed when the low refractive index dielectric film 141 and the adhesive dielectric film 142 are laminated on the transparent conductive film 13. It can be formed by laminating the dielectric film 141 and the adhesive dielectric film 142 and then removing the mask pattern.

  In the first modification, when a forward bias voltage is applied with a bump P interposed between the p electrode 16 and the n electrode 15, the p electrode 16 transfers to the conductive region C2 of the reflective conductive film 143, and the conductive region C2 starts. A current flows to the transparent conductive film 13. The transparent conductive film 13 has a higher resistance than the reflective conductive film 143, and the conduction region C2 is provided in a lattice shape that can be averagely arranged with no deviation from the transparent conductive film 13, A current diffuses through the transparent conductive film 13 from each conductive region C2 toward a region where there is no conductive region C2. Accordingly, current can be diffused over a wide range of the entire transparent conductive film 13. The current flowing in a wider range flows to the n-electrode 15 via the p-type nitride semiconductor layer 123, the nitride light emitting layer 122, and the n-type nitride semiconductor layer 121.

  Thus, since the current spreads and flows through the entire nitride light emitting layer 122, the light emission efficiency can be improved. In particular, in the present embodiment, since the dot-shaped conduction regions C2 are arranged in a lattice pattern and are arranged point-symmetrically with the center of the transparent conductive film 13 as the center of symmetry, the transparent conductive film 13 is more effectively formed. Current can be diffused.

  Further, since the conduction region C2 is provided smaller than the contour of the bump P, the reflection region R2 can be secured widely. In the first modification, the reflection region R2 can secure an area of about 90% with respect to the transparent conductive film 13. Therefore, the light extraction efficiency can be improved.

  Further, in order to ensure a wide reflection region R2, the conduction region C2 is provided smaller than the contour of the bump P. However, the conduction region C2 is provided at a position other than the position corresponding to the bump P, so It can be avoided that the impact acts on the peripheral portion of the through-hole 145 and the reflective conductive film 143 is peeled off from the adhesive dielectric film 142. Therefore, it is possible to improve the impact resistance while improving the light extraction efficiency.

  In FIG. 10, the light emitting element according to this modification is compared with the comparative example described above and the light emitting element according to the first embodiment. As a result, it has been found that in the light emitting device according to this modification, effective current diffusion can be realized without reducing the occupation ratio and the shear strength of the low refractive index dielectric film as compared with the first embodiment.

(Second to fifth modifications of the first embodiment)
Second to fifth modifications of the light-emitting element according to Embodiment 1 of the present invention will be described with reference to the drawings.

  In the second to fifth modifications, the conductive region for conducting the reflective conductive film with the transparent conductive film is not only the peripheral edge of the transparent conductive film, but also a groove shape or a dot shape having a smaller contour than the bump. It is something.

  The second modification shown in FIG. 6A is a grid-like groove 146 that connects the through holes 145 (see FIG. 5) of the first modification. In the dot-shaped through-holes 145, the size of each dot-shaped mask pattern is small, so there is a concern about pattern loss. However, by making the conductive region C3 a groove 146, the mask pattern is made more dot-shaped. Also, a high strength can be given to the mask pattern for forming the groove 146. In addition, since one groove 146 has both end portions, the chemical solution easily permeates during etching or the like. Further, the reflection region R3 can be secured. Therefore, by forming the conduction region C3 as the groove 146, it can be easily and accurately formed.

  In the third modification shown in FIG. 6B, a plurality of rectangular grooves 147 sharing the center are used as the conduction region C4. In the third modification, two rectangular grooves 147 are provided, and an inner groove 147a is provided so as to surround the bump P0 located at the center. The outer groove 147b is provided so as to surround the eight bumps P1 that surround the periphery adjacent to the bump P0 located at the center. Further, the reflection region R4 can be secured. Since the conductive region C4 is formed as the groove 147 in this way, the mask pattern can be given higher strength than the dot pattern, as in the second modification. Therefore, the conductive region C4 can be easily formed. Can be formed.

  In the fourth modification shown in FIG. 7C, a dot-shaped through hole 145 is provided along a diagonal line connecting corners where the n-electrode 15 is not provided, and the conduction region C5 is arranged. In the fourth modification example, a step is provided from one corner to the other corner along the periphery of the bump P2 located on the diagonal line. By providing such a through-hole 145, the position away from the n-electrode 15 becomes the conduction region C5, so that the current diffuses toward the n-electrode 15 while diffusing on the transparent conductive film 13, so Uniformity can be achieved. In addition, by forming the conduction region C5 in a dot shape, the area of the low refractive index dielectric film 141 can be ensured wider than that of the groove, so that the reflection region R5 can be secured widely.

  In the fifth modification shown in FIG. 7D, a plurality of L-shaped grooves 148 provided at the corners where the n-electrode 15 is not provided are used as the conduction region C6. In the fifth modification, a groove 148a is provided between the bump P2 located at the corner and the three adjacent bumps P3, and a groove 148b is provided between the bump P3 and the five adjacent bumps P4. Yes. Thereby, the reflection region R6 can be secured. By providing such a groove 148, the position away from the n electrode 15 becomes a conduction region C 6, and the current diffuses toward the n electrode 15 while diffusing on the transparent conductive film 13. Can be planned.

  Also in the second modification to the fifth modification, as in the first modification, the conduction regions C3 to C6 are provided at positions other than the positions corresponding to the bumps P, so that the impact at the time of mounting can be reduced in the through holes 145. It is possible to avoid the reflective conductive film 143 from being peeled off from the adhesive dielectric film 142 by acting on the peripheral edge portion or the peripheral wall portions of the grooves 146 to 148. Therefore, it is possible to improve the impact resistance while improving the light extraction efficiency.

(Embodiment 2)
A light-emitting element according to Embodiment 2 of the present invention will be described with reference to the drawings. In FIG. 8, the same components (materials) as those in FIG. The light emitting element according to the second embodiment is characterized in that an oxygen deficient film from which a part of oxygen constituting the oxide is eliminated is further provided as an adhesive dielectric film between the adhesive dielectric film and the reflective conductive film. It is what.

As shown in FIG. 8, an adhesive dielectric film 144 is provided between the adhesive dielectric film 142 and the reflective conductive film 143. The adhesive dielectric film 142 is formed of any one of Al ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ , and Nb ₂ O ₅ . The adhesion dielectric film 144 is a thin film formed in a state where a part of oxygen of Al ₂ O ₃ is desorbed and lost. That is, the adhesion dielectric film 144 can be expressed as Al ₂ O _3-x (where 0 <n <3). Therefore, in the second embodiment, the adhesive dielectric film 144 is formed of a dielectric material deficient in oxygen at the interface with the reflective conductive film. The adhesion dielectric film 144 can be formed by sputtering.

  By providing such an adhesive dielectric film 144 between the adhesive dielectric film 142 and the reflective conductive film 143, a dangling bond is generated in the adhesive dielectric film and becomes a bond with the reflective conductive film. Adhesion can be improved.

  Since the present invention can achieve high light extraction efficiency while ensuring high impact resistance, a semiconductor layer including a light emitting layer is laminated on a substrate, and conductive reflection that reflects light from the light emitting layer toward the substrate. It is suitable for a light emitting element provided with a film.

DESCRIPTION OF SYMBOLS 11 Translucent board | substrate 12 Semiconductor layer 121 N type nitride semiconductor layer 122 Nitride light emitting layer 123 P type nitride semiconductor layer 13 Transparent conductive film 14 Reflective layer 141 Low refractive index dielectric film 142 Adhesive dielectric film 143 Reflective conductive film 145 Through Hole 146 Groove 147, 147a, 147b Groove 148, 148a, 148b Groove 15 N electrode 16 P electrode

Claims (8)

A substrate having optical transparency;
A semiconductor layer in which an n-type layer, a light-emitting layer, and a p-type layer are stacked on the substrate;
A transparent electrode film laminated on the p-type layer and having a refractive index smaller than that of the p-type layer;
A low-refractive-index dielectric film that is laminated on the transparent electrode film so as to exclude a conductive region and is formed of a silicon compound having a refractive index smaller than that of the p-type layer;
An adhesive dielectric film laminated on the low refractive index dielectric film and formed of a dielectric made of an oxide of a metal element;
A reflective conductive film made of a metal layer bonded to the adhesive dielectric film and conductive to the transparent conductive film in the conductive region;
A p-electrode formed on the reflective conductive film;
A plurality of bumps joined to the p-electrode;
The light-emitting element, wherein the conduction region is provided outside a projection region obtained by projecting a joint surface between the p-electrode and the bump onto the transparent conductive film. The light-emitting element according to claim 1, wherein the conduction region is provided at a peripheral portion of the transparent electrode film. The light-emitting element according to claim 1, wherein the conduction region is provided between the plurality of bumps and has a smaller outline than the bumps. The light-emitting element according to claim 2, wherein the conductive regions are arranged point-symmetrically with respect to the center of the transparent conductive film. 5. The adhesive dielectric film according to claim 1, wherein the adhesive dielectric film is formed of a dielectric film of any one of Al ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ , Nb ₂ O ₅ , and TiO ₂ . Light emitting element. 6. The light emitting device according to claim 5, wherein an oxygen deficient film from which a part of oxygen constituting the oxide is released is provided as an adhesive dielectric film between the adhesive dielectric film and the reflective conductive film. The light emitting device according to claim 6, wherein the adhesion dielectric film is formed of Al ₂ O _3-x (where 0 <n <3). The light emitting device according to claim 1, wherein the adhesive dielectric film is formed thinner than the low refractive index dielectric film.

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