Semiconductor light-emitting element and substrate for semiconductor light-emitting element

Abstract

To provide a semiconductor light-emitting element and a substrate for the semiconductor light-emitting element, which can constitute a light-emitting device that has a narrow-angle light distribution, a high output and high efficiency.SOLUTION: The semiconductor light-emitting element includes: a substrate that has an uneven structure in which gimlet-shaped protrusions are periodically arrayed on a first surface; a semiconductor laminate that has a first semiconductor layer having a first conductivity type, an active layer, and a second semiconductor layer having a second conductivity type which is different from the first conductivity type formed in this order, on the first surface of the substrate, on which the uneven structure is formed; and a reflective layer that is formed on the semiconductor laminate and reflects the emitted light which is emitted from the active layer. The substrate has translucency with respect to the emitted light; and when a period at which the protrusions are arrayed is represented by P and a wavelength of the emitted light is represented by λ, the period satisfies 0.8≤P / λ≤1.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a semiconductor light-emitting element and a substrate for a semiconductor light-emitting element. [Background technology]

[0002] One of the means for increasing the output of a lighting device is to distribute the light emitted from a light source at a narrow angle.

[0003] For example, Patent Document 1 discloses an illumination device including a substrate constituting a light source, a wavelength conversion layer disposed adjacent to the light source, and an antenna array disposed on the substrate and within the wavelength conversion layer, and discloses that in the illumination device, the antenna array can emit light within a predetermined angular range. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6381645 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, consider a case where a light emitting diode (LED), which consumes less power than a laser, is used as a light source in the above-mentioned lighting device. LEDs have a characteristic of having a Lambertian light distribution. Therefore, in order to efficiently allow the light from the LED to enter the wavelength conversion layer, it has been an issue to narrow the angle of the light emitted from the LED.

[0006] In addition, in the above-mentioned lighting device, in order to prevent the return light from the wavelength conversion layer to the LED from being lost, a multilayer film configured to transmit light in the wavelength range of the light emitted from the LED and to reflect the wavelength-converted light from the wavelength conversion layer is provided between the LED and the wavelength conversion layer. In this case, due to the influence of the so-called blue shift in the reflectance-wavelength characteristics of the multilayer film, in which the wavelength range with high reflectance shifts to the short wavelength side as the incident angle increases, the light from the LED that is incident on the multilayer film at a large angle is reflected by the multilayer film and is lost. Therefore, from the viewpoint of efficiently entering the light from the LED into the multilayer film, it has been an issue to narrow the angle of the light emitted from the LED.

[0007] The present invention has been made in consideration of the above-mentioned points, and aims to provide a semiconductor light-emitting element and a substrate for a semiconductor light-emitting element that can constitute a light-emitting device with a narrow light angle and high output and high efficiency. [Means for solving the problem]

[0008] The semiconductor light-emitting element according to the present invention comprises a substrate having a first surface on which a concave-convex structure is formed, in which pyramidal convex portions are periodically arranged; a semiconductor laminate having a first semiconductor layer having a first conductivity type, an active layer, and a second semiconductor layer having a second conductivity type different from the first conductivity type, formed in this order on the first surface of the substrate on which the concave-convex structure is formed; and a reflective layer formed on the semiconductor laminate and configured to reflect emitted light from the active layer, wherein the substrate is translucent to the emitted light, and wherein when a period at which the convex portions are arranged is P and a wavelength of the emitted light is λ, the period satisfies 0.8≦P / λ≦1.

[0009] The substrate for a semiconductor light-emitting element according to the present invention is a substrate for a semiconductor light-emitting element used in the manufacture of a semiconductor light-emitting element having a semiconductor laminate including an active layer and a reflective layer formed on the semiconductor laminate and reflecting light emitted from the active layer, characterized in that a concavo-convex structure in which pyramidal convex portions are periodically arranged is formed on a first surface forming the semiconductor laminate, the substrate has translucency to the emitted light, and the period at which the convex portions are arranged is P and the wavelength of the emitted light is λ, the period satisfies 0.8≦P / λ≦1. [Brief description of the drawings]

[0010] [Figure 1] 1 is a top view showing a configuration of a semiconductor light emitting device according to a first embodiment. [Diagram 2] 1 is a cross-sectional view showing a configuration of a semiconductor light emitting device according to a first embodiment. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of a portion of the cross-sectional view of FIG. 2. [Figure 4] FIG. 2 is a diagram showing an example of reflectance versus incident angle of a dielectric multilayer film. [Diagram 5] FIG. 4 is a diagram showing the reflection diffraction angle versus the incident angle of light on the sapphire substrate in Example 1. [Figure 6] FIG. 4 is a diagram showing the transmission diffraction angle versus the incident angle of light on the sapphire substrate in Example 1. [Figure 7] 1 is a diagram showing a schematic diagram of a refractive index distribution near an interface between a substrate and GaN in Example 1 and Comparative Example 1. FIG. [Figure 8] FIG. 2 is a diagram showing the calculation results of light transmittance according to Example 1 and Comparative Example 1. [Figure 9] 1 is a diagram showing light distribution characteristics of semiconductor light emitting elements according to Example 1 and Comparative Example 1. FIG. [Figure 10] 1 is a diagram showing output characteristics of semiconductor light emitting devices according to Example 1 and Comparative Example 1. FIG. [Figure 11] FIG. 11 is a cross-sectional view showing the configuration of a semiconductor light emitting device according to Example 2. [Figure 12] FIG. 9 is an enlarged cross-sectional view of a portion of the cross-sectional view of FIG. 8. [Figure 13]FIG. 11 is a diagram showing the light distribution characteristics of semiconductor light emitting devices according to Example 2 and a comparative example. [Figure 14] FIG. 13 is a diagram showing the results of evaluating the total luminous flux of semiconductor light emitting devices according to Example 2 and a comparative example. [Figure 15] FIG. 11 is a cross-sectional view showing the configuration of a semiconductor light-emitting element according to Example 3. [Figure 16] 11 is a diagram showing a simulation result of the light distribution characteristics of the semiconductor light emitting elements according to the first and third examples. FIG. [Figure 17] 1 is a diagram showing a light distribution ratio of the semiconductor light emitting elements according to the first and third embodiments. [Figure 18] 13 is a diagram showing light distribution characteristics of the semiconductor light emitting devices according to a modified example of Example 3 and Example 1. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In the following, preferred embodiments of the present invention will be described, which may be modified and combined as appropriate. In the following description and accompanying drawings, substantially the same or equivalent parts are designated by the same reference numerals. EXAMPLES

[0012] First Embodiment A configuration of a light emitting device 10 including a light emitting element 13 as a semiconductor light emitting element according to a first embodiment of the present invention will be described with reference to the accompanying drawings.

[0013] 1 is a top view showing an outline of the configuration of a light emitting device 10. The light emitting device 10 includes a mounting substrate 11 having a rectangular top surface shape, and a light emitting element 13 arranged on the mounting substrate 11 and having a multilayer film 15 on its uppermost surface, the light emitting element 13 also having a rectangular top surface shape.

[0014] 2 is a cross-sectional view of the light emitting device 10 taken along line 2-2 in FIG. 1. As described above, the mounting substrate 11 is a flat substrate having a rectangular upper surface. The mounting substrate 11 is an insulating substrate such as an aluminum nitride (AlN) ceramic substrate. The mounting substrate 11 may be a substrate made of other materials, such as alumina. The mounting substrate 11 is preferably a heat dissipating substrate made of a material having heat dissipation properties, such as aluminum nitride (AlN).

[0015] A p-type wiring electrode 11A and an n-type wiring electrode 11B, which are metal electrodes spaced apart from each other, are formed on the upper surface of the mounting substrate 11. The p-type wiring electrode 11A and the n-type wiring electrode 11B are electrically connected to an external power supply (not shown).

[0016] The light-emitting element 13 is an LED element including a substrate 17, a semiconductor laminate 22 consisting of a plurality of nitride-based semiconductor layers including an active layer formed on the lower surface 17A side of the substrate 17, and a multilayer film 15 formed on the upper surface 17B of the substrate 17.

[0017] The substrate 17 is a flat sapphire substrate having a rectangular upper surface. The substrate 17 is a growth substrate for the semiconductor layers constituting the light emitting element 13. A concave-convex structure (not shown in FIG. 2) described later is formed on a lower surface 17A serving as a first surface, which is one of the main surfaces of the substrate 17. In this embodiment, the concave-convex structure serves as a diffraction grating, contributing to improving the light extraction efficiency of the light emitting device 10.

[0018] The multilayer film 15 is formed on an upper surface 17B as a third surface, which is the main surface opposite to the lower surface 17A on which the concave-convex structure of the substrate 17 is formed. The multilayer film 15 is a dielectric multilayer film reflector in which a plurality of dielectric films having different refractive indices are laminated and configured to reflect light in a predetermined wavelength range that is incident at a predetermined angle range. In this embodiment, the multilayer film 15 is configured by laminating 23 pairs of niobium oxide film (Nb2O5) and silicon oxide film (SiO2).

[0019] The buried layer 18 is formed on the lower surface 17A of the substrate 17 by, for example, metal organic chemical vapor deposition (MOCVD) so as to fill the uneven structure of the substrate 17. The buried layer 18 is an undoped GaN layer that is not doped with impurities. The buried layer 18 serves to improve the flatness of the semiconductor layer formed thereon.

[0020] The semiconductor laminate 22 is a laminated structure including a plurality of semiconductor layers formed so as to cover the lower surface of the buried layer 18. The semiconductor laminate 22 includes an n-type semiconductor layer 19, an active layer 20, and a p-type semiconductor layer 21, which are epitaxially grown in this order on the buried layer 18 by the MOCVD method.

[0021] The n-type semiconductor layer 19 as the first semiconductor layer is formed so as to cover the lower surface of the buried layer 18, and is an n-type GaN layer doped with an n-type impurity as a first conductivity type. The n-type semiconductor layer 19 is doped with, for example, Si as the n-type impurity.

[0022] The n-type semiconductor layer 19 has a mesa shape. Specifically, the n-type semiconductor layer 19 has a recessed region 1 (the right side of FIG. 2) along the outer edge of the lower surface to which the n-electrode 27 is connected, and the other regions other than the region 1 form a plateau. The region 1 has a surface 19E that is recessed further than the surfaces of the plateau portions of the other regions.

[0023] The active layer 20 is formed on a mesa-shaped plateau portion on the lower surface of the n-type semiconductor layer 19. The wavelength of the light emitted from the active layer depends on the material and composition of the semiconductor laminate 22. In this embodiment, the active layer 20 is a semiconductor layer having a multi-quantum well (MQW) structure made up of an InGaN well layer and a GaN barrier layer. In this embodiment, the emission peak wavelength of the active layer 20 is within the range of 445±5 nm.

[0024] The p-type semiconductor layer 21 as the second semiconductor layer is formed across the lower surface of the active layer 20, and is a layer including a p-type GaN layer doped with p-type impurities as a second conductive type, and is composed of a plurality of semiconductor layers. The p-type GaN layer of the p-type semiconductor layer 21 is doped with, for example, Mg as a p-type impurity. The p-type semiconductor layer 21 is configured by, for example, stacking an electron block layer, a p-type cladding layer, and a contact layer on the lower surface of the active layer 20 in this order.

[0025] The p-electrode 23 is formed across the lower surface of the p-type semiconductor layer 21. The p-electrode 23 is formed by stacking a light-transmitting electrode layer 23A, which is an indium tin oxide (ITO) electrode having light-transmitting properties, and a metal layer 23B, which is a layer made of a metal containing at least silver (Ag), in this order on the lower surface of the p-type semiconductor layer 21. The metal layer 23B does not have to be made of silver (Ag), and may contain, for example, aluminum (Al) or gold (Au). The p-electrode 23 is electrically connected to the p-wiring electrode 11A on the mounting substrate 11 by AnSu eutectic via a conductive p-type electrode pad 25. The p-electrode 23 has a property of reflecting light emitted from the active layer 20 due to the metal layer 23B included in the p-electrode 23. In other words, the metal layer 23B of the p-electrode 23 also functions as a reflective layer.

[0026] The n-electrode 27 is a metal electrode provided on the exposed surface 19E of the n-type semiconductor layer 19. The n-electrode 27 is electrically connected to the n-type semiconductor layer 19. The n-electrode 27 is also electrically connected to the n-wiring electrode 11B on the mounting substrate 11 by AnSu eutectic via a conductive n-type electrode pad 29.

[0027] As described above, the light emitting element 13 is flip-chip mounted on the mounting substrate 11, and the upper surface 15S of the multilayer film 15 formed on the surface of the substrate 17 serves as the light emitting surface of the light emitting element 13.

[0028] Although the light-emitting element 13 has been described as having a mesa shape, this is not limited thereto, and the n-type semiconductor layer 19 and the n-wiring electrode 11B may be electrically connected via a through hole provided in the semiconductor laminate 22 and extending from the p-type semiconductor layer 21 to the n-type semiconductor layer 19.

[0029] With the above configuration, when a current is injected into the light emitting device 10 via the p-electrode 11A and the n-electrode 11B, the active layer 20 of the light emitting element 13 emits blue light having a peak emission wavelength of 445±5 nm.

[0030] As described above, multilayer film 15 is formed on upper surface 17B of substrate 17. Multilayer film 15 is designed to reflect light in the wavelength band of fluorescence emitted from a phosphor that is excited by the emitted light from the active layer and emits yellow fluorescence.

[0031] For example, when a phosphor layer (wavelength conversion layer) containing the above phosphor is provided in contact with the upper surface of the multilayer film 15, the fluorescence emitted from the phosphor has no directionality, and therefore returning light traveling toward the active layer 20 is generated. Such returning light is attenuated in the semiconductor layer and lost. Therefore, by making the multilayer film 15 have the function of reflecting light whose wavelength has been converted by the phosphor, the returning light is reflected by the multilayer film 15, and the optical loss can be reduced.

[0032] Multilayer film 15, which is a dielectric multilayer film reflector, is designed to reflect light in the yellow wavelength range and transmit light in the blue wavelength range from active layer 20. However, as the angle of incidence of blue light increases, the effective wavelength in multilayer film 15 becomes longer, resulting in a characteristic in which the reflectance in the blue wavelength range increases.

[0033] Therefore, in the light emitting element 13, of the light emitted from the active layer 20, light that is incident on the multilayer film 15 at an angle greater than a predetermined angle is reflected by the multilayer film 15 toward the active layer, and is not extracted from the light emitting element 13, resulting in light loss.

[0034] Furthermore, for example, in the absence of the uneven structure described below, when the light emitted from active layer 20 reaches the interface between buried layer 18, which is a GaN layer, and substrate 17, if the light is incident at an angle greater than the critical angle (i.e., the total reflection angle), it is reflected at the interface and lost.

[0035] Therefore, in this embodiment, the uneven structure provided on substrate 17 is made to function as a diffraction grating, so that the angle of incidence of light incident on multilayer film 15 and substrate 17 is controlled to be a narrow angle within an angle range in which the light is not reflected by multilayer film 15 and substrate 17.

[0036] The structure and function of the concave-convex structure 17U provided on the lower surface of the substrate 17 will be described in detail with reference to Fig. 3. Fig. 3 is an enlarged cross-sectional view of a portion A surrounded by a dashed line in Fig. 2. As shown in Fig. 3, the concave-convex structure 17U including convex portions 17C and concave portions 17D is formed on the lower surface 17A of the substrate 17. The convex portions 17C are arranged at a constant period P.

[0037] In this embodiment, the convex portion 17C has a truncated cone shape. In Fig. 3, the diameter of the bottom surface of the convex portion is W1, the diameter of the top surface is W2, and the height is H1. The convex portions 17C are arranged at a constant period P in a plane parallel to the substrate 17.

[0038] Specifically, the convex portions 17C have a bottom diameter W1 of 300 nm, a top diameter W2 of 150 nm, a height H of 400 nm, and are arranged in a hexagonal lattice pattern with a period of 440 nm. The convex portions 17C may be arranged in other ways, and for example, the convex portions 17C of the concave-convex structure 17U may be arranged in a square lattice pattern.

[0039] Next, a description will be given of the optical function of the concave-convex structure 17U. The concave-convex structure 17U functions as a transmission type diffraction grating or a reflection type diffraction grating for light incident from the active layer side.

[0040] In the following description, the incident surface when light from the active layer is incident on the concave-convex structure 17U is a virtual optical interface 17R (hereinafter also simply referred to as the optical interface) located on a line at ½ of height H1 (dashed line in FIG. 3).

[0041] More specifically, the concave-convex structure 17U functions as a transmissive diffraction grating when the angle of light incident on the optical interface 17R, which is a virtual incident surface, is less than the critical angle θC at the virtual incident surface 17R. Moreover, the concave-convex structure 17U functions as a reflective diffraction grating when the angle of light incident on the virtual incident surface 17R is equal to or greater than the critical angle θC.

[0042] 3 is incident on a virtual optical interface 17R at an incident angle θ1 (θ1<θC) less than the critical angle θC, the light L1 is diffracted (referred to as transmission diffraction) so as to pass through the optical interface 17R. The transmitted and diffracted light L2 has an emission angle (hereinafter referred to as transmission diffraction angle) of θ2 with respect to the optical interface 17R.

[0043] Light L2 travels through substrate 17, emerges from upper surface 17B of substrate 17, and enters multilayer film 15 provided thereon. The angle of incidence of light L2 on multilayer film 15 is θ2, which is the same as the transmission diffraction angle. In this embodiment, since the average refractive index of multilayer film 15 is equivalent to that of substrate 17, refraction at the interface between substrate 17 and multilayer film 15 can be ignored.

[0044] The magnitude of the transmission diffraction angle θ2 relative to the incident angle θ1 varies depending on the period P of the concave-convex structure 17U. In this embodiment, the period P is set so that when θ1 is less than the critical angle θC, the transmission diffraction angle θ2 is narrow enough (for example, 30° or less) to transmit through the multilayer film 15. Therefore, the light L2 transmits through the multilayer film 15, and the light L3 is extracted to the outside.

[0045] On the other hand, in FIG. 3, light L4 emitted from active layer 20 and incident on optical interface 17R at an incident angle θ3 (θ3≧θC) equal to or greater than the critical angle θC is diffracted so as to be reflected at optical interface 17R (hereinafter referred to as reflective diffraction).

[0046] The reflection angle (hereinafter referred to as the reflection diffraction angle) of light L5, which is light L4 reflected and diffracted by a virtual optical interface 17R (optical interface), with respect to the optical interface 17R is set to θ4. Light L5 travels through the semiconductor laminate 22, is reflected by the metal layer 23B of the p-electrode 23, and is incident again on the optical interface 17R. The incidence angle on the p-electrode 23 and the incidence angle when it is incident again on the optical interface 17R are both the same as the reflection diffraction angle, θ4.

[0047] As shown in Fig. 3, light L5 passes through the light-transmitting electrode layer 23A and is reflected by an upper surface 23BS (second surface) of the metal layer 23B serving as a reflective layer. Note that in Fig. 3, light 5 is shown diagrammatically with refraction at the interface between the p-type semiconductor layer 21 and the light-transmitting electrode layer 23A omitted.

[0048] The magnitude of the reflective diffraction angle θ4 relative to the incident angle θ3 varies depending on the period P of the concave-convex structure 17U. In this embodiment, the period P is set so that the reflective diffraction angle θ4 is less than the critical angle θc, i.e., an angle at which the light is not totally reflected at the interface between the embedded layer 18 and the substrate 17 and is an angle at which the light can be transmitted through the multilayer film 15.

[0049] Therefore, light L5 is incident on optical interface 17R at incident angle θ4 less than critical angle θc, and thus, similar to the above-mentioned light L1, is transmitted and diffracted by uneven structure 17U and enters substrate 17. Since transmission diffraction angle θ5 is an angle (e.g., 30° or less) at which light L5 can be transmitted through multilayer film 15, similar to transmission diffraction angle θ2, transmitted and diffracted light L6 is transmitted through multilayer film 15, and light L7 is extracted to the outside.

[0050] That is, in this embodiment, the uneven structure 17U functions as a reflective diffraction grating, thereby preventing total reflection of light (e.g., light L4) incident at a wide angle equal to or greater than the critical angle θc on the interface between the buried layer 18, which is a GaN layer, and the substrate 17 made of sapphire. The light incident at the wide angle is reflectively diffracted and reflected by the p-electrode 23, and then incident on the substrate 17 at a narrow angle less than the critical angle θc, and can be transmitted through the substrate 17.

[0051] Furthermore, the light incident at a narrow angle after the reflection and diffraction is incident at a narrow angle on the multilayer film 15 because the concave-convex structure 17U functions as a transmission type diffraction grating. Therefore, the optical loss due to total reflection at the GaN / sapphire interface and the optical loss due to reflection by the multilayer film 15 are reduced.

[0052] [Coherence length] Like the above-mentioned light L3 and light L7, in order to reliably extract light transmitted through the multilayer film 15 as emitted light from the light emitting device 10, it is necessary to make the phases of the emitted light constructive rather than canceling each other out. On the other hand, the optical path length of the emitted light from the active layer 20 until it enters the substrate 17 varies depending on the direction and angle at which the light is emitted from the active layer 20.

[0053] More specifically, the light emitted from the active layer 20 includes light directed from the active layer 20 toward the substrate 17 (upper side in FIG. 3) and light directed from the active layer 20 toward the p-electrode 23 (lower side in FIG. 3). Furthermore, as described above, of the light emitted from the active layer 20 toward the upper side, light (light L1) that enters the concave-convex structure 17U at a narrow angle is transmitted and diffracted by the concave-convex structure 17U and enters the substrate 17. Furthermore, of the light emitted from the active layer 20 toward the upper side, light that enters the concave-convex structure 17U at a wider angle than light L1 is reflected and diffracted by the concave-convex structure 17U, reflected by the metal layer 23B, and transmitted and diffracted by the concave-convex structure 17U, and enters the substrate 17.

[0054] Therefore, in the present invention, the coherence length of the light emitted from the active layer 20 is used to take into account the optical path length from the active layer 20 until the light emitted from the active layer 20 is incident on the lower surface 17A of the substrate 17, so that the phases of the emitted light having various optical path lengths are reinforced with each other.

[0055] The coherence length Lc, which is the upper limit of the optical path length difference at which the emitted lights from the active layer 20 can interfere with each other, is expressed as follows: Lc=λ where λ is the central wavelength of the emitted light from the active layer 20 and Δλ is the wavelength linewidth of the emitted light. 2 In this embodiment, the wavelength λ is 445 nm and the line width Δλ is 20 nm, so that Lc is approximately 10 μm.

[0056] In this embodiment, when considering the optical path length from the active layer 20 until the light emitted from the active layer 20 is incident on the lower surface 17A (first surface) of the substrate 17, the position of the virtual optical interface 17R, which is a position of 1 / 2 the height H of the convex portion 17C of the concave-convex structure 17U, is set to the position in the layer thickness direction of the lower surface 17A. When considering the optical path length, the lower surface 20A of the active layer 20 is set to the position in the layer thickness direction of the active layer 20.

[0057] 3, the distance between an upper surface 23BS (second surface) of the metal layer 23B serving as a reflective layer of the p-electrode 23 and a virtual optical interface 17R of the substrate 17 is defined as D1. Also, the distance D2 from the lower surface 20A of the active layer 20 to the optical interface 17R is defined. Also, the distance D3 from the lower surface 20A of the active layer 20 to the upper surface 23BS of the metal layer 23B is defined.

[0058] The distance from the lower surface of the active layer 20 to the optical interface 17R (for example, D2 in FIG. 3) is preferably within the coherence length Lc. In addition, when considering light that is emitted from the active layer 20 to the p-electrode 23 side (lower side in FIG. 3) and reflected by the upper surface 23BS of the metal layer 23B of the p-electrode 23 to become emitted light, the sum of the distance D1 between the upper surface 23BS as the second surface and the optical interface 17R as the first surface, and the distance D3 between the upper surface 23BS of the metal layer 23B and the lower surface of the active layer 20 (distance D1+distance D3) is preferably equal to or less than the coherence length Lc. As a result, the light emitted downward from the active layer 20 and extracted as emitted light and the light emitted upward from the active layer 20 and extracted as emitted light interfere with each other constructively.

[0059] The distance D1 may be set to be equal to or smaller than the coherence length Lc. When the distance D2 is sufficiently smaller than the coherence length Lc, instead of controlling the distance D1 to be equal to or smaller than the coherence length Lc, the distance D3 between the upper surface 23BS of the metal layer 23B and the lower surface of the active layer 20 may be set to be equal to or smaller than the coherence length Lc.

[0060] In the above description, the distance D1 is defined as the distance from the lower surface of the active layer 20 to the optical interface 17R, but in actual manufacturing, the distance D1 may be treated as the dimension from the lower surface of the active layer 20 to the lowest end of the lower surface 17A of the substrate 17 (i.e., the tip of the convex portion 17C) or the position of the base of the convex portion 17C on the lower surface 17A (i.e., the position of the bottom of the concave portion 17D). In other words, film formation may be performed so that the distance from the lower surface of the active layer 20 to the tip of the convex portion 17C or the bottom surface of the concave portion 17D is equal to or less than the coherence length Lc. In addition, the distance D2 may be the distance from the center of the film thickness of the active layer 20 or the upper surface 20B to the optical interface 17R, and the distance D3 may be the distance from the center of the film thickness of the active layer 20 or the upper surface 20B to the upper surface 23BS of the metal layer 23B.

[0061] 4 to 6, a method for setting the period P of the concave-convex structure 17U of the substrate 17 in this embodiment will be described with reference to specific numerical values. First, a target value for the incident angle of light incident on the multilayer film 15 was set based on the characteristics of the multilayer film 15.

[0062] [Multilayer film characteristics] Fig. 4 is a diagram showing the incidence angle dependency of the reflectance of light having wavelengths of 435 to 480 nm by the multilayer film 15. The graph shown in Fig. 4 is a result of simulating the reflectance wavelength characteristics of the multilayer film 15 employed in this embodiment for each incidence angle.

[0063] As shown in FIG. 4, in the wavelength range of 445 nm±5 nm, which is the emission wavelength of the light emitting element 13, the reflectance is 0% at the incidence angles of 0° and 15°, and the reflectance is high at the incidence angle of 30°. Therefore, in order to increase the components of light transmitted through the multilayer film 15, the incidence angle to the multilayer film 15 needs to be 30° or less, more preferably less than 30°, and even more preferably 15° or less. In addition, as shown in FIG. 4, when the upper limit of the incidence angle is set to 30°, the adoptable wavelength range can be set to a range from 440 nm to 455 nm. In addition, when the upper limit of the incidence angle is set to 30°, a wavelength range of 440 nm or less with a lower reflectance may be adopted. For example, the adopted wavelength range is appropriately determined in consideration of the characteristics of the multilayer film 15, the target emission color, the material system of the light emitting element, and the like.

[0064] In this embodiment, the target value of the incident angle was determined according to the wavelength of the light emitting element. Specifically, the target value of the incident angle was set to 30° or less so that the light with a wavelength of 445 nm±10 nm emitted from the active layer 20 would pass through the multilayer film 15. For example, the target incident angle and wavelength may be determined from the results of FIG. 4, and the composition of the light emitting element 13 may be adjusted so that the emission wavelength becomes the target wavelength. For example, from among a plurality of types of multilayer films designed to reflect yellow light, one that transmits blue light, which is the light emitted from the active layer, in a desired angle range may be selected.

[0065] [Reflection diffraction angle] Next, a target value of the reflective diffraction angle when the concave-convex structure 17U is made to function as a reflective diffraction grating was set based on the target value of the incident angle to the multilayer film 15, and an acceptable value of the period P of the concave-convex structure was estimated so as to achieve the target reflective diffraction angle. The target value of the reflective diffraction angle was set within ±30°.

[0066] FIG. 5 is a diagram showing the results of calculating the reflection / diffraction angle for the incident angle from 0° to 80° of light with a wavelength λ of 445 nm for each period P based on the following formula (1). nkPsinθin-nkPsinθref = m (1) In equation (1), n ​​is the refractive index of GaN, k is the wave number (2π / λ), P is the period of uneven structure 17U, θin is the angle of incidence, θref is the reflected diffraction angle, and m is the order of diffraction. Figure 5 shows the result of calculating the reflected diffraction angle θref for each period P when m=1. Note that 47° in Figure 5 indicates the critical angle of the interface between GaN and sapphire when light is incident from the GaN layer to the sapphire substrate.

[0067] As shown in Fig. 5, the reflective diffraction angle for the same incident angle varies depending on the period P. From Fig. 5, it can be seen that when the period P is 300 nm, 360 nm, or 440 nm, the reflective diffraction angle is generally within ±30° for incident angles of 0° to 80°. For example, when the incident angle is 50°, the reflective diffraction angle is 15°. Therefore, it was found that, for the emission wavelength of this embodiment, in order to keep the reflective diffraction angle within ±30°, a period P of 300 nm to 440 nm can be adopted for the concave-convex structure 17U.

[0068] Furthermore, the inventors discovered that when the wavelength of the light-emitting element is λ and the period of the uneven structure 17U is P, the reflection diffraction angle can be kept within ±30° by setting the period P and the wavelength λ so that 0.8≦P / λ≦1.

[0069] [Transmission diffraction angle] In this embodiment, the period P is set in consideration of the transmission diffraction angle when the concave-convex structure 17U functions as a transmission type diffraction grating. As described above, the transmission diffraction angle with respect to the incident angle also differs depending on the period P.

[0070] The relationship between the transmission and diffraction angles is expressed by equation (2). nkPsinθin-nskPsinθout = m (2)Here, n is the refractive index of GaN, ns is the refractive index of the sapphire substrate, k is the wave number (2π / λ), P is the period of the unevenness structure 17U, θin is the angle of incidence, θout is the transmission diffraction angle, and m is the order of diffraction. Figure 6 is a diagram showing the results of calculating the transmission diffraction angle θout for light with a wavelength λ=445 nm for angles of incidence from 0° to 80° for each period P based on the above formula (2).

[0071] As described above, in this embodiment, there are two possible patterns in which the concave-convex structure 17U functions as a transmission type diffraction grating. One is when light from the active layer 20 is incident at an incident angle of 47° or less, which is the critical angle of the interface between GaN and sapphire when the light is incident from the GaN layer to the sapphire substrate (for example, light L1). The other is when light reflected by the p-electrode 23 is incident at an incident angle of 30° or less (for example, light L5 in FIG. 3). Therefore, the transmission diffraction angle for an incident angle of 47° or less is considered.

[0072] 6, when the period P is 360 nm and 440 nm, it can be said that, of the light incident at an incident angle of 47° or less, the transmission diffraction angle is within ±30° when the incident angle is at least 10° or more. Also, since it is considered that, of the transmitted and diffracted light, light with an incident angle of 10° or more and less than 47° is more prevalent than light with an incident angle of 0° or more and less than 10°, it can be said that, when the period P is 360 nm or 440 nm, the transmission diffraction angle is substantially within ±30° if the incident angle is less than 47°.

[0073] Therefore, either 360 nm or 440 nm can be used as the period P. Considering the data in Fig. 6 for incident angles of less than 10°, the transmission diffraction angle is slightly wider when the period P is 360 nm than when it is 440 nm at an incident angle of 0°, so it can be said that 440 nm is more preferable. For this reason, 440 nm was used in this embodiment.

[0074] Since the period P is determined as described above, the light emitted from the active layer 20 is reflected and diffracted or transmitted and diffracted by the uneven structure 17U, and the emission angle from the substrate 17, i.e., the incident angle to the multilayer film 15, is substantially within 30°.

[0075] 3, the incident angle θ1 of the light L1 is less than 47°, so the light L1 is diffracted by the concave-convex structure 17U and the transmitted diffraction angle θ2 is within 30°. Therefore, the incident angle θ2 of the transmitted and diffracted light L2 on the multilayer film 15 is also within 30°, so that the light L2 can transmit through the multilayer film 15.

[0076] 3, the incident angle θ3 of the light L3 is 47° or more, so it is reflected and diffracted by the concave-convex structure 17U, and the reflected diffraction angle θ4 is within 30°. Therefore, the incident angle θ4 when the reflected and diffracted light L5 is again incident on the concave-convex structure 17U is also within 30°. Since the incident angle θ4 of the light L5 is less than 47°, it is transmitted and diffracted by the concave-convex structure 17U, and the transmitted diffraction angle θ5 is also within 30°. Therefore, the incident angle θ5 of the transmitted and diffracted light L6 to the multilayer film 15 is also within 30°, so that the light L6 can transmit through the multilayer film 15.

[0077] In this embodiment, the reflection diffraction angle θ4 is set to within 30°, but the reflection diffraction angle θ4 may be set to an angle larger than 30° as long as it is less than the critical angle θc. Even if it is set in this way, for example, as shown in FIG. 6, the transmission diffraction angle of light incident at an incident angle of 47° or less, which is the critical angle at the interface between GaN and sapphire, is substantially within 30°, so that the incident angle to the multilayer film 15 is also substantially within 30°. In other words, by setting the reflection angle when the emitted light from the active layer is reflected by the lower surface 17A as the first surface of the substrate 17 to be less than the critical angle at the interface between the substrate 17 and the buried layer 18 that is in contact with the substrate 17 at the lower surface 17A, the emission angle from the substrate 17, i.e., the incident angle to the multilayer film 15, can be set to a narrow angle of substantially within 30°.

[0078] [Narrowing] As described above, according to this embodiment, the concave-convex structure 17U functions as a reflective diffraction grating, and narrows the incident angle of the light emitted from the active layer 20 onto the multilayer film 15 and the substrate 17. This reduces optical loss caused by total reflection of the emitted light by the multilayer film 15 and the substrate 17. To narrow the incident angle, the period P at which the nano-sized pyramidal convex portions 17C are arranged in the concave-convex structure U is set to a size that narrows the reflective diffraction angle. In particular, by making the emission wavelength λ of the light-emitting element 13 and the period P satisfy 0.8≦P / λ≦1, the reflective diffraction angle by the concave-convex structure 17U can be controlled to a narrow angle of 30° or less.

[0079] As described above, the light-emitting element 13 is an LED element, and the light emitted from the active layer 20 has a Lambertian distribution, which means that there are more wide-angle components compared to a directional light source such as a laser, and therefore the light loss can be significantly reduced by the uneven structure 17U.

[0080] [Reducing refractive index difference] Furthermore, the uneven structure 17U reduces the refractive index difference at the interface between the buried layer 18, which is a GaN layer, and the substrate 17 made of sapphire.

[0081] FIG. 7 is a diagram showing a schematic distribution of the refractive index in the layer thickness direction in the vicinity of the interface between the GaN layer and the sapphire substrate.

[0082] Figure 7(a) shows the refractive index distribution in the layer thickness direction near the interface between the GaN layer and the surface of a flat sapphire substrate with no unevenness. As shown in Figure 7(a), when there is no unevenness, the interface between GaN and sapphire is clear, and the refractive index changes sharply from the GaN refractive index of 2.5 to the sapphire refractive index of 1.8 from the GaN layer toward the sapphire substrate.

[0083] 7(b) shows the refractive index distribution in the thickness direction near the interface between the buried layer 18 and the lower surface 17A of the substrate 17, which is a sapphire substrate having the concave-convex structure 17U of this embodiment. When the concave-convex structure is present, the interface between the GaN and the sapphire is not clear from a macroscopic perspective, and the region of the concave-convex structure in the thickness direction is a region where GaN and sapphire are mixed. In this case, as shown in FIG. 7(b), the refractive index distribution in the thickness direction changes gradually from the GaN layer toward the sapphire substrate.

[0084] Here, we consider Fresnel reflection at the interface between two layers with different refractive indices. The proportion of incident light that is reflected by Fresnel reflection varies depending on the angle of incidence and the refractive index. Furthermore, for the same angle of incidence, the greater the difference in refractive index between the two layers, the greater the proportion of reflection and the lower the transmittance.

[0085] Therefore, it is considered that the light incident on the sapphire substrate from the GaN layer is less susceptible to the effects of Fresnel reflection when the refractive index changes gradually as in FIG. 7(b) than when the refractive index changes sharply as in FIG. 7(a).

[0086] 8 is a diagram showing the results of calculating the transmittance of light incident from the GaN layer to the sapphire substrate at angles of incidence of 0° to 30° based on the reflectance due to Fresnel reflection in the configuration of the light emitting device 10 of Example 1 and the configuration of the light emitting device of Comparative Example 1. The light emitting device of Comparative Example 1 is configured similarly to the light emitting device 10 of Example 1, except that the substrate 17 does not have the uneven structure 17U. As shown in FIG. 8, the configuration of Example 1 showed a result in which the light transmittance was 5 to 10% higher than that of Comparative Example 1.

[0087] It has been found that by providing the uneven structure 17U, the optical loss caused by total reflection due to the above-mentioned reflection diffraction is reduced for the light incident on the substrate 17, and in addition, the optical loss caused by Fresnel reflection is reduced by mitigating the refractive index difference between the GaN layer and the sapphire substrate.

[0088] From the viewpoint of reducing such a refractive index difference, each of the protrusions 17C constituting the concave-convex structure 17U preferably has a sidewall that forms an angle of 60° or more with respect to the substrate surface.

[0089] [Evaluation Results of Example 1] The results of light distribution evaluation and output evaluation of the light emitting device 10 of Example 1 will be described in comparison with the light emitting device of Comparative Example 1. The light emitting device of Comparative Example 1 is configured similarly to the light emitting device 10 of Example 1, except that the substrate 17 does not have the uneven structure 17U.

[0090] FIG. 9 is a diagram showing the results of light distribution evaluation of the total luminous flux of the light emitting device 10 of Example 1 and the light emitting device of Comparative Example 1. In FIG. 9, (a) shows the light distribution evaluation result of Comparative Example 1, and (b) shows the light distribution evaluation result of Example 1. FIG. 9 shows the distribution of light intensity (luminous intensity) in directions of ±90°, with the direction perpendicular to the light exit surface being set as 0°. As shown in FIG. 9, compared to Comparative Example 1, In Example 1, a narrow-angle light distribution characteristic was obtained in which the light intensity was high when the emission direction was within ±30°.

[0091] Fig. 10 is a diagram showing the measurement results of the light output of the light emitting device 10 of Example 1 and the light emitting device of Comparative Example 1. As shown in Fig. 10, in Example 1, a light output three times higher than that of Comparative Example 1 was obtained for the same current value.

[0092] From the above evaluation results, it can be said that a light emitting device with narrower light distribution angle and higher output was obtained in Example 1 than in Comparative Example 1. This is because the period P of the uneven structure was appropriately set in relation to the wavelength of the emitted light from the active layer 20, which caused reflection diffraction and transmission diffraction at an appropriate angle, making it possible to extract more narrow-angle light, and because the uneven structure has an effect of mitigating the refractive index difference.

[0093] [Manufacturing method] An example of a manufacturing method of the light emitting device 10 of Example 1 will be described. First, a concave-convex structure was formed on one of the main surfaces as the first surface of the sapphire substrate. Specifically, a resist pattern was formed on a sapphire substrate having a thickness of 430 μm by electron beam lithography. Dry etching was performed using the resist pattern as a mask to form a concave-convex structure 17U in which convex portions 17C each having a bottom diameter W1 of 300 nm, a top diameter W2 of 150 nm, and a height H of 400 nm were arranged in a hexagonal lattice pattern with a period of 440 nm. A wafer on which the concave-convex structure 17U has been formed in advance may be prepared.

[0094] Next, each semiconductor layer was formed on the concave-convex structure 17U by metal organic chemical vapor deposition (MOCVD). An undoped GaN layer was formed to a thickness of 1 μm as the buried layer 18, and the surface was flattened. An n-type GaN layer doped with Si as an n-type impurity was formed to a thickness of 3 μm as the n-type semiconductor layer 19 on the buried layer 18.

[0095] A lattice-matched layer was formed on the n-type GaN layer, in which a 2 nm undoped GaN layer, a 100 nm n-type GaN layer, a 100 nm undoped GaN layer, a 50 nm n-type GaN layer, and a 163 nm n-type AlGaN layer were laminated in this order. Eight pairs of 3 nm GaN layers and 2.1 nm InGaN layers were alternately laminated on the lattice-matched layer, and a 2 nm GaN layer was laminated on top of them to form an underlayer for the active layer.

[0096] In this embodiment, the n-type semiconductor layer 19 is configured to include the lattice matching layer and underlayer described above, but the configuration of the n-type semiconductor layer 19 is not limited to this, and for example, it may not include the lattice matching layer or underlayer.

[0097] Then, an active layer having a multiple quantum well structure in which five pairs of 5.7 nm GaN barrier layers and 3.8 nm InGaN well layers were stacked was formed on the underlayer. A p-type semiconductor layer 21 consisting of a spacer layer, an electron blocking layer, a p-type cladding layer, and a p-type contact layer was formed on the active layer.

[0098] An undoped GaN layer was formed to a thickness of 13.7 nm as a spacer layer, and an AlGaN layer and an InN layer were formed to a thickness of 8.3 nm as an electron blocking layer on the spacer layer.

[0099] On the electron blocking layer, a p-type GaN layer doped with Mg as a p-type impurity was formed to a thickness of 98 nm as a p-type cladding layer. On the p-type cladding layer, a p-type GaN layer doped with Mg at a higher concentration than the p-type cladding layer was formed to a thickness of 5 nm as a p-type contact layer. The layers were formed so that the total layer thickness from the upper surface of the substrate (the upper surface of the convex portion 17C of the lower surface 17A in FIG. 3) to the p-type contact layer was within 10 μm.

[0100] ITO is formed on the upper surface of the p-type semiconductor layer 21 by sputtering to a thickness of 100 nm. Here, the film thickness when ITO is formed may be adjusted appropriately. By photolithography, ITO is left in the region corresponding to the p-electrode surface to form the transparent electrode layer 23A, and the ITO is etched and removed from the other regions. Next, the periphery of the ITO pattern is masked by photolithography, and an Ag film or an alloy containing Ag is sputtered only on the ITO pattern to form the metal layer 23B. In this way, the reflective p-electrode 23 is formed. After that, the p-type semiconductor layer 21, the active layer 20, and the n-type semiconductor layer 19 in the unmasked areas are masked by photolithography, and a mesa structure is formed by etching a part of the p-type semiconductor layer 21, the active layer 20, and the n-type semiconductor layer 19. As a protective film on the side of the mesa, a SiO2 film is formed by sputtering, and unnecessary parts of the film are removed by photolithography and etching. Furthermore, surface 19E of n-type semiconductor layer 19 exposed by the formation of the mesa structure was patterned by photolithography, and n-electrode 27 made of Ti / Al was formed by EB deposition. Note that in order to prevent diffusion of p-electrode 23, a diffusion prevention layer such as Ni / Pd / Au or Ti / Pt / Au may be provided on part of the upper surface and the side surface of p-electrode 23.

[0101] In addition, the portions other than the plateau portion were masked by photolithography, and Ti / Pt / Au films were formed on the unmasked portions by electron beam deposition (EB deposition), forming the p-type electrode pad 25 and the n-type electrode pad 29, respectively. In addition, the light reflectance of the p-electrode 23 was measured and confirmed to be 80% or more. The metal layer 23B (reflective layer) of the p-electrode 23 is preferably Ag, Rh, Al, or an alloy containing these, and for example, other metal layers such as an alloy containing Ag or Al may be laminated on the upper or lower layer. For example, the metal layer 23B may have a reflectance of 80% or more for light of the emission wavelength of the light emitting element 13.

[0102] Then, the substrate 17 was turned upside down so that the substrate 17 was on top, and the surface of the substrate 17 opposite to the main surface on which the uneven structure 17U was formed was polished to a thickness of 80-150 μm, which is suitable for singulation.

[0103] Thereafter, on the polished surface, that is, on the principal surface opposite to the principal surface on which the concave-convex structure 17U is formed, 23 pairs of 48.5 nm Nb2O5 and 76 nm SiO2 were laminated to form the multilayer film 15.

[0104] As described above, in this embodiment, the multilayer film 15 is formed directly on the substrate 17, but the present invention is not limited to this, and another substrate on which the multilayer film 15 is formed may be bonded to the substrate 17 using, for example, a resin adhesive. As a method that does not use an adhesive, another substrate on which the multilayer film 15 is formed may be bonded to the substrate 17 by direct bonding in which surfaces activated by plasma are bonded to each other.

[0105] In this embodiment, by directly bonding the substrate on which the multilayer film 15 is formed to the substrate 17, it is not necessary to attach the multilayer film 15 using, for example, an adhesive, and factors that may affect the light emission can be eliminated. By the above steps, a wafer on which a plurality of light-emitting elements 13 are formed was obtained.

[0106] Thereafter, the light emitting element 13 was divided into individual pieces by dicing, and flip-chip mounted on the mounting substrate 11. Specifically, the light emitting element 13 was placed on a mounting substrate having a p-wiring electrode 11A and an n-wiring electrode 11B on which an AuSn pattern was formed, so that the p-type electrode pad 25 connected to the p-electrode 23 and the n-type electrode pad 29 connected to the n-electrode 27 were in contact with the p-wiring electrode 11A and the n-wiring electrode 11B, respectively. Flip-chip mounting was performed by AuSn eutectic bonding using heat and pressure. In this manner, the light emitting device 10 was produced. Note that the manufacturing method of the light emitting device 10 described above is an example, and is not limited to the above method.

[0107] As described above in detail, the light emitting device 10 of this embodiment is a light emitting device in which the light emitting element 13 is flip-chip mounted. The light emitting element 13 has a substrate on whose first surface a concave-convex structure in which pyramidal convex portions are periodically arranged is formed, and a semiconductor laminate in which an n-type semiconductor layer as a first semiconductor layer, an active layer, and a p-type semiconductor layer as a second semiconductor layer are formed in this order on the first surface, which is the main surface on which the concave-convex structure of the substrate is formed. The light emitting element 13 also has a reflective layer formed on the semiconductor laminate and reflecting the emitted light emitted from the active layer. The substrate has translucency for the emitted light from the active layer.

[0108] Furthermore, the light-emitting element 13 has a feature that, when the period at which the convex portions of the concave-convex structure are arranged is P and the wavelength of the light emitted from the active layer is λ, the period P satisfies 0.8≦P / λ≦1.

[0109] With the above-mentioned configuration, when the light emitted from the active layer reaches the concave-convex structure of the substrate, the concave-convex structure functions as a reflective diffraction grating or a transmissive diffraction grating depending on the angle of incidence. The concave-convex structure functions as a transmissive diffraction grating for light incident at a narrow angle less than the critical angle (total reflection angle), and the incident light is diffracted while passing through the substrate (transmission diffracted).

[0110] In addition, the concave-convex structure functions as a reflective diffraction grating for incident light at a wide angle equal to or greater than the critical angle, and the incident light is diffracted and reflected to the substrate (reflected and diffracted). At that time, the period P satisfies 0.8≦P / λ≦1, so that the reflective diffraction angle is a narrow angle of 30° or less.

[0111] As a result, the reflected and diffracted light is reflected by the reflective layer, then re-enters the concave-convex structure at an angle equal to the angle of reflection and diffraction, and the re-entered light passes through the substrate while being diffracted (transmitted and diffracted). In other words, the concave-convex structure reduces the components that would otherwise be reflected by the substrate and lost, improving the light extraction efficiency.

[0112] In addition, the presence of the uneven structure reduces the refractive index difference at the interface between the substrate and the semiconductor layer, thereby reducing the components reflected by Fresnel reflection among narrow-angle light incident on the uneven structure, i.e., light incident at an incident angle that can be transmitted and diffracted, and also contributes to improving the light extraction efficiency.

[0113] Furthermore, since the transmission and diffraction angle of the transmitted and diffracted light is also narrow as described above, the light emitted from the surface opposite to the surface having the concave-convex structure of the substrate has a narrow-angle light distribution.

[0114] Therefore, according to this embodiment, it is possible to provide a semiconductor light emitting element and a substrate for a semiconductor light emitting element that can constitute a light emitting device with a narrow light angle, high output, and high efficiency.

[0115] Furthermore, in the light emitting element 13 of this embodiment, a multilayer film is formed on the main surface opposite to the main surface on which the concave-convex structure is formed. The multilayer film reflects light emitted from the active layer that is incident at a wide angle, but since the light emitted from the substrate is at a narrow angle as described above, the angle of incidence of the light incident on the multilayer film is also narrow. Therefore, the emitted light that passes through the substrate via the concave-convex structure is extracted to the outside without being reflected by the multilayer film.

[0116] Therefore, even when a multilayer film is provided on a substrate, it is possible to provide a semiconductor light emitting element and a substrate for a semiconductor light emitting element that can configure a light emitting device with narrow light angle, high output, and high efficiency. For example, when a wavelength conversion layer containing a phosphor is provided on the multilayer film, the component reflected by the multilayer film is reduced, and most of the light can be introduced to the wavelength conversion layer.

[0117] The light emitting device 13 according to the first embodiment described above can be used for various purposes requiring a narrow-angle light distribution, without being limited to cases where a wavelength conversion layer is provided on a multilayer film.

[0118] Furthermore, in the light emitting element 13, a multilayer film may not be provided on the substrate when a wavelength conversion layer is not provided on the light emitting element 13. Even in a configuration in which a multilayer film is not provided, as described above, the uneven structure can provide light emitted from the upper surface of the substrate with a narrow light distribution angle.

[0119] Although an example has been described in which the light emitting element 13 has the embedding layer 18, an n-type GaN layer (n-type cladding layer) may be formed directly on the uneven structure without providing the embedding layer 18. In this case, too, the uneven structure functions as a diffraction grating and reduces the refractive index difference at the interface between the n-type cladding layer and the substrate, as in this embodiment, and the angle of emitted light is narrowed and the light extraction efficiency is improved, resulting in a high-output and high-efficiency light emitting device.

[0120] In addition, in the first embodiment, the multilayer film is configured to reflect yellow light, but the present invention is not limited to this. For example, when no wavelength conversion layer is provided, the multilayer film 15 may be configured to simply reflect blue light incident at a wide angle. EXAMPLES

[0121] A configuration of a light emitting device 30 including a light emitting element 31 according to Example 2 will be described with reference to Fig. 11 and Fig. 12. Fig. 11 is a cross-sectional view of the light emitting device 30. Fig. 12 is an enlarged view of a portion B surrounded by a dashed line in Fig. 11.

[0122] The light emitting device 30 differs from the light emitting device 10 of Example 1 in that the light emitting element 31 has a phosphor layer 33 on the multilayer film 15, but is otherwise configured similarly to the light emitting device 10. An upper surface 33S of the phosphor layer 33 serves as a light emitting surface of the light emitting element 31.

[0123] The phosphor layer 33 is a layer containing a wavelength conversion material such as a phosphor that emits fluorescence when excited by the light emitted from the active layer 20. In this embodiment, the phosphor layer 33 is a ceramic phosphor plate made of a single crystal of yttrium aluminum garnet (YAG:Ce) with cerium as the luminescence center. The phosphor layer 33 may be a plate in which a thin film containing a phosphor is formed on the surface of a support made of glass, for example. The phosphor layer 33 may be a resin layer containing phosphor particles such as a YAG:Ce phosphor. The light incident on the phosphor layer 33 from the multilayer film 15 is narrow-angled, and in order to maintain the narrow-angle light distribution, the material of the phosphor layer 33 is preferably a highly transparent phosphor, for example a single crystal phosphor.

[0124] The phosphor as described above is excited by blue light with a wavelength of about 450 nm to emit yellow fluorescence with a wavelength of about 460 to 750 nm. Therefore, in this embodiment, when blue light with a wavelength of 445±5 nm emitted from the active layer 20 passes through the substrate 17 and the multilayer film 15 via transmission diffraction or reflection diffraction as described above and is introduced into the phosphor layer 33, a part of the blue light is wavelength-converted to become yellow fluorescence. The remaining blue light passes through the phosphor layer 33 without being wavelength-converted. Therefore, the blue light that has passed through the phosphor layer 33 and the yellow fluorescence from the phosphor contained in the phosphor layer 33 are emitted from the upper surface 33S of the phosphor layer 33.

[0125] White light is extracted from the light emitting device 30 by mixing the blue light and yellow fluorescence emitted from the upper surface 33S of the phosphor layer 33. In order to achieve stable white light, the phosphor layer 33 preferably has a thickness within a range of 40 to 200 μm. In this embodiment, the thickness of the phosphor layer 33 is 100 μm.

[0126] The blue light that has passed through phosphor layer 33 and the yellow light emitted by the phosphors contained in phosphor layer 33 have different light distribution characteristics, which makes color unevenness more likely to occur.

[0127] Therefore, in this embodiment, a nanoantenna (not shown in Figure 11) having a diffraction function is provided on the upper surface 33S of the phosphor layer 33, and the fluorescence emitted from the upper surface 33S is diffracted, thereby narrowing the light distribution angle of the fluorescence.

[0128] As shown in Fig. 12, a plurality of nanoantennas 35 are arranged on the upper surface 33S of the phosphor layer 33. Fig. 12 is an enlarged cross-sectional view of a portion B surrounded by a dashed line in Fig. 11. The nanoantennas 35 are columnar structures made of a metal or a dielectric and arranged at a distance from each other on the upper surface 33S. In this embodiment, the nanoantennas 35 are made of Al (aluminum). The nanoantennas 35 are arranged in a plane parallel to the upper surface 33S, in other words, when viewed from above, with a constant period and a constant arrangement pattern to form an antenna array.

[0129] In this embodiment, the antenna array made of the nanoantennas 35 is formed on the entire upper surface 33S of the phosphor layer 33. The antenna array may be formed in any region of the upper surface 33S of the phosphor layer 33. For example, the antenna array may be formed in a region corresponding to a region in which the semiconductor laminate 22 of the light emitting element 31 is formed, as viewed from above.

[0130] In this embodiment, the antenna period AP, which is the period at which the nanoantennas 35 are arranged, is 450 nm or less. Each of the nanoantennas 35 has a quadrangular prism shape, and the length W3 of one side in a top view is, for example, 200 nm. Furthermore, the height H11 of each of the nanoantennas 45 is, for example, 130 nm.

[0131] The shape of the nanoantenna 45 may be a columnar or pyramidal shape, and may be, other than a quadrangular columnar shape, a cylindrical shape, a conical shape, a pyramidal shape, etc. The nanoantenna 45 may be formed of metals such as Au, Ag, Ni, etc., or metal oxides such as TiO2, Al2O3, etc., in addition to Al.

[0132] The nanoantennas 35 can be formed, for example, by forming a resist pattern by nanoimprinting or the like on the surface of an Al film formed on the upper surface 33S of the phosphor layer 33 by EB deposition or the like, and then performing RIE etching.

[0133] The multiple nanoantennas 35 strongly diffract light in the yellow wavelength region among the light emitted from the upper surface 33S of the phosphor layer 33. In other words, the multiple nanoantennas 35 function as a diffractive optical element. Specifically, the multiple nanoantennas 35 change the traveling direction of light in the yellow wavelength region so that the exit angle θout from the upper surface 33S is smaller than the incident angle θin from the phosphor layer 33 to the upper surface 33S. In other words, the antenna array of the nanoantennas 35 narrows the light distribution angle of the yellow light.

[0134] Multilayer film 15 is designed to reflect yellow light emitted by the YAG:Ce phosphor in phosphor layer 33. Specifically, multilayer film 15 reflects yellow fluorescent light having a wavelength of approximately 460 to 750 nm.

[0135] As described above, when the YAG:Ce phosphor in phosphor layer 33 is excited by blue light that has passed through multilayer film 15 and entered phosphor layer 33, fluorescence is isotropically emitted from the phosphor, resulting in not only light traveling toward top surface 33S of phosphor layer 33, but also fluorescence traveling toward multilayer film 15. Such fluorescence is not extracted from top surface 33S and is lost. Multilayer film 15 reflects the fluorescence that enters multilayer film 15 from phosphor layer 33, thereby reducing the above-mentioned loss.

[0136] In this example, phosphor layer 33 with nanoantenna 35 formed thereon was attached to the upper surface of multilayer film 15 formed on upper surface 17B of substrate 17 in the same manner as in Example 1. Note that, for example, a multilayer film may be formed on one surface of phosphor layer 33 and nanoantenna 35 may be formed on the other surface, and the resulting product may be attached to upper surface 17B of substrate 17.

[0137] With the above-mentioned configuration, according to the second embodiment, similarly to the light emitting device 10 of the first embodiment, narrow-angle and high-output blue light is emitted from the upper surface 17B of the substrate 17, and in addition, the blue light enters the phosphor layer 33, where a part of the blue light is wavelength-converted to emit isotropically as yellow fluorescence. The isotropically emitted yellow light is diffracted by the nanoantenna 35 to have a narrow-angle light distribution, and is emitted from the upper surface 33S of the phosphor layer 33. The blue light that passes through the phosphor layer 33 without exciting the phosphor is emitted from the upper surface 33S while maintaining the narrow-angle light distribution.

[0138] Furthermore, the fluorescence that is isotropically emitted and travels toward the multilayer film 15 is reflected by the multilayer film 15 and travels toward the upper surface 33S. Therefore, it is possible to achieve a narrow-angle light distribution for both the yellow fluorescence and the blue light while reducing the loss of the fluorescence. Therefore, according to this embodiment, it is possible to provide a semiconductor light-emitting element and a substrate for a semiconductor light-emitting element that can configure a light-emitting device that has a narrow-angle light distribution, high output, and emits white light with little color unevenness.

[0139] [Evaluation Results of Example 2] The light distribution evaluation and total luminous flux evaluation results of the light emitting device 30 according to Example 2 will be described in comparison with the light emitting device of Comparative Example 2. The light emitting device of Comparative Example 2 differs from the configuration of the light emitting device 30 in that the substrate 17 does not have the uneven structure 17U and that the phosphor layer 33 does not have the nanoantenna 35, but is otherwise configured similarly to the light emitting device 30.

[0140] 13 is a diagram showing the results of light distribution evaluation of the light emitting device 30 of Example 2 and the light emitting device of Comparative Example 2. In FIG. FIG. 13 shows the distribution of light intensity (luminous intensity) of the total luminous flux in directions of ±90°, with the direction perpendicular to the light exit surface being taken as 0°.

[0141] 13(a) shows that the intensity is low overall and the Lambertian light distribution is uniformly diffused in all directions in Comparative Example 2. As shown in FIG. 13(b) in Example 2, a narrow-angle light distribution characteristic in which the intensity of light is high when the emission direction is within ±30° is obtained.

[0142] 14 is a diagram showing the measurement results of the total luminous flux of the light emitting device 30 of Example 2 and the light emitting device of Comparative Example 2. Note that the light output was evaluated for the light emitting device 10 of Example 1, which is a blue light source, but the light emitting device 30 of Example 2, which is a white light source, was evaluated based on the total luminous flux, which can be evaluated from the viewpoint of brightness perceived by the human eye.

[0143] As shown in FIG. 14, in Example 2, the total luminous flux was approximately 3.5 times higher than in Comparative Example 2.

[0144] From the above evaluation results, it can be said that Example 2 provided a brighter light emitting device with narrower light distribution angle and higher output than Comparative Example 2. In Example 2, it is considered that narrow-angle, high-output blue light was introduced from substrate 17 to phosphor layer 33 due to the above-mentioned functions of uneven structure 17U, i.e., the function as a reflective diffraction grating and a transmissive diffraction grating and the function of reducing the refractive index difference.

[0145] Of the blue light introduced into phosphor layer 33, the light that passes through phosphor layer 33 without exciting the phosphor maintains a narrow-angle light distribution, while the remaining blue light excites the phosphor, and the yellow light isotropically emitted from the phosphor is diffracted by nanoantenna 35 to form a narrow-angle light distribution, resulting in an overall narrow-angle light distribution characteristic.

[0146] Moreover, it is considered that the yellow light isotropically emitted from the phosphor and directed toward the active layer is reflected by the multilayer film 15 and returned to the phosphor, reducing the loss of fluorescence. Also, it is considered that the light emitted from the light emitting device 30 is white light with little color unevenness because both the blue light and the yellow light have a narrow-angle light distribution. On the other hand, in Comparative Example 2, it is considered that the light reflected by the substrate 17 and the multilayer film 15 is not extracted and is lost. EXAMPLES

[0147] The configuration of a light emitting device 40 according to Example 3 will be described with reference to Figs. 15 to 17. Fig. 15 is a cross-sectional view of the light emitting device 40. The light emitting device 40 is configured similarly to the light emitting device 10, except that a side reflecting member 41 is formed on the light emitting element 13. As in Example 1, in the light emitting device 40, the substrate 17 of the light emitting element 13 is a substrate (also referred to as a Nano Pattern Sapphire Substrate: NPSS) structure substrate) having an uneven structure 17U formed on a lower surface 17A.

[0148] 15, the side reflector 41 is formed on a side surface of a laminated structure (hereinafter also referred to as a side surface of the light emitting element 13) in which the multilayer film 15, the substrate 17, the embedded layer 18, the semiconductor laminate 22, and the p-electrode 23 are laminated in this order. In this embodiment, the side surface of the light emitting element 13 will be described as a surface perpendicular to the upper surface 17B of the substrate 17.

[0149] 15, in the portion of the side surface of the light emitting element 13 on the upper surface 15S side of the light emitting element 13 adjacent to the surface 19E recessed from the surface of the mesa-shaped base portion on which the n-electrode 27 is formed, the side surface reflector 41 is formed on the side surfaces of the multilayer film 15, the substrate 17, the embedded layer 18, and the n-type semiconductor layer 19. In addition, in the portion of the mesa-shaped side surface, the side surface reflector 41 is formed on the side surfaces of the n-type semiconductor layer 19, the active layer 20, the p-type semiconductor layer 21, and the p-electrode 23.

[0150] The side reflecting member 41 has a function of reflecting light that reaches the side surface of the light emitting element 13 out of the light emitted from the active layer 20 .

[0151] In this embodiment, a side reflecting member 41 is provided on the side of the light emitting element 13, and light from the active layer 20 that reaches the side of the light emitting element 13 is reflected and returned to the inside of the light emitting element 13. This causes the light that reaches the side of the light emitting element 13 to exit from the upper surface of the multilayer film 15 rather than from the side. This reduces stray light from the side of the light emitting element 13 and increases the proportion of light that is exited from the upper surface 15S of the light emitting element 13, making it possible to suppress uneven light distribution that results in a non-uniform light distribution intensity distribution, and to achieve a narrow-angle light distribution.

[0152] For example, of the light reflected by side reflecting member 41, the light that propagates within substrate 17 and enters multilayer film 15 at a narrow angle passes through multilayer film 15 as is and is extracted to the outside from the upper surface of multilayer film 15.

[0153] For example, among the light reflected by the side reflecting member 41, the light that propagates within the substrate 17 and enters the multilayer film 15 at a wide angle is once reflected by the multilayer film 15. Thereafter, the angle of the light is narrowed by reflection and diffraction due to the uneven structure 17U (see FIG. 3 ) provided on the lower surface 17A of the substrate 17, and the light is incident on the multilayer film 15 at a narrow angle, so that the light passes through the multilayer film 15 and is extracted to the outside from the upper surface of the multilayer film 15.

[0154] Furthermore, for example, light reflected by the side reflector 41 at the side of the semiconductor laminate 22 is thought to enter the substrate 17 via reflective diffraction or transmitted diffraction by the uneven structure 17U of the substrate 17, reflection by the metal layer 23B of the p-electrode 23, etc.

[0155] In this embodiment, the side reflecting member 41 is a multilayer film reflecting mirror formed on the side of the light emitting element 13. The side reflecting member 41 is a dielectric multilayer film reflecting mirror in which a plurality of dielectric films having different refractive indices are laminated, and configured to reflect light in a predetermined wavelength range that is incident at a predetermined angle range.

[0156] In this embodiment, the side reflector 41 is designed to reflect light in the wavelength region of blue light incident from the active layer 20 at a predetermined angle range. In this embodiment, the side reflector 41 is configured by laminating three pairs of 48.5 nm niobium oxide film (Nb2O5) and 76 nm silicon oxide film (SiO2).

[0157] In this embodiment, the side reflecting member 41 is formed on the entire side surface of the light emitting element 13, but this is not limited to the above. The side surface 17E of the substrate 17 accounts for a large proportion of the side surface of the light emitting element 13. Therefore, if the side reflecting member 41 is not provided, it is considered that the light emitted from the side surface 17E of the substrate 17 accounts for a large proportion of the light emitted from the side surface of the light emitting element 13. Therefore, it is preferable to provide the side reflecting member 41 on at least the side surface 17E of the substrate 17.

[0158] [Production method example] A light emitting device 40 having a side reflector 41 can be formed, for example, as follows. In the manufacturing method described in Example 1, in the manufacture of a wafer on which a plurality of light emitting elements 13 are formed, the process up to the step of engraving a mesa shape is carried out. Before singulation, for example, a resist is applied to the surface on the side on which the p-type electrode pad 25 and the n-type electrode pad 29 are formed (i.e., the surface opposite to the side on which the multilayer film 15 is formed) to form a protective resist film. Here, after application of the protective resist film, only the region on which the side reflector 41 is to be formed is removed by photolithography.

[0159] Then, the light emitting element 13 was divided into individual pieces by dicing, thereby exposing the side surface of the light emitting element 13. Then, using the protective resist film as a mask, a dielectric multilayer film was formed on the side surface of the divided light emitting element 13 by, for example, ALD (Atomic Layer Deposition) to form a side surface reflecting member 41. As the side surface reflecting member 41, three pairs of a niobium oxide film (Nb2O5) of 48.5 nm and a silicon oxide film (SiO2) of 76 nm were laminated. This makes it possible to form a film on both the side surface on the substrate side and the side surface of the semiconductor layer. Not limited to this, a multilayer film may be formed only on the side surface of the semiconductor layer. Then, the protective resist film was removed, and the light emitting device 40 was obtained by flip-chip mounting on the mounting substrate 11.

[0160] [Light distribution] A simulation was carried out to compare the light distribution of the light emitting device 40 with that of the light emitting device 10 of Example 1, which is configured without the side reflecting member 41.

[0161] [Simulation conditions] The conditions used in the simulation are as follows: First, as a common condition for light emitting device 10 and light emitting device 40, the period at which convex portions of concave-convex structure 17U of substrate 17 are arranged is set to 360 nm.

[0162] The thickness of substrate 17 was 150 μm. The thickness of substrate 17 was defined as the height from the position of the tip of protrusion 17C (the lowest end of protrusion 17C in FIG. 3) formed on lower surface 17A of substrate 17 to upper surface 17B.

[0163] The layer structure and dimensions of the semiconductor laminate laminated on the lower surface 17A of the substrate 17 were the same as those exemplified in the manufacturing method of Example 1. Specifically, the buried layer 18 was an undoped GaN layer of 1 μm in thickness. The n-type semiconductor layer 19 on the buried layer 18 was an n-type GaN layer doped with Si of 3 μm in thickness.

[0164] The lattice matching layer on the n-type GaN layer had a structure in which a 2 nm undoped GaN layer, a 100 nm n-type GaN layer, a 100 nm undoped GaN layer, a 50 nm n-type GaN layer, and a 163 nm n-type AlGaN layer were laminated in this order.

[0165] The underlayer of the underlayer on the lattice-matching layer was formed by alternately laminating eight pairs of 3 nm GaN layers and 2.1 nm InGaN layers, and laminating a 2 nm GaN layer thereon.

[0166] The active layer had a multiple quantum well structure in which five pairs of 5.7 nm GaN barrier layers and 3.8 nm InGaN well layers were stacked. The p-type semiconductor layer 21 on the active layer was made up of a spacer layer, an electron blocking layer, a p-type cladding layer, and a p-type contact layer.

[0167] The spacer layer was a 13.7 nm undoped GaN layer, the electron blocking layer was an 8.3 nm AlGaN layer and an 8.3 nm InN layer, the p-type cladding layer was a 98 nm Mg-doped p-type GaN layer, and the p-type contact layer was a 5 nm p-type GaN layer doped with more Mg than the p-type cladding layer.

[0168] The transparent electrode layer 23A on the p-type semiconductor layer 21 was made of 100 nm ITO. The metal layer 23B was made of an Ag film or an alloy film containing Ag. The multilayer film 15 formed on the upper surface 17B of the substrate 17 was made of 23 pairs of niobium oxide films (Nb2O5) and silicon oxide films (SiO2) stacked together.

[0169] For the light emitting device 40, three pairs of 48.5 nm niobium oxide films (Nb2O5) and 76 nm silicon oxide films (SiO2) were laminated on the side surfaces of the light emitting element 30 to form the side reflecting members 41.

[0170] A light distribution calculation was performed for the above configuration. First, the wave optical characteristics of the concave-convex structure 17U (NPSS structure) were calculated when light with a wavelength of 450 nm was emitted from the center in the layer thickness direction of the active layer 20. The calculation results of the wave optical characteristics include transmittance and reflectance characteristics taking into account the reflection diffraction angle and transmission diffraction angle of the concave-convex structure 17U. After that, the light distribution was calculated for each of the light emitting device 40 and the light emitting device 10 by ray tracing simulation, reflecting the results of the wave optical characteristics.

[0171] [Simulation results] Fig. 16 is a diagram showing the results of a simulation of the light distribution of total luminous flux in a configuration with and without side reflecting member 41 in light emitting device 40 according to Example 3. In Fig. 16, (a) shows the results of a simulation of the light distribution for light emitting device 40 of Example 3 without side reflecting member 41 (configuration in which period P is 360 nm in Example 1), and (b) shows the results of a simulation of the light distribution for light emitting device 40 of Example 3. Fig. 16 shows the distribution of light intensity (luminous intensity) in directions of ±90°, with the direction perpendicular to the light emitting surface being set to 0°.

[0172] In this embodiment, in addition to the narrow-angle light distribution with high light intensity within an emission direction of ±30°, it is preferable that the light distribution within ±30° is uniform, and if there are any parts where the light intensity is non-uniform in the light distribution within ±30°, it is determined that there is uneven light distribution.

[0173] As can be seen from Fig. 16, both the light emitting device 10 and the light emitting device 40 have narrow-angle light distributions with high light intensity within ±30°, but as shown in (a) of Fig. 16, there are areas of extremely low light intensity near ±20° in the light distribution of the light emitting device 10. In contrast, as shown in (b) of Fig. 16, there are no areas of extremely low light intensity like those of the light emitting device 10 in the light distribution of the light emitting device 40, and the light distribution is more uniform than that of the light emitting device 10, with reduced unevenness in the light distribution.

[0174] It is believed that the provision of side reflecting member 41 has increased the amount of light that reaches the side surface of light emitting element 13 but is returned into light emitting element 13 without being emitted from the side surface of light emitting element 13, and that the light returned into light emitting element 13 is emitted from multilayer film 15. It is believed that this has increased the amount of light emitted in directions within ±30°, resulting in a more uniform light distribution.

[0175] 17 is a diagram showing the light distribution ratio versus the thickness of the substrate 17 for the light emitting device 10 and the light emitting device 40 according to Examples 1 and 3. Here, the period P in Example 1 is 360 nm, similar to the period in Example 3.

[0176] [Light distribution ratio] Regarding the distribution of light emitted from a light emitting device, the light distribution ratio is defined as the ratio of the light output within ±30° of the total luminous flux to the light output within ±30° when the light output of the same total luminous flux is distributed to have a Lambertian light distribution. The higher the light distribution ratio, the narrower the light distribution angle, with higher light intensity within ±30°. The light emitting device 10 and the light emitting device 40 were compared using the light distribution ratio as an index.

[0177] Specifically, for the light emitting device 40 of Example 3 and the light emitting device 10 of Example 1, the light distribution ratios were calculated by simulation under a number of conditions of the thickness of the sapphire substrate serving as the substrate 17, and compared.

[0178] As can be seen from FIG. 17, in any of the configurations, the smaller the thickness of the substrate 17, the higher the light distribution ratio.

[0179] 17, it can be seen that the amount of change in light distribution ratio relative to the amount of change in substrate thickness is larger in Example 1, which does not include side reflecting member 41. This is thought to be because, when side reflecting member 41 is not provided, the thicker substrate 17 is, the greater the amount of light (stray light) emitted from side surface 17E of substrate 17 of light emitting element 13 is, and as a result, the amount of light emitted in directions within ±30° is reduced.

[0180] In addition, in Example 1, when the thickness of the substrate is reduced (thinned) to about 40 μm, the light distribution ratio is approximately 1.6 times at maximum. In contrast, in the case of Example 3, the light distribution ratio is 1.65 times or more when the thickness of the substrate is approximately 150 μm or less (dashed line in FIG. 17). In other words, in Example 3, a higher light distribution ratio was obtained even though the thickness of the substrate 17 was greater than that of Example 1.

[0181] In Example 3, the side reflecting member 41 reflects the light that reaches the side 17E of the substrate 17 of the light-emitting element 13 back to the light-emitting element 13, thereby increasing the amount of light emitted at a narrow angle from the top surface of the multilayer film 15.

[0182] In this Example 3, by setting the thickness of the substrate 17 to, for example, 300 μm or less, a light distribution ratio equal to or greater than the maximum light distribution ratio (about 1.6) of Example 1 is obtained, which is preferable. As described above, the smaller the thickness of the substrate 17, the more preferable it is in terms of obtaining a high light distribution ratio, and in consideration of the thickness that is easy to process when dividing the substrate 17, setting the thickness to 150 μm or less is preferable since it increases the yield.

[0183] As described above, the light emitting device 40 of this embodiment has a side reflecting member 41 that covers the side surface of the light emitting element 13 and reflects the light emitted from the active layer 20. By providing the side reflecting member 41, the light from the active layer 20 that reaches the side surface of the light emitting element 13 is reflected by the side reflecting member 41 and returns to the inside of the light emitting element 13. This suppresses uneven light distribution, which is a non-uniform light distribution within ±30°, and provides a higher light output within ±30°, in other words a narrower light distribution angle.

[0184] The light returned to the light-emitting element 13 is considered to be incident on the multilayer film 15 at a narrow angle and passes through the multilayer film 15, or, even if it is incident on the multilayer film 15 at a wide angle and is reflected by the multilayer film 15, it is considered to be incident on the multilayer film 15 at a narrow angle after undergoing reflection diffraction or transmission diffraction due to the uneven structure U of the substrate 17.

[0185] This increases the amount of light incident on multilayer film 15 at a narrow angle, and increases the amount of light that passes through multilayer film 15 and is extracted to the outside from the top surface of multilayer film 15. In other words, light at an angle that suppresses optical loss due to multilayer film 15 is now emitted from the top surface of substrate 17 and incident on multilayer film 15.

[0186] Therefore, according to this embodiment, it is possible to provide a semiconductor light emitting element that can constitute a light emitting device with a narrow light angle, high output, and high efficiency.

[0187] As described above, in this embodiment, an example in which the side reflecting member 41 is formed on the entire side surface of the light emitting element 13 has been described, but the present invention is not limited to this. Since the side surface 17E of the substrate 17 occupies a large proportion of the side surface of the light emitting element, it is considered that the light emitted from the side surface of the light emitting element is largely emitted from the side surface 17E of the substrate 17. Therefore, it is sufficient that the side reflecting member 41 is provided on at least the side surface 17E of the substrate 17. In other words, it is sufficient that the side reflecting member 41 is formed on a surface including the side surface E of the substrate 17.

[0188] In order to suppress the light from the active layer from being emitted from the side surface of the semiconductor laminate 22, it is preferable to provide the side surface reflector 41 also on the side surface of the semiconductor laminate 22. In other words, the side surface reflector 41 may be formed on a surface including the side surface 17E of the substrate 17 and the side surface of the semiconductor laminate 22.

[0189] In addition, as in this embodiment, by arranging the side reflector 41 so as to cover the side of the light-emitting element 13, including the side 17E of the substrate 17 and the side of the semiconductor laminate 22, it is believed that light emission from the side of the light-emitting element 13 can be reliably suppressed.

[0190] [Variations] The configuration and light distribution of a light emitting device 40 according to a modification of Example 3 will be described with reference to Fig. 15 and Fig. 18. In this modification, the light emitting device 40 uses a side reflecting member 41, which is a resin member made of a so-called white resin in which light-scattering particles are dispersed in a transparent resin, instead of a multilayer film reflecting mirror. In this modification, the side reflecting member 41 is made of a silicone resin in which titanium oxide (TiO2) is dispersed and hardened.

[0191] TiO2 particles were dispersed in silicone resin at a concentration of 25 wt%, ink-jet ejected, patterned around the element, and thermally cured to form a white resin layer of approximately 100 μm thick on the side of the light-emitting element 13, forming the side reflector 41.

[0192] In addition to silicone resin, the resin constituting the side reflector 41 of this modified example may be a thermosetting resin or a photosetting resin such as epoxy resin, acrylic resin, polycarbonate resin, polyimide resin, etc. In addition to titanium oxide, the scattering particles of the side reflector 41 of this modified example may be metal oxide particles such as zinc oxide (ZnO) and alumina (Al2O3).

[0193] In this embodiment, the period at which the convex portions of the concave-convex structure 17U of the substrate 17 are arranged is set to 440 nm. In other respects, the light emitting device 40 of this modified example is configured in the same manner as in the third embodiment.

[0194] 18 is a diagram showing the results of measuring the light distribution of the total luminous flux for light emitting device 40 of this modified example and light emitting device 10 of Example 1. In light emitting device 10 of Example 1, side reflecting member 41 is not provided on the side surface of light emitting element 13, and the period at which convex portions of uneven structure 17U are arranged is 440 nm.

[0195] In Fig. 18, (a) shows the light distribution for Example 1, and (b) shows the light distribution for this modified example. Fig. 18 shows the distribution of light intensity (luminous intensity) in directions of ±90°, with the direction perpendicular to the light exit surface being set to 0°.

[0196] 18 indicates a Lambertian light distribution with the same total luminous flux as the total luminous flux of the measurement results of each of light emitting device 40 and light emitting device 10. In Fig. 18, the light intensity in each direction is shown normalized with the light intensity of the Lambertian light distribution at 0° being 1.0, and the light intensity of the Lambertian light distribution at 0° is equivalent for light emitting device 40 and light emitting device 10.

[0197] As shown in (a) of Figure 18, in the light emitting device 10, contrast (three mountain-like parts) occurs within ±15°, and the light intensity drops off sharply around 20° to 30° compared to within ±15°.

[0198] 18(b), in the light distribution of light emitting device 40 according to this modification, the contrast within ±15° is alleviated, the distribution of light intensity is uniform, and the drop in light intensity around 20° to 30° is also more gradual than in (a). It can be said that light emitting device 40 has a more uniform light distribution than light emitting device 10, and the unevenness of the light distribution is reduced.

[0199] Furthermore, when the light distribution ratio was calculated from the light distribution measurement result of the total luminous flux in Fig. 18 using the same method as in Example 3, the light distribution ratio of the light emitting device 10 was 1.3 times, and the light distribution ratio of the light emitting device 40 was 1.4 times. It can be said that the light distribution of the light emitting device 40 is a narrower angle light distribution with higher light intensity within ±30° compared to the light emitting device 10.

[0200] As described above, even when the side reflecting member 41 is made of white resin, the light distribution is uniform within ±30° and a narrow angle light distribution can be obtained, which is the same effect as in Example 3. It is considered that the light emitted from the active layer 20 and reaching the side surface of the light emitting element 13 is reflected by the side reflecting member 41 made of white resin and returned to the inside of the light emitting element 13 without being emitted from the side surface of the light emitting element 13, and the light emitted from the upper surface 15S of the multilayer film 15 is increased.

[0201] [Phosphor] 11 may be provided on the multilayer film 15 of the light emitting device 40. An antenna array made of nanoantennas 35 is provided on the upper surface 33S of the phosphor layer 33. By providing the side reflecting member 41, blue light can be made incident on the phosphor layer 33 at a narrower angle and with a more uniform light intensity distribution.

[0202] A portion of the blue light is wavelength converted and the yellow fluorescent light emitted isotropically is diffracted by the nanoantenna 35 to have a narrow-angle light distribution, and is mixed with the blue light from the light-emitting device 40, which has a narrow angle and a uniform light intensity distribution.

[0203] Furthermore, as described above, when the phosphor layer 33 is provided on the multilayer film 15 in the third embodiment and the modified example, a side reflector 41 may also be provided on the side surface of the phosphor layer 33. This makes it possible to reflect light that has reached the side surface of the phosphor layer 33 back into the phosphor layer 33. This makes it possible to improve, for example, the optical output of light emitted from the upper surface of the phosphor layer 33 and improve the light extraction efficiency.

[0204] The configurations in the above-mentioned embodiments are merely examples, and can be appropriately changed or combined depending on the application, etc. In the above-mentioned embodiments, the period P is determined so that the reflection diffraction angle is the target value of the exit angle from the substrate or the target value of the incident angle to the multilayer film, but this is not limited to this. For example, the target value of the reflection diffraction angle and the period P may be determined so that the transmission diffraction angle is the target value of the exit angle from the substrate or the target value of the incident angle to the multilayer film. [Explanation of symbols]

[0205] 10, 30, 40 Light-emitting device 11 Substrate 13, 31 Light emitting element 15 Multilayer film 17 Sapphire 19 n-type semiconductor layer 20 Active layer 21 p-type semiconductor layer 22 Semiconductor laminate 23p electrode 23A Transparent electrode layer 23B Metal layer 25 p-type electrode pad 27 n electrode 29 n-type electrode pad 31 Light emitting element 33 Phosphor layer 35 Nano Antenna 41 Side reflector

Claims

1. a substrate having a first surface on which a concavo-convex structure in which pyramidal convex portions are periodically arranged is formed; a semiconductor laminate in which a first semiconductor layer having a first conductivity type, an active layer, and a second semiconductor layer having a second conductivity type different from the first conductivity type are formed in this order on the first surface of the substrate on which the uneven structure is formed; a reflective layer formed on the semiconductor laminate and configured to reflect light emitted from the active layer; the substrate is translucent to the emitted light, A semiconductor light-emitting element, characterized in that, when a period at which the convex portions are arranged is P and a wavelength of the emitted light is λ, the period satisfies 0.8≦P / λ≦1.

2. 2. The semiconductor light emitting element according to claim 1, wherein the emitted light is reflected by the first surface at an angle of reflection of 30[deg.] or less.

3. The semiconductor light emitting element according to claim 1 , wherein the protrusion has a sidewall that is inclined at an angle of 60° or more with respect to the first surface of the substrate.

4. the reflective layer has a second surface opposite to the first surface, When the wavelength of the emitted light is λ and the wavelength line width of the emitted light is Δλ, the coherence length Lc of the emitted light is expressed as follows: Lc=λ ２ 2. The semiconductor light-emitting element according to claim 1, wherein the coherence length is expressed as Lc / Δλ, and a sum of a distance from the active layer to the second surface and a distance from the first surface to the second surface is equal to or less than the coherence length Lc.

5. 2. The semiconductor light-emitting element according to claim 1, further comprising a third surface, the surface of the substrate opposite to the first surface on which the uneven structure is formed, and a dielectric multilayer film reflector formed on the third surface.

6. a dielectric multilayer film reflector provided on a third surface of the substrate opposite to the first surface on which the concave-convex structure is formed; a phosphor layer provided on the dielectric multilayer film reflector and including a phosphor that is excited by the emitted light to emit fluorescent light; and 2. The semiconductor light-emitting element according to claim 1, wherein the dielectric multilayer reflector is configured to reflect the fluorescent light from the phosphor layer and transmit the emitted light.

7. The semiconductor light-emitting element according to claim 6 , wherein the phosphor layer includes nano-antennas arranged at a predetermined interval on a surface opposite to a surface in contact with the dielectric multilayer film reflector.

8. 2. The semiconductor light emitting element according to claim 1, further comprising a burying layer formed between the first surface of the substrate and the first semiconductor layer, burying the uneven structure.

9. a substrate having a first surface on which a concavo-convex structure in which pyramidal convex portions are periodically arranged is formed; a semiconductor laminate in which a first semiconductor layer having a first conductivity type, an active layer, and a second semiconductor layer having a second conductivity type different from the first conductivity type are formed in this order on the first surface of the substrate on which the uneven structure is formed; a reflective layer formed on the semiconductor laminate and configured to reflect light emitted from the active layer; the substrate is translucent to the emitted light, a refractive index of the substrate and a layer in contact with the substrate at the first surface is greater than a refractive index of the substrate; A semiconductor light-emitting device, characterized in that a reflection angle when the emitted light is reflected by the first surface is less than a critical angle at an interface between the substrate and a layer in contact with the substrate.

10. 9. The semiconductor light emitting device according to claim 1, further comprising a side reflecting member covering a side surface of the substrate and reflecting the emitted light.

11. 11. The semiconductor light-emitting element according to claim 10, wherein the side reflecting member is a dielectric multilayer film reflecting mirror formed on a surface including the side surface of the substrate.

12. The semiconductor light-emitting element according to claim 10 , wherein the side reflector is a resin material containing light-scattering particles.

13. The semiconductor light emitting element according to claim 10 , wherein a side surface of the semiconductor laminate is covered with the side surface reflector.

14. 11. The semiconductor light emitting device according to claim 10, wherein the thickness of the substrate is 150 [mu]m or less.

15. a substrate having a first surface on which a concavo-convex structure in which pyramidal convex portions are periodically arranged is formed; a semiconductor laminate in which a first semiconductor layer having a first conductivity type, an active layer, and a second semiconductor layer having a second conductivity type different from the first conductivity type are formed in this order on the first surface of the substrate on which the uneven structure is formed; a reflective layer formed on the semiconductor laminate and configured to reflect light emitted from the active layer; a dielectric multilayer film reflector provided on a third surface of the substrate opposite to the first surface on which the concave-convex structure is formed; a phosphor layer provided on the dielectric multilayer film reflector and including a phosphor that is excited by the emitted light to emit fluorescent light; a side reflecting member that covers a side surface of the substrate and a side surface of the phosphor layer and reflects the emitted light; having the substrate is translucent to the emitted light, When a period at which the convex portions are arranged is P and a wavelength of the emitted light is λ, the period satisfies 0.8≦P / λ≦1, The semiconductor light-emitting element is characterized in that the dielectric multilayer film reflector is configured to reflect the fluorescent light from the phosphor layer and transmit the emitted light.

16. The semiconductor light-emitting element according to claim 15 , wherein the phosphor layer includes nano-antennas arranged at a predetermined period on a surface opposite to a surface in contact with the dielectric multilayer film reflector.

17. A substrate for a semiconductor light emitting device used in the manufacture of a semiconductor light emitting device, the substrate having a semiconductor laminate including an active layer and a reflective layer formed on the semiconductor laminate and reflecting light emitted from the active layer, the substrate comprising: a first surface on which the semiconductor laminate is formed is provided with a concavo-convex structure in which pyramidal convex portions are periodically arranged; A substrate for a semiconductor light-emitting element, characterized in that the substrate has a translucency with respect to the emitted light, and when the period at which the convex portions are arranged is P and the wavelength of the emitted light is λ, the period satisfies 0.8≦P / λ≦1.

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