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

Abstract

Provided are a semiconductor light-emitting element capable of constituting a light-emitting device that has a narrow-angle light distribution and has high output and high efficiency, and a substrate for a semiconductor light-emitting element.　This semiconductor light-emitting element comprises: a substrate on which an uneven structure is formed in which conical protrusions are periodically arranged on a first surface; 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 has been formed; and a reflection layer that is formed on the semiconductor laminate and that reflects emission light emitted from the active layer. The substrate has translucency to the emission light. Where a period in which the protrusions are arranged is P and a wavelength of the emission light is λ, the period satisfies 0.8 ≤ P / λ ≤ 1.

Description

Semiconductor light emitting element and substrate for semiconductor light emitting element

[0001] The present invention relates to a semiconductor light-emitting device and a substrate for the semiconductor light-emitting device.

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

[0003] For example, U.S. Patent No. 6,277,949 discloses an illumination device including a substrate constituting a light source, a wavelength-converting layer disposed adjacent to the light source, and an antenna array disposed on the substrate and within the wavelength-converting layer, and the illumination device is disclosed in U.S. Patent No. 6,277,949, in which the antenna array can emit light within a predetermined angular range.

[0004] Patent No. 6381645

[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-described lighting device. LEDs have a Lambertian light distribution characteristic. Therefore, in order to efficiently transmit light from the LED to the wavelength conversion layer, it has been necessary to narrow the angle of the emitted light from the LED.

[0006] In addition, in the above-described lighting device, in order to prevent light loss due to return light from the wavelength conversion layer to the LED, a multilayer film configured to transmit light within the wavelength range of light emitted from the LED and 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 so-called blue shift in the reflectance-wavelength characteristics of the multilayer film, the wavelength range with high reflectance shifts to shorter wavelengths as the incident angle increases, light from the LED that is incident on the multilayer film at a large angle is reflected by the multilayer film and lost. Therefore, in order to efficiently transmit light from the LED into the multilayer film, it has been necessary to narrow the angle of incidence 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 form a light-emitting device with a narrow light angle, high output, and high efficiency.

[0008] A semiconductor light-emitting element according to the present invention comprises: a substrate having a first surface on which a concave-convex structure in which conical convex portions are periodically arranged is formed; 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 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.

[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, wherein a concave-convex structure in which conical convex portions are periodically arranged is formed on a first surface forming the semiconductor laminate, the substrate has transparency to the emitted light, and is characterized in that, 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.

[0010] 11 is a top view showing the configuration of a semiconductor light-emitting element according to Example 1. FIG. 12 is a cross-sectional view showing the configuration of a semiconductor light-emitting element according to Example 1. FIG. 13 is an enlarged cross-sectional view showing a portion of the cross-sectional view of FIG. 2. FIG. 14 is a diagram showing an example of reflectivity versus angle of incidence of a dielectric multilayer film. FIG. 15 is a diagram showing a reflection diffraction angle versus angle of incidence of light on a sapphire substrate according to Example 1. FIG. 16 is a diagram showing a transmission diffraction angle versus angle of incidence of light on a sapphire substrate according to Example 1. FIG. 17 is a diagram showing a refractive index distribution near the interface between a substrate and GaN according to Example 1 and Comparative Example 1. FIG. 18 is a diagram showing calculation results of light transmittance according to Example 1 and Comparative Example 1. FIG. 19 is a diagram showing light distribution characteristics of semiconductor light-emitting elements according to Example 1 and Comparative Example 1. FIG. 19 is a cross-sectional view showing the configuration of a semiconductor light-emitting element according to Example 2. FIG. 19 is an enlarged cross-sectional view showing a portion of the cross-sectional view of FIG. 11. FIG. 19 is a diagram showing light distribution characteristics of semiconductor light-emitting elements according to Example 2 and Comparative Example. FIG. 20 is a diagram showing total luminous flux evaluation results of semiconductor light-emitting elements according to Example 2 and Comparative Example. FIG. 21 is a cross-sectional view showing the configuration of a semiconductor light-emitting element according to Example 3. FIG. 22 is a diagram showing simulation results of light distribution characteristics of semiconductor light-emitting elements according to Examples 1 and 3. FIG. 23 is a diagram showing light distribution ratios of semiconductor light-emitting elements according to Examples 1 and 3. 10A and 10B are diagrams illustrating light distribution characteristics of semiconductor light emitting elements according to a modified example of Example 3 and Example 1.

[0011] In the following, preferred embodiments of the present invention will be described, but these 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.

[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, 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.

[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 with a rectangular top surface. The mounting substrate 11 is an insulating substrate such as an aluminum nitride (AlN) ceramic substrate. The mounting substrate 11 may also be a substrate made of other materials, such as alumina. The mounting substrate 11 is preferably a heat-dissipating substrate made of a material with 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 that constitute the light-emitting element 13. A concave-convex structure (not shown in FIG. 2 ), which will be described later, is formed on a lower surface 17A, which serves as a first surface that is one of the main surfaces of the substrate 17. In this embodiment, the concave-convex structure functions 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, which is the third surface of the substrate 17 and is the main surface opposite to the lower surface 17A on which the concave-convex structure is formed. The multilayer film 15 is a dielectric multilayer film reflector in which a plurality of dielectric films with different refractive indices are stacked, and is 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 a niobium oxide film (Nb ２ O ５ ) and silicon oxide film (SiO ２ ) and 23 pairs are stacked.

[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 stack 22 is a stacked structure including a plurality of semiconductor layers formed to cover the lower surface of the buried layer 18. The semiconductor stack 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 MOCVD.

[0021] The n-type semiconductor layer 19 as a 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 n-type impurities 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 in FIG. 2 ), which is a region 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 the mesa-shaped plateau portion on the lower surface of the n-type semiconductor layer 19. The wavelength of light emitted from the active layer depends on the material and composition of the semiconductor stack 22. In this embodiment, the active layer 20 is a semiconductor layer having a multi-quantum well (MQW) structure made up of InGaN well layers and GaN barrier layers. 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 made up of multiple semiconductor layers including a p-type GaN layer doped with p-type impurities as a second conductivity type. The p-type GaN layer of the p-type semiconductor layer 21 is doped with, for example, Mg as the p-type impurity. The p-type semiconductor layer 21 is configured by stacking, for example, 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 transparent electrode layer 23A, which is a translucent indium tin oxide (ITO) electrode, 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. Note that 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 via a conductive p-type electrode pad 25 by an AnSu eutectic. The p-electrode 23 has the 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 an 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 15 S 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, the present invention is not limited to this, and the n-type semiconductor layer 19 and the n-wiring electrode 11B may be electrically connected to each other via a through-hole that is provided in the semiconductor laminate 22 and extends 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, blue light having a peak emission wavelength of 445±5 nm is emitted from the active layer 20 of the light emitting element 13.

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

[0031] For example, if a phosphor layer (wavelength conversion layer) containing the above-described 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 occurs. Such returning light is attenuated within 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 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, light emitted from the active layer 20 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 optical loss.

[0034] Furthermore, for example, if there is no uneven structure described below, when the light emitted from the active layer 20 reaches the interface between the buried layer 18, which is a GaN layer, and the substrate 17, if it is incident at a wide angle exceeding 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 the substrate 17 is made to function as a diffraction grating, so that the angle of incidence of light incident on the multilayer film 15 and the substrate 17 is controlled to a narrow angle within an angle range in which the light is not reflected by the multilayer film 15 and the substrate 17.

[0036] The structure and function of the uneven 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, an uneven structure 17U including protrusions 17C and recesses 17D is formed on the lower surface 17A of the substrate 17. The protrusions 17C are arranged at a constant period P.

[0037] In this embodiment, the convex portions 17C have a truncated cone shape. In Fig. 3, the diameter of the bottom surface of each 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, and a height H of 400 nm, and are arranged in a hexagonal lattice pattern with a period of 440 nm. Note that 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, the optical function of the concave-convex structure 17U will be described. 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 enters the uneven structure 17U is defined as a virtual optical interface 17R (hereinafter also simply referred to as the optical interface) located on a line 1 / 2 of the height H1 (dashed line in Figure 3).

[0041] More specifically, the concave-convex structure 17U functions as a transmissive diffraction grating when the angle of incidence 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. On the other hand, the concave-convex structure 17U functions as a reflective diffraction grating when the angle of incidence of light incident on the virtual incident surface 17R is equal to or greater than the critical angle θC.

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

[0043] Light L2 travels through substrate 17, emerges from top surface 17B of substrate 17, and is incident on 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 example, 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 is considered negligible.

[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 allow transmission through the multilayer film 15. Therefore, the light L2 is transmitted 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 the active layer 20 and incident on the optical interface 17R at an incident angle θ3 greater than or equal to the critical angle θC (θ3≧θC) is diffracted so as to be reflected at the 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 θ4. Light L5 travels through the semiconductor stack 22, is reflected by the metal layer 23B of the p-electrode 23, and is incident again on the optical interface 17R. The angle of incidence on the p-electrode 23 and the angle of incidence when it is again incident on the optical interface 17R are both the same as the reflection-diffraction angle, θ4.

[0047] 3, light L5 passes through the light-transmitting electrode layer 23A and is reflected by the upper surface 23BS (second surface) of the metal layer 23B, which serves as a reflective layer. Note that in FIG. 3, light L5 is schematically illustrated without illustrating refraction at the interface between the p-type semiconductor layer 21 and the light-transmitting electrode layer 23A.

[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 total reflection does not occur at the interface between the buried layer 18 and the substrate 17 and at which light can be transmitted through the multilayer film 15.

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

[0050] That is, in this embodiment, the concave-convex 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 sapphire substrate 17. The light incident at this 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 that has been reflectively diffracted and is incident at a narrow angle on the multilayer film 15 is incident at a narrow angle on the multilayer film 15 because the concave-convex structure 17U functions as a transmission 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] In order to reliably extract light transmitted through the multilayer film 15 as emitted light from the light emitting device 10, such as the light L3 and light L7 described above, it is necessary to ensure that the phases of the emitted light components reinforce each other rather than cancel each other out. On the other hand, the optical path length of the light emitted from the active layer 20 before 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 upward from the active layer 20, 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 upward from the active layer 20, 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 then 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 is incident on the lower surface 17A of the substrate 17, so that the phases of the emitted light with 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 that allows interference between light beams emitted from the active layer 20, is expressed as follows: Lc=λ where λ is the central wavelength of the light beam emitted from the active layer 20 and Δλ is the wavelength line width 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≈10 μm.

[0056] In this embodiment, when considering the optical path length from the active layer 20 until the light is incident on the lower surface 17A (first surface) of the substrate 17, the position of the virtual optical interface 17R, which is half the height H of the convex portion 17C of the concave-convex structure 17U, is taken as the position in the layer thickness direction of the lower surface 17A. In addition, when considering the optical path length, the lower surface 20A of the active layer 20 is taken as 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 (e.g., D2 in FIG. 3 ) is preferably within the coherence length Lc. Furthermore, when considering light that is emitted from the active layer 20 toward the p-electrode 23 (the 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 within the coherence length Lc. As a result, the light that is emitted downward from the active layer 20 and extracted as emitted light and the light that is emitted upward from the active layer 20 and extracted as emitted light interfere constructively with each other.

[0059] The distance D1 may be set to be equal to or shorter than the coherence length Lc. If the distance D2 is sufficiently smaller than the coherence length Lc, instead of controlling the distance D1 to be equal to or shorter 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 shorter than the coherence length Lc.

[0060] In the above description, distance D1 is defined as the distance from the lower surface of active layer 20 to optical interface 17R. However, in actual manufacturing, distance D1 may be treated as the dimension from the lower surface of active layer 20 to the lowest end of lower surface 17A of substrate 17 (i.e., the tip of convex portion 17C) or the base of convex portion 17C on lower surface 17A (i.e., the bottom of concave portion 17D). In other words, film formation may be performed so that the distance from the lower surface of active layer 20 to the tip of convex portion 17C or the bottom of concave portion 17D is equal to or less than coherence length Lc. Furthermore, distance D2 may be defined as the distance from the center of the film thickness of active layer 20 or upper surface 20B to optical interface 17R, and distance D3 may be defined as the distance from the center of the film thickness of active layer 20 or upper surface 20B to upper surface 23BS of 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 graph showing the incidence angle dependence of the reflectance of the multilayer film 15 for light of wavelengths of 435 to 480 nm. The graph shown in Fig. 4 is the result of simulating the reflectance wavelength characteristics of the multilayer film 15 employed in this example 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 incident angles of 0° and 15°, and high at an incident angle of 30°. Therefore, in order to increase the light component transmitted through the multilayer film 15, the incident angle on the multilayer film 15 must be 30° or less, more preferably less than 30°, and even more preferably 15° or less. As shown in FIG. 4 , when the upper limit of the incident angle is 30°, the usable wavelength range can be 440 nm to 455 nm. When the upper limit of the incident angle is 30°, a wavelength range of 440 nm or less, which has a lower reflectance, may be employed. For example, the wavelength range to be employed can be determined appropriately taking into consideration the characteristics of the multilayer film 15, the desired emission color, the material system of the light-emitting element, and the like.

[0064] In this example, 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 light with a wavelength of 445 nm±10 nm emitted from the active layer 20 would be transmitted through the multilayer film 15. It should be noted that, 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 is the target wavelength. It should be noted that, for example, from among multiple types of multilayer films designed to reflect yellow light, one that transmits blue light, which is emitted from the active layer, within a desired angle range may be selected.

[0065] [Reflection Diffraction Angle] Next, a target value of the reflection 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 on the multilayer film 15, and an applicable value of the period P of the concave-convex structure was estimated so as to achieve the target reflection diffraction angle. The target value of the reflection diffraction angle was set to within ±30°.

[0066] 5 is a diagram showing the results of calculating the reflection / diffraction angle for the incident angle from 0° to 80° for light with a wavelength λ of 445 nm for each period P based on the following formula (1): ｉｎ -nkP sinθ ｒｅｆ = m (1) In formula (1), n ​​is the refractive index of GaN, k is the wave number (2π / λ), P is the period of the concave-convex structure 17U, and θ is the angle of incidence. ｉｎ , the reflection diffraction angle is θ ｒｅｆ , the order of diffraction is m. In FIG. 5, m=1, and the reflection diffraction angle θ ｒｅｆ 5. The angle 47° in FIG. 5 indicates the critical angle of the interface between GaN and sapphire when light is incident from the GaN layer onto the sapphire substrate.

[0067] As shown in Figure 5, the reflective diffraction angle for the same incident angle varies depending on the period P. Figure 5 shows 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 example, a period P of 300 nm to 440 nm can be used for the concave-convex structure 17U in order to keep the reflective diffraction angle within ±30°.

[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 example, the period P was set in consideration of the transmission diffraction angle when the concave-convex structure 17U functions as a transmission 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 the following equation (2): ｉｎ -nskPsinθ ｏｕｔ = m (2) where 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 concave-convex structure 17U, and θ is the angle of incidence. ｉｎ , the transmission diffraction angle is θ ｏｕｔ , and the order of diffraction is m. FIG. 6 shows the transmission diffraction angle θ for the incident angle from 0° to 80° for light with a wavelength λ of 445 nm. ｏｕｔ 10 is a diagram showing the results of calculation for each period P based on the above formula (2).

[0071] As described above, in this embodiment, two patterns are considered for the case where the concavo-convex structure 17U functions as a transmission diffraction grating. One is the case where 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 it enters the sapphire substrate from the GaN layer (e.g., light L1). The other is the case where light reflected by the p-electrode 23 is incident at an incident angle of 30° or less (e.g., light L5 in FIG. 3). Therefore, consider the transmission diffraction angle for an incident angle of 47° or less.

[0072] 6, when the period P is 360 nm or 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. Furthermore, it is considered that, of the transmitted and diffracted light, light at an incident angle of 10° or more and less than 47° is more dominant than light at an incident angle of 0° or more and less than 10°. Therefore, when the period P is 360 nm or 440 nm, it can be said that the transmission diffraction angle is substantially within ±30° when 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 for incident angles of less than 10° in Fig. 6, 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 example.

[0074] Since the period P is determined in the above manner, the light emitted from the active layer 20 is reflected, 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°, and therefore the light L1 is transmitted and diffracted by the concave-convex structure 17U, with the transmitted and diffracted light L2 having an incident angle θ2 of 30° or less. Therefore, the incident angle θ2 of the transmitted and diffracted light L2 on the multilayer film 15 is also 30° or less, and the light L2 can be transmitted through the multilayer film 15.

[0076] 3 , the incident angle θ3 of 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°. Because the incident angle θ4 of 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 on 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 30° or less, but the reflection diffraction angle θ4 may be set to an angle greater than 30° as long as it is less than the critical angle θc. Even in this case, as shown in FIG. 6 , for example, 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 30° or less, and therefore the incident angle on the multilayer film 15 is also substantially 30° or less. In other words, by setting the reflection angle when the light emitted from the active layer is reflected by the lower surface 17A, which serves 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, which is in contact with the substrate 17 at the lower surface 17A, the output angle from the substrate 17, i.e., the incident angle on the multilayer film 15, can be set to a narrow angle of substantially 30° or less.

[0078] [Narrowing the Angle] As described above, according to this embodiment, the concave-convex structure 17U functions as a reflective diffraction grating, narrowing the angle of incidence of light emitted from the active layer 20 onto the multilayer film 15 and the substrate 17. This reduces optical loss due to total reflection of the emitted light by the multilayer film 15 and the substrate 17. To narrow the angle of incidence in this manner, 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 angle of reflection diffraction. In particular, by ensuring that the emission wavelength λ of the light-emitting element 13 and the period P satisfy 0.8≦P / λ≦1, the angle of reflection diffraction 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 uneven structure 17U can significantly reduce light loss.

[0080] [Reducing the 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, which is made of sapphire.

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

[0082] 7A 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 without a concave-convex structure. As shown in FIG. 7A, when there is no concave-convex structure, the interface between GaN and sapphire is clear, and the refractive index changes sharply from the refractive index of GaN (2.5) to the refractive index of sapphire (1.8) from the GaN layer toward the sapphire substrate.

[0083] 7B 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 clearly defined 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. 7B, the refractive index distribution in the thickness direction gradually changes 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, at 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 (b) of FIG. 7 than when the refractive index changes sharply as in (a) of FIG. 7.

[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 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 has the same configuration as light-emitting device 10 of Example 1, except that substrate 17 does not have uneven structure 17U. As shown in FIG. 8, the configuration of Example 1 resulted in a 5 to 10% increase in light transmittance compared to the configuration 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 light incident on the substrate 17, and in addition, the optical loss caused by Fresnel reflection is reduced by mitigating the difference in refractive index between the GaN layer and the sapphire substrate.

[0088] From the viewpoint of reducing such a difference in refractive index, it is preferable that each of the convex portions 17C constituting the concave-convex structure 17U 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 the light distribution evaluation and output evaluation of the light emitting device 10 of Example 1 will be explained 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] 9 is a diagram showing the results of a 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 emitting surface being set to 0°. As shown in FIG. 9, compared to Comparative Example 1, Example 1 achieved a narrow-angle light distribution characteristic in which the light intensity was high when the emitting direction was within ±30°.

[0091] 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 or more 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 a narrower light angle and higher output power was obtained in Example 1 than in Comparative Example 1. This can be said to be due to the fact that the period P of the concave-convex structure was appropriately set in relation to the wavelength of the light emitted from the active layer 20, which caused reflective diffraction and transmitted diffraction at appropriate angles, making it possible to extract more narrow-angle light, and also due to the effect of mitigating the refractive index difference by providing the concave-convex structure.

[0093] [Manufacturing Method] An example of a manufacturing method for the light-emitting device 10 of Example 1 will be described. First, a concave-convex structure was formed on one main surface, which served as the first surface, of a sapphire substrate. Specifically, a resist pattern was formed on a 430 μm-thick sapphire substrate by electron beam lithography. Dry etching was performed using the resist pattern as a mask to form a concave-convex structure 17U in which truncated cone-shaped 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. Alternatively, a wafer on which the concave-convex structure 17U was previously formed 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 planarized. 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, which consisted of 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 stacked in this order. Eight pairs of 3-nm GaN layers and 2.1-nm InGaN layers were stacked alternately on the lattice-matched layer, and a 2-nm GaN layer was stacked thereon 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 the 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 the underlayer.

[0097] Then, an active layer having a multiple quantum well structure was formed on the underlayer, in which five pairs of 5.7 nm GaN barrier layers and 3.8 nm InGaN well layers were stacked. 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 of 8.3 nm and an InN layer of 8.3 nm were formed on the spacer layer as electron blocking layers.

[0099] A 98-nm thick p-type GaN layer doped with Mg as a p-type impurity was formed on the electron blocking layer as a p-type cladding layer. A 5-nm thick p-type GaN layer doped with Mg at a higher concentration than the p-type cladding layer was formed on the p-type cladding layer 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 to a thickness of 100 nm on the upper surface of the p-type semiconductor layer 21 by sputtering. Here, the film thickness when forming the ITO may be adjusted as appropriate. By photolithography, the ITO is left in the region corresponding to the p-electrode surface to form the light-transmitting electrode layer 23A, and the ITO is etched and removed from 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, a mesa structure is formed by masking by photolithography, and etching the unmasked portions of the p-type semiconductor layer 21, active layer 20, and n-type semiconductor layer 19. SiO is used as a protective film on the side of the mesa. ２ A film was formed by sputtering, and unnecessary portions of the film were removed by photolithography and etching. Furthermore, a surface 19E of the n-type semiconductor layer 19 exposed by the formation of the mesa structure was patterned by photolithography, and an n-electrode 27 made of Ti / Al was formed by EB deposition. To prevent diffusion of the p-electrode 23, a diffusion prevention layer such as Ni / Pd / Au or Ti / Pt / Au may be provided on part of the top surface and side surfaces of the 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 evaporation (EB evaporation) to form p-type electrode pad 25 and n-type electrode pad 29, respectively. The light reflectance of p-electrode 23 was measured and confirmed to be 80% or higher. The metal layer 23B (reflective layer) of p-electrode 23 is preferably made of Ag, Rh, Al, or an alloy containing these. For example, other metal layers, such as an alloy containing Ag or Al, may be stacked on top or bottom. For example, metal layer 23B may have a reflectance of 80% or higher for light of the wavelength emitted by light-emitting element 13.

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

[0103] Thereafter, on the polished surface, i.e., on the main surface opposite to the main surface on which the concave-convex structure 17U is formed, a 48.5 nm Nb ２ O ５ and 76 nm of SiO ２ The multilayer film 15 was formed by laminating 23 pairs of the above.

[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. Furthermore, 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 use an adhesive to bond the multilayer film 15, and factors that may affect light emission can be eliminated. By the above steps, a wafer on which a plurality of light-emitting elements 13 are formed is obtained.

[0106] Thereafter, the light emitting element 13 was separated 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 p-type wiring electrodes 11A and n-type wiring electrodes 11B on which AuSn patterns were 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 contacted the p-type wiring electrodes 11A and the n-type wiring electrodes 11B, respectively. Flip-chip mounting was performed by AuSn eutectic bonding using heat and pressure. In this manner, the light emitting device 10 was fabricated. Note that the above-described method for manufacturing the light emitting device 10 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 includes a substrate having a first surface on which a concave-convex structure in which conical convex portions are periodically arranged is formed, and a semiconductor laminate having an n-type semiconductor layer as a first semiconductor layer, an active layer, and a p-type semiconductor layer as a second semiconductor layer formed in this order on the first surface, which is the main surface on which the concave-convex structure is formed of the substrate. The light-emitting element 13 also includes a reflective layer formed on the semiconductor laminate and which reflects light emitted from the active layer. The substrate is translucent to light emitted from the active layer.

[0108] Furthermore, the light-emitting element 13 has the characteristic that, when the period at which the convex portions of the uneven 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-described 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 incident light at a narrow angle less than the critical angle (total reflection angle), and the incident light is diffracted while passing through the substrate (transmission diffraction).

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

[0111] As a result, the reflected and diffracted light is reflected by the reflective layer and then re-enters the concave-convex structure at an angle equal to the angle of reflection and diffraction, and the re-entered light is diffracted while passing through the substrate (transmission and diffraction). 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 difference in refractive index at the interface between the substrate and the semiconductor layer, thereby reducing the component 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, which also contributes to improving the light extraction efficiency.

[0113] Furthermore, since the transmission 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 because the light emitted from the substrate has a narrow angle as described above, the angle of incidence 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 constitute a light-emitting device with a 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 into the wavelength conversion layer.

[0117] The light emitting element 13 according to the first embodiment described above is not limited to the case where a wavelength conversion layer is provided on a multilayer film, but can be used in various applications where a narrow-angle light distribution is required.

[0118] Furthermore, in the light emitting element 13, a configuration may be adopted in which a multilayer film is not 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 the example in which the light emitting element 13 has the buried layer 18 has been described, an n-type GaN layer (n-type cladding layer) may be formed directly on the uneven structure without providing the buried layer 18. In this case, as in this example, 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, thereby narrowing the angle of emitted light and improving the light extraction efficiency, resulting in a high-output, high-efficiency light emitting device.

[0120] In addition, in the first embodiment, an example in which the multilayer film is configured to reflect yellow light has been described, but this is not limiting. For example, if no wavelength conversion layer is provided, the multilayer film 15 may simply be configured to reflect blue light incident at a wide angle.

[0121] The 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 in the same manner as the light emitting device 10. An upper surface 33S of the phosphor layer 33 is the 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 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 also be a plate in which a thin film containing a phosphor is formed on the surface of a glass support. The phosphor layer 33 may also 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 has a narrow beam angle. To maintain this narrow beam angle, the material of the phosphor layer 33 is preferably a highly transparent phosphor, such as a single crystal phosphor.

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

[0125] White light is extracted from the light emitting device 30 by mixing the blue light and yellow fluorescent light 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 the phosphor layer 33 and the yellow light emitted by the phosphor contained in the 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) with 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 one another on the upper surface 33S. In this embodiment, the nanoantennas 35 are made of aluminum (Al). The nanoantennas 35 are arranged at a regular interval and in a regular arrangement pattern in a plane parallel to the upper surface 33S, in other words, when viewed from above, to form an antenna array.

[0129] In this embodiment, the antenna array made up of nanoantennas 35 is formed over 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 the region where the semiconductor stack 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 rectangular 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 can be a columnar or pyramidal shape, and can be a rectangular columnar shape, a cylindrical shape, a conical shape, a pyramidal shape, etc. The nanoantenna 45 can be made of metal such as Au, Ag, Ni, or TiO ２ , Al ２ O ３ It may also be formed from a metal oxide such as

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

[0133] The nanoantennas 35 strongly diffract light in the yellow wavelength range among the light emitted from the upper surface 33S of the phosphor layer 33. In other words, the nanoantennas 35 function as diffractive optical elements. Specifically, the nanoantennas 35 strongly diffract light in the yellow wavelength range from the phosphor layer 33 to the upper surface 33S at an incident angle θ ｉｎ The angle of emergence θ from the upper surface 33S is ｏｕｔ In other words, the antenna array of the nanoantenna 35 narrows the light distribution angle of the yellow light.

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

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

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

[0137] With the above-described configuration, according to Example 2, similarly to the light-emitting device 10 of Example 1, narrow-angle, high-power blue light is emitted from the upper surface 17B of the substrate 17. In addition, the blue light enters the phosphor layer 33, where a portion of the blue light is wavelength-converted to isotropically emit 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 fluorescent light 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 fluorescent light and the blue light while reducing the loss of the fluorescent light. 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 be used to 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 evaluation results of the light distribution and total luminous flux of the light emitting device 30 according to Example 2 will be explained 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] Fig. 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. 13, (a) shows the light distribution evaluation result of Comparative Example 2, and (b) shows the light distribution evaluation result of Example 2. 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 set to 0°.

[0141] 13A, Comparative Example 2 exhibits a Lambertian light distribution with low overall intensity and uniform diffusion in all directions. As shown in FIG. 13B, Example 2 exhibits a narrow-angle light distribution characteristic with high light intensity within an emission direction of ±30°.

[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 about 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 a narrower light 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 functions of uneven structure 17U described above, i.e., its function as a reflective diffraction grating and a transmissive diffraction grating and its function of reducing the refractive index difference.

[0145] Of the blue light introduced into the phosphor layer 33, the light that passes through the 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 that is isotropically emitted from the phosphor is diffracted by the nanoantenna 35 to form a narrow-angle light distribution, resulting in an overall narrow-angle light distribution characteristic.

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

[0147] The configuration of a light-emitting device 40 according to Example 3 will be described with reference to Figures 15 to 17. Figure 15 is a cross-sectional view of the light-emitting device 40. The light-emitting device 40 has the same configuration as the light-emitting device 10, except that a side reflector 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 a concave-convex structure 17U formed on the 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 that is recessed relative to the surface of the mesa-shaped plateau 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, side reflecting members 41 are provided on the side surfaces of the light emitting element 13, and light from the active layer 20 that reaches the side surfaces of the light emitting element 13 is reflected and returned to the light emitting element 13. As a result, the light that reaches the side surfaces of the light emitting element 13 is emitted from the top surface of the multilayer film 15 rather than from the side surfaces. This reduces stray light from the side surfaces of the light emitting element 13 and increases the proportion of light that is emitted from the top surface 15S of the light emitting element 13, making it possible to suppress uneven light distribution, which results in a non-uniform light intensity distribution, and achieve a narrow light distribution angle.

[0152] 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 narrow angle passes through the multilayer film 15 as is and is extracted to the outside from the top surface of the multilayer film 15.

[0153] For example, among the light reflected by the side reflecting member 41, light that propagates within the substrate 17 and strikes the multilayer film 15 at a wide angle is first reflected by the multilayer film 15. Thereafter, the angle of incidence is narrowed by reflection and diffraction by 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, thereby passing through the multilayer film 15 and being 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 after undergoing 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 with different refractive indices are stacked, and is configured to reflect light within 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 range of blue light from the active layer 20 that is incident within a predetermined angle range. In this embodiment, the side reflector 41 is made of a niobium oxide film (Nb ２ O ５ ) and a 76 nm silicon dioxide film (SiO ２ ) are stacked in three pairs.

[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 this. The side surface 17E of the substrate 17 accounts for a large proportion of the side surface of the light emitting element 13. For this reason, if the side reflecting member 41 is not provided, it is thought 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] [Manufacturing Method Example] A light-emitting device 40 having a side reflector 41 can be formed, for example, as follows. Using the manufacturing method described in Example 1, a wafer on which a plurality of light-emitting elements 13 are formed is fabricated, and 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 which the p-type electrode pad 25 and the n-type electrode pad 29 are formed (i.e., the surface opposite 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 area where the side reflector 41 is to be formed is removed using photolithography.

[0159] Thereafter, the light emitting elements 13 were separated into individual pieces by dicing, thereby exposing the side surfaces of the light emitting elements 13. Then, using the protective resist film as a mask, a dielectric multilayer film was formed on the side surfaces of the separated light emitting elements 13 by, for example, ALD (Atomic Layer Deposition), to form the side surface reflecting members 41. As the side surface reflecting members 41, a 48.5 nm thick niobium oxide film (Nb ２ O ５ ) and a 76 nm silicon dioxide film (SiO ２ ) were laminated in three pairs. This allows for film formation on both the substrate side and the semiconductor layer side. Alternatively, a multilayer film may be formed only on the semiconductor layer side. The protective resist film was then removed, and the device was flip-chip mounted on the mounting substrate 11 to obtain the light-emitting device 40.

[0160] [Light Distribution] A simulation was performed 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 the convex portions of concave-convex structure 17U of substrate 17 are arranged is set to 360 nm.

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

[0163] The layer structure and dimensions of the semiconductor laminate layered 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 thick. The n-type semiconductor layer 19 on the buried layer 18 was an n-type GaN layer doped with Si of 3 μm thick.

[0164] The lattice-matched layer on the n-type GaN layer was 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 stacking eight pairs of 3 nm GaN layers and 2.1 nm InGaN layers, and then stacking 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 composed 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 Mg at a higher concentration than the p-type cladding layer.

[0168] The transparent electrode layer 23A on the p-type semiconductor layer 21 was made of ITO with a thickness of 100 nm. 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 a niobium oxide film (Nb ２ O ５ ) and silicon oxide film (SiO ２ ) and 23 pairs were stacked.

[0169] The light emitting device 40 is made of a 48.5 nm niobium oxide film (Nb ２ O ５ ) and a 76 nm silicon dioxide film (SiO ２ ) were laminated on the side surfaces of the light emitting element 13 in three pairs to form the side reflecting member 41 .

[0170] Light distribution calculations were performed for the above configuration. First, the wave optics 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 of the active layer 20 in the layer thickness direction. The calculation results of the wave optics optical characteristics include transmittance and reflectance characteristics that take into account the reflection diffraction angle and transmission diffraction angle of the concave-convex structure 17U. Then, 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 optics characteristics.

[0171] [Simulation Results] Fig. 16 is a diagram showing the results of a simulation of the light distribution of total luminous flux for light-emitting device 40 according to Example 3 with and without side reflector 41. In Fig. 16, (a) shows the light-emitting device 40 of Example 3 without side reflector 41 (the configuration in which the 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 exit surface being 0°.

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

[0173] 16, both light emitting device 10 and 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 light emitting device 10. In contrast, as shown in (b) of Fig. 16, there are no areas of extremely low light intensity like in light emitting device 10 in the light distribution of light emitting device 40, and the light distribution is more uniform than that of light emitting device 10, with reduced unevenness in light distribution.

[0174] It is believed that the provision of the side reflecting member 41 increases the amount of light that reaches the side surface of the light emitting element 13 but is returned to the light emitting element 13 without being emitted from the side surface of the light emitting element 13, and that the light returned to the light emitting element 13 is then emitted from the multilayer film 15. It is believed that this has resulted in an increase in the amount of light emitted in directions within ±30°, thereby making the light distribution uniform.

[0175] 17 is a diagram showing the light distribution ratio with respect to 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 set to 360 nm, the same as the period in Example 3.

[0176] [Light Distribution Ratio] Regarding the light distribution of light emitted from a light-emitting device, the light distribution ratio was 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 form a Lambertian light distribution. The higher the light distribution ratio, the narrower the light distribution angle, with higher light intensity within ±30°. Light-emitting device 10 and 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 ratio was calculated by simulation under a number of conditions for the thickness of the sapphire substrate serving as the substrate 17, and the results were compared.

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

[0179] 17 also shows 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, less light is emitted in directions within ±30°.

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

[0181] In Example 3, the side reflecting member 41 reflects the light that reaches the side surface 17E of the substrate 17 of the light-emitting element 13 and returns it 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, it is preferable to set the thickness of the substrate 17 to, for example, 300 μm or less, because this will result in a light distribution ratio equal to or greater than the maximum light distribution ratio (approximately 1.6) of Example 1. Furthermore, 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, it is preferable to set the thickness to 150 μm or less, because this will increase 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 light emitted from the active layer 20. By providing the side reflecting member 41, 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 light emitting element 13. This suppresses uneven light distribution, which is a non-uniformity in the light distribution within ±30°, and also provides higher light output within ±30°, in other words, a narrower light distribution angle.

[0184] The light returned to the light-emitting element 13 is either 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 thought to be incident on the multilayer film 15 at a narrow angle after undergoing reflection diffraction or transmission diffraction by the uneven structure U of the substrate 17.

[0185] As a result, the amount of light incident on the multilayer film 15 at a narrow angle has increased, and the amount of light that passes through the multilayer film 15 and is extracted to the outside from the top surface of the multilayer film 15 has increased. In other words, light at an angle that suppresses light loss due to the multilayer film 15 is now emitted from the top surface of the substrate 1 and incident on the 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, the side reflector 41 is formed on the entire side surface of the light-emitting element 13, but this is not limiting. Because the side surface 17E of the substrate 17 accounts for a large proportion of the side surface of the light-emitting element, it is thought 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. Therefore, it is sufficient that the side reflector 41 is provided on at least the side surface 17E of the substrate 17. In other words, it is sufficient that the side reflector 41 is formed on a surface including the side surface E of the substrate 17.

[0188] Furthermore, 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] 15 and 18, the configuration and light distribution of a light emitting device 40 according to a modification of the third embodiment will be described. In this modification, the light emitting device 40 uses 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 reflector as the side reflector 41. In this modification, the side reflector 41 is made of a silicone resin containing titanium oxide (TiO ２) is dispersed and hardened.

[0191] In the silicone resin, TiO was added at 25 wt %. ２ The particles were dispersed and ejected by inkjet printing to form a pattern around the element, and then thermally cured to form a white resin layer with a thickness of about 100 μm on the side surface of the light emitting element 13, which served as the side reflector 41.

[0192] The resin constituting the side reflector 41 of this modification may be a thermosetting resin or a photosetting resin such as an epoxy resin, an acrylic resin, a polycarbonate resin, or a polyimide resin, in addition to a silicone resin. The scattering particles of the side reflector 41 of this modification may be, for example, zinc oxide (ZnO), alumina (Al), or the like, in addition to titanium oxide. ２ O ３ ) or other metal oxide particles can be used.

[0193] In this example, 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 Example 3.

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

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

[0196] 18 indicates a Lambertian light distribution with the same total luminous flux as the total luminous flux measured for 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 the same 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 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 gentler than in (a). It can be said that light-emitting device 40 has a more uniform light distribution and reduced unevenness in light distribution than light-emitting device 10.

[0199] 18 , the light distribution ratio was calculated using the same method as in Example 3. The light distribution ratio of light emitting device 10 was 1.3 times, and the light distribution ratio of light emitting device 40 was 1.4 times. It can be said that the light distribution of light emitting device 40 was a narrower-angle light distribution with higher light intensity within ±30° compared to light emitting device 10.

[0200] As described above, even when side reflecting member 41 is made of white resin, the same effect as in Example 3, that is, the luminous intensity distribution is uniform within ±30° and a narrow angle luminous intensity distribution is obtained, is obtained. Of the light emitted from active layer 20, the light that reaches the side surface of light-emitting element 13 is reflected by side reflecting member 41 made of white resin and returned to light-emitting element 13 without being emitted from the side surface of light-emitting element 13, and it is thought that this increases the amount of light emitted from upper surface 15S of multilayer film 15.

[0201] 11 may be provided on the multilayer film 15 of the light-emitting device 40. An antenna array made up 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 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 isotropically emitted yellow fluorescence is diffracted by the nanoantenna 35 to form a narrow-angle light distribution, which 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 Example 3 and the modified example, side reflectors 41 may also be provided on the side surfaces of the phosphor layer 33. This allows light that has reached the side surfaces of the phosphor layer 33 to be reflected 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-described embodiments are merely examples, and can be modified or combined as appropriate depending on the application, etc. In the above-described embodiments, the period P is determined so that the reflection diffraction angle becomes 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 becomes the target value of the exit angle from the substrate or the target value of the incident angle to the multilayer film.

[0205] REFERENCE SIGNS LIST 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 23 P-electrode 23A Light-transmitting 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 Nanoantenna 41 Side reflector

Claims

1. A semiconductor light-emitting device comprising: a substrate having a first surface on which a concave-convex structure is formed with a periodic arrangement of pyramidal convex portions; 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 that 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 for reflecting light emitted from the active layer, wherein the substrate is translucent to the emitted light, and wherein 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.

2. The semiconductor light-emitting element according to claim 1, wherein the angle of reflection of the emitted light on the first surface is 30° or less.

3. The semiconductor light-emitting element according to claim 1, wherein said convex portion has a sidewall that forms an angle of 60° or more with respect to said first surface of said substrate.

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

6. The semiconductor light-emitting element described in claim 1, further comprising: a dielectric multilayer reflector provided on a third surface of the substrate opposite the first surface on which the uneven structure is formed; and a phosphor layer provided on the dielectric multilayer reflector and containing a phosphor that is excited by the emitted light to emit fluorescence, wherein the dielectric multilayer reflector is configured to reflect the fluorescence from the phosphor layer and transmit the emitted light.

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

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

9. A semiconductor light-emitting element comprising: a substrate having a first surface on which a concave-convex structure is formed in which pyramidal convexities 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 for reflecting emitted light from the active layer, wherein 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, and a reflection angle when the emitted light is reflected at the first surface is less than a critical angle at the interface between the substrate and the layer in contact with the substrate.

10. A semiconductor light-emitting element according to any one of claims 1 to 8, further comprising a side reflecting member covering a side surface of said substrate and reflecting said emitted light.

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 reflecting member is a resin member containing scattering particles having light scattering properties.

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. The semiconductor light-emitting device according to claim 10, wherein the thickness of the substrate is 150 μm or less.

15. A semiconductor laminate having a first surface on which a concave-convex structure in which pyramidal convex portions are periodically arranged, and 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; a reflective layer formed on the semiconductor laminate and reflecting 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 containing a phosphor that is excited by the emitted light to emit fluorescence; and a side reflecting member covering a side surface of the substrate and a side surface of the phosphor layer and reflecting the emitted light, wherein the substrate is translucent to the emitted light, and 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, characterized in that the phosphor layer includes nanoantennas arranged at a predetermined period on the surface opposite to the surface in contact with the dielectric multilayer film reflector.

17. 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 for reflecting light emitted from the active layer, wherein 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 wherein, 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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