Patent Publication Number: US-11393954-B2

Title: Light emitting element and light emitting device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 16/835,725, filed on Mar. 31, 2020, which is a continuation of U.S. patent application Ser. No. 16/277,243, filed on Feb. 15, 2019, now U.S. Pat. No. 10,644,203, which claims priority to Japanese Patent Application No. 2018-026347, filed on Feb. 16, 2018, Japanese Patent Application No. 2018-195754, filed on Oct. 17, 2018, and Japanese Patent Application No. 2019-011449, filed on Jan. 25, 2019, the disclosures of which are hereby incorporated by reference in their entireties. 
    
    
     BACKGROUND 
     The present disclosure relates to a light emitting element and a light emitting device. 
     A light emitting device having a rectangular light emitting surface from which light is extracted is known. Such a light emitting device includes, for example, a light emitting element having a rectangular external shape as seen in a plan view, and typically has a parallelepiped overall external appearance. Such a light emitting device having a parallelepiped external appearance is combined with a light guide plate and used for a backlight unit of a liquid crystal display device, for example. Japanese Patent Publication No. 2016-143682 discloses a group-III nitride semiconductor light emitting element having a structure in which an n-type semiconductor layer and a p-type semiconductor layer are stacked on a rectangular sapphire substrate. 
     SUMMARY 
     Exemplary embodiments of the present disclosure provide a light emitting element having an improved reliability. 
     In one embodiment, a light emitting element includes a semiconductor structure including a first semiconductor layer of a first conductivity type including a first region and a second region located inward of the first region, an active layer located on the second region, and a second semiconductor layer of a second conductivity type located on the active layer, the first region including an outer peripheral region located along an outer perimeter of the second region as seen in a plan view and a plurality of extending portions each extending into the second region from the outer peripheral region; a light-reflective electrode covering a top surface of the second semiconductor layer; a first insulating layer covering the semiconductor structure and the light-reflective electrode and including first through-holes respectively located on the extending portions of the first region and a second through-hole located on the second region; a first internal electrode located on the first insulating layer and electrically connected with the first semiconductor layer via the first through-holes; a second internal electrode located on the first insulating layer and electrically connected with the light-reflective electrode via the second through-hole; a second insulating layer covering the first internal electrode and the second internal electrode and electrically insulating the first internal electrode and the second internal electrode from each other, the second insulating layer including a third through-hole located on the first internal electrode and a fourth through-hole located on the second internal electrode; a first external electrode electrically connected with the first internal electrode via the third through-hole and including a plurality of corner portions; and a second external electrode electrically connected with the second internal electrode via the fourth through-hole and including a plurality of corner portions. As seen in a plan view, the plurality of extending portions of the first region are each located in an area, on a top surface of the first semiconductor layer, other than an area overlapping any of the plurality of corner portions of the first external electrode and other than an area overlapping any of the plurality of corner portions of the second external electrode. 
     According to the above embodiment, a light emitting element having an improved reliability is provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an example of the external appearance of a light emitting device in an embodiment according to the present disclosure. 
         FIG. 2  is a schematic cross-sectional view taken along line II-II in  FIG. 1 . 
         FIG. 3  is a schematic bottom see-through view of an example of light emitting element in an embodiment according to the present disclosure. 
         FIG. 4  is a schematic cross-sectional view taken along line IV-IV in  FIG. 3 . 
         FIG. 5  is a schematic cross-sectional view taken along line V-V in  FIG. 3 . 
         FIG. 6  is a schematic plan view provided to describe the positional relationship between a p-type semiconductor layer  120   p  and an n-type semiconductor layer  120   n.    
         FIG. 7  is a schematic plan view showing a state in which a first insulating layer  140  is formed on a light-reflective electrode  130 . 
         FIG. 8  is a schematic plan view showing a state in which a first internal electrode  150   n  and a second internal electrode  150   p  are formed on the first insulating layer  140 . 
         FIG. 9  is a schematic plan view showing a state in which a second insulating layer  160  is formed on the first internal electrode  150   n  and the second internal electrode  150   p.    
         FIG. 10  is a plan view schematically showing a semiconductor structure  112 A, a first external electrode  170 An and a second external electrode  170 Ap among components of a light emitting element  100 A. 
         FIG. 11  is a perspective view showing another example of the external appearance of a light emitting device in an embodiment according to the present disclosure. 
         FIG. 12  is a schematic cross-sectional view taken along line XII-XII in  FIG. 11 . 
         FIG. 13  is a schematic see-through view of a light emitting element in a comparative example including a plurality of extending portions and a plurality of through-holes provided in an insulating layer, the extending portions and the through-holes being located at positions overlapping corner portions of an external electrode. 
         FIG. 14  is a schematic cross-sectional view taken along line XIV-XIV in  FIG. 13 . 
         FIG. 15  is a view provided to describe an example of relationship between the shape of each of the first external electrode  170 An and the second external electrode  170 Ap and the positional arrangement of the plurality of extending portions Ep. 
         FIG. 16  is a schematic see-through view showing another example of light emitting element ( 100 B) in an embodiment according to the present disclosure. 
         FIG. 17A  is a schematic plan view showing a semiconductor structure, a first external electrode  170 Bn and a second external electrode  170 Bp among components of the light emitting element  100 B shown in  FIG. 16 . 
         FIG. 17B  is a schematic see-through view showing still another example of light emitting element ( 100 C) in an embodiment according to the present disclosure. 
         FIG. 18  shows calculation results on absolute values of shear stress on a sample in reference example 1. 
         FIG. 19  shows calculation results on absolute values of shear stress on a sample in reference example 2. 
         FIG. 20  shows calculation results on absolute values of shear stress on a sample in reference example 3. 
         FIG. 21  shows calculation results on absolute values of shear stress on a sample in reference example 4. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the attached drawings. The following embodiments are illustrative, and the light emitting device according to the present disclosure is not limited to any of light emitting devices in the following embodiments. For example, the numerical values, shapes, materials, steps, the order of the steps, and the like shown in the following embodiments are merely examples, and may be modified in various manners as long as no technological contradiction occurs. 
     In the drawings, the sizes, the shapes or the like may be exaggerated for clear illustration, and may not reflect the sizes, the shapes and the size relationship among the components in an actual light emitting device. A part of the components may be omitted in order to avoid the drawings from being excessively complicated. 
     In the following description, components having substantially the same functions will be represented by the same reference signs, and the descriptions thereof may be omitted. In the following description, terms showing specific directions or positions (e.g., “top”, “above”, “bottom”, “below”, “right”, “left” and terms including these terms”) may be used. These terms are merely used to show relative directions or positions in a drawing referred to, for easier understanding. The components merely need to be arranged in the directional or positional relationship as described by use of the term “top”, “above”, “bottom”, “below” or the like with reference to a drawing referred to. In any drawing other than those in the present disclosure, an actual product, an actual production device or the like, the components do not need to be positionally arranged as exactly shown in a drawing referred to. In the present disclosure, the term “parallel” encompasses a case in which two straight lines, sides, planes or the like make an angle in the range of approximately 0°±5° unless otherwise specified. In the present disclosure, the terms “vertical” and “perpendicular” encompass a case in which two straight lines, sides, planes or the like make an angle in the range of approximately 90°±5° unless otherwise specified. 
     (Embodiment of Light Emitting Element and Light Emitting Device) 
       FIG. 1  shows an example of the external appearance of a light emitting device in an embodiment according to the present disclosure.  FIG. 2  is a schematic cross-sectional view taken along line II-II in  FIG. 1 . For reference,  FIG. 1  and  FIG. 2  show an X axis, a Y axis and a Z axis perpendicular to each other. The other drawings of the present disclosure also show the X axis, the Y axis and the Z axis. 
     The light emitting device  300  shown in  FIG. 1  and  FIG. 2  generally includes a light emitting element  100  including a light-transmissive first substrate and a semiconductor structure on the first substrate, and a support  200  as a second substrate supporting the light emitting element  100 . In the structure shown in  FIG. 1 , the light emitting element  100  is covered with a light-reflective member  190 . Light from the light emitting element  100  is output generally in the Z direction in  FIG. 1  via a light-transmissive member  182  located on a front surface (in  FIG. 1 ) of the light emitting element  100 . 
     As shown in  FIG. 1  and  FIG. 2 , the support  200  includes an insulating base  230 , and a first wiring portion  210  and a second wiring portion  220  on the base  230 . As shown in  FIG. 2 , the light emitting element  100  generally includes a light emitting structure  110  including, in a part thereof, the first substrate and the semiconductor structure described above. The light emitting element  100  further includes a first external electrode  170 An and a second external electrode  170 Ap supplying an electric current to the light emitting structure  110 . As schematically shown in  FIG. 2 , the first wiring portion  210  and the second wiring portion  220  of the support  200  are provided to cover the base  230  from a top surface  230   a  to a bottom surface  230   b  of the base  230 . The first wiring portion  210  is connected with the first external electrode  170 An of the light emitting element  100 , and the second wiring portion  220  is connected with the second external electrode  170 Ap of the light emitting element  100 . The first wiring portion  210  and the second wiring portion  220  are electrically and physically connected with the light emitting structure  110  of the light emitting element  100  respectively via the first external electrode  170 An and the second external electrode  170 Ap. The light emitting structure  110  will be described in detail below. 
     In the structure shown in  FIG. 2 , the light emitting device  300  includes a wavelength conversion member  180  and the light-transmissive member  182  above the light emitting element  100 . The wavelength conversion member  180  is, for example, a plate-like member formed of a silicone resin and particles of YAG-based phosphor or the like dispersed in the silicone resin. The light-transmissive member  182  is, for example, a plate-like member mainly formed of a silicone resin. A light guide member  174  is located between the wavelength conversion member  180  and the light emitting element  100 . The light guide member  174  is, for example, a light-transmissive member formed of a silicone resin. As shown in  FIG. 2 , a part of the light guide member  174  covers lateral surfaces  110   c  of the light emitting structure  110 . The light-reflective member  190  described above encloses the components on the support  200 . As schematically shown in  FIG. 2 , a top surface  182   a  of the light-transmissive member  182  is exposed from the light-reflective member  190 . The top surface  182   a  of the light-transmissive member  182  is a part of a top surface  300   a  of the light emitting device  300 . The light-reflective member  190  includes, for example, a matrix formed of a resin material containing a silicone resin and a light-scattering filler dispersed in the resin material. 
     Hereinafter, the light emitting element  100  will be described in detail with reference to the drawings.  FIG. 3  is a schematic bottom see-through view of a light emitting element in an embodiment according to the present disclosure.  FIG. 4  is a schematic cross-sectional view taken along line IV-IV in  FIG. 3 .  FIG. 5  is a schematic cross-sectional view taken along line V-V in  FIG. 3 . 
     The light emitting element  100 A shown in  FIG. 3  through  FIG. 5  is an example of the light emitting element  100  described above with reference to  FIG. 1  and  FIG. 2 . In the structure shown in  FIG. 3  through  FIG. 5 , the light emitting element  100 A is rectangular and is longer in the Y direction than in the X direction as in from a plan view. The light emitting element  100 A has a length in the X direction of, for example, about 100 μm to about 300 μm. The light emitting element  100 A has a length in the Y direction of, for example, about 700 μm to about 1400 μm, preferably about 900 μm to about 1200 μm. 
     As shown in  FIG. 4  and  FIG. 5 , a light emitting structure  110 A of the light emitting element  100 A includes a light-transmissive first substrate  111  and a semiconductor structure  112 A supported by the first substrate  111 . The first substrate  111  is typically a sapphire substrate. The semiconductor structure  112 A typically contains a nitride semiconductor (In x Al y Ga 1-x-y N, 0≤x, 0≤y, x+y≤1) capable of emitting light of a wavelength in an ultraviolet light region to a visible light region. 
     The semiconductor structure  112 A includes an n-type semiconductor layer  120   n  as a first semiconductor layer having a first conductivity type, a p-type semiconductor layer  120   p  as a second semiconductor layer having a second conductivity type, and an active layer  120   a  located between the n-type semiconductor layer  120   n  and the p-type semiconductor layer  120   p . The light emitting structure  110 A of the light emitting element  100 A includes a plurality of insulating layers and a plurality of electrodes in addition to the semiconductor structure  112 A. As shown in  FIG. 4  and  FIG. 5 , the light emitting structure  110 A includes a first insulating layer  140 , a second insulating layer  160 , a light-reflective electrode  130  located between the p-type semiconductor layer  120   p  and the first insulating layer  140 , a first internal electrode  150   n , and a second internal electrode  150   p.    
     Among the components of the semiconductor structure  112 A, the n-type semiconductor layer  120   n  is located on the first substrate  111  and covers generally the entirety of a top surface  111   a  of the first substrate  111 . As shown in  FIG. 3 , the n-type semiconductor layer  120   n  includes a first region R 1  and a second region R 2  located inward of the first region R 1 . In other words, a top surface of the n-type semiconductor layer  120   n  includes the first region R 1  and the second region R 2  located inward of the first region R 1 . The active layer  120   a  is selectively formed on the second region R 2  of the n-type semiconductor layer  120   n . The p-type semiconductor layer  120   p  on the active layer  120   a  is also located generally just above the second region R 2 . In other words, a part of the n-type semiconductor layer  120   n  that is in the first region R 1  is not covered with the active layer  120   a  or the p-type semiconductor layer  120   p , and is exposed from these layers. 
       FIG. 6  shows the positional relationship between the p-type semiconductor layer  120   p  and the n-type semiconductor layer  120   n .  FIG. 6  corresponds to a figure showing the n-type semiconductor layer  120   n , the active layer  120   a  and the p-type semiconductor layer  120   p , among the components of the light emitting structure  110 A. As described above, the active layer  120   a  and the p-type semiconductor layer  120   p  covers the second region R 2  of the n-type semiconductor layer  120   n . The active layer  120   a  is not explicitly shown in  FIG. 6  but may be considered to occupy substantially the same area as the area occupied by the p-type semiconductor layer  120   p.    
     As shown in  FIG. 6 , the first region R 1  of the n-type semiconductor layer  120   n  includes an outer peripheral region Pp located along an outer perimeter of the second region R 2  as seen in a plan view and a plurality of extending portions Ep.  FIG. 6  shows areas that correspond to the extending portions Ep of the first region R 1  as shaded areas for easier understanding. As shown in  FIG. 6 , the plurality of extending portions Ep are parts of the first region R 1  that extend into the second region R 2  from the outer peripheral region Pp. From another perspective, it may be considered that the second region R 2  includes a plurality of recessed portions (notches) as seen in a plan view, and the extending portions Ep of the first region R 1  are formed in the recessed portions. The active layer  120   a  and the p-type semiconductor layer  120   p  may each be considered to include a plurality of recessed portions (notches) at positions corresponding to the extending portions Ep of the first region R 1  as seen in a plan view. 
     In this example, the n-type semiconductor layer  120   n  has a rectangular external shape including a first longer side LS 1  and a second longer side LS 2  facing each other as seen in a plan view. Four extending portions Ep are provided closer to the second longer side LS 2  than to the first longer side LS 1 . In this example, the first longer side LS 1  and the second longer side LS 2  are parallel to the Y direction. 
     The semiconductor structure  112 A may be formed by a known semiconductor process. For example, the n-type semiconductor layer  120   n , the active layer  120   a  and the p-type semiconductor layer  120   p  may be formed as follows. Nitride semiconductor layers are formed on the top surface  111   a  of the first substrate  111  by metal organic chemical vapor deposition (referred to also as MOCVD), metal organic vapor phase epitaxy (referred to also as MOVPE), hydride vapor phase epitaxy (HVPE) or the like. Then, a part of each of the layers to be the active layer  120   a  and the p-type semiconductor layer  120   p  that is on the first region R 1  is removed by photolithography and etching. 
     Referring to  FIG. 4  and  FIG. 5 , the light-reflective electrode  130  covers a top surface  120   pa  of the p-type semiconductor layer  120   p  and is electrically connected with the p-type semiconductor layer  120   p . The light-reflective electrode  130  has a function of providing an electric current to a greater area of the p-type semiconductor layer  120   p . The light-reflective electrode  130  is provided to cover substantially the entirety of the top surface  120   pa  of the p-type semiconductor layer  120   p . With such a structure, light traveling toward a top surface of the light emitting element  100 A in  FIG. 4  and  FIG. 5 , in other words, light traveling in a direction opposite to a direction toward the first substrate  111 , is reflected by the light-reflective electrode  130 , so that the light travels toward the first substrate  111  of the light emitting element  100 A. Thus, an effect of improving the light extraction efficiency is provided. The light-reflective electrode  130  may be formed of a film of, for example, Ag, Al or an alloy containing at least one of Ag and Al. The light-reflective electrode  130  may be formed as follows. A metal film or an alloy film is formed by, for example, sputtering, and an unnecessary part of the film is removed by etching. 
     The first insulating layer  140  is provided on the light-reflective electrode  130 . The first insulating layer  140  is formed of, for example, an oxide or a nitride containing at least one selected from the group consisting of Si, Ti, Zr, Nb, Ta, Al and Hf. The first insulating layer  140  is typically an insulating layer formed of SiO 2 . The first insulating layer  140  covers the semiconductor structure  112 A and the light-reflective electrode  130 . An SiN layer may be provided between the light-reflective electrode  130  and the first insulating layer  140  and serve as a barrier layer suppressing migration of the material of the light-reflective electrode  130 . 
       FIG. 7  schematically shows a state in which the first insulating layer  140  is formed on the light-reflective electrode  130 . In  FIG. 7 , the area where the material of the first insulating layer  140  is provided is hatched. As schematically shown in  FIG. 7 , the first insulating layer  140  includes first through-holes  141  located at positions corresponding to the extending portions Ep 1  through Ep 4  of the first region R 1  of the n-type semiconductor layer  120   n , and also includes a second through-hole  142  located above the second region R 2  of the n-type semiconductor layer  120   n . In this example, four first through-holes  141  are provided along the second longer side LS 2  of the rectangular external shape of the n-type semiconductor layer  120   n . The extending portions Ep are located along one of the longer sides of the rectangular external shape (in this example, the second longer side LS 2 ), so that the luminance non-uniformity is made less conspicuous. 
     At the four first through-holes  141 , the extending portions Ep 1  through Ep 4  are exposed from the first insulating layer  140 . At the second through-hole  142 , a surface of the light-reflective electrode  130  is exposed from the first insulating layer  140 . The first through-holes  141  may, for example, have a diameter longer in the Y direction than a diameter in the X direction. With such a shape, even in the case in which the n-type semiconductor layer  120   n  has a lengthy rectangular external shape as in this embodiment, each portion of the top surface of the n-type semiconductor layer  120   n  that is to be connected with the first internal electrode  150   n  described below may have a relatively large area size, and the area size of the active layer  120   a  is suppressed from being decreased due to the provision of the first through-holes  141 . Needless to say, the shape and the number of the second through-hole  142  in  FIG. 7  are mere examples. The shape of each of the first through-holes  141  is not limited to the shape shown in  FIG. 7 . 
     As shown in  FIG. 4 , the first internal electrode  150   n  and the second internal electrode  150   p  are provided on the first insulating layer  140 . The first internal electrode  150   n  and the second internal electrode  150   p  may be formed of, for example, Ag, Al or an alloy containing at least one of Ag and Al. Especially, Al and an Al alloy provide a high reflectance and are less easily migrated than Ag, and thus are advantageous as a material of the first internal electrode  150   n  and the second internal electrode  150   p.    
       FIG. 8  schematically shows a state in which the first internal electrode  150   n  and the second internal electrode  150   p  are formed on the first insulating layer  140 . The first internal electrode  150   n  is electrically connected with the n-type semiconductor layer  120   n  at the positions of the extending portions Ep 1  through Ep 4  via the first through-holes  141 . The second internal electrode  150   p  is electrically connected with the light-reflective electrode  130  via the second through-hole  142 . Namely, the second internal electrode  150   p  is electrically connected with the p-type semiconductor layer  120   p.    
     Referring to  FIG. 4 , the second insulating layer  160  is formed on the first internal electrode  150   n  and the second internal electrode  150   p  and covers the first internal electrode  150   n  and the second internal electrode  150   p . Like the first insulating layer  140 , the second insulating layer  160  may be formed of, for example, an inorganic material such as SiO 2  or the like, and electrically insulates the first internal electrode  150   n  and the second internal electrode  150   p  from each other. 
       FIG. 9  shows a state in which the second insulating layer  160  is formed on the first internal electrode  150   n  and the second internal electrode  150   p . The second insulating layer  160  includes a through-hole  163  at a position overlapping the first internal electrode  150   n  as seen in a plan view, and also includes a fourth through-hole  164  at a position overlapping the second internal electrode  150   p  as seen in a plan view. As schematically shown in  FIG. 9 , a surface of the first internal electrode  150   n  is exposed from the second insulating layer  160  at the third through-hole  163 , and a surface of the second internal electrode  150   p  is exposed from the second insulating layer  160  at the fourth through-hole  164 . Needless to say, the shape and the number of each of the third through-hole  163  and the fourth through-hole  164  are not limited to those shown in  FIG. 9 . 
     As shown in, for example,  FIG. 4 , the first external electrode  170 An and the second external electrode  170 Ap described above are located on the second insulating layer  160 . As can be seen from  FIG. 3  and  FIG. 4 , the first external electrode  170 An is electrically connected with the first internal electrode  150   n  via the third through-hole  163  of the second insulating layer  160 . Since the first internal electrode  150   n  is connected with the n-type semiconductor layer  120   n  at the extending portions Ep 1  through Ep 4  of the n-type semiconductor layer  120   n , the first external electrode  170 An is electrically connected with the n-type semiconductor layer  120   n  via the first internal electrode  150   n . The second external electrode  170 Ap is electrically connected with the second internal electrode  150   p  via the fourth through-hole  164  of the second insulating layer  160 , and thus is electrically connected with the p-type semiconductor layer  120   p  via the second internal electrode  150   p  and the light-reflective electrode  130 . 
       FIG. 10  shows the semiconductor structure  112 A, the first external electrode  170 An and the second external electrode  170 Ap, among the components of the light emitting element  100 A.  FIG. 10  also shows the first through-holes  141  of the first insulating layer  140  with dashed lines. 
     The first external electrode  170 An and the second external electrode  170 Ap each typically have an external shape having a plurality of corner portions as seen in a plan view. As shown in  FIG. 10 , in this example, the external shape of each of the first external electrode  170 An and the second external electrode  170 Ap is rectangular with four corner portions as seen in a plan view. In the structure shown in  FIG. 10 , the external shape of the first external electrode  170 An is generally rectangular and includes four corner portions CA 1  through CA 4  as seen in a plan view. Similarly, in this example, the external shape of the second external electrode  170 Ap is generally rectangular and includes four corner portions CA 5  through CA 8  as seen in a plan view. 
     The first external electrode  170 An and the second external electrode  170 Ap are formed of, for example, Ti, Pt, Rh, Au, Ni, Ta, Zr or the like. The first external electrode  170 An and the second external electrode  170 Ap may each have a single-layer structure or a stack structure including a plurality of layers. For example, the first external electrode  170 An and the second external electrode  170 Ap may each be a metal layer having a stack structure including a Ti layer, a Pt layer and an Au layer stacked in this order. 
     As schematically shown in  FIG. 10 , in an embodiment according to the present disclosure, none of the plurality of extending portions Ep of the first region R 1  of the n-type semiconductor layer  120   n  is located at a position in the top surface of the n-type semiconductor layer  120   n  that overlaps any of the plurality of corner portions of the first external electrode  170 An as seen in a plan view. None of the plurality of extending portions Ep of the first region R 1  of the n-type semiconductor layer  120   n  is located at a position in the top surface of the n-type semiconductor layer  120   n  that overlaps any of the plurality of corner portions of the second external electrode  170 Ap as seen in a plan view. In the example shown in  FIG. 10 , the four extending portions Ep 1  through Ep 4  located in series along the second longer side LS 2  of the rectangular external shape of the n-type semiconductor layer  120   n  are located in areas other than an area overlapping any of the corner portions CA 1  through CA 4  of the first external electrode  170 An and other than an area overlapping any of the corner portions CA 5  through CA 8  of the second external electrode  170 Ap. 
     In this example, the first external electrode  170 An and the second external electrode  170 Ap each have recessed portions (notches) corresponding to the extending portions Ep of the first region R 1  as seen in a plan view. In the example shown in  FIG. 10 , the external shape of the first external electrode  170 An as seen in a plan view includes a recessed portion CV 1  as a first recessed portion at a position corresponding to the extending portion Ep 1  and also includes a recessed portion CV 2  as a second recessed portion at a position corresponding to the extending portion Ep 2 . Similarly, the external shape of the second external electrode  170 Ap as seen in a plan view includes a recessed portion CV 3  as a third recessed portion at a position corresponding to the extending portion Ep 3  and also includes a recessed portion CV 4  as a fourth recessed portion at a position corresponding to the extending portion Ep 4 . Namely, in this example, the first external electrode  170 An and the second external electrode  170 Ap each have a shape that does not overlap any of the plurality of extending portions Ep located in the first region R 1  of the n-type semiconductor layer  120   n  as seen in a plan view. The first external electrode  170 An and the second external electrode  170 Ap each have an external shape having recessed portions at the positions corresponding to the extending portions Ep as seen in a plan view. Since such a shape is adopted for the first external electrode  170 An and the second external electrode  170 Ap, an undesirable possibility may be decreased that a heat stress is concentrated in, or in the vicinity of, an area where the p-type semiconductor layer  120   p  of the semiconductor structure  112 A is selectively removed and the n-type semiconductor layer  120   n  is exposed and as a result, the insulating layers or the electrodes are peeled off. 
     The first external electrode  170 An and the second external electrode  170 Ap of the light emitting element  100 A are electrically and physically connected respectively with the first wiring portion  210  and the second wiring portion  220  by eutectic bonding. With such a structure, the light emitting element  100 A may be mounted on the support  200 . The base  230  of the support  200  is formed of, for example, bismaleimide-triazine resin (BT resin), and the first wiring portion  210  and the second wiring portion  220  of the support  200  are typically Cu lines. 
       FIG. 11  shows a light emitting device having another example of the external shape in an embodiment according to the present disclosure. The light emitting device  300 A shown in  FIG. 11  generally includes the light emitting element  100 , the light-transmissive member  182 , and a light-reflective member  190 A. As shown in  FIG. 11 , the light-reflective member  190 A is parallelepiped and is longer in the Y direction than in the X direction, like the light-reflective member  190  in the light emitting device  300  shown in  FIG. 1 . 
     Unlike the light emitting device  300  described above with reference to  FIG. 1 , the light emitting device  300 A shown in  FIG. 11  does not include the support  200  supporting the light emitting element  100 . It should be noted that the light emitting device  300 A includes a set of lines, more specifically, a first wiring portion  210 A and a second wiring portion  220 A located on a bottom surface  190   b  of the light-reflective member  190 . The bottom surface  190   b  is located on the side opposite to the top surface  300   a  of the light emitting device  300 . 
       FIG. 12  is schematic cross-sectional view taken along line XII-XII in  FIG. 11 . In other words,  FIG. 12  corresponds to  FIG. 2  referred to above. As shown in  FIG. 12 , the first wiring portion  210 A is connected with the first external electrode  170 An of the light emitting element  100 , and the second wiring portion  220 A is connected with the second external electrode  170 Ap of the light emitting element  100 . As in this example, the first wiring portion  210 A connected with the first external electrode  170 An of the light emitting element  100  and the second wiring portion  220 A connected with the second external electrode  170 Ap of the light emitting element  100  may be located on the bottom surface  190   b  located opposite to the top surface  300   a  of the light emitting device  300 A. In an embodiment according to the present disclosure, the base  230  supporting the first wiring portion and the second wiring portion is not absolutely necessary. 
     (Suppression of Occurrence of a Leak) 
     As described below by way of examples (i.e., Reference examples 1 through 4), the studies made by the present inventors have found the following. An external electrode provided to electrically and physically connect a light emitting element with a support such as a printed wiring board or the like may have an external shape including a corner portion as seen in a plan view. In such a case, when the external electrode is connected with a conducting line on the printed wiring board or the like (e.g., circuit trace) by eutectic bonding, a heat stress is likely to be concentrated on the corner portion of the external electrode. If a component that electrically connects an n-type semiconductor layer with an electrode located above the n-type semiconductor layer and inside a light emitting structure, for example, a through-hole provided in an insulating layer, overlaps the corner portion of the external electrode as seen in a plan view, a crack may be caused in the insulating layer due to the heat stress. When this occurs, a leak may occur between the external electrode and the electrode located inside the light emitting structure. Especially in the case in which a bonding member used for the eutectic bonding is formed of AuSn, a stronger bonding is realized than in the case in which AgSn, CuSn or the like is used. However, AuSn has a higher melting point than AgSn, CuSn or the like, and therefore, the heat stress caused in the external electrode is likely to be increased. In the case in which a conducting line on the printed wiring board connected with the light emitting element is formed of Cu, which has a relatively high thermal conductivity and a relatively large coefficient of thermal expansion among various metal materials, heat dissipation is easily provided with certainty but a larger heat stress is likely to be caused in the external electrode due to the difference in the coefficient of thermal expansion between the Cu conducting line and the light emitting element. 
     The present inventors have found that provision of a through-hole at a position not overlapping the corner portion of the external electrode suppresses the leak from being caused due to the heat stress, and may improve the reliability of the light emitting element. Hereinafter, this will be described with reference to the drawings. 
       FIG. 13  shows a light emitting element in a comparative example. The light emitting element  500  shown in  FIG. 13  includes a plurality of extending portions and a plurality of through-holes provided in an insulating layer. The extending portions and the through-holes are located at positions overlapping the corner portions of an external electrode. A main difference between the light emitting element  500  and the light emitting element  100 A shown in  FIG. 3  and the like is that the light emitting element  500  includes a first external electrode  570   n  and a second external electrode  570   p  instead of the first external electrode  170   n  and the second external electrode  170   p.    
       FIG. 13  is a schematic bottom see-through view of the light emitting element  500 , like  FIG. 3 . The first external electrode  570   n  and the second external electrode  570   p  are depicted as shaded regions for easier understanding. As shown in  FIG. 13 , in this comparative example, the first external electrode  570   n  has a generally rectangular external shape, and includes a recessed portion CV 5  in a left bottom corner portion in the paper sheet of  FIG. 13  among four corner portions of the rectangular external shape. The recessed portion CV 5  overlaps the extending portion Ep 2  as seen in a plan view. Similarly, the second external electrode  570   p  also has a generally rectangular external shape, and includes a recessed portion CV 6  in a right bottom corner portion in the paper sheet of  FIG. 13  among the four corner portions of the rectangular external shape. The recessed portion CV 6  overlaps the extending portion Ep 3  as seen in a plan view. 
       FIG. 14  is a schematic cross-sectional view taken along line XIV-XIV in  FIG. 13 . A cross-sectional view taken along line IV-IV in  FIG. 13  may be substantially the same as the cross-sectional view in  FIG. 4 . Thus, the cross-sectional view taken along line IV-IV in  FIG. 13  will not be shown, and the structure in this cross-sectional view will not be described. 
     In this comparative example, the extending portion Ep 2  is located substantially just below the recessed portion CV 5  of the first external electrode  570   n , and one of the first through-holes  141  of the first insulating layer  140  is also located substantially just below the recessed portion CV 5 . As schematically shown in  FIG. 14 , a part of the first internal electrode  150   n  is a via  150   nv , which fills the first through-hole  141  to electrically connect the first internal electrode  150   n  with the n-type semiconductor layer  120   n.    
     As schematically shown in  FIG. 14 , the first internal electrode  150   n  covers a lateral surface of the first insulating layer  140  in the vicinity of the first through-hole  141  and is connected with the n-type semiconductor layer  120   n . According to the studies made by the present inventors, when a heat stress caused by eutectic bonding is concentrated in, and in the vicinity of, an area of the n-type semiconductor layer  120   n  that is not covered with the active layer  120   a  or the p-type semiconductor layer  120   p , a crack may be caused in the first insulating layer  140 , specifically, for example, at a stepped portion of the first insulating layer  140 . If, for example, the crack is caused in the first insulating layer  140 , short-circuiting may occur between a p-side electrode and an n-side electrode (e.g., the light-reflective electrode or the n-side internal electrode) due to the migration of the material of the electrode located inside the light emitting structure. Namely, a leak may occur, and the reliability of the light emitting element  500  may be decreased. 
     By contrast, in this embodiment, the extending portions Ep, on which the first through-holes  141  of the first insulating layer  140  are provided, are located at positions not overlapping any of the corner portions CA 1  through CA 4  of the first external electrode  170 An or any of the corner portions CA 5  through CA 8  of the second external electrode  170 Ap. The heat stress is highly possibly concentrated on the corner portions CA 1  through CA 4  and the corner portions CA 5  through CA 8 . Such a structure provides an effect of suppressing a leak from being caused due to the short-circuiting between, for example, the light-reflective electrode  130  and the first internal electrode  150   n . A presumable reason for this is that the concentration of the heat stress in, or in the vicinity of, a conductive component that provides electrical connection to the n-type semiconductor layer  120   n  such as, for example, the via  150   vn , is avoided and therefore, generation of a crack in the first insulating layer  140  may be avoided. 
     As described above, in an embodiment according to the present disclosure, the occurrence of a leak in the light emitting element is suppressed and thus the reliability of the light emitting element can be improved. The first external electrode  170 An and the second external electrode  170 Ap are located in areas other than an area overlapping any of the plurality of extending portions Ep as seen in a plan view; or as shown in  FIG. 10 , the first external electrode  170 An and the second external electrode  170 Ap each have an external shape not overlapping any of the plurality of extending portions Ep as seen in a plan view. Since such a positional arrangement or such a shape is adopted for the first external electrode  170 An and the second external electrode  170 Ap, the occurrence of a leak is suppressed more advantageously. 
     (Relationship Between the Shape of the External Electrode and the Positional Arrangement of the Plurality of Extending Portions) 
     Hereinafter, the relationship between the shape of each of the first external electrode  170 An and the second external electrode  170 Ap and the positional arrangement of the plurality of extending portions Ep will be described in more detail. 
       FIG. 15  is provided to describe an example of relationship between the shape of each of the first external electrode  170 An and the second external electrode  170 Ap and the positional arrangement of the plurality of extending portions Ep. Like  FIG. 10 ,  FIG. 15  shows the semiconductor structure  112 A, the first external electrode  170 An and the second external electrode  170 Ap, among the components of the light emitting element  100 A. 
     In the structure shown in  FIG. 15 , the first external electrode  170 An and the second external electrode  170 Ap each have a generally rectangular external shape. In this example, the external shape of the first external electrode  170 An includes a set of shorter sides, more specifically, a first shorter side SS 1  and a second shorter side SS 2  facing each other. Similarly, in this example, the external shape of the second external electrode  170 Ap includes a set of shorter sides, more specifically, a third shorter side SS 3  and a fourth shorter side SS 4  facing each other. In this example, the first external electrode  170 An and the second external electrode  170 Ap each have a generally rectangular external shape as seen in a plan view. The shapes of the first external electrode  170 An and the second external electrode  170 Ap as seen in a plan view do not need to match each other. 
     In the example shown in  FIG. 15 , the first through fourth shorter sides SS 1  through SS 4  are all perpendicular to the second longer side LS 2  of the rectangular external shape of the n-type semiconductor layer  120   n . As shown in  FIG. 15 , the first shorter side SS 1  is located farther from the second external electrode  170 Ap than the second shorter side SS 2  is, and the third shorter side SS 3  is located closer to the first external electrode  170 An than the fourth shorter side SS 4  is. 
     In this example, the first region R 1  of the n-type semiconductor layer  120   n  includes the first through fourth extending portions Ep 1  through Ep 4 . As schematically shown in  FIG. 15 , a first imaginary line L 1  perpendicular to the second longer side LS 2  of the external shape of the n-type semiconductor layer  120   n  and passing through the center of the rectangular external shape of the first external electrode  170 An as seen in a plan view is assumed. The extending portion Ep 1  as the first extending portion is located between the first imaginary line L 1  and the first shorter side SS 1 . The extending portion Ep 2  as the second extending portion is located between the first imaginary line L 1  and the second shorter side SS 2 . Therefore, in this example, the first through-hole  141  provided on the extending portion Ep 1  and the recessed portion CV 1  of the first external electrode  170 An are also located between the first imaginary line L 1  and the first shorter side SS 1 . The first through-hole  141  provided on the extending portion Ep 2  and the recessed portion CV 2  of the first external electrode  170 An are also located between the first imaginary line L 1  and the second shorter side SS 2 . 
     Similarly, a second imaginary line L 2  perpendicular to the second longer side LS 2  and passing through the center of the rectangular external shape of the second external electrode  170 Ap as seen in a plan view is assumed. The extending portion Ep 3  as the third extending portion is located between the second imaginary line L 2  and the third shorter side SS 3 . The extending portion Ep 4  as the fourth extending portion is located between the second imaginary line L 2  and the fourth shorter side SS 4 . The first through-hole  141  provided on the extending portion Ep 3  and the recessed portion CV 3  of the second external electrode  170 Ap are also located between the second imaginary line L 2  and the third shorter side SS 3 . The first through-hole  141  provided on the extending portion Ep 4  and the recessed portion CV 4  of the second external electrode  170 Ap are also located between the second imaginary line L 2  and the fourth shorter side SS 4 . 
     In the structure shown in  FIG. 15 , a distance represented by two-headed arrow da 1  between the extending portion Ep 1  and the first imaginary line L 1  is shorter than a distance represented by two-headed arrow da 2  between the extending portion Ep 1  and the first shorter side SS 1 . Herein, the “distance between an extending portion and a imaginary line or a side” is a distance from the center of the extending portion to the imaginary line or the side measured along the second longer side LS 2 . In this example, as seen in a plan view, the extending portion Ep 1  is located farther from the first shorter side SS 1 , along which the corner portion CA 2  of the first external electrode  170 An is located, than from the first imaginary line L 1  passing through the center of the first external electrode  170 An. With such a structure, the influence exerted on the extending portion Ep 1  and the vicinity thereof by the heat stress caused in the corner portion CA 2  may be decreased. Similarly, in the example shown in  FIG. 15 , a distance represented by two-headed arrow da 3  between the extending portion Ep 2  and the first imaginary line L 1  is shorter than a distance represented by two-headed arrow da 4  between the extending portion Ep 2  and the second shorter side SS 2 . Namely, the extending portion Ep 2  is located farther from the second shorter side SS 2 , along which the corner portion CA 3  of the first external electrode  170 An is located, than from the first imaginary line L 1 . With such a structure, an effect of suppressing a leak from being caused by the heat stress in the corner portion CA 3  is expected. 
     In this example, a positional arrangement similar to that of the extending portions Ep 1  and Ep 2  is adopted for the extending portions Ep 3  and Ep 4 . This will be described more specifically. The second imaginary line L 2  perpendicular to the second longer side LS 2  and passing through the center of the rectangular external shape of the second external electrode  170 Ap as seen in a plan view is assumed. The extending portion Ep 3  is located between the second imaginary line L 2  and the third shorter side SS 3 . As schematically shown in  FIG. 15 , a distance represented by two-headed arrow db 1  between the extending portion Ep 3  and the second imaginary line L 2  is shorter than a distance represented by two-headed arrow db 2  between the extending portion Ep 3  and the third shorter side SS 3 . The extending portion Ep 3  is located farther from the third shorter side SS 3 , along which the corner portion CA 6  of the second external electrode  170 Ap is located, than from the second imaginary line L 2 . A distance represented by two-headed arrow db 3  between the extending portion Ep 4  and the second imaginary line L 2  is shorter than a distance represented by two-headed arrow db 4  between the extending portion Ep 4  and the fourth shorter side SS 4 . The extending portion Ep 4  is located farther from the fourth shorter side SS 4 , along which the corner portion CA 7  of the second external electrode  170 Ap is located, than from the second imaginary line L 2 . With such a structure, an effect of suppressing a leak from being caused in the extending portion Ep 3  or Ep 4  by the heat stress in the corner portion CA 6  or CA 7  is expected. 
     (Modification) 
       FIG. 16  shows another example of light emitting element in an embodiment according to the present disclosure.  FIG. 16  shows a light emitting element  100 B, which is another example of the light emitting element  100  described above with reference to  FIG. 1  and  FIG. 2 .  FIG. 16  is a schematic bottom see-through view of the light emitting element  100 B, like  FIG. 3 . A cross-sectional view taken along line IV-IV in  FIG. 16  and a cross-sectional view taken along line V-V in  FIG. 16  may be substantially the same as the cross-sectional views in  FIG. 4  and  FIG. 5 , respectively. Thus, the cross-sectional views taken along line IV-IV and line V-V in  FIG. 16  will not be shown, and the structures in these cross-sectional views will not be described. 
     The light emitting element  100 B shown in  FIG. 16  includes a first external electrode  170 Bn and a second external electrode  170 Bp instead of the first external electrode  170 An and the second external electrode  170 Ap included in the light emitting element  100 A described above with reference to  FIG. 3  and the like. In the structure shown in  FIG. 16 , the first external electrode  170 Bn has a generally rectangular external shape including a set of shorter sides, more specifically, a first shorter side SS 1  and a second shorter side SS 2  facing each other. Similarly, the second external electrode  170 Bp has a generally rectangular external shape including a set of shorter sides, more specifically, a third shorter side SS 3  and a fourth shorter side SS 4  facing each other. The first through fourth shorter sides SS 1  through SS 4  are all perpendicular to the second longer side LS 2  of the rectangular external shape of the n-type semiconductor layer  120   n.    
       FIG. 17A  schematically shows a semiconductor structure, the first external electrode  170 Bn and the second external electrode  170 Bp, among the components of the light emitting element  100 B shown in  FIG. 16 . The semiconductor structure  112 B shown in  FIG. 17A  includes the n-type semiconductor layer  120   n  including a first region R 1  and a second region R 2 , the active layer  120   a  (not shown in  FIG. 17A ) located on the second region R 2  of the n-type semiconductor layer  120   n , and the p-type semiconductor layer  120   p  located on the active layer  120   a . Like in the above-described examples, the first region R 1  of the n-type semiconductor layer  120   n  includes an outer peripheral region Pp located along an outer perimeter of the second region R 2  as seen in a plan view and a plurality of extending portions Ep extending into the second region R 2  from the outer peripheral region Pp. 
     In this example, the first region R 1  of the n-type semiconductor layer  120   n  includes three extending portions Ep 1  through Ep 3  located in series along the second longer side LS 2  of the n-type semiconductor layer  120   n .  FIG. 17A  shows areas that correspond to the extending portions Ep 1  through Ep 3  of the first region R 1  as shaded areas, like  FIG. 6 . Among the extending portions Ep 1  through Ep 3 , the extending portion Ep 3  is located between the first external electrode  170 Bn and the second external electrode  170 Bp as seen in a plan view. In the example shown in  FIG. 16  and  FIG. 17A , the p-type semiconductor layer  120   p  and the active layer  120   a  each have a smaller area removed than in the examples described above with reference to  FIG. 3  through  FIG. 15 . This is advantageous from the point of view of suppressing a decrease in the size of an area involved in light emission. 
     In the structure shown in  FIG. 17A , the extending portion Ep 1  is located on an imaginary line L 1  perpendicular to the second longer side LS 2  of the external shape of the n-type semiconductor layer  120   n  and passing through the center of the rectangular external shape of the first external electrode  170 Bn. The extending portion Ep 2  is located on an imaginary line L 2  perpendicular to the second longer side LS 2  and passing through the center of the rectangular external shape of the second external electrode  170 Bp. Since such a positional arrangement is adopted, the extending portion Ep 1  may be located far from the corner portions CA 2  and CA 3  of the first external electrode  170 Bn, and the extending portion Ep 2  may be located far from the corner portions CA 6  and CA 7  of the second external electrode  170 Bp. In this example, the extending portion Ep 3  is located on a third imaginary line L 3  perpendicular to the second longer side LS 2  and passing through the center of the second longer side LS 2 . 
     As schematically shown in  FIG. 17A , in this example, the rectangular external shape of the first external electrode  170 Bn includes a recessed portion CV 1  as the first recessed portion at a position corresponding to the extending portion Ep 1  as seen in a plan view. The rectangular external shape of the second external electrode  170 Bp includes a recessed portion CV 2  as the second recessed portion at a position corresponding to the extending portion Ep 2  as seen in a plan view. Namely, in this example also, the first external electrode  170 Bn and the second external electrode  170 Bp each have a shape that does not overlap any of the plurality of extending portions Ep 1  through Ep 3  as seen in a plan view. 
     Like in the examples described above with reference to  FIG. 3  through  FIG. 15 , in the example shown in  FIG. 16  and  FIG. 17A  also, the extending portion Ep, on which a conductive component electrically connecting the n-type semiconductor layer  120   n  and the first internal electrode  150   n  to each other may be provided, is located in an area other than areas overlapping the corner portions of the first external electrode  170 Bn and other than areas overlapping the corner portions of the second external electrode  170 Bp. Such a positional arrangement may suppress short-circuiting from occurring between, for example, the light-reflective electrode  130  and the first internal electrode  150   n  due to the heat stress caused in the first external electrode  170 Bn or the second external electrode  170 Bp. 
       FIG. 17B  shows still another example of light emitting element in an embodiment according to the present disclosure.  FIG. 17B  shows a light emitting element  100 C, which is still another example of the light emitting element  100  described above with reference to  FIG. 1  and  FIG. 2 .  FIG. 17B  is a schematic bottom see-through view of the light emitting element  100 C, like  FIG. 3  and  FIG. 16 . 
     The light emitting element  100 C shown in  FIG. 17B  includes a first external electrode  170 Cn and a second external electrode  170 Cp instead of the first external electrode  170 Bn and the second external electrode  170 Bp included in the light emitting element  100 B described above with reference to  FIG. 16 . The first external electrode  170 Cn and the second external electrode  170 Cp respectively have substantially the same structures as those of the first external electrode  170 Bn and the second external electrode  170 Bp except for the external shapes. In  FIG. 17B , the first external electrode  170 Cn and the second external electrode  170 Cp are hatched so that the shapes thereof are better understood. 
     In the structure shown in  FIG. 17B , a distance, in a longer direction (longitudinal direction) of the n-type semiconductor layer  120   n  having the rectangular external shape, between an outer perimeter of the light-reflective electrode  130  and an outer perimeter of the external electrode (the first external electrode  170 Cn or the second external electrode  170 Cp) is longer than a distance, in a shorter direction (transverse direction) of the n-type semiconductor layer  120  having the rectangular external shape, between the outer perimeter of the light-reflective electrode  130  and the outer perimeter of the external electrode. For example, the distance between the outer perimeter, along the shorter side of the n-type semiconductor layer  120   n , of the light-reflective electrode  130  and the outer perimeter, along the shorter side of the n-type semiconductor layer  120   n , of the second external electrode  170 Cp (in  FIG. 17B , the distance is schematically shown by two-headed arrow Lg) is longer than the distance between the outer perimeter, along the longer side of the n-type semiconductor layer  120   n , of the light-reflective electrode  130  and the outer perimeter, along the longer side of the n-type semiconductor layer  120   n , of the second external electrode  170 Cp (in  FIG. 17B , the distance is schematically shown by two-headed arrow Sg). Similarly, the distance between the outer perimeter, along the shorter side of the n-type semiconductor layer  120   n , of the light-reflective electrode  130  and the outer perimeter, along the shorter side of the n-type semiconductor layer  120   n , of the first external electrode  170 Cn may be longer than the distance between the outer perimeter, along the longer side of the n-type semiconductor layer  120   n , of the light-reflective electrode  130  and the outer perimeter, along the longer side of the n-type semiconductor layer  120   n , of the first external electrode  170 Cn. 
     A light emitting element having a rectangular external shape as seen in a plan view may possibly be warped, at an end thereof, in a −Z direction in the figures. In the case where a light emitting element warped in this manner is mounted on a member including a wiring (e.g., the support  200  described above) by the eutectic bonding, the wiring and the electrodes in the light emitting element are bonded to each other. As a result, a stress is applied to the end of the light emitting element in such a direction as to correct the warp. In this case, as the electrodes, in the light emitting elements, bonded with the wiring by eutectic bonding have a larger surface area size, a larger bonding strength is obtained but the load applied to the end of the light emitting element is larger. According to the studies made by the present inventors, this stress may be increased as being farther from the center of the light emitting element. Therefore, a crack may be generated in the light emitting element, especially, at a position close to the shorter side of the rectangular external shape thereof, by the stress caused by the eutectic bonding. 
     In the example shown in  FIG. 17B , the distance from the outer perimeter of the light-reflective electrode  130  to the outer perimeter of the external electrode is longer in the longer direction of the rectangular shape of the light emitting element than in the shorter direction of the light emitting element. Such a structure provides an effect of alleviating the stress applied, by the eutectic bonding, to a position close to the shorter side of the rectangular shape of the light emitting element, and therefore, decreases the possibility of the generation of the crack. The first external electrode  170 Cn may have a surface area size smaller than that of the first external electrode  170 Bn. Similarly, the second external electrode  170 Cp may have a surface area size smaller than that of the second external electrode  170 Bp. 
     In the example shown in  FIG. 17B , the distance between the outer perimeter, along the shorter side of the n-type semiconductor layer  120   n , of the light-reflective electrode  130  and the outer perimeter, along the shorter side of the n-type semiconductor layer  120   n , of the external electrode is in the range of, for example, 3% or higher and 7% or lower, preferably in the range of 4% or higher and 5% or lower, of the length of the light emitting element in the longer direction (X direction in  FIG. 17B ). The distance represented by the two-headed arrow Lg in  FIG. 17B  may be, for example, about 40 μm to about 50 μm. By contrast, the distance between the outer perimeter, along the longer side of the n-type semiconductor layer  120   n  (e.g., along the second longer side LS 2 ), of the light-reflective electrode  130  and the outer perimeter, along the longer side of the n-type semiconductor layer  120   n  (e.g., along the second longer side LS 2 ), of the external electrode is, for example, in the range of 10% or higher and 15% or lower, preferably in the range of 12% or higher and 15% or lower, of the length of the light emitting element in the shorter direction (Y direction in  FIG. 17B ). The distance represented by the two-headed arrow Sg in  FIG. 17B  may be, for example, about 20 μm to about 30 μm. The distance between the outer perimeter, along the second longer side LS 2 , of the light-reflective electrode  130  and the outer perimeter, along the second longer side LS 2 , of the external electrode may be equivalent to the distance between the outer perimeter, along the first longer side LS 1 , of the light-reflective electrode  130  and the outer perimeter, along the first longer side LS 1 , of the external electrode. 
     In general, a light emitting element is warped less along the shorter direction (X direction in  FIG. 17B ) than along the longer direction (Y direction in the figures). Therefore, even if the outer perimeter of the external electrode is located close to the outer perimeter of the light-reflective electrode  130  in the shorter direction, the light emitting element is not easily cracked. The outer perimeter of the external electrode may be located close to the outer perimeter of the light-reflective element  130  in the shorter direction of the light emitting element (X direction in  FIG. 17B ), so that the external electrode avoids having an excessively small surface area size, and thus the bonding strength is suppressed from being excessively decreased. 
     The distance between the outer perimeter of the light-reflective electrode  130  and the outer perimeter of the external electrode at the position of the extending portion Ep (extending portion Ep 1  or Ep 3 ) of the n-type semiconductor layer  120   n  (in  FIG. 17B , the distance is schematically represented by two-headed arrow Mg) may be shorter than the distance represented by the two-headed arrow Sg. The distance between the outer perimeter of the light-reflective electrode  130  and the outer perimeter of the external electrode at the position of the extending portion Ep may be, for example, about 10 μm to about 20 μm. As described above, the stress applied to the end of the light emitting element close to the longer side thereof tends to be smaller than the stress applied to the end of the light emitting element close to the shorter side thereof. Therefore, the outer perimeter of the external electrode may be located close to the outer perimeter of the light-reflective electrode  130  in the shorter direction (X direction in  FIG. 17B ) with less problem. As in this example, the distance between the outer perimeter of the light-reflective electrode  130  and the outer perimeter of the external electrode may be shorter at the position of, for example, the extending portion Ep, than at the other positions, so that the load applied to the end of the light emitting element by the stress on the light emitting element is suppressed from increasing while the surface area size of the external electrode avoids being excessively decreased. Namely, the bonding strength may be suppressed from being excessively decreased by a decrease in the surface area size of the external electrode. 
     EXAMPLES 
     The magnitude of a shear stress applied on an external electrode was evaluated by a simulation, and thus the relationship between the shape of the external electrode as seen in a plan view and the area on which the heat stress is likely to be concentrated was investigated. Hereinafter, this will be described. 
     Reference Example 1 
     As a shape of an external electrode as seen in a plan view, the shape of the first external electrode  170 An and the second external electrode  170 Ap shown in  FIG. 10  and the like each having two recessed portions corresponding to two extending portions was assumed. In the case in which a light emitting element is mounted on a support by eutectic bonding, the temperature is decreased during a reflow. At this point, a stress is caused in a surface of the semiconductor layer. This stress was calculated. The value obtained by the calculation is a shear stress in the X direction of an XZ plane. The drawings to be referred to hereinafter show the strength of the shear stress by the darkness/lightness of the color based on an absolute value of τ YX . τ YX  is one of components of stress tensor. In reference examples 1 through 4 described below, the calculation conditions are the same. In  FIG. 18  through  FIG. 21 , the same value of shear stress is shown with the same darkness/lightness. 
       FIG. 18  shows the results of calculation on a sample of reference example 1. In  FIG. 18 , dark areas represent areas with a large absolute value of shear stress. A relatively large heat stress is applied to these areas. It has been found based on the results shown in  FIG. 18  that in the case in which, for example, a rectangular shape is adopted as an external shape of the external electrode, it is highly possible that the stress is concentrated especially on the corner portions CA 1  through CA 8  in a step of bonding the light emitting element to the support  200  or the like. It has also been found that the heat stress on a side connecting two corner portions is relatively small. 
     Reference Example 2 
     As a shape of an external electrode as seen in a plan view, the shape of the first external electrode  170 Bn and the second external electrode  170 Bp shown in  FIG. 17A  and the like each having one recessed portion corresponding to one extending portion was assumed. The absolute values of shear stress τ YX  were calculated in substantially the same manner as for the sample in reference example 1. 
       FIG. 19  shows the results of calculation on a sample of reference example 2. Like in the case of the results shown in  FIG. 18 , it has been found based on the results shown in  FIG. 19  that it is highly possible that the stress is concentrated especially on the corner portions CA 1  through CA 8  of the external electrode. 
     Reference Example 3 
     As in the example described above with reference to  FIG. 13 , it was assumed to locate extending portions of the n-type semiconductor layer at positions overlapping the corner portions of a rectangular external electrode. The absolute values of shear stress τ YX  were calculated in substantially the same manner as for the sample in reference example 1. 
       FIG. 20  shows the results of calculation on a sample of reference example 3. It has been found based on the results shown in  FIG. 20  that the heat stress may be more concentrated on the extending portion Ep 2  overlapping the corner portion CA 3  of the rectangular external electrode and the vicinity thereof, and also on the extending portion Ep 3  overlapping the corner portion CA 6  of the rectangular external electrode and the vicinity thereof, than on the extending portions Ep 1  and Ep 4  located on a side of the rectangular external electrode. 
     Reference Example 4 
     A semiconductor structure including no extending portion in the n-type semiconductor layer was assumed. The absolute values of shear stress τ YX  were calculated in substantially the same manner as for the sample in reference example 1. 
       FIG. 21  shows the results of calculation on a sample of reference example 4. It has been found based on the results shown in  FIG. 21  that the heat stress is more likely to be concentrated at positions overlapping corner portions of the rectangular external electrode than at positions on a side of the rectangular external electrode. 
     From a comparison between the results shown in  FIG. 20  and  FIG. 21  and the results shown in  FIG. 18  and  FIG. 19 , it has been found that in the case in which the extending portions are located on areas other than areas overlapping the corner portions of the external electrode, the shear stress on the extending portions and the vicinity thereof may be decreased, and thus the concentration of the heat stress on the extending portions and the vicinity thereof is avoided, so that a crack or the like is suppressed from being caused in the insulating layer at the positions corresponding to the extending portions. In an embodiment according to the present disclosure, the extending portions Ep are located in such areas that do not easily cause a leak. Therefore, the leak may be suppressed from being caused inside the light emitting structure. 
     A light emitting element and a light emitting device in an embodiment according to the present disclosure are useful for light sources for various lighting devices, on-board light sources, light sources for displays, and the like. A light emitting element and a light emitting device in an embodiment according to the present disclosure are especially advantageously usable for backlight units for liquid crystal display devices. 
     While exemplary embodiments of the present invention have been described, it will be apparent to those skilled in the art that the disclosed invention may be modified in numerous ways and may assume many embodiments other than those specifically described above. Accordingly, it is intended by the appended claims to cover all modifications of the invention that fall within the true spirit and scope of the invention.