Patent Publication Number: US-9893237-B2

Title: Light emitting element

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/869,667, filed on Sep. 29, 2015, now U.S. Pat. No. 9,553,237, which claims priority to Japanese Patent Application No. 2014-201511, filed on Sep. 30, 2014, the entire disclosures of which are hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a light emitting element that includes a semiconductor layer, an upper electrode disposed on an upper surface of the semiconductor layer, and a lower electrode disposed on a lower surface of the semiconductor layer. 
     2. Background Art 
     There have been light emitting elements in which a “pad” is disposed on at each of two adjacent corners of an approximately rectangular upper surface of a semiconductor layer, and a “fine wire electrode” is disposed in a grid shape extending from the pad electrode, as described in JP2013-197197A. 
     However, with such a conventional structure, uneven emission tends to occur. Generally, a higher current density occurs in a region close to the pad to which the wire for supplying current from an external power source is connected, and even with a fine wire electrode, the current density decreases as the distance from the pad increases. As a result, stronger emission occurs near the pad, which tends to result in uneven brightness in the emission of the light emitting element as a whole. 
     Certain embodiments of the present invention have been devised in view of such circumstances, and an object thereof is to provide a light emitting element that can emit light more uniformly. 
     According to certain embodiments of the present invention, a light emitting element includes a semiconductor layer, an upper electrode disposed on an upper surface of the semiconductor layer, and a lower electrode disposed on a lower surface of the semiconductor layer. The light emitting element has an approximately rectangular shape in a plan view. In the plan view, the upper electrode includes a first extending portion extending in an approximately rectangular shape with four sides, along outer periphery of the semiconductor layer, a first pad portion connected to a first side among the four sides of the first extending portion, a second pad portion connected to a second side which is opposite to the first side, and a second extending portion and a third extending portion each disposed in a region surrounded by the first extending portion and respectively connecting the first pad portion and the second pad portion. With respect to a first straight line connecting the first pad portion and the second pad portion with a shortest distance, the second extending portion is disposed in a region closer to the third side of the four sides, and the third extending portion is disposed in a region closer to the forth side which is opposite to the third side. On a second straight line perpendicularly bisecting the first straight line, a distance between the second extending portion and the third extending portion is equal to or greater than a shortest distance between the first extending portion and the second extending portion, and equal to or greater than a shortest distance between the first extending portion and the third extending portion. 
     According to certain embodiments of the present invention, it is possible to obtain a light emitting element in which uneven current density on the upper surface of the semiconductor layer can be reduced, which allows for more uniform emission. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic plan view, seen from an upper electrode side, of a light emitting element according to a first embodiment. 
         FIG. 2  is a schematic cross sectional view taken along line L 1  of  FIG. 1 . 
         FIG. 3  is a schematic cross sectional view taken along line L 2  of  FIG. 1 . 
         FIG. 4  is a diagram illustrating an emission intensity distribution of the light emitting element according to the first embodiment. 
         FIG. 5  is a schematic plan view, seen from an upper electrode side, of a light emitting element according to a second embodiment. 
         FIG. 6  is a schematic plan view, seen from an upper electrode side, of a light emitting element according to a third embodiment. 
         FIG. 7  is a diagram illustrating an emission intensity distribution of the light emitting element according to Comparative Example 1. 
         FIG. 8  is a diagram illustrating an emission intensity distribution of the light emitting element according to Comparative Example 2. 
     
    
    
     DETAILED DESCRIPTION 
     A light emitting element according to embodiments the present invention will be described below with reference to the accompanying drawings. The embodiments shown below are intended as illustrative to give concrete form to technical ideas of the present invention, and the scope of the invention is not limited to those described below. Further, in the description below, the same designations or the same reference numerals denote the same or like members and duplicative descriptions will be appropriately omitted. 
     First Embodiment 
       FIG. 1  is a schematic plan view, seen from an upper electrode side, of a light emitting element  100  according to a first embodiment.  FIG. 2  is a schematic cross sectional view taken along line L 1  of  FIG. 1A , and  FIG. 3  is a schematic cross sectional view taken along line L 2  of  FIG. 1 .  FIG. 4  is a diagram illustrating an emission intensity distribution of the light emitting element  100  according to the first embodiment, at an injection current of 500 mA. 
     As shown in  FIGS. 1 to 4 , the light emitting element  100  according to the first embodiment includes a semiconductor layer  10 , an upper electrode disposed on an upper surface  12  of the semiconductor layer  10 , and a lower electrode  50  disposed on a lower surface of the semiconductor layer  10 , and has an approximately rectangular shape in a plan view. In a plan view, the upper electrode includes a first extending portion  20  extending in an approximately rectangular shape with four sides along an outer periphery of the semiconductor layer  10 , a first pad portion  26  connected to a first side among the four sides of the first extending portion  20 , a second pad portion  28  connected to a second side  20   b  which is opposite to the first side  20   a , and a second extending portion  22  and a third extending portion  24 , each disposed in a region surrounded by the first extending portion  20  and respectively connecting the first pad portion  26  and the second pad portion  28 . With respect to a first straight line L 1  connecting the first pad portion  26  and the second pad portion  28  with a shortest distance, the second extending portion  22  is disposed in a region closer to the third side  20   c  of the four sides, and the third extending portion  24  is disposed in a region closer to the forth side  20   d  opposite to the third side  20   c . On a second straight line L 2  perpendicularly bisecting the first straight line L 1 , a distance X 2  between the second extending portion  22  and the third extending portion  24  is equal or greater than a shortest distance X 1  between the first extending portion  20  and the second extending portion  22 , and equal or greater than a shortest distance X 3  between the first extending portion  20  and the third extending portion  24 . 
     With this arrangement, uneven current density on the upper surface  12  of the semiconductor layer  10  can be reduced and more uniform emission can be obtained. 
     Generally, an electrically conductive member such as a wire is connected to the pad portion to inject current to the light emitting element. As a result, a higher current density occurs in a region close to the pad portion and the current density decreases as the distance from the pad portion increases. In order to compensate for uneven current density, an extending portion extending from the pad portion may be provided to diffuse the electric current in a wider region. However, even when such an extending portion is provided, the current density decreases as the distance from the pad portion increases. Thus, uniform emission of the light emitting element as a whole has been difficult to obtain. 
     Accordingly, in the light emitting element  100 , among the four sides of the first extending portion  20  having an approximately rectangular shape, the first pad portion  26  is disposed connected to the first side  20   a  and the second pad portion  28  is disposed connected to the second side  20   b  opposite the first side  20   a . Thus, excessive distribution of current density in a region closer to one of opposite sides of the first extending portion  20  can be reduced. Further, a second extending portion and a third extending portion are respectively disposed in a region surrounded by the first extending portion, so as to connect the first pad portion and the second pad portion respectively. This arrangement allows for an increase in the amount of electric current flows into the second extending portion  22  and the third extending portion  24  which are closer to each pad portion  26  and  28  than to the first extending portion  20 . In addition, with respect to the first straight line L 1  connecting the first pad portion  26  and the second pad portion in a shortest distance, the second extending portion  22  is arranged in a region closer to the third side  20   c , and the third extending portion  24  is arranged in a region closer to the fourth side  20   d  which is opposite to the third side. According to this configuration, a center portion C which is spaced apart from the first pad portion  26  and the second pad portion  28  and has a low electric current density can be surrounded by the second extending portion  22  and the third extending portion  24 , so that the electric current can be concentrated from the high current density portions around the pad electrodes  26  and  28 . Further, on a second straight line L 2  perpendicularly bisecting the first straight line L 1 , a distance X 2  between the second extending portion  22  and the third extending portion  24  is equal to or greater than a shortest distance X 1  between the first extending portion  20  and the second extending portion  22 , and equal to or greater than a shortest distance X 3  between the first extending portion  20  and the third extending portion  24 . With this configuration, excessively high electrical density in a region surrounded by the second extending portion  22  and the third extending portion  24  can be prevented compared to a region between the third side  20   c  of the first extending portion  20  and the second extending portion  22  ( 22   c ), and the region between the fourth side  22   d  of the first extending portion  20  and the third extending portion  24  ( 24   c ). Accordingly, uneven distribution of current density in the upper surface  12  of the semiconductor layer  10  can be reduced and as shown in  FIG. 4 , more uniform light emission becomes possible to obtain. In the specification, the term “center portion C” refers to an intersection point of two straight lines which are crossing each other and equally or approximately equally dividing the upper surface  12  of the semiconductor layer  10  in four areas. For example, as shown in  FIG. 1 , in the case where the upper surface  12  of the semiconductor layer  10  has a square shape, the intersection point of two diagonal lines can serve as the “center portion C”. 
     The main components of the light emitting element  100  will be described below. 
     Semiconductor Layer  10   
     The materials and/or the structure of the semiconductor layer  10  are not specifically limited and can be selected from various appropriate materials and structures. In the first embodiment, a structure in which an n-type semiconductor layer  10   a , an active layer  10   b , a p-type semiconductor layer  10   c  are stacked in this order is employed; nitride semiconductors such as In X Al Y Ga 1-X-Y N (0=&lt;X&lt;1, 0=&lt;Y&lt;1, 0=&lt;X+Y&lt;1) are used as the material of each layer. The nitride semiconductors have higher internal resistance compared to that of other materials such as GaAs, so that efficient current spreading is difficult to obtain. Accordingly, an especially effective result can be expected in the case of forming the semiconductor layer with nitride semiconductors in the first embodiment. 
     In the first embodiment, the n-type semiconductor layer  10   a  is referred to as the upper surface  12  and the p-type semiconductor layer  10   c  is referred to as the lower surface. In the light emitting element  100 , the upper surface  12  serves as the light extracting surface, and the lower surface is electrically connected to a support member  30  or the like, which will be described below. The upper surface  12  preferably has a rectangular shape. Generally, individual light emitting elements are singulated from a wafer, so that in view of manufacturing yield, the upper surface  12  preferably has a square shape or an approximately square shape. 
     In the first embodiment, the upper surface  12  has a square shape with a side of about 1.0 mm, but the size of the upper surface  12  can be appropriately selected. In the case of the upper surface  12  having a square shape (or an approximately square shape), a side may be 0.5 mm or greater, preferably 0.8 mm or greater. This is because with a small planar dimension of the upper surface  12 , the electric current density between the first pad portion  26  and the second pad portion  28  will be excessively high, which may be undesirable. The upper limit for a side is not specifically limited, but in order not to have excessively low electric current density around the center portion C, a side may be 2.0 mm or less, preferably 1.5 mm or less. 
     Upper Electrode  20 ,  22 ,  24 ,  26 ,  28   
     The upper electrode is provided on the upper surface  12  of the semiconductor layer  10 , and at least includes the first pad portion  26 , the second pad portion  28 , the first extending portion  20 , the second extending portion, and the third extending portion  24 . More specifically, in a plan view of the light emitting element  100  seen from an upper surface  12  side, of the four sides of the rectangular shape of the outer periphery of the semiconductor layer  10 , the first pad portion  26  is disposed near one of the four sides and the second pad portion is disposed near the side which is opposite to the one of the four sides. The first pad portion  26  and the second pad portion  28  are the portions to which electric current is supplied from outside via conductive members such as wires. 
     The first pad portion  26  and the second pad portion  28  are connected to the first extending portion  20  which extends in an approximately rectangular shape along the outer periphery of the semiconductor layer  10 . More specifically, in the region surrounded by the first extending portion  20 , the first pad portion  26  is connected to the first side  20   a  among the four sides of the first extending portion  10 , and the second pad portion  28  is connected to the second side  20   b  that is opposite to the first side  20   a . As described above, the first pad portion  26  and the second pad portion  28  are connected in the regions surrounded by the first extending portion  20 , that is, connected to inner sides than the first extending portion  20 , so that the region surrounded by the first extending portion  20  can be increased. Thus, this configuration is preferable, allowing for a larger light emitting surface area of the light emitting element  100 . The first pad portion  26  and the second pad portion  28  are respectively arranged on a third straight line L 3  passing through the intersection point of the diagonal lines of the first extending portion  20 . With this arrangement, the pad portions  26  and  28  are arranged substantially point symmetrical to the center portion C, so that uneven distribution of electric current density in the region surrounded by the first extending portion  20  can be reduced. Further, in this configuration, the first pad portion  26  and the second pad portion  28  are arranged such that the straight line L 1  connecting the first pad portion  26  and the second pad portion  28  in a shortest distance is approximately in parallel to the third side  20   c  and the fourth side  20   d , which are, among the four sides of the first extending portion  20 , not provided with the pad portion  26  or  28 . In other words, the first straight line L 1  and the third straight line L 3  are overlapped with each other. The first pad portion  26  and the second pad portion  28  have the same shortest distance from the third side  20   c  and the fourth side  20   d , so that the electric current density can be prevented from being higher in a region closer to the third side  20   c  or the fourth side  20   d.    
     The second extending portion  22  and the third extending portion  24  are disposed in a region surrounded by the first extending portion  20  so as to be spaced apart from each other and connected to both the first pad portion  26  and the second pad portion  28  at positions spaced apart from each other. With this configuration, the second extending portion  22  and the third extending portion  24  are spaced apart from each other and also connected to the first pad portion  26  and the second pad portion  28  respectively. Thus, a narrow region surrounded by the second extending portion and the third extending portion  24  at the connecting portions to the pad portions  26  and  28  (the corner portions formed by  22   a  and  24   a ,  22   b  and  24   b ) can be eliminated, which allows for suppressing the electric current density near the pad portions  26  and  28  from being excessively high. Particularly, it is preferable that the first extending portion  20  and the second extending portion  22  ( 22   a ,  22   b ) are connected to the first pad portion  26  and the second pad portion  28  respectively at equal intervals from adjacent extending portions, more specifically, at intervals of 60 degrees. With this configuration, uneven distribution of electric current density near the pad portions  26  and  28  can be further decreased. 
     The second extending portion  22  and the third extending portion  24  are disposed at opposite sides with respect to the first straight line L 1  (a region closer to the third side  20   c  and a region closer to the fourth side  20   d  of the first extending portion  20 ), respectively, in approximately trapezoidal shapes at each side of the first straight line L 1  in a plan view (i.e., with a base of the trapezoids being the first straight line L 1 , and the remaining sides of the trapezoids being the second extending portion  22  and the third extending portion  24 , respectively). This allows for surrounding a wide area including the center portion C which is spaced apart from the pad portions  26  and  28  and the electric current density tends to decrease. More specifically, the second extending portion  22  is disposed closer to the third side  20   c  among the four sides of the first extending portion  20  with respect to the first straight line L 1 . That is, the second extending portion  22  has extending portions  22   a ,  22   b  extending from outer edges of the first pad portion  26  and the second pad portion  28 , respectively, that are in the region closer to the third side  20   c , in a straight line shape and at an angle so that the extending portions  22   a  and  22   b  are approaching each other and connected to respective ends of the extending portion  22   c  which is approximately parallel to the third side  20   c . As described above, the second extending portion  22  includes a portion approximately in parallel to the third side  20   c . More specifically, the approximately in parallel portion  22   c  of the second extending portion  22  with a length of a half or greater than the length of the third side  20   c  is preferable, in which case more uniform electric current density distribution can be obtained between the first extending portion  20  and the second extending portion  22 . Meanwhile, the third extending portion  24  is disposed closer to the fourth side  20   d  which is closer to the third side  20   c . More specifically, the third extending portion  24  has extending portions  24   a ,  24   b  extending from outer edges of the first pad portion  26  and the second pad portion  28 , respectively, that are in the region closer to the fourth side  20   d , in a straight line shape and at an angle so that the extending portions  24   a  and  24   b  are approaching each other and connected to respective ends of the extending portion  24   c  which is approximately in parallel to the fourth side  20   d . As described above, the third extending portion  24  includes a portion approximately in parallel to the fourth side  20   d . More specifically, the approximately in parallel portion  24   c  of the third extending portion  24  with a length of a half or greater than the length of the fourth side  20   d  is preferable, in which more uniform electric current density distribution can be obtained between the first extending portion  20  and the third extending portion  24 . 
     In the first embodiment, on the second straight line L 2  perpendicularly bisecting the first straight line L 1 , a distance X 2  between the second extending portion  22  and the third extending portion  24  is equal to or greater than a shortest distance X 1  between the first extending portion  20  and the second extending portion  22 , and equal to or greater than a shortest distance X 3  between the first extending portion  20  and the third extending portion  24 . With this configuration, uneven distribution of electric current density in a region between the second extending portion  22  and the third extending portion  24  along the second straight line L 2 . 
     On the second straight line L 2 , the shortest distance X 1  between the first extending portion  20  and the second extending portion  24  and the shortest distance X 3  between the first extending portion  20  and the third extending portion  24  are preferably the same or the same. With this configuration, the electrical density in a region surrounded by the third side  20   c  of the first extending portion  20  and the second extending portion  22  ( 22   c ) and a region between the fourth side  20   d  of the first extending portion  20  and the third extending portion  24  ( 24   c ) can be made substantially uniform. Further, it is preferable that (i) the ratio of the shortest distance X 1  between the first extending portion  20  and the second extending portion  22 , the distance between the second extending portion  22  and the third extending portion  23 , and the shortest distance between the first extending portion  20  and the third extending portion  24  on the straight line L 2  and (ii) the ratio of the shortest distance Y 1  between the first extending portion  20  and the second extending portion  22 , the distance between the second extending portion  22  and the third extending portion  23 , and the shortest distance between the first extending portion  20  and the third extending portion  24  on the diagonal line of the first extending portion  20 , are the same. With this configuration, the state of spreading the electric current in the direction in the diagonal direction of the first extending portion  20  can be made similar to the state of spreading the electric current in the direction along the second straight line L 2 . Thus, concentration of the electric current in the direction along the second straight line L 2  can be reduced and excessive reduction in the current electric current density in the vicinity of the corner portions of the first extending portion  20  can be reduced. The term “same” used in the specification is not limited to the case where the extending portions are arranged at precisely the same distance or at precisely the same rate. For example, a difference within ±10%, preferably within ±5%, more preferably within ±2%, may be regarded as arranged at a substantially the same distance or ratio and referred to as “the same”. 
     The structure and the material of the upper electrode is not specifically limited and can be selected from various appropriate structures and the materials. In the first embodiment, the upper electrode has a stacked-layer structure of Ti/Pt/Au (Ti, Pt, Au are stacked in this order from the semiconductor layer side). The first pad electrode portion  26  and the second pad electrode portion  28  have an appropriate circular shape with a diameter of about 100 μm. The sizes of the pad portions  26 ,  28  can be determined according to the amount of the electric current supplied to the light emitting element  100  and the size of the upper surface  12  of the semiconductor layer  10 . Also, the widths of the first extending portion  20 , the second extending portion  22 , and the third extending portion  24  are about 15 μm, which can be adjusted according to the amount of injecting current or the like. The thicknesses of the first extending portion  20 , the second extending portion  22 , and the third extending portion  24  are also not to be limited, but for example, in view of electrically conducting property, about 1 μm to about 5 μm is preferable and about 1 μm to about 3 μm is more preferable. 
     Lower Electrode  50   
     The lower electrode  50  is an electrode disposed on a lower surface of the semiconductor layer  10 . The lower electrode  50  is preferably disposed at a position so as not to overlap the upper electrode when seen through the upper surface  12  side of the semiconductor layer  10 . This is because as described above, shifting the positions of the upper electrode and the lower electrode  50  so as not to overlap each other allows for the electric current separately flowing in the semiconductor layer  10 , which can further reduce the uneven distribution of electric current density. Accordingly, an insulating film  60  such as SiO 2  is preferably provided in a region on the lower surface of the semiconductor layer  10  where the lower electrode  50  is not provided. This is because the bonding layer  70  which will be described below can be prevented from being connected to the lower surface of the semiconductor layer  10  at The support member is not limited and a known support member can be used. For example, in the first embodiment, the lower electrode  50  has a stacked-layer structure of Ag/Ni/Ti/Pt, in this order from the semiconductor layer  10  side. 
     Supporting Member  30   
     The supporting member  30  is not an essential component, but the light emitting element  100  includes the supporting member  30  to support the semiconductor layer  10 , and the supporting member  30  is electrically connected to the lower electrode  50  through the bonding layer  70  which will be described below. The materials and/or the structure of the supporting member  30  are not specifically limited and can be selected from various appropriate materials and structures. For example, in the first embodiment, Si is used as the material of the supporting member  30 , and in view of bonding property at the time of mounting the light emitting element  100 , a metal layer  80  which contains Au or the like is preferably provided on the entire lower surface of the supporting member  30 . 
     Bonding Layer  70   
     The bonding layer  70  is an electrically conductive member for bonding the supporting member  30  to the lower electrode  50  and the insulating film  60 . The materials and/or the structure of the bonding layer  70  are not specifically limited and can be selected from various appropriate materials and structures. For example, in the first embodiment, the bonding layer  70  has a stacked-layer structure of Ti/Pt/Au/Pt/Ti, in this order from the semiconductor layer  10  side. 
     Protective Film  40   
     The protective film  40  is a member for protecting the semiconductor layer  10  from physical damages caused by short circuit or by adhesion of dust or the like. The protective film  40  defines openings in conformity to the upper surfaces of the pad portions  26 ,  28  for providing regions for connecting wires or the like, and is disposed to cover the upper surface  12  and the side surfaces of the semiconductor layer  10 . The materials and/or the structure of the protecting film  40  are not specifically limited and can be selected from various appropriate materials and structures, and for example, SiO 2  is used in the present embodiment. 
     Second Embodiment 
       FIG. 5  is a schematic plan view, seen from an upper electrode side, of a light emitting element  200  according to a second embodiment. Next, the configurations different from those in the first embodiment will be described. 
     The light emitting element  200  according to the second embodiment differs from the light emitting element  100  in that the second extending portion  22  and the third extending portion  24  are arranged at opposite side of the first straight line L 1  (in the region closer to the third side  20   c  and the region adjacent to the fourth side  20   d  of the first extending portion  20 , respectively), each in a curved shape. 
     Accordingly, the area of the second extending portion  22  and the third extending portion  24  on the area of the upper surface  12  of the semiconductor layer  10  can be reduced and thus the light extraction efficiency can be enhanced. Further, bending portions can be eliminated from the second extending portion  22  and the third extending portion  24 , so that the distribution of electric current density near the second extending portion  22  and the third extending portion  24  can be made more uniform. 
     Third Embodiment 
       FIG. 6  is a schematic plan view, seen from an upper electrode side, of a light emitting element according to a third embodiment. Next, a light emitting device according to the second embodiment will be described. 
     The light emitting element  300  according to the third embodiment differs from the light emitting element  100  in that the first straight line L 1  connecting the first pad portion  26  and the second pad portion  28  in a shortest distance is arranged passing through the intersection point of the diagonal lines of the first extending portion  20  and at an angle to the third side  20   c  and the fourth side  20   d  which are among the four sides of the first extending portion  20  and are not provided with the pad portion  26  or  28 . The second extending portion  22  and the third extending portion  24  each connecting the pad portions  26  and  28  are arranged symmetrically with respect to the inclined first straight line L 1 . 
     This configuration allows for a longer distance between the pad portions  26  and  28 , which can increase the region surrounded by the first extending portion  20 , so that the region with a low electric current density can be reduced. 
     EXAMPLES 
     Effects of the light emitting element according to certain embodiments of the present invention will be described below with reference to  FIG. 4  (Example 1),  FIG. 7  (Comparative Example 1), and  FIG. 8  (Comparative Example 2), which have different arrangements of the upper electrodes.  FIG. 4 ,  FIG. 7 , and  FIG. 8  show the light emission intensity measured from the upper surface (the light extracting surface) side of the semiconductor layer at an injection current of 500 mA. 
     Example 1 
     The light emitting element according to Example 1 has an electrode shape similar to that of the light emitting element  100  according to the first embodiment, and as shown in  FIG. 4 , the deviation in the distribution of the light emission intensity within the light extracting surface is improved compared to that in Comparative Example 1 ( FIG. 7 ) and Comparative Example 2 ( FIG. 8 ). In this case shown in  FIG. 4 , the forward voltage (Vf) is 3.70V, the optical output (Po) is 586 mW, and the luminous efficiency (WPE) is 31.7%. 
     Comparative Example 1 
     The light emitting element according to Comparative Example 1 includes the upper electrode having an extending portion with a rectangular ring shape extending in an approximately rectangular shape along the outer periphery of the semiconductor layer and two linear extending portions that divide the region surrounded by the rectangular ring shape in three equal parts. Further, two pad portions are respectively disposed at two intersections of one of four sides of the rectangular ring shape with the two linear extending portions. 
     As shown in  FIG. 7 , the light emission intensity is higher in the regions at the side where the pad portions are provided and lower in other regions, indicating occurrence of deviation in the distribution of the light emission intensity within the light extracting surface. In this case shown in  FIG. 7 , the forward voltage (Vf) is 3.74V, the optical output (Po) is 579 mW, and the luminous efficiency (WPE) is 31.0%. 
     Comparative Example 2 
     The light emitting element according to Comparative Example 2 differs from that of Comparative Example 1 in that the pad portions are arranged at two corners at the same side of the rectangular ring shape, which is an approximately the shape of the electrode of conventional light emitting elements (see JP 2013-197197 A). 
     As shown in  FIG. 8 , the light emission intensity is higher in the regions at the side where the pad portions are provided and lower in other regions, indicating occurrence of deviation in the distribution of the light emission intensity within the light extracting surface. In this case shown in  FIG. 8 , the forward voltage (Vf) is 3.74V, the optical output (Po) is 582 mW, and the luminous efficiency (WPE) is 31.1%. 
     The forward voltages (Vf), the optical outputs (Po), and the luminous efficiencies (WPE) of Example 1, Comparative Example 1, and Comparative Example 2 are shown in Table 1 for the ease of comparison. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Vf (V) 
                 Po (mW) 
                 WPE (%) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 Example 1 
                 3.70 
                 586 
                 31.7 
               
               
                   
                 Comparative Example 1 
                 3.74 
                 579 
                 31.0 
               
               
                   
                 Comparative Example 2 
                 3.74 
                 582 
                 31.1 
               
               
                   
                   
               
            
           
         
       
     
     As shown in Table 1, with respect to Comparative Example 1, Example 1 shows a 0.04 V lower Vf value, a 7 mW higher Po value, and a 0.7% higher WPE value. Further, with respect to Comparative Example 2, Example 1 shows a 0.4 V lower Vf value, a 4 mW higher Po value, and a 0.6% higher WPE value. Thus, any values obtained in Example 1 are higher than that of Comparative Example 1 and Comparative Example 2. 
     The light emitting elements according to embodiments of the present invention can be used, in addition to for general lighting, for various light sources for backlights of liquid crystals, headlights for vehicles, signals, large-scale displays, exposure devices, or the like. It is to be understood that although the present invention has been described with regard to preferred embodiments thereof, various other embodiments and variants may occur to those skilled in the art, which are within the scope and spirit of the invention, and such other embodiments and variants are intended to be covered by the following claims.