Patent Publication Number: US-2023163244-A1

Title: Light emitting diode device and light emitting apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Chinese Invention Patent Application No. 202111395331.6, filed on Nov. 23, 2021. The entire content of the Chinese patent application is incorporated herein by reference. 
     FIELD 
     The disclosure relates to a semiconductor device, and more particularly to a light emitting diode device and a light emitting apparatus including the same. 
     BACKGROUND 
     Light emitting diodes (LEDs) are usually made of semiconductor materials such as gallium nitride (GaN), gallium arsenide (GaAs), gallium phosphide (GaP), gallium arsenide phosphide (GaAsP), etc. An LED includes a P-N junction having a light emitting property. By applying a forward bias to the LED, electrons flow from an N region to a P region of the LED while holes flow from the P region to the N region, then charge carriers recombine at the P-N junction to emit light. The LEDs are considered to be one of the light sources having the most potential as they offer advantages such as high luminous intensity, high efficiency, small size and long lifespan. The LEDs are widely applied in various fields in daily life, for example, lighting, signal display, backlight source, vehicle lamp and big screen display. A trend to develop an LED device with increased brightness and light emitting efficiency has emerged in recent years to meet the market&#39;s various demands of applications. 
     In the current LED device, a high concentration of charge carriers may easily be accumulated at connected regions between metal pad(s) and extending electrode(s) (e.g., finger electrode), causing current crowding. In particular, as the LED device ages, these connected regions (i.e., where current crowding occurs) may face a high risk of burnout, so performance of the LED device may be reduced and the LED device may even be destroyed. 
     Therefore, optimizing the configuration of the LED device having the extended electrode(s) so as to reduce current crowding becomes an issue awaiting to be resolved. 
     SUMMARY 
     Therefore, an object of the disclosure is to provide a light emitting diode (LED) device and a light emitting apparatus that can alleviate at least one of the drawbacks of the prior art. 
     According to a first aspect of the disclosure, the LED device includes an epitaxial layered structure, a first electrode and a second electrode. The epitaxial layered structure includes a first semiconductor layer, a light emitting layer and a second semiconductor layer sequentially disposed in such an order. The first electrode is disposed on the epitaxial layered structure and is electrically connected to the first semiconductor layer. The second electrode is disposed on the epitaxial layered structure, is electrically connected to the second semiconductor layer, and includes a body portion and at least one extending portion that is connected to the body portion and that extends in a direction away from the body portion. The extending portion includes at least one curved section. A projection of the curved section on the epitaxial layered structure includes a first curved side and a second curved side that are opposite to each other and that are curved in an identical direction. The first curved side has a first imaginary center of curvature and a first radius of curvature. The second curved side has a second imaginary center of curvature, and a second radius of curvature that is larger than the first radius of curvature. A distance between the first imaginary center of curvature and the second imaginary center of curvature is equal to or smaller than 5 μm. 
     According to a second aspect of the disclosure, the light emitting apparatus includes the aforementioned LED device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiments with reference to the accompanying drawings. It is noted that various features may not be drawn to scale. 
         FIG.  1    is a schematic top view illustrating a first embodiment of a light emitting diode (LED) device according to the disclosure. 
         FIG.  2    is a schematic sectional view illustrating the first embodiment of the LED device. 
         FIG.  3    is an enlarged view illustrating a second electrode of the first embodiment of the LED device. 
         FIG.  4    is an enlarged view of a circular region B of  FIG.  3   . 
         FIGS.  5  to  8    are schematic top views illustrating consecutive steps for manufacturing the first embodiment of the LED device. 
         FIG.  9    is a schematic top view illustrating a second embodiment of the LED device according to the disclosure. 
         FIG.  10    is an enlarged view illustrating a second electrode of the second embodiment of the LED device. 
         FIG.  11    is an enlarged view of a circular region C of  FIG.  10   . 
         FIG.  12    is a schematic top view illustrating a second electrode of a third embodiment of the LED device according to the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Before the disclosure is described in greater detail, it should be noted that where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics. 
     Referring to  FIGS.  1  to  4   , a first embodiment of a light emitting diode (LED) device  1  according to the disclosure includes a substrate  10  having a substrate surface  10   a , an epitaxial layered structure  12  having an epitaxial surface  12   a  opposite to the substrate surface  10   a , a first electrode  21  and a second electrode  22 . 
     The substrate  10  may be a light-transmissible substrate, an opaque substrate or a semi-transparent substrate. In a case of the substrate  10  being a light-transmissible or semi-transparent substrate, light emitted from the epitaxial layered structure  12  may pass through the substrate  10  and reach a side of the substrate  10  opposite to the epitaxial layered structure  12 . The substrate  10  may be, but is not limited to, a flat sapphire substrate, a patterned sapphire substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate or a glass substrate. 
     In certain embodiments, the substrate  10  is a patterned substrate that a protruding configuration (not shown), which may be a monolayer structure or a multi-layered structure containing at least one light extraction layer, is disposed on. The light extraction layer may have a refractive index lower than that of the substrate  10 , and a thickness that is greater than half of a height of the protruding configuration, which may enhance the light exiting efficiency of the LED device  1 . In certain embodiments, the protruding configuration may be formed as a dome-shaped structure, and the refractive index of the light extraction layer may be smaller than 1.6. For example, the light extraction layer may be made of silicon dioxide (SiO 2 ). In certain embodiments, the substrate  10  may be thinned or removed so as to form a thin film-type LED chip. 
     The epitaxial layered structure  12  is disposed on the substrate surface  10   a  of the substrate  10  and includes a first semiconductor layer  121 , a light emitting layer  122  and a second semiconductor layer  123  that are sequentially disposed on the substrate surface  10   a  in such order. 
     The first semiconductor layer  121  is formed on the substrate surface  10   a  of the substrate  10  and may be doped with n-type dopants. For example, the first semiconductor layer  121  may be, but is not limited to, a gallium nitride (GaN)-based semiconductor layer doped with silicon (Si). In certain embodiments, the epitaxial layered structure  12  further includes a buffer layer (not shown) that is disposed between the first semiconductor layer  121  and the substrate  10 . In certain embodiments, the first semiconductor layer  121  may be connected to the substrate  10  through a bonding layer (not shown). 
     The light emitting layer  122  is disposed on the first semiconductor layer  121  opposite to the substrate  10  and may have a quantum well (QW) structure. In certain embodiments, the light emitting layer  122  may have a multiple quantum well (MQW) structure that includes multiple well layers and multiple barrier layers alternately and repetitively stacked. Additionally, the wavelength of the light emitted by the light emitting layer  122  may be determined by the composition and the thickness of the well layers. That is to say, by adjusting the composition of the well layers and the barrier layers, the light emitting layer  122  may emit different colors of light, such as ultraviolet light, blue light or green light. 
     The second semiconductor layer  123  is disposed on the light emitting layer  122  opposite to the first semiconductor layer  121  and may be a semiconductor layer doped with p-type dopants. For example, the second semiconductor layer  123  may be, but is not limited to, a GaN-based semiconductor layer doped with magnesium (Mg). Each of the first semiconductor layer  121  and the second semiconductor layer  123  may have a monolayer structure or a multi-layered structure that includes a superlattice layer. In certain embodiments, the first semiconductor layer  121  may be doped with p-type dopants and the second semiconductor layer  123  may be doped with n-type dopants, i.e., the first semiconductor layer  121  is a p-type semiconductor layer and the second semiconductor layer  123  is an n-type semiconductor layer. 
     The LED device  1  according to the disclosure may further include an electrically conductive layer  14  and an insulating layer  16 . The electrically conductive layer  14  is light-transmissible and is disposed on the second semiconductor layer  123  to spread current. In certain embodiments, a projection of the electrically conductive layer  14  on the substrate  10  substantially falls within a projection of the second semiconductor layer  123  on the substrate  10  so as to achieve a more uniform current distribution and enhance the performance of light exiting. The electrically conductive layer  14  may include a transparent and electrically conductive material (e.g., a transparent and electrically conductive oxide) so as to increase the reliability of the LED device  1 . The transparent and electrically conductive material may be, but is not limited to, indium tin oxide (ITO), indium zinc oxide (IZO), indium oxide (InO), tin oxide (SnO), cadmium tin oxide (CTO), antimony tin oxide (ATO), aluminum zinc oxide (AZO), zinc tin oxide (ZTO), gallium doped zinc oxide (GZO), tungsten doped indium oxide (IWO), zinc oxide (ZnO) and combinations thereof. 
     The insulating layer  16  covers the epitaxial layered structure  12  and the transparent and electrically conductive layer  14 . In other words, the insulating layer  16  may be disposed on the epitaxial surface  12   a  (i.e., in contact with the first semiconductor layer  121  and the second semiconductor layer  123 ) and side surfaces of the epitaxial layered structure  12  that connect the epitaxial surface  12   a  and the substrate surface  10   a , and may extend to be disposed on a portion of the substrate surface  100   a  that is exposed from the epitaxial layered structure  12 . The insulating layer  16  is formed with a first opening  161  exposing the first semiconductor layer  121  and a second opening  162  exposing the second semiconductor layer  123 . 
     The insulating layer  16  may perform different functions depending on its location in the LED device  1 . For example, the insulating layer  16  covering the side surfaces of the epitaxial layered structure  12  may prevent electrically conductive material(s) from electrically connecting to the first semiconductor layer  121  and the second semiconductor layer  123 , thereby avoiding a short circuit of the LED device  1 . The insulating layer  16  may include a non-conductive material such as an inorganic material (e.g., silicone) or a dielectric material. Examples of the dielectric material may include, but are not limited to, aluminum oxide (AlO), silicon nitride (SiNx), silicon oxide (SiOx), titanium oxide (TiOx), magnesium fluoride (MgFx), tantalum oxide, niobium oxide, barium titanate and combinations thereof. In certain embodiments, the insulating layer  16  may include a diffracted Bragg reflector (DBR) that is formed out of a periodic structure of layers of two of the aforementioned materials, which are repetitively stacked. 
     The first electrode  21  is disposed on the epitaxial layered structure  12  and is electrically connected to the first semiconductor layer  121 . The second electrode  22  is disposed on the epitaxial layered structure  12  and is electrically connected to the second semiconductor layer  123 . In this embodiment, the first electrode  21  fills the first opening  161  of the insulating layer  16  and is electrically connected to the first semiconductor layer  121 , and the second electrode  22  fills the second opening  162  of the insulating layer  16  and is electrically connected to the second semiconductor layer  123 . 
     The second electrode  22  includes a body portion  221 , and at least one extending portion  220  connected to the body portion  221  and extending in a direction away from the body portion  221 . In this embodiment, the second electrode  22  includes two extending portions  220  connected to opposite sides of the body portion  221 . Each of the extending portions  220  may include a curved section  223 , a connecting section  222  that connects the body portion  221  and the curved section  223 , and a straight section  224  that connects to the curved section  223  opposite to the connecting section  222 . 
     As shown in  FIGS.  1  and  3   , a projection of the curved section  223  on the epitaxial layered structure  12  includes a first curved side  2231 , and a second curved side  2232  that are opposite to each other. The first curved side  2231  has a first imaginary center of curvature (C 1 ) and a first radius of curvature (R 1 ). The second curved side  2232  has a second imaginary center of curvature (C 2 ), and a second radius of curvature (R 2 ) that is larger than the first radius of curvature (R 1 ). The first curved side  2231  and the second curved side  2232  are curved in an identical direction. In this embodiment, the first curved side  2231  and the second curved side  2232  are curved outwardly in a direction away from the first electrode  21 . A distance (S 1 ) between the first imaginary center of curvature (C 1 ) and the second imaginary center of curvature (C 2 ) is equal to or smaller than 5 μm. By optimizing the design of the first curved side  2231  and the second curved side  2232  (e.g., increasing the distance (S 1 ) between the first and second imaginary center of curvatures (C 1 , C 2 )), current crowding present in the curved section  223  may effectively be reduced and an area of injection of charge carriers may be expanded so that burnout of the curved section  223  may be prevented as the LED device  1  ages. 
     The imaginary center of curvature (C 1 ) of the first curved side  22  and the imaginary center of curvature (C 2 ) of the second curved side  22  are respectively referred to as centers of a first imaginary circle  31  completing the first curved side  2231  and a second imaginary circle  32  completing the second curved side  22 . To be specific, the first curved side  2231  is a part of the first imaginary circle  31  (illustrated with a dot-dashed circle) and the second curved side  2232  is a part of the second imaginary circle  32  (illustrated with a dot-dashed circle). The first imaginary center of curvature (C 1 ) and the second imaginary center of curvature (C 2 ) coincide with centers of the first imaginary circle  31  and the second imaginary circle  32 , respectively. The first radius of curvature (R 1 ) of the first curved side  2231  and the second radius of curvature (R 2 ) of the second curved side  2232  are radii of the first imaginary circle  31  and the second imaginary circle  32 , respectively. 
     In this embodiment, as shown in  FIG.  3   , the first imaginary circle  31  is internally tangent to the second imaginary circle  32 . In certain embodiments, the distance (S 1 ) between the first imaginary center of curvature (C 1 ) and the second imaginary center of curvature (C 2 ) is equal to or greater than 1 μm. A width of the projection of the curved section  223  on the epitaxial layered structure  12  may gradually decrease in an extending direction from the connecting section  222  toward the straight section  224  so that current crowding in the curved section  223  may effectively be reduced. 
     In certain embodiments, the first curved side  2231  has an arc length equal to or smaller than one fourth of a circumference of the first imaginary circle  31 , and the second curved side  2232  has an arc length equal to or smaller than one fourth of a circumference of the second imaginary circle  32 . In this embodiment, the LED device  1  has a width that is smaller than 9 mil. In such case, the arc length of the first curved side  2231  may be equal to or smaller than one sixth of the circumference of the first imaginary circle  31 , and the arc length of the second curved side  2232  is equal to or smaller than one fifth of the circumference of the second imaginary circle  32 . In certain embodiments, a proportion of the arc length of the first curved side  2231  to the circumference of the first imaginary circle  31  is smaller than a proportion of the arc length of the second curved side  2232  to the circumference of the second imaginary circle  32 . For example, the arc length of the first curved side  2231  may account for 10% of the circumference of the first imaginary circle  31 , and the arc length of the second curved side  2232  may account for more than 10% of the circumference of the second imaginary circle  32 . 
     In addition, a point of tangency between the first imaginary circle  31  and the second imaginary circle  32  is defined as a first point (f 1 ), while a point on the second imaginary circle  32  that is the farthest from the first point (f 1 ) is defined as a second point (f 2 ). A first straight line (L 1 ) connects the first point (f 1 ) and the second point (f 2 ). A second straight line (L 2 ) that is perpendicular to the first straight line (L 1 ) and passing through the second point (f 2 ) passes through a geometric center (G) of a projection of the body portion  221  on the epitaxial layered structure  12 . In certain embodiments, the second point (f 2 ) coincides with the geometric center (G) of the projection of the body portion  221  on the epitaxial layered structure  12 . With such arrangement, each of the extending portions  220  is configured to extend from the body portion  221  away from the second straight line (L 2 ) and to be formed with the first curved side  2231  and the second curved side  2232 , which is conducive to improve current spreading in the LED device  1  and thereby reduce current crowding. 
     In certain embodiments, when the body portion  221  is located in a position offset from its intended position, the second straight line (L 2 ) may not pass through the geometric center (G) of the projection of the body portion  221  on the epitaxial layered structure  12  (i.e., there is a distance between the second straight line (L 2 ) and the geometric center (G) of the projection of the body portion  221  on the epitaxial layered structure  12 ), which causes the width of the projection of the curved section  223  on the epitaxial layered structure  12  to gradually vary in the extending direction from the connecting section  223  toward the straight section  224 . 
     In certain embodiments, the centers of the first imaginary circle  31  and the second imaginary circle  32  and the geometric center (G) of the projection of the body portion  221  are collinear. The extending portions  220  extend from the body portion  221  in a mirror symmetric manner relative to a straight line connecting the center of the first imaginary circle  31  and the geometric center (G) of the projection of the body portion  221 . By forming two extending portions  220  on opposite sides of the body portion  221 , current spreading in the LED device  1  of this disclosure may be improved and current crowding reduced. 
     The straight section  224  connects to the curved section  223  opposite to the connecting section  222 . That is to say, the connecting section  222 , the curve section  223  and the straight section  224  are connected in such order in a direction from the body portion  221  toward the first electrode  21 . In certain embodiments, a projection of the connection section  222  on the epitaxial layered structure  12  has a width (W) that is equal to or greater than the width of the projection of the curved section  223  on the epitaxial layered structure  12 . The width (W) of the projection of the straight section  224  on the epitaxial layered structure  12  ranges from 2 μm to 4 μm. In certain embodiments, a difference between the first radius of curvature (R 1 ) and the second radius of curvature (R 2 ) is equal to the width (W) of the projection of the straight section  224 , i.e., R 2 −R 1 =W. In certain embodiments, the width (W) of the projection of the straight section  224  is equal to or smaller than the width of the projection of the curved section  223  on the epitaxial layered structure  12 . When the width of the projection of the curved section  223  on the epitaxial layered structure  12  gradually decreases in the extending direction from the connecting section  222  toward the straight section  224 , a projection of a connecting region between the straight section  224  and the curved section  223  has a width that is equal to a minimum width of the projection of the curved section  223  (i.e., a distance from a first connecting point that interconnects the first curved side  2231  and a projection of the straight section  224  on epitaxial layered structure  12  to a second connecting point that interconnects the second curved side  2232  and the projection of the straight section  224 ). In certain embodiments, the width of the projection of the curved section  223  is equal to or greater than the width (W) of the projection of the straight section  224  and is equal to or smaller than two times the width (W) of the projection of the straight section  224 . 
     As used herein, the width of the projection of the curved section  223  refers to a distance between a given point on the first curved sides  2231  and a corresponding given point on second curved side  2232 , which are respectively located on a first tangent line and on a line perpendicular to the first tangent line and to the first curved side  2231  at the given point. 
     Referring to  FIGS.  3  and  4   , the projection of the connecting section  222  on the epitaxial layered structure  12  includes a first connecting side  2221  and a second connecting side  2222  opposite to each other. The first connecting side  2221  is connected to the first curved side  2231  and has a third radius of curvature (R 3 ). The second connecting side  2222  is connected to the second curved side  2232  and has a fourth radius of curvature (R 4 ). The first connecting side  2221  and the second connecting side  2222  are curved in opposite directions. In other words, the first connecting side  2221  may be curved outwardly in the direction away from the first electrode  21 , and the second connecting side  2222  may be curved inwardly in a direction toward the first electrode  21 . The third radius of curvature (R 3 ) and the fourth radius of curvature (R 4 ) are smaller than the first radius of curvature (R 1 ). In certain embodiments, each of the third radius of curvature (R 3 ) and the fourth radius of curvature (R 4 ) is equal to or greater than 10 μm. In certain embodiments, the third radius of curvature (R 3 ) is equal to the fourth radius of curvature (R 4 ). For example, each of the third radius of curvature (R 3 ) and the fourth radius of curvature (R 4 ) may be 10 μm or 15 μm. 
     Referring to  FIGS.  5  to  8   , consecutive steps for manufacturing the first embodiment of the LED device  1  are illustrated and described as follows. It should be noted that the shadow region depicted in each of  FIGS.  5  to  8    represents an additional feature formed by a corresponding step in a given figure as compared to the previous figure. 
     First, referring to  FIG.  5   , the epitaxial layered structure  12  that includes the first semiconductor layer  121 , the light emitting layer  122  and the second semiconductor layer  123  is formed on the substrate  10 . Then, the epitaxial layered structure  12  is etched in a direction from the second semiconductor layer  123  toward the substrate surface  10   a  until an opening that exposes a portion of the first semiconductor layer  121  is formed. In addition, a peripheral portion of the epitaxial layered structure  12  may selectively be etched to expose the substrate surface  10   a , which may facilitate a fabrication process (e.g., cutting) that follows. 
     Next, referring to  FIG.  6   , the electrically conductive layer  14  is selectively formed on the second semiconductor layer  123  for spreading current and increasing the reliability of the LED device  1 . The electrically conductive layer  14  is not in contact with the first semiconductor layer  121 . 
     Next, referring to  FIG.  7   , the insulating layer  16  is formed on and covers the epitaxial layered structure  12 , and further covers the electrically conductive layer  14 . The insulating layer  16  is formed with the first opening  161  and the second opening  162  that expose the first semiconductor layer  121  and the second semiconductor layer  123 , respectively. The insulating layer  16  is configured to isolate electrical conduction and protect components that are covered thereby. 
     Afterwards, referring to  FIG.  8   , the first electrode  21  and the second electrode  22  formed on the insulating layer  16  are illustrated with different patterns. To be specific, the first electrode  21  is formed to be electrically connected to the first semiconductor layer  121  through the first opening  161 , and the second electrode  22  is formed to be electrically connected to the second semiconductor layer  123  through the second opening  162 . In certain embodiments, the body portion  221  of the second electrode  22  covers and fills the second opening  162  so that adhesion between the second electrode  22  and the electrically conductive layer  14  is enhanced and the second electrode  22  becomes difficult to be peeled off from the electrically conductive layer  14 . 
     Referring to  FIGS.  9  to  11   , a second embodiment of the LED device  2  according to the disclosure is generally similar to the first embodiment of the LED device  1 , except for the configuration of the second electrode  22 . Specifically, the second embodiment of the LED device  2  has a width greater than that of the LED device  1 , e.g., equal to or greater than 9 mil, and the extending portion  220  of the second electrode  22  thereof is designed to have the following configuration. 
     Referring to  FIG.  10   , in the second embodiment, the first curved side  2231  and the second curved side  2232  are parts of the first imaginary circle  31  and the second imaginary circle  32  (illustrated with dot-dashed circles), respectively. The first imaginary circle  31  is internally tangent to the second imaginary circle  32 . The point of tangency between the first imaginary circle  31  and the second imaginary circle  32  is defined as the first point (f 1 ). The point on the second imaginary circle  32  that is the farthest from the first point (f 1 ) is defined as the second point (f 2 ). The first straight line (L 1 ) connecting the first point (f 1 ) and the second point (f 2 ) passes through the center of the second imaginary circle  32 . A point on the first imaginary circle ( 31 ) that is the farthest from the first point (f 1 ) is defined as a third point (f 3 ). A line connecting the first point (f 1 ) and the third point (f 3 ) passes through the center of the first imaginary circle  31 . A third straight line (L 3 ) connects the second point (f 2 ) and the third point (f 3 ). A fourth straight line (L 4 ) that passes through a center of the third straight line (L 3 ) and that is perpendicular to the third straight line (L 3 ) passes through the geometric center (G) of the projection of the body portion  221  on the epitaxial layered structure  12 . 
     A fifth straight line (L 5 ) in a horizontal direction passes through the geometric center (G) of the projection of the body portion  221 . Moreover, a sixth straight line (L 6 ) is perpendicular to the fifth straight line (L 5 ) and passes through the geometric center (G) of the projection of the body portion  221  on the epitaxial layered structure  12 . The fifth straight line (L 5 ) coincides with the fourth straight line (L 4 ). In this embodiment, two extending portions  220  extend from opposite sides of the body portion  221  and are arranged in a mirror symmetric manner relative to the sixth straight line (L 6 ). In certain embodiments, each of the extending portions  220  extends from the body portion  221  along the fifth straight line (L 5 ). In certain embodiments, the second electrode further includes a straight extending portion  230  extending from the body portion  221  along the sixth straight line (L 6 ), and the first imaginary circle  31  and the second imaginary circle  32  are respectively tangent to two opposite sides of the straight extended portion  230  relative to the sixth straight line (L 6 ). 
     In certain embodiments, the arc length of the first curved side  2231  is equal to one fourth of the circumference of the first imaginary circle  31 , and the arc length of the second curved side  2232  is equal to one fourth of the circumference of the second imaginary circle  32 . The distance from the first connecting point that interconnects the first curved side  2231  and the projection of the straight section  224  to the second connecting point that interconnects the second curved side  2232  and the projection of the straight section  224  is equal to the width (W) of the projection of the straight section  224 . A distance from a third connecting point that interconnects the projection of the connecting section  222  on epitaxial layered structure  12  and the first curved side  2231  to a fourth connecting point that interconnects the projection of the connecting section  222  and the second curved side  2232  (i.e., a distance between the second point (f 2 ) and the third point (f 3 )) is two times the width (W) of the projection of the straight section  224 . In other words, the projection of the curved section  223  has a width of  2 W at an end adjacent to the connecting section  222 , and a width of W at an end adjacent to the straight section  224 . This means that the width of the projection of the curved section  223  is equal to or greater than the width (W) of the projection of the straight section  224  and is equal to or smaller than two times the width (W) of the projection of the straight section  224 . 
     In addition, the first connecting side  2221  and the second connecting side  2222  are curved in opposite directions. To be specific, as shown in  FIG.  11   , the first connecting side  2221  and the second connecting side  2222  are disposed opposite to each other and are convex toward the fifth straight line (L 5 ). The third radius of curvature (R 3 ) of the first connecting side  2221  is equal to the fourth radius of curvature (R 4 ) of the second connecting side  2222 , such as 10 μm or 15 μm. 
     In certain embodiments, the first imaginary circle  31  may not be internally tangent to the second imaginary circle  32 . For example, the first imaginary center of curvature (C 1 ) of the first curved side  2231  may coincide with the second imaginary center of curvature (C 2 ) of the second curved side  2232 . That is to say, the distance between the first imaginary center of curvature (C 1 ) and the second imaginary center of curvature (C 2 ) is zero. In such case, the projection of the curved section  223  may have a fixed width rather than a width that gradually decreases in the extending direction from the connecting section  222  toward the straight direction  224 . With such arrangement, a surface area of the projection of the curved section  223  may be minimized so that the influence of light absorption may greatly be reduced and the brightness of the LED device  2  may be increased. The diameter of the first imaginary circle  31  may be adjusted and predetermined according to the size of the LED device  2  and the environment in which the LED device  2  is to be used. 
     Referring to  FIG.  13   , a third embodiment of the LED device according to the disclosure is generally similar to the first embodiment of the LED device  1 , except for the configuration of the second electrode  22 . 
     Specifically, in the third embodiment, the two extending portions  220  are respectively extended from left and right sides of the body portion  221 , in which only one extending portion  220  on the left side of the body portion  221  includes the curved section  223 . That is to say, the left-side extending portion  220  includes the connecting section  222 , the curved section  223  and the straight section  224  in a direction away from the body portion  221 . On the other hand, the right-side extending portion  220  only includes the connecting section  222  and the straight section  224  in the direction away from the body portion  221 . With this arrangement, current crowding present in the curved section  223  of the second electrode  22  may still be reduced and the area of injection of the charge carriers may also be expanded. 
     The disclosure also provides a light emitting apparatus that includes the LED device  1  and/or the LED device  2  as mentioned above. 
     It should be noted that the distance (S 1 ) between the first imaginary center of curvature (C 1 ) and the second imaginary center of curvature (C 2 ) may readily be measured by those skilled in the art using any well-known equipment, such as a scanning electron microscope (SEM) or an atomic force microscope (AFM). For example, an image of the LED device is captured by the equipment. Then, three points on each of the first curved side  2231  and the second curved side  2232  are selected to form a respective one of the first imaginary circle  31  having the first imaginary center of curvature (C 1 ) and the second imaginary circle  32  having the second imaginary center of curvature (C 2 ) using a software installed in the equipment, followed by measurement of the distance (S 1 ) between the first imaginary center of curvature (C 1 ) and the second imaginary center of curvature (C 2 ). 
     Additionally, in certain embodiments, each of the first curved side  2231  and the second curved side  2232  may be formed out of a plurality of line segments having gradually varied slopes. 
     In summary, by optimizing the configuration of the extending portion  220  of the second electrode  22 , i.e., widening the width of the curved section  223 , the LED device  1 ,  2  of this disclosure may achieve a reduced current crowding effect and increase the area of injection of the charge carrier, thereby preventing burnout of the LED device  1 ,  2  during aging. 
     In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment(s). It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects; such does not mean that every one of these features needs to be practiced with the presence of all the other features. In other words, in any described embodiment, when implementation of one or more features or specific details does not affect implementation of another one or more features or specific details, said one or more features may be singled out and practiced alone without said another one or more features or specific details. It should be further noted that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure. 
     While the disclosure has been described in connection with what is(are) considered the exemplary embodiment(s), it is understood that this disclosure is not limited to the disclosed embodiment(s) but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.