Abstract:
The invention discloses a light-emitting diode which includes a substrate on which a first conducting-type semiconductor layer, an illuminating layer and a second conducting-type semiconductor layer are formed sequentially, a transparent insulating material, a first transparent conducting layer, and a second transparent conducting layer. The top surface of the first conducting-type semiconductor layer includes a first region and a second region surrounded by the first region. Plural pillar-like holes are formed at the first region and protrude into the first conducting-type semiconductor layer. The transparent insulating material fills up the holes. The first transparent conducting layer is formed on the second conducting-type semiconductor layer, and the second transparent conducting layer is formed on the top surface of the transparent insulating material and on the first region.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a light-emitting diode and a manufacturing method thereof, and more particularly, to a light-emitting diode with high illuminating efficiency and the manufacturing method thereof. 
     2. Description of the Prior Art 
     Until now, the light-emitting diode (LED) has been widely applied, such as a keyboard, a backlight module of a mobile phone monitor, an illuminative system of a vehicle, an ornamental lamp, and a remote controlling product, etc. In order to make the LED have higher functional stability and lower energy consumption, the illuminating efficiency of the LED should be required. 
     Please refer to  FIG. 1 .  FIG. 1  illustrates a well-known light-emitting diode  1 . As shown in  FIG. 1 , the light-emitting diode  1  includes a substrate  10 , a n-type GaN layer  11 , an illuminating layer  12 , a p-type GaN layer  13 , and the electrodes  14 ,  15 . In order to conduct the p-type GaN layer  13  and the n-type GaN layer  11  to operate the light-emitting diode  1 , the electrode  15  is formed upon the p-type GaN layer  13 , and the electrode  14  is formed upon the p-type GaN layer  11 . 
     Theoretically, the illuminating efficiency of the light-emitting diode relates to its internal quantum efficiency and light-extraction efficiency. The internal quantum efficiency is decided by the material property and the quality; the light-extraction efficiency means the radiation proportion emitted from the inside of the light-emitting diode to the environment or the inside of the packaged epoxy resin. Although various light-emitting diodes of different structures have been disclosed, how to increase the light-extraction efficiency and illuminating efficiency of the light-emitting diode is still a question to be overcome urgently. 
     SUMMARY OF THE INVENTION 
     Accordingly, a scope of the present invention is to provide a light-emitting diode with high illuminating efficiency. 
     According to an embodiment of the invention, the light-emitting diode comprises a substrate, a first conducting-type semiconductor layer, a transparent insulating material, an illuminating layer, a second conducting-type semiconductor layer, a first transparent conducting layer, a second transparent conducting layer, a first electrode, and a second electrode. 
     The first conducting-type semiconductor layer is formed on the substrate and the first conducting-type semiconductor layer has an upper surface. The upper surface comprises a first region and a second region surrounded by the first region. Specifically, a plurality of pillar-like holes is formed in the first region and protrudes into the first conduction-type semiconductor layer. The transparent insulating material is filled into the plurality of pillar-like holes, so that the filled transparent insulating material is about the same height as the plurality of pillar-like holes. 
     Additionally, the illuminating layer is formed on the second region, and the second conducting-type semiconductor layer is formed on the illuminating layer. The first transparent conducting layer is formed on the second conducting-type semiconductor layer. The second transparent conducting layer is formed on a top surface of the transparent insulating material and the first region. Additionally, the first electrode is formed upon the first transparent conducting layer, and the second electrode is formed upon the second transparent conducting layer. 
     A scope of the present invention is to provide a light-emitting diode with high illuminating efficiency. 
     According to an embodiment of the invention, the light-emitting diode comprises a substrate, a first conducting-type semiconductor layer, an illuminating layer, a second conducting-type semiconductor layer, a first transparent conducting layer, a second transparent conducting layer, a first electrode, and a second electrode. 
     The first conducting-type semiconductor layer is formed on the substrate and the first conducting-type semiconductor layer has an upper surface. The upper surface comprises a first region and a second region surrounded by the first region. The illuminating layer is formed on the second region, and the second conducting-type semiconductor layer is formed on the illuminating layer. The first transparent conducting layer is formed on the second conducting-type semiconductor layer. The second transparent conducting layer is formed on the first region, wherein a plurality of pillar-like holes is formed in the second transparent conducting layer and protrudes into the first conduction-type semiconductor layer. In an embodiment, a transparent insulating material is filled into the plurality of pillar-like holes, so that the filled transparent insulating material is about the same height as the plurality of pillar-like holes. The first electrode is formed upon the first transparent conducting layer, and the second electrode is formed upon the second transparent conducting layer. 
     A scope of the present invention is to provide a light-emitting diode with high illuminating efficiency. 
     According to an embodiment of the invention, the light-emitting diode comprises a substrate, a first conducting-type semiconductor layer, an illuminating layer, a second conducting-type semiconductor layer, a first transparent conducting layer, a second transparent conducting layer, a first electrode, and a second electrode. 
     Wherein, the first conducting-type semiconductor layer is formed on the substrate and the first conducting-type semiconductor layer has an upper surface. The upper surface comprises a first region and a second region surrounded by the first region. And, a plurality of pillar-like holes is formed in the first region and protrudes into the first conduction-type semiconductor layer. 
     Additionally, the illuminating layer of the LED is formed on the second region, the second conducting-type semiconductor layer is formed on the illuminating layer, and the first transparent conducting layer is formed on the second conducting-type semiconductor layer. The second transparent conducting layer is coated on the surface of the plurality of pillar-like holes and the first region. The first electrode is formed upon the first transparent conducting layer, and the second electrode is formed upon the second transparent conducting layer. 
     Compared to prior arts, the light-emitting diode of the invention includes the plurality of pillar-like holes as mentioned above; therefore, the light-extraction efficiency of the light-emitting diode can be increased. Furthermore, filling the transparent insulating material having high refractive index into the plurality of pillar-like holes can not only lower the total reflection of the ray in the light-emitting diode, but also increase the anti-breakdown strength of the component. Additionally, the coating of the transparent conducting layer can make the driving current of the light-emitting diode surrounds with the primary illuminating region, so that the invention has various advantages of good current diffusion effect, good lighting uniformity, and decreasing the instantaneous discharge. 
     The objective of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE APPENDED DRAWINGS 
         FIG. 1  illustrates a well-known light-emitting diode. 
         FIG. 2A  illustrates a cross-sectional view of the light-emitting diode according to an embodiment of the invention. 
         FIG. 2B  illustrates a cross-sectional view of the rough surface of the pillar-like holes. 
         FIG. 2C  illustrates a cross-sectional view of the counter-trapezoid cross-section of the pillar-like holes. 
         FIG. 2D  illustrates a cross-sectional view of the light-emitting diode shown in  FIG. 2A  in another embodiment. 
         FIG. 3A˜FIG .  3 H illustrate a cross-sectional view of the manufacturing method of the light-emitting diode shown in  FIG. 2A . 
         FIG. 3I  illustrates a top view of the structure shown in  FIG. 3B . 
         FIG. 3J  illustrates a top view of the structure shown in  FIG. 3C . 
         FIG. 3K  illustrates a top view of the pillar-like holes arranged as an inner ring-like circle and an outer ring-like circle. 
         FIG. 4A˜FIG .  4 I illustrate a cross-sectional view of the manufacturing method of the light-emitting diode according to another embodiment of the invention. 
         FIG. 4J  illustrates a cross-sectional view of the light-emitting diode shown in  FIG. 4I  in another preferred embodiment. 
         FIG. 5A  illustrates a cross-sectional view of the light-emitting diode according to an embodiment of the invention. 
         FIG. 5B  illustrates a cross-sectional view of the light-emitting diode according to an embodiment of the invention. 
         FIG. 5C  illustrates a cross-sectional view of the light-emitting diode shown in  FIG. 5A  in another preferred embodiment. 
         FIG. 5D  illustrates a cross-sectional view of the light-emitting diode shown in  FIG. 5B  in another preferred embodiment. 
         FIG. 6A˜FIG .  6 F illustrate a cross-sectional view of the manufacturing method of the light-emitting diode shown in  FIG. 5A . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Please refer to  FIG. 2A .  FIG. 2A  illustrates a cross-sectional view of the light-emitting diode  5  according to an embodiment of the invention. 
     The light-emitting diode  5  includes a substrate  50 , a first conducting-type semiconductor layer  52 , a transparent insulating material  54 , an illuminating layer  56 , a second conducting-type semiconductor layer  58 , a first transparent conducting layer  60 , a second transparent conducting layer  62 , a first electrode  64 , and a second electrode  66 . 
     The first conducting-type semiconductor layer  52  is formed on the substrate  50  and the first conducting-type semiconductor layer  52  has an upper surface. The upper surface comprises a first region  5200  and a second region  5202  surrounded with the first region  5200 , wherein a plurality of pillar-like holes  53  is formed in the first region  5200  and protrudes into the first conduction-type semiconductor layer  52 . And, the transparent insulating material  54  is filled into the plurality of pillar-like holes  53 , so that the filled transparent insulating material is about the same height as the plurality of pillar-like holes  53 . In piratical applications, a cutting way is defined upon the substrate  50  (not shown in  FIG. 2A ), and the majority of pillar-like holes  53  are located on the cutting way approximately. 
     The illuminating layer  56  is formed on the second region  5202 ; the second conducting-type semiconductor layer  58  is formed on the illuminating layer  56 , and the first transparent conducting layer  60  is formed on the second conducting-type semiconductor layer  58 . 
     In practical applications, the first conducting-type semiconductor layer  52 , the illuminating layer  56 , and the second conducting-type semiconductor layer  58  can be formed by a nitride material. And in a preferred embodiment, the refractive index of the transparent insulating material  54  is between the refractive index of the air and the refractive index of the nitride material. 
     The second transparent conducting layer  62  is formed on a top surface of the transparent insulating material  54  and the first region  5200 . Additionally, the first electrode  64  is formed upon the first transparent conducting layer  60 , and the second electrode  66  is formed upon the second transparent conducting layer  62 . In a preferred embodiment, the light-emitting diode  5  further includes a reflective layer  59  formed on a bottom surface of the substrate  50  to make the light-emitting diode  5  light upward. 
     It should be noticed that the surface outline of the plurality of pillar-like holes  53  can be designed to further increase the illumining output efficiency of the LED. In a preferred embodiment, the plurality of pillar-like holes  53  has a rough sidewall and a rough bottom, as shown in  FIG. 2B . In another preferred embodiment, the plurality of pillar-like holes  53  has a counter-trapezoid cross-section, i.e., generally tapered cross-section, as shown in  FIG. 2C . 
     Please refer to  FIG. 2D .  FIG. 2D  illustrates a cross-sectional view of the light-emitting diode  5  shown in  FIG. 2A  in another embodiment. As shown in  FIG. 2D , a part of the first transparent conducting layer  60  is removed, so that a part of the top surface of the second conducting-type semiconductor layer  58  is exposed. The first electrode  64  is formed upon the exposed top surface of the second conducting-type semiconductor layer  58  and the first electrode  64  contacts with the first transparent conducting layer  60 . Additionally, a part of the second transparent conducting layer  62  is removed, so that a part of the first region  5200  on the upper surface of the first conducting-type semiconductor layer  52  is exposed. The second electrode  66  is formed upon the exposed first region  5200  and the second electrode  66  contacts with the second transparent conducting layer  62 . 
     Please refer to  FIG. 3A  to  FIG. 3H  together.  FIG. 3A  to  FIG. 3H  illustrate a cross-sectional view of the manufacturing method of the light-emitting diode  5  in the above-mentioned embodiment. 
     Firstly, as shown in  FIG. 3A , the first conducting-type semiconductor layer  52 , the illuminating layer  56  and the second conducting-type semiconductor layer  58  are formed on the substrate  50  by the method to make a semiconductor stack structure  51 . In a preferred embodiment, the method further forms a reflective layer  59  on a bottom surface of the substrate  50  to make the light-emitting diode  5  light upward. 
     Next, as shown in  FIG. 3B , a first etching process is performed on the semiconductor stack structure  51  shown in  FIG. 3A  until a surrounding region  5204  of an upper surface of the first conducting-type semiconductor layer  52  is exposed. Please also refer to  FIG. 3B  and  FIG. 3I ,  FIG. 3I  illustrates a top view of the structure shown in  FIG. 3B . It should be noticed that the surrounding region  5204  in  FIG. 3I  refers to first region  5200  in  FIG. 2A , and the position of the dotted-line can represent the position of the cutting line defined on the substrate  50 . 
     Then, as shown in  FIG. 3C , a second etching process is performed on the exposed surrounding region  5204 , so that the plurality of pillar-like holes  53  is formed in the surrounding region  5204  and the plurality of pillar-like holes  53  protrudes into the first conduction-type semiconductor layer  52 . Please refer to  FIG. 3C  and  FIG. 3J  together.  FIG. 3J  illustrates a top view of the structure shown in  FIG. 3C , and the plurality of pillar-like holes  53  can be uniformly distributed on the surrounding region  5204 . Comparing  FIG. 3I  with  FIG. 3J , the majority of pillar-like holes  53  can be located on the cutting way approximately. 
     Moreover, in an embodiment, the plurality of pillar-like holes  53  can form at least one ring-like circle to surround the illuminating layer, and each ring-like circle is formed by mutually connecting the plurality of pillar-like holes  53  approximately. As shown in  FIG. 3K , the plurality of pillar-like holes  53  can be arranged and formed a pattern of an inner ring-like circle and an outer ring-like circle to guarantee that the plurality of pillar-like holes  53  will guide all the lights emitted by the light outputting plane to the illuminating layer of the light-emitting diode. 
     Next, as shown in  FIG. 3D , the method is performed to cover the transparent insulating material  54  with the entire component, and also fill the transparent insulating material  54  into the plurality of pillar-like holes  53 , as shown in  FIG. 3C . 
     Next, as shown in  FIG. 3E , the method can use a selective etching method to remove the unnecessary insulating material  54 , so that the filled transparent insulating material  54  is about the same height as the plurality of pillar-like holes  53 . 
     Next, as shown in  FIG. 3F , the method is performed to form the transparent conducting layer  60  to cover the entire component shown in  FIG. 3E . 
     Next, as shown in  FIG. 3G , the method can use the etching method to remove both of the transparent conducting layer  60  on the sidewall of the central stack structure, and the transparent conducting layer  60  between the central stack structure and the pillar-like holes  53  to avoid current leakage. 
     At last, as shown in  FIG. 3H , the first electrode  64  and the second electrode  66  are formed on the transparent conducting layer  60  of the central stack structure respectively, and the first electrode  64  and the second electrode  66  are formed on the transparent conducting layer  60  of the surrounding region respectively. 
     Please refer to  FIG. 4A˜FIG .  4 I.  FIG. 4A˜FIG .  4 I illustrate a cross-sectional view of the manufacturing method of the light-emitting diode according to another embodiment of the invention. 
     Firstly, as shown in  FIG. 4A , the method continuously forms the first conducting-type semiconductor layer  52 , the illuminating layer  56 , and the second conducting-type semiconductor layer  58  on the substrate  50  to make a semiconductor stack structure  51 . In a preferred embodiment, the method further forms a reflective layer  59  on a bottom surface of the substrate  50  to make the light-emitting diode  5  light upward. 
     Next, as shown in  FIG. 4B , an etching process is performed on the semiconductor stack structure  51  in  FIG. 4A  until a surrounding region  5204  on an upper surface of the first conducting-type semiconductor layer  52  is exposed. 
     Next, as shown in  FIG. 4C , a transparent conducting layer  60 ′ is formed to fully coat the entire component shown in  FIG. 4B . 
     Next, as shown in  FIG. 4D , the method can use the etching method to remove the transparent conducting layer  60 ′ on the sidewall of the central stack structure. 
     Then, as shown in  FIG. 4E , a etching process is performed on the transparent conducting layer  60 ′ of the surrounding region, so that the plurality of pillar-like holes  53  is formed in the transparent conducting layer  60 ′ and the plurality of pillar-like holes  53  protrudes into the first conduction-type semiconductor layer  52 . 
     Afterward, as shown in  FIG. 4F , the first electrode  64  and the second electrode  66  are formed on the transparent conducting layer  60 ′ of the central stack structure respectively and the first electrode  64  and the second electrode  66  are formed on the transparent conducting layer  60 ′ of the surrounding region respectively. 
     In an embodiment, after the step shown in  FIG. 4E , the method is performed to cover the transparent insulating material  54  with the entire component shown in  FIG. 4E , and also fill the transparent insulating material  54  into the plurality of pillar-like holes  53 , as shown in  FIG. 4G . 
     Next step, as shown in  FIG. 4H , the method can use the selective etching method to remove the unnecessary insulating material  54 , so that the transparent insulating material  54  filled into the plurality of pillar-like holes  53  is about the same height as the plurality of pillar-like holes  53 . Afterward, as shown in  FIG. 4I , the first electrode  64  and the second electrode  66  are formed on the transparent conducting layer  60 ′ of the central stack structure and the transparent conducting layer  60 ′ of the surrounding region respectively. 
     Please refer to  FIG. 4J .  FIG. 4J  illustrates a cross-sectional view of the light-emitting diode in another preferred embodiment shown in  FIG. 4I . Basically, the locating method related to the first electrode  64  and the second electrode  66  shown in  FIG. 4J  is the same with that of  FIG. 2D , so it will no longer be explained here. 
     Please refer to  FIG. 5A .  FIG. 5A  illustrates a cross-sectional view of the light-emitting diode  9  according to an embodiment of the invention. 
     The light-emitting diode  9  includes a substrate  90 , a first conducting-type semiconductor layer  92 , an illuminating layer  96 , a second conducting-type semiconductor layer  98 , a first transparent conducting layer  100 , a second transparent conducting layer  102 , a first electrode  104 , and a second electrode  106 . 
     The first conducting-type semiconductor layer  92  is formed on the substrate  90  and the first conducting-type semiconductor layer  92  has an upper surface. The upper surface includes a first region  9200  and a second region  9202  surrounded by the first region  9200 . Wherein, a plurality of pillar-like holes  93  is formed in the first region  9200  and the plurality of pillar-like holes  93  protrudes into the first conduction-type semiconductor layer. In practical applications, a cutting way (not shown in  FIG. 5A ) is defined upon the substrate, and the majority of pillar-like holes can be located on the cutting way approximately. 
     As shown in  FIG. 5A , the illuminating layer  96  is formed on the second region  9202 , and the second conducting-type semiconductor layer  98  is formed on the illuminating layer  96 . The first transparent conducting layer  100  is formed on the second conducting-type semiconductor layer  98 , and the second transparent conducting layer  102  is coated on the surface of the plurality of pillar-like holes  93  and the first region  9200 . It should be noticed, in practical applications, the second transparent conducting layer  102  can further be filled into the plurality of pillar-like holes  93 , as shown in  FIG. 5B . 
     As shown in  FIG. 5A , the first electrode  104  is formed upon the first transparent conducting layer  100 , and the second electrode  106  is formed upon the second transparent conducting layer  102 . In a preferred embodiment, the light-emitting diode  9  further includes a reflective layer  99  formed on a bottom surface of the substrate  90  to make the light-emitting diode  9  light upward. 
     It should be noticed that the surface outline of the plurality of pillar-like holes  93  can be designed to further increase the illumining output efficiency. In a preferred embodiment, the plurality of pillar-like holes  53  has a rough sidewall and a rough bottom (please refer to  FIG. 2B  again). In another preferred embodiment, the plurality of pillar-like holes  93  has a counter-trapezoid cross-section (please refer to  FIG. 2C  again). 
     Please refer to  FIG. 5C  and  FIG. 5D .  FIG. 5C  illustrates a cross-sectional view of the light-emitting diode  9  in another embodiment shown in  FIG. 5A .  FIG. 5D  illustrates a cross-sectional view of the light-emitting diode  9  in another embodiment shown in  FIG. 5B . Basically, the locating method of the first electrode  104  and the second electrode  106  shown in  FIG. 5C  and  FIG. 5D  is the same with that of  FIG. 2D , so it will no longer be explained here. 
     Please refer to  FIG. 6A  to  FIG. 6F  together.  FIG. 6A  to  FIG. 6F  illustrate cross-sectional views of the manufacturing method of the light-emitting diode  9  in the above-mentioned embodiment. 
     Firstly, as shown in  FIG. 6A , the method continuously forms the first conducting-type semiconductor layer  92 , the illuminating layer  96 , and the second conducting-type semiconductor layer  98  on the substrate  90  to make a semiconductor stack structure  91 . In a preferred embodiment, the method further forms a reflective layer  99  on a bottom surface of the substrate  90  to make the light-emitting diode  9  light upward. 
     Next, as shown in  FIG. 6B , a first etching process is performed on the semiconductor stack structure  91  shown in  FIG. 6A  until a surrounding region  9204  on an upper surface of the first conducting-type semiconductor layer  92  is exposed. 
     Next, as shown in  FIG. 6C , a second etching process is performed on the exposed surrounding region  9204 , so that the plurality of pillar-like holes  93  is formed in the surrounding region  9204  and the plurality of pillar-like holes  93  protrudes into the first conduction-type semiconductor layer  92 . In practical applications, a cutting way is defined upon the substrate  90 , and the plurality of pillar-like holes  93  can be located on the cutting way approximately. 
     Next, as shown in  FIG. 6D , the transparent conducting layer  100  is formed to cover the entire component shown in  FIG. 6C . 
     Next, as shown in  FIG. 6E , the method can use the etching method to remove both of the transparent conducting layer  100  on the sidewall of the central stack structure and the transparent conducting layer  100  between the central stack structure and the pillar-like holes  93 . It should be noticed, in practical applications, the second transparent conducting layer  100  can further be filled into the plurality of pillar-like holes  93 , as shown in  FIG. 5B . 
     At last, as shown in  FIG. 6F , the first electrode  104  and the second electrode  106  are formed on the transparent conducting layer  100  of the central stack structure and the transparent conducting layer  100  of the surrounding region respectively. 
     Compared to prior arts, the light-emitting diode of the invention includes the plurality of pillar-like structures or the plurality of pillar-like holes as mentioned above, so that the light-emitting diode can increase the light-extraction efficiency. Furthermore, filling the transparent insulating material with the high refractive index into the plurality of pillar-like holes can not only lower the total reflection of the ray in the light-emitting diode, but also increase the anti-breakdown strength of the component. Additionally, the coating of the transparent conducting layer can make the driving current of the light-emitting diode surround the primary illuminating region, so that the invention has various advantages of good current diffusion effect, good lighting uniformity, and decreasing the instantaneous discharge. 
     Although the present invention has been illustrated and described with reference to the preferred embodiment thereof, it should be understood that it is in no way limited to the details of such embodiment but is capable of numerous modifications within the scope of the appended claims.