Abstract:
A light emitting diode (LED) includes a base, an LED die grown on the base, a transparent electrically conductive layer formed on a side of the LED die, a protecting layer covering the transparent electrically conductive layer, and a phosphor layer formed on the protecting layer. Through holes extend through the phosphor layer and the protecting layer to make part of light emitted from the LED die directly traveling out from the through holes to illuminate. A method for manufacturing the LED is also provided.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to semiconductor devices and, more particularly, to a light emitting diode (LED). 
     2. Description of Related Art 
     In recent years, LEDs have been widely used in devices to provide illumination. Typically, an LED includes an LED die and a phosphor layer directly formed on a light outputting surface of the LED die and entirely covering the light outputting surface. Light emitted from the LED die radiates from the light outputting surface and excites phosphor substance of the phosphor layer to emit excitation light, thereby obtaining a mixed white light. However, the phosphor layer will absorbs part of light of the LED die and reflects part of light of the LED die. Thus, a light outputting efficiency of the LED will be unfavorably affected. 
     Accordingly, it is desirable to provide an LED which can overcome the described limitations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of an LED according to an exemplary embodiment of the present disclosure. 
         FIG. 2  is a cross sectional view of the LED of  FIG. 1 , taken along II-II line thereof. 
         FIG. 3  shows light paths of the LED. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of an LED will now be described in detail below and with reference to the drawings. 
     Referring to  FIGS. 1-2 , an LED  100  according to an exemplary embodiment is shown. The LED  100  includes a base  10 , an LED die  20  grown on the base  10 , a transparent electrically conductive layer  30  formed on the LED die  20 , a P-type electrode  40 , an N-type electrode  50 , a protecting layer  60  formed on the transparent electrically conductive layer  30 , and a phosphor layer  70  formed on the protecting layer  60 . 
     The base  11  is electrically insulated and made of sapphire, SiC, Si, GaAs, LiAlO 2 , MgO, ZnO, GaN, AlO, or InN. In this embodiment, the base  11  is made of sapphire. 
     The LED die  20  includes a buffer layer  21  formed on a top surface of the base  10 , an N-doped region  22  formed on a top surface of the buffer layer  21 , an active layer  23  formed on a top surface the N-doped region  22 , a P-doped region  24  formed on a top surface of the active layer  23 . In this embodiment, the buffer layer  21  may be made of GaN, AlGaN, AN, or InGaN. The active layer  23  may be a single quantum well structure, a multiple quantum well structure, and/or quantum dot structure. 
     The transparent electrically conductive layer  30  is formed on a top surface of the P-doped region  24 . Right sides of the transparent electrically conductive layer  30 , the P-doped region  24 , the active layer  23  are etched to expose a right side of the N-doped region  22 . In this embodiment, a top portion of the right side of the N-doped region  22  is etched also. In this embodiment, the transparent electrically conductive layer  30  is formed by evaporating or sputtering and made of Ni/Au, Indium Tin Oxide, Indium Zinc Oxide, Indium Tungsten Oxide, or Indium Gallium Oxide. Alternatively, the transparent electrically conductive layer  30  is made of Zinc oxide or Indium Gallium Zinc Oxide. 
     The P-type electrode  40  is formed on the transparent electrically conductive layer  30 . The N-type electrode  50  is formed on a top surface of the exposed right side of the N-doped region  22 . In this embodiment, the P-type electrode  40  and the N-type electrode  50  are formed by evaporating or sputtering. 
     The protecting layer  60  is transparent and covers a top surface of the transparent electrically conductive layer  30 , lateral edges of the P-type electrode  40  and the N-type electrode  50 , and the top surface of the exposed right side of the N-doped region  22 , right ends of the P-doped region  24  and the active layer  23 . A central portion of a top surface of the P-type electrode  40  and a central portion of a top surface of the N-type electrode  50  are exposed. In this embodiment, a material of the protecting layer  60  is selected from SiO 2 , epoxy, Si 3 N 4 , TiO 2 , and AlN. A top end of the transparent electrically conductive layer  30  is etched to define a plurality of recesses  31  therein. The recesses  31  act as a roughened structure of the LED die  20  to reflect light oriented thereto toward different directions to change an incidence angle of the light, thereby improving the light extraction efficiency of the LED  100 . 
     The phosphor layer  70  covers the protecting layer  60  located on the transparent electrically conductive layer  30 . In this embodiment, the active layer  23  emits blue light. The phosphor layer  70  is formed by yellow phosphor, or mixed by red phosphor and green phosphor. The phosphor layer  70  and a part of the protecting layer  60  located between the transparent electrically conductive layer  30  and the phosphor layer  70  are etched along a height direction of the LED  100  to define a plurality of through holes  80  therein. The through holes  80  are evenly spaced from each other and respectively aligned with the recesses  31 . The transparent electrically conductive layer  30  is exposed via the through holes  80 . In this embodiment, a rate of surface areas of the phosphor layer  70  and the through holes  80  is ranged from 0.2 to 0.4. 
     Referring to  FIG. 3 , a part of the light emitted from the active layer  23  directly travels out from the through holes  80  to form a first light with a first wavelength, and another part of the light travels through the phosphor layer  70  to excite the phosphor layer  70  to emit a second light with a second wavelength. The first light and the second light are mixed to form a determined white light. 
     In this disclosure, because a part of the light emitted from the active layer  23  directly travels through the through holes  80 , without traveling through the phosphor layer  70 , thus, the light absorbed by the phosphor layer  70  relative to the conventional LED is decreased. Therefore, the light outputting efficiency of the LED  100  is improved. 
     A method for manufacturing the LED  100  includes following steps. 
     The first step is providing the base  10 . 
     The second step is growing the LED die  20  on the base  10 . 
     The third step is forming the transparent electrically conductive layer  30  on the LED die  20  by evaporating or sputtering. 
     The fourth step is etching the right sides of the transparent electrically conductive layer  30 , the P-doped region  24  and the active layer  23  to expose the right side of the N-doped region  22 , and forming the N-type electrode  50  and the P-type electrode  40  on the exposed right side of the N-doped region  22  and the transparent electrically conductive layer  30 . 
     The fifth step is forming the protecting layer  60  on the LED die  20 . 
     The sixth step is forming the phosphor layer  70  on the protecting layer  60  located on the transparent electrically conductive layer  30 . 
     The seventh step is etching the phosphor layer  70 , a part of the protecting layer  60  located between the transparent electrically conductive layer  30  and the phosphor layer  70 , and the top end of the transparent electrically conductive layer  30  to define the through holes  80  through the etching the phosphor layer  70  and the protecting layer  60 , and the recesses  31  of the transparent electrically conductive layer  30 . 
     It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.