Abstract:
A light-emitting diode array includes a substrate, an adhesive layer formed on the substrate, and a plurality of electrically connected epitaxial light-emitting stack layer disposed on the adhesive layer. Each of the epitaxial light-emitting stack layer has a P-contact and an N-contact coplanar to the P-contact. The light-emitting diode array has improved heat ventilation characteristics.

Description:
BACKGROUND OF INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a light-emitting diode, and more particularly, to a light-emitting diode array having an adhesive layer.  
         [0003]     2. Description of the Prior Art  
         [0004]     Light-emitting diodes (LEDs) are employed in a wide variety of applications including optical display devices, traffic lights, data storage equipment, communications devices, illumination apparatuses, and medical treatment equipment. One of the most important goals of engineers who design LEDs is to increase the brightness of the light emitted.  
         [0005]     U.S. Pat. No. 6,547,249 discloses monolithic serial/parallel LED arrays formed on highly resistive substrates. According to the patent, a Group III-V nitride light-emitting stack layer is formed on an insulating substrate. A portion of the stack layer is etched away to form a trench, and in result to form the LED array, which includes a plurality of light-emitting diodes divided by the trench. Since the insulating substrate is not conductive, both P-contacts and N-contacts for the LED array have to be formed on the same side of the LED array. In use, two LED arrays can be connected either in series or in parallel. However, the LED array disclosed by the patent cannot be applied to a quaternary Al—In—Ga—P light-emitting diode, which comprises a conductive substrate rather than an insulating substrate, P-contacts formed on one side of the conductive substrate, and N-contacts having to be formed on the other side. Therefore, two quaternary Al—In—Ga—P light-emitting diode arrays can be connected neither in series nor in parallel. Moreover, as the size of the LED array become larger, the operating voltage of the LED array becomes higher accordingly, and heat dissipation becomes an important concern for the LED array.  
       SUMMARY OF INVENTION  
       [0006]     It is therefore a primary objective of the claimed invention to provide an LED array having an adhesive layer to overcome the drawbacks of the prior art.  
         [0007]     According to the claimed invention, the light-emitting diode array includes a substrate, a reflective layer formed on the substrate, an insulating transparent adhesive layer formed on the reflective layer, a transparent conductive layer formed on the insulating transparent adhesive layer, a first conductive semiconductor stack layer formed on the transparent conductive layer, a light-emitting layer formed on the first conductive semiconductor stack layer, and a second conductive semiconductor stack layer formed on the light-emitting layer.  
         [0008]     A trench is formed by etching away a portion of the second conductive semiconductor stack layer, the light-emitting layer, the first conductive semiconductor stack layer, the transparent conductive layer, and the insulating transparent adhesive layer sequentially, and therefore the LED array is divided into a first LED and a second LED, both of which have the substrate in common. Moreover, a transparent conductive layer exposed surface region is formed by etching both of the first LED and the second LED deeply into the transparent conductive layer. The LED array further includes an insulating layer formed surrounding the first LED and the second LED for electrically isolating the first LED from the second LED. First contacts formed on the second conductive semiconductor stack layer of the first LED and the second conductive semiconductor stack layer of the second LED respectively. Second contacts formed on the transparent conductive layer exposed surface region of the first LED and the transparent conductive layer exposed surface region of the second LED respectively, and a conductive line for electrically connecting a second contact of the first LED to a first contact of the second LED.  
         [0009]     The substrate comprises at least one material selected from a material group consisting of GaP, GaAs, Si, SiC, Al 2 O 3 , glass, quartz, GaAsP, AIN, metal, and AlGaAs. The insulating transparent adhesive layer comprises at least one material selected from a material group consisting of polyimide (PI), benzocyclobutene (BCB), and perfluorocyclobutene (PFCB). The reflective layer comprises at least one material selected from a material group consisting of In, Sn, Al, Au, Pt, Zn, Ge, Ag, Ti, Pb, Pd, Cu, AuBe, AuGe, Ni, PbSn, AuZn, and indium-tin oxide (ITO). The light-emitting layer comprises at least one material selected from a material group consisting of AlGaInP, GaN, InGaN, AlInGaN, and ZnSe. The transparent conductive layer comprises at least one material selected from a material group consisting of indium-tin oxide (ITO), cadmium-tin oxide (CTO), antimony-tin oxide (ATO), zinc oxide, and zinc-tin oxide. The insulating layer comprises at least one material selected from a material group consisting of SiO 2  and SiN x . The first semiconductor stack layer comprises at least one material selected from a material group consisting of AlInP, AIN, GaN, InGaN, AlGaN, and AlInGaN. The second semiconductor stack layer comprises at least one material selected from a material group consisting of AlInP, AIN, GaN, InGaN, AlGaN, and AlInGaN.  
         [0010]     These and other objectives 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 that is illustrated in the various figures and drawings. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0011]      FIG. 1  is a cross sectional schematic diagram of a light-emitting diode array having an adhesive layer of the preferred embodiment according to the present invention.  
         [0012]      FIG. 2  is a top view of a schematic diagram of a plurality of serially connected LED arrays shown in  FIG. 1  according to the present invention.  
         [0013]      FIG. 3  is an equivalent circuit diagram of the LED arrays shown in  FIG. 2  according to the present invention.  
         [0014]      FIG. 4  is a top view of a schematic diagram of a plurality of serially and parallelly connected LED arrays shown in  FIG. 1  according to the present invention.  
         [0015]      FIG. 5  is an equivalent circuit diagram of the LED arrays shown in  FIG. 4  according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0016]     Please refer to  FIG. 1 , which is a cross sectional schematic diagram of a light-emitting diode array  100  of the preferred embodiment according to the present invention. The LED array  100  comprises a substrate  10 , a reflective layer  11  formed on the substrate  10 , an insulating transparent adhesive layer  12  formed on the reflective layer  11 , a transparent conductive layer  13  formed on the insulating transparent adhesive layer  12 , a first conductive semiconductor stack layer  14  formed on the transparent conductive layer  13 , a light-emitting layer  15  formed on the first conductive semiconductor stack layer  14 , a second conductive semiconductor stack layer  16  formed on the light-emitting layer  15 .  
         [0017]     A trench is formed by etching away a portion of the second conductive semiconductor stack layer  16 , the light-emitting layer  15 , the first conductive semiconductor stack layer  14 , the transparent conductive layer  13 , and the insulating transparent adhesive layer  12  sequentially, and therefore the LED array  100  is divided into a first LED  110  and a second LED  120 , both of which have the substrate  10  in common. Moreover, a transparent conductive layer exposed surface region is formed by etching both of the first LED  110  and the second LED  120  moderately to the transparent conductive layer  13 . The LED array  100  further comprises an insulating layer  17  formed surrounding the first LED  110  and the second LED  120  for electrically isolating the first LED  110  from the second LED  120 . First contacts  18  formed on the second conductive semiconductor stack layer  16  of the first LED  110  and the second conductive semiconductor stack layer  16  of the second LED  120  respectively. Second contacts  19  formed on the transparent conductive layer exposed surface region of the first LED  110  and the transparent conductive layer exposed surface region of the second LED  120  respectively, and a conductive line for electrically connecting a second contact of the first LED  110  to a first contact of the second LED  120 .  
         [0018]      FIG. 2  is a top view of a schematic diagram of a plurality of LED arrays  100  connected in series according to the present invention.  FIG. 3  is an equivalent circuit diagram of the LED arrays shown in  FIG. 2 .  FIG. 4  is a top view of a schematic diagram of a plurality of LED arrays  100  connected in series and in parallel according to the present invention.  FIG. 5  is an equivalent circuit diagram of the LED arrays shown in  FIG. 4 .  
         [0019]     The reflective layer  11  can be also formed between the transparent conductive layer  13  and the adhesive layer  12 . The reflective layer  11  is installed to increase the luminance of the LED array  100  by reflecting light projected onto the substrate  10 . However, the LED array  100  still can operate without the reflective layer  11 .  
         [0020]     The insulating transparent adhesive layer  12  is installed to electrically isolate the first LED  110  and the second LED  120  from the substrate  10 . The insulating transparent adhesive layer  12  can be replaced by a conductive adhesive layer made of metal or solder. However, an insulating layer providing electrical isolation has to be installed additionally between the substrate  10  and the conductive adhesive layer  12  or between the conductive adhesive layer  12  and the transparent conductive layer  13  to electrically isolate the first LED  110  and the second LED  120  from the substrate  10 .  
         [0021]     The trench together with the insulating layer  17  electrically isolates the first LED  110  from the second LED  120 . However, the LED array  100  can further comprise an ion-implanted region formed between the first LED  110  and the second LED  120  for electrically isolating the first LED  110  from the second LED  120 .  
         [0022]     The substrate  10  comprises at least one material selected from a material group consisting of GaP, GaAs, Si, SiC, Al 2 O 3 , glass, quartz, GaAsP, AIN, metal, and AlGaAs. The insulating transparent adhesive layer  12  comprises at least one material selected from a material group consisting of polyimide (PI), benzocyclobutene (BCB), and perfluorocyclobutene (PFCB). The reflective layer  11  comprises at least one material selected from a material group consisting of In, Sn, Al, Au, Pt, Zn, Ge, Ag, Ti, Pb, Pd, Cu, AuBe, AuGe, Ni, PbSn, AuZn, and indium-tin oxide (ITO). The light-emitting layer  15  comprises at least one material selected from a material group consisting of AlGaInP, GaN, InGaN, AlInGaN, and ZnSe. The transparent conductive layer  13  comprises at least one material selected from a material group consisting of indium-tin oxide (ITO), cadmium-tin oxide (CTO), antimony-tin oxide (ATO), zinc oxide, and zinc-tin oxide. The insulating layer  17  comprises at least one material selected from a material group consisting of SiO 2  and SiN x . The first conductive semiconductor stack layer  14  comprises at least one material selected from a material group consisting of AlInP, AIN, GaN, InGaN, AlGaN, and AlInGaN. The second conductive semiconductor stack layer  16  comprises at least one material selected from a material group consisting of AlInP, AIN, GaN, InGaN, AlGaN, and AlInGaN.  
         [0023]     Since the insulating transparent adhesive layer  12  has a high resistance and is capable of electrically isolating the substrate  10  from the first LED  110  and the second LED  120  when being installed between them, the first LED  110  and the second LED  120  can comprise not only a Group III-V nitride material, but also a quaternary material. Moreover, since the substrate  10  is electrically isolated from the LEDs  110  and  120 , the substrate  10  can be an insulating substrate, a substrate having a high resistance, a conductive substrate, or a substrate having a high thermal conduvtivity, which has a capability to improve the heat-dissipation efficiency of the LED array  100 .  
         [0024]     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.