Abstract:
A light emitting diode including a substrate, a semiconductor stacking layer, a first electrode and a second electrode is provided. The semiconductor stacking layer including an n-type doped semiconductor layer, a p-type doped semiconductor layer and an active layer is disposed on the substrate. The n-type doped semiconductor layer has In dopant. The active layer is disposed between the n-type doped semiconductor layer and the p-type doped semiconductor layer. In addition, the first electrode is disposed on the n-type doped semiconductor layer while the second electrode is disposed on the p-type doped semiconductor layer. In the light emitting diode mentioned above, no crack, open or pin hole are found in the n-type doped semiconductor layer, thus the light emitting diode mentioned above has lower power consumption, higher manufacturing yield and better reliability.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the priority benefit of Taiwan application serial no. 94137093, filed on Oct. 24, 2005. All disclosure of the Taiwan application is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of Invention  
         [0003]     The present invention relates to a semiconductor device. More particularly, the present invention relates to a light emitting diode (LED).  
         [0004]     2. Description of Related Art  
         [0005]     Light emitting diode is one of semiconductor devices and the material of its light emitting chip is mostly III-V group elements in semiconductor components, such as GaP, GaAs, and GaN. The principle of emitting light of light emitting diodes is converting electrical energy into light. That is, through applying electrical current to semiconductor components, electrons and holes are combined and the surplus energy is emitted in a way of light, so that an emission of light is formed. Other than by heating or discharging, the light of light emitting diodes belongs to a cold luminescence, so that the life of light emitting diodes can be longer than 100,000 hours and no idling time is needed. In addition, light emitting diodes have many advantages, such as fast response (about 10 −9  second), small volume, less electricity expense, less pollution (no mercury), high reliability, adapted for mass production and so on, therefore, it can be used in extensive areas, for example, the light source of scanners requiring a fast response, the back light source or front light source of liquid crystal displays, the illumination of auto instrument panels, traffic lights, and general illuminating devices.  
         [0006]     GaN is the main material of the conventional light emitting diodes and fabricated by an epitaxy method. Wherein, a light emitting diode mainly includes a substrate, an active layer, a p-type and an n-type doped semiconductor layers respectively disposed on the upside and downside of the active layer, and two external-connection electrodes. When a forward bias voltage is applied to the active layer by the external-connection electrodes, the current via the external-connection electrodes flows through the semiconductor layers. At this moment, electrons and holes inside the active layer are combined, causing the active layer to emit light.  
         [0007]     In a usual light emitting diode, the n-type doped semiconductor layer usually has Si dopants in a high concentration. However, the Si dopants in high concentration make the n-type doped semiconductor layer likely to crack or break. When the n-type doped semiconductor layer cracks or breaks, it would be much difficult to fabricate electrodes on the n-type doped semiconductor layer. To be specific, if the n-type doped semiconductor layer cracks or breaks, the external-connection electrodes can not tightly contact the n-type doped semiconductor layer, causing the electrical characteristics of the light emitting diode worse, the operating voltage increased, the manufacturing yield decreased, and the cost relatively higher.  
         [0008]     In addition, in an n-type doped semiconductor layer with Si dopant, pin holes are likely to occur, which make the light emitting diode produce a severe current leakage, and further decrease the reliability and poor ability of electrostatic resistance for the light emitting diode.  
       SUMMARY OF THE INVENTION  
       [0009]     Accordingly, the present invention is directed to provide a light emitting diode with high reliability and ability of electrostatic resistance.  
         [0010]     For achieving the above or other objectives, the present invention provides a light emitting diode including a substrate, a semiconductor stacking layer, a first electrode and a second electrode. The semiconductor stacking layer including an n-type doped semiconductor layer, a p-type doped semiconductor layer, and an active layer is disposed on the substrate. The n-type doped semiconductor layer has In dopants. The active layer is disposed between the n-type doped semiconductor layer and the p-type doped semiconductor layer. In addition, the first electrode is disposed on the n-type doped semiconductor layer while the second electrode is disposed on the p-type doped semiconductor layer.  
         [0011]     In an embodiment of the present invention, the material of the substrate includes sapphire, 6H—SiC, 4H—SiC, Si, ZnO, GaAs, MgAl 2 O 4 , or one of single crystal oxides whose lattice constant is close to nitride semiconductor.  
         [0012]     In an embodiment of the present invention, the indium dopants are uniformly distributed in the n-type doped semiconductor layer.  
         [0013]     In an embodiment of the present invention, the n-type doped semiconductor layer with the indium dopants further includes Si dopants.  
         [0014]     In an embodiment of the present invention, the n-type doped semiconductor layer with the indium dopants further includes Si dopants and Mg dopants.  
         [0015]     In an embodiment of the present invention, the material of the n-type doped semiconductor layer includes indium doped Al x Ga 1-x N; 0≦x&lt;1, In—Si doped Al x Ga 1-x N; 0≦x&lt;1, or In—Si—Mg doped Al x Ga 1-x N; 0≦x&lt;1.  
         [0016]     In an embodiment of the present invention, the n-type doped semiconductor layer includes a plurality of local indium doped regions and a plurality of undoped regions, wherein the local indium doped regions and undoped regions are disposed alternately along the thickness direction of the n-type doped semiconductor layer.  
         [0017]     In an embodiment of the present invention, the n-type doped semiconductor layer with indium dopants further includes Si dopants.  
         [0018]     In an embodiment of the present invention, the n-type doped semiconductor layer with indium dopants further includes Si dopants and Mg dopants.  
         [0019]     In an embodiment of the present invention, the material of the undoped regions includes GaN or AlGaN.  
         [0020]     In an embodiment of the present invention, comparing with the material of nitride semiconductor of the local indium doped regions, the material of nitride semiconductor of the undoped regions has a larger band gap width.  
         [0021]     In an embodiment of the present invention, the n-type doped semiconductor layer includes a buffer layer, a first contact layer, and a first cladding layer. Wherein, the buffer layer is disposed over the substrate; the first contact layer is disposed over the buffer layer; the first cladding layer is disposed over the first contact layer.  
         [0022]     In an embodiment of the present invention, the n-type doped semiconductor layer further includes a nucleation layer disposed between the buffer layer and the first contact layer.  
         [0023]     In an embodiment of the present invention, the p-type doped semiconductor layer includes a second cladding layer and a second contact layer. Wherein, the second cladding layer is disposed on the active layer while the second contact layer is disposed on the second cladding layer.  
         [0024]     The n-type doped semiconductor layer of the light emitting diode of the present invent has In dopant, which can avoid the breaks and cracks of the conventional n-type doped semiconductor layer and make the n-type doped semiconductor layer and the electrodes contact each other tightly, so that the light emitting diode has high electrical conductivity and reliability.  
         [0025]     In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, a preferred embodiment accompanied with figures is described in detail below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIG. 1  is a cross-sectional view of a light emitting diode of the first embodiment of the present invention.  
         [0027]      FIG. 2  is a cross-sectional view of a light emitting diode of the second embodiment of the present invention.  
         [0028]      FIG. 3  is a cross-sectional view of a light emitting diode of the third embodiment of the present invention.  
         [0029]      FIG. 4  is a cross-sectional view of a light emitting diode of the fourth embodiment of the present invention.  
         [0030]      FIG. 5  is a cross-sectional view of a light emitting diode of the fifth embodiment of the present invention.  
         [0031]      FIG. 6  is a cross-sectional view of a light emitting diode of the sixth embodiment of the present invention. 
     
    
     DESCRIPTION OF EMBODIMENTS  
     The First Embodiment  
       [0032]      FIG. 1  is a cross-sectional view of a light emitting diode of the first embodiment of the present invention. Referring to  FIG. 1 , a light emitting diode  100  includes a substrate  100 , a semiconductor stacking layer  120 , a first electrode  160  and a second electrode  170 . Wherein, the semiconductor stacking layer  120  including an n-type doped semiconductor layer  130 , a p-type doped semiconductor layer  140  and an active layer  150  is disposed over the substrate  110 . The n-type doped semiconductor layer  130  has In dopants. The active layer  150  is disposed between the n-type doped semiconductor layer  130  and the p-type doped semiconductor layer  140 . In addition, the first electrode  160  is disposed over the n-type doped semiconductor layer  130  while the second electrode  170  is disposed over the p-type doped semiconductor layer  140 .  
         [0033]     To be specific, the material of the substrate  110  in the present embodiment is for example sapphire. In the other embodiments, the material of the substrate  110  can be 6H-SiC, 4H-SiC, Si, ZnO, GaAs, MgAl 2 O 4 , or one of single crystal oxides whose lattice constant is close to nitride semiconductor. Manufacturers can select a proper material of the substrate  110  according to requirements.  
         [0034]     Following the above, in the semiconductor stacking layer  120  of the present embodiment, the n-type doped semiconductor layer  130 , the active layer  150 , and the p-type doped semiconductor layer  140  are stacked over the substrate  110  in sequence from down to up. Namely, the n-type doped semiconductor layer  130  in the semiconductor stacking layer  120  is disposed on the substrate  110 . Especially, in the light emitting diode  100 , the material of the n-type doped semiconductor layer is In doped Al x Ga 1-x N with 0≦x&lt;1. In dopants are uniformly distributed in the n-type doped semiconductor layer  130  and effectively improve the electrical characteristics of the light emitting diode  100 . In more detail, the radius of an indium atom in the n-type doped semiconductor layer  130  is larger than the radius of a Ga atom, therefore, the In dopants in the n-type doped semiconductor layer  130  not only can overcome the dislocation of the n-type doped semiconductor layer  130  to avoid cracks and breaks of the conventional n-type doped semiconductor layer, but also can make the n-type doped semiconductor layer  130  have a smooth surface.  
         [0035]     Known from  FIG. 1  the active layer  150  is disposed on a portion of the n-type doped semiconductor layer  130 , and a portion of the n-type doped semiconductor layer  130  is exposed; that is, the active layer  150  does not wholly cover the n-type doped semiconductor layer  130 . Generally, the active layer  150  has a multiple quantum well structure, and the material of the active layer  150  is for example III-V group semiconductor components, such as the familiar material of GaP, GaAsP, AlGaAs, AlInGaP, or GaN.  
         [0036]     Referring to  FIG. 1  again, the p-type doped semiconductor layer  140  is disposed on the active layer  150 , and the material of the p-type doped semiconductor layer  140  is for example Mg doped Al x Ga 1-x N with 0≦x&lt;1; or In, Si, Mg (main dopant) doped Al x Ga 1-x N with 0≦x&lt;1. In addition, the second electrode  170  is disposed on the p-type doped semiconductor layer  140  while the first electrode  160  is disposed on the exposed portion of the n-type doped semiconductor layer  130 .  
         [0037]     When a forward bias voltage is applied to the active layer  150  through the first electrode  160  and the second electrode  170 , the current flows through the semiconductor stacking layer  120 , and the electrons and holes inside the active layer  150  are combined, which makes the active layer  150  emits light.  
         [0038]     Note that the n-type doped semiconductor layer  130  has In dopants, so the n-type doped semiconductor layer  130  has a smooth surface and is not easy to crack or break. On the other hand, because the n-type doped semiconductor layer  130  has a smooth surface, when the first electrode  160  is formed on the n-type doped semiconductor layer  130 , the first electrode  160  can tightly contact the n-type doped semiconductor layer  130 . As a result, the light emitting diode  100  has high electrical conductivity and production yield.  
         [0039]     Following the above, for decreasing the operating voltage of the light emitting diode  100 , Si dopants can be doped into the n-type doped semiconductor layer  130  with In dopants. Therefore, when a forward bias voltage is applied to the active layer  150  through the first electrode  160  and the second electrode  170 , only a low operating voltage is needed for the light emitting diode  100  to emit light. In a preferred embodiment, besides the In dopants and the Si dopants, a little amount of Mg dopants can further be doped into the n-type doped semiconductor layer  130 . Noting that, the n-type doped semiconductor layer  130  has less the Mg dopants than the Si dopants. The In—Si—Mg dopants in the n-type doped semiconductor layer  130  can decrease the ionization energy of electrons and holes and increase the mobility of carriers in the n-type doped semiconductor layer  130 , so as to increase the probability of the combination of electrons and holes in the active layer  150 .  
         [0040]     To summary, the material of the n-type doped semiconductor layer of the light emitting diode of the present invention is the In doped Al x Ga 1-x N with 0≦x&lt;1. The In dopants can overcome the dislocation of the n-type doped semiconductor layer, so that the light emitting diode of the present invention has high electrical characteristics and production yield.  
       The Second Embodiment  
       [0041]      FIG. 2  is a cross-sectional view of a light emitting diode of the second embodiment of the present invention. In  FIG. 1  and  FIG. 2 , the same or similar numerals indicate the same or similar elements whose functions and locations have been in detail described above, here they would not be repeated in description. As shown in  FIG. 2 , comparing with the first embodiment, in the semiconductor stacking layer  120   a  of the present embodiment, the p-type doped semiconductor layer  140 , the active layer  150  and the n-type doped semiconductor layer  130  are stacked over the substrate  110  in a sequence from down to up.  
         [0042]     Known from the aforementioned two embodiments that the light emitting diode of the present invention does not limit the disposed locations of the p-type doped semiconductor layer and the n-type doped semiconductor layer in the semiconductor stacking layer. The disposed locations of the p-type doped semiconductor layer and the n-type doped semiconductor layer can be exchanged while the active layer always need to be disposed between the p-type doped semiconductor layer and the n-type doped semiconductor layer.  
         [0043]     For convenience, the following schematic views are illustrated according to the n-type doped semiconductor layer  130  being disposed on the substrate  110 , and the same or similar labels indicate the same or similar elements which have been described above, so would not be repeated.  
       The Third Embodiment  
       [0044]      FIG. 3  is a cross-sectional view of a light emitting diode of the third embodiment of the present invention. Referring to  FIG. 3 , different from the first and second embodiments, for decreasing the operating voltage and the leakage current of the light emitting diode  100   b,  the n-type doped semiconductor layer  130   b  of the present embodiment includes a plurality of local In doped regions  132  and undoped regions  134 , which are stacked alternately. Wherein, comparing with the material of nitride semiconductor of the local In doped regions  132 , the material of nitride semiconductor of the undoped regions  134  has larger band gap width. For example, the material of the local In doped regions  132  of the present embodiment is the In doped Al x Ga 1-x N with 0≦x&lt;1, while the material of the undoped regions  134  is undoped GaN or undoped AlGaN. In the n-type doped semiconductor layer  130   b,  the quantity of both of the local In doped regions  132  and the undoped regions  134  is between 10 and 200. The spreading thickness of the local In doped regions  132  is for example between 10 and 200 nanometers while the spreading thickness of the undoped regions  134  is for example between 1 and 20 nanometers, and the thickness ratio of the local In doped regions  132  to the undoped regions  134  is about 10:1.  
         [0045]     To be specific, the local In doped regions  132  and the undoped regions  134  are disposed alternately along the thickness direction of the n-type doped semiconductor layer  130   b.  When a forward bias voltage is applied to the active layer  150  through the first electrode  160  and the second electrode  170 , the local In doped regions  132  and the undoped regions  134  disposed alternately can avoid the leakage current of the light emitting diode  100   b  and decrease the operating voltage of the light emitting diode  100   b.    
       The Fourth Embodiment  
       [0046]      FIG. 4  is a cross-sectional view of a light emitting diode of the fourth embodiment of the present invention. Referring to  FIG. 4 , the present embodiment is similar to the third embodiment. Comparing with the third embodiment, the material of the local In doped regions  132 ′ of the light emitting diode  100   c  is In—Si doped Al x Ga 1-x N with 0≦x&lt;1. In the n-type doped semiconductor layer  130   c,  the quantity of both of the local In doped regions  132 ′ and the undoped regions  134  is between 10 and 200. The spreading thickness of the local In doped regions  132 ′ is for example between 10 and 200 nanometers while the spreading thickness of the undoped regions  134  is for example between 1 and 20 nanometers, and the thickness ratio of the local In doped regions  132 ′ to the undoped regions  134  is about 10:1.  
       The Fifth Embodiment  
       [0047]      FIG. 5  is a cross-sectional view of a light emitting diode of the fifth embodiment of the present invention. The present embodiment is similar to the fourth embodiment. Comparing with the fourth embodiment, the material of the local In doped regions  132 ″ of the light emitting diode  100   d  is In—Si—Mg doped Al x Ga 1-x N with 0≦x&lt;1. In the n-type doped semiconductor layer  130   d,  the quantity of both of the local In doped regions  132 ″ and the undoped regions  134  is between 10 and 200. The spreading thickness of the local In doped regions  132 ″ is for example between 10 and 200 nanometers while the spreading thickness of the undoped regions  134  is for example between 1 and 20 nanometers, and the thickness ratio of the local In doped regions  132 ″ to the undoped regions  134  is about 10:1.  
         [0048]     Remarkably, in the n-type doped semiconductor layer  130   d,  the quantity of Mg dopants is less than the quantity of Si dopants. The In dopants, the Si dopants and the Mg dopants in the n-type doped semiconductor layer  130  can decrease the ionization energy of electrons and holes and increase the mobility of carriers (electrons and holes) in the n-type doped semiconductor layer  130 , so as to increase the probability of the combination of electrons and holes in the active layer  150 .  
       The Sixth Embodiment  
       [0049]      FIG. 6  is a cross-sectional view of a light emitting diode of the sixth embodiment of the present invention. Referring to  FIG. 6 , in order that the light emitting diode has desired optical and electrical characteristics, buffer layers, nucleation layers and cladding layers, which have different functions, can further be disposed in the semiconductor stacking layer of the light emitting diode of the aforementioned embodiments.  
         [0050]     In the present embodiment, the n-type doped semiconductor layer  130   e  includes a buffer layer  135  disposed over the substrate  110 , a first contact layer  136  disposed over the buffer layer  135 , and a first cladding layer  137  disposed over the first contact layer  136 . The buffer layer  135  in the light emitting diode  100   e  can improve the quality of the epitaxy, so as to improve the optical and electrical characteristics of the light emitting diode  100   e.    
         [0051]     Following the above, the n-type doped semiconductor layer  130   e  further includes a nucleation layer  138  disposed between the buffer layer  135  and the first contact layer  136 . The nucleation layer  138  can accelerate the epitaxy rate of the first contact layer  136 , arrange the lattices in order, and make the first contact layer  136  have a smooth surface.  
         [0052]     Knowing from  FIG. 6 , the first cladding layer  137  and the second cladding layer  142  are disposed over the upside and downside of the active layer  150 . When a forward bias voltage is applied to the first electrode  160  and the second electrode  170  of the light emitting diode  110   e,  the first cladding layer  137  and the second cladding layer  142  can limit the carriers to the active layer  150  to increase the probability of the combination of electrons and holes in the active layer  150 , so that the light emitting diode  110   e  has an improved light emitting efficiency.  
         [0053]     Referring to  FIG. 6  again, the p-type doped semiconductor layer  140   e  of the present embodiment includes a second cladding layer  142  and a second contact layer  144 . Wherein, the second cladding layer  142  is disposed over the active layer  150  while the second contact layer  144  is disposed over the second cladding layer  142 .  
         [0054]     In summary, the light emitting diode of the present invention has at least the following advantages:  
         [0055]     In the present invention, the In dopants, the In—Si doped dopants, or the In—Si—Mg doped dopants are doped into the n-type doped semiconductor layer, so that the structure strength and surface evenness of the n-type doped semiconductor layer can be improved, and the electrodes can be tightly connected with the n-type doped semiconductor layer. As a result, the light emitting diode  100  has high electrical conductivity and production yield.  
         [0056]     In the present invention, a plurality of local In doped regions and undoped regions are disposed alternately along the thickness direction of the n-type doped semiconductor layer, so that the operating voltage of the light emitting diode can be decreased, the reliability of the light emitting diode can be increased, and the leakage current of the light emitting diode can be effectively reduced.  
         [0057]     The present invention is disclosed above with its preferred embodiments. It is to be understood that the preferred embodiment of present invention is not to be taken in a limiting sense. It will be apparent to those skill in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. The protection scope of the present invention is in accordant with the scope of the following claims and their equivalents.