Abstract:
A light emitting diode of one embodiment includes a light emitting device having a plurality of N-type semiconductor layers including a first N-type semiconductor layer and a second N-type semiconductor layer on the first N-type semiconductor layer, an active layer on an upper layer of the plurality of N-type semiconductor layers, and a P-type semiconductor layer on the active layer. The first N-type semiconductor layer includes a first Si doped Nitride layer and the second N-type semiconductor layer includes a second Si doped Nitride layer. The first and second N-type semiconductor layers have a Si impurity concentration different from each other.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of co-pending application Ser. No. 12/107,256, filed on Apr. 22, 2008, that claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2007-0039534, filed on Apr. 23, 2007, the entire contents of which are hereby incorporated by reference and for which priority is claimed under 35 U.S.C. §120. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The embodiment relates to a light emitting diode and a method for manufacturing the same. 
         [0004]    2. Discussion of the Related Art 
         [0005]    A light emitting diode is formed by sequentially stacking a buffer layer, an unintentionally doped GaN layer (Un-GaN layer), an N-type GaN layer, an active layer, and a P-type GaN layer on a substrate. 
         [0006]    The light emitting diode has a characteristic in which electrons are inserted into holes on the active layer to emit light if power is applied to the N-type GaN layer and the P-type GaN layer. 
         [0007]    Meanwhile, since the substrate has a lattice constant different from that of the N-type GaN layer, dislocation may occur, and the buffer layer and the Un-GaN layer reduce a difference between lattice constants of the substrate and the GaN layer. 
         [0008]    However, the buffer layer and the Un-GaN layer have a limitation in the reduction of the difference of the lattice constants, and the dislocation density may be increased due to the Un-GaN layer. 
       SUMMARY OF THE INVENTION 
       [0009]    The embodiment provides a light emitting device and a method for manufacturing the same. 
         [0010]    The embodiment provides a light emitting device and a method for manufacturing the same, capable of reducing dislocation density. 
         [0011]    The embodiment provides a light emitting device and a method for manufacturing the same, capable of reducing lattice mismatching, thereby improving a light emitting characteristic. 
         [0012]    According to the embodiment, a light emitting device comprises a plurality of N-type semiconductor layers including a first N-type semiconductor layer and a second N-type semiconductor layer on the first N-type semiconductor layer; an active layer on an upper layer of the plurality of N-type semiconductor layers; and a P-type semiconductor layer on the active layer, wherein the first N-type semiconductor layer comprises a Si doped Nitride layer and the second N-type semiconductor layer comprises a Si doped Nitride layer, and wherein the first and second N-type semiconductor layers have a Si impurity concentration different from each other. 
         [0013]    According to the embodiment, a light emitting device comprises a plurality of N-type semiconductor layers including a first N-type semiconductor layer and a second N-type semiconductor layer on the first N-type semiconductor layer; an active layer on a first portion of an upper layer of the plurality of N-type semiconductor layers; a P-type semiconductor layer on the active layer, a first electrode on a second portion of the upper layer of the plurality of N-type semiconductor layers; and a second electrode on the P-type semiconductor layer, wherein the first N-type semiconductor layer comprises a Si doped Nitride layer and the second N-type semiconductor layer comprises a Si doped Nitride layer, and wherein the first and second N-type semiconductor layers have a Si impurity concentration different from each other. 
         [0014]    According to the embodiment, a light emitting device comprises a sapphire substrate; a first N-type semiconductor layer including a GaN layer on the sapphire substrate; a second N-type semiconductor layer including a GaN layer on the first N-type semiconductor layer; an undoped GaN layer on the second N-type semiconductor layer; an active layer on the undoped GaN layer; and a P-type GaN layer on the active layer, wherein the first and second N-type semiconductor layers have a Si impurity concentration different from each other. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a view used to explain a light emitting diode according to the first embodiment; and 
           [0016]      FIG. 2  is a view used to explain a light emitting diode according to the second embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    In the description of the embodiments, when layers (films), regions, patterns, or elements are described in that they are formed on or under substrates, layers (films), regions, or patterns, it means that they are formed directly or indirectly on or under the substrates, layers (films), regions, or patterns. 
         [0018]    The thickness and size of each layer shown in the drawings can be simplified or exaggerated for the purpose of convenience or clarity. In addition, the elements may have sizes different from those shown in drawings in practice. 
         [0019]    Hereinafter, a light emitting diode and a method for manufacturing the same with reference to accompanying drawings. 
         [0020]      FIG. 1  is a view used to explain a light emitting diode according to a first embodiment. 
         [0021]    The light emitting diode according to the first embodiment comprises a substrate  10 , a buffer layer  20 , a first Un-GaN layer  31 , a first N-type GaN layer  32 , a second Un-GaN layer  33 , a second N-type GaN layer  34 , an active layer  40 , a P-type GaN layer  50 , and an ohmic electrode layer  60 . A first electrode layer  70  is formed on the second N-type GaN layer  34 , and a second electrode layer  80  is formed on the ohmic electrode layer  60 . 
         [0022]    As shown in  FIG. 1 , the light emitting diode according to the first embodiment includes the first and second Un-GaN layers  31  and  33  and the first and second N-type GaN layers  32  and  34 , which are alternatively and repeatedly stacked on the buffer layer  20 . 
         [0023]    As shown in  FIG. 1 , the Un-GaN layer and the N-type GaN layer are repeated twice. 
         [0024]    According to the first embodiment, the first N-type GaN layer  32  is formed between the first and second Un-GaN layers  31  and  33 , thereby preventing the occurrence of a dislocation density due to the first and second Un-GaN layers  31  and  33 . According to the first embodiment, a plurality of Un-GaN layers are provided, in which each Un-GaN layer is thinner than an Un-GaN layer provided in a single layer structure of the Un-GaN layer and an N-type GaN layer according to the related art. Similarly, each N-type GaN layer may be thin a conventional N-type GaN layer. 
         [0025]    In other words, the increase of dislocation density occurring as the Un-GaN layer becomes thick is prevented by forming a plurality of thin Un-GaN layers. 
         [0026]    For example, the first and second Un-GaN layer  31  and  33  may have thicknesses in the range of 0.5 μm to 1 μm, and the first and second N-type GaN layers  32  and  34  may have thicknesses in the range of 1 μm to 1.5 μm. 
         [0027]    According to the first embodiment, the dislocation density of the first and second N-type GaN layers  32  and  34  is reduced as the N-type GaN layers become close to the active layer  40 , that is, distant from the buffer layer  20 . 
         [0028]    To this end, the first and second Un-GaN layers  31  and  33  and the first and second N-type GaN layers  32  and  34  are formed in a chamber having a higher temperature and a lower pressure while reducing the amount of TMGa flowed into the chamber as the Un-GaN layers and the N-type GaN layers are close to the active layer  40 . 
         [0029]    Further, since a dislocation density may be increased as the concentration of impurities is increased in the first and second N-type GaN layers  32  and  34 , the concentration of N-type impurities is decreased as the N-type GaN layers become close to the active layer  40 . 
         [0030]      FIG. 2  is a view used to explain a light emitting diode according to a second embodiment. 
         [0031]    The light emitting diode according to the second embodiment comprises a substrate  10 , a buffer layer  20 , a first Un-GaN layer  31 , a first N-type GaN layer  32 , a second Un-GaN layer  33 , a second N-type GaN layer  34 , a third Un-GaN layer  35 , a third N-type GaN layer  36 , an active layer  40 , a P-type GaN layer  50 , and an ohmic electrode layer  60 . A first electrode layer  70  is formed on the third N-type GaN layer  36 , and a second electrode layer  80  is formed on the ohmic electrode layer  60 . 
         [0032]    As shown in  FIG. 2 , the light emitting diode according to the second embodiment has the first, second, and third Un-Ga layers  31 ,  33 , and  35  and the first, second, and third N-type GaN layers  32 ,  34 , and  36  alternatively stacked on the buffer layer  20 . 
         [0033]    As shown in  FIG. 2 , the Un-GaN layers and the N-type GaN layers are repeated three times. 
         [0034]    Although it is not shown, the Un-GaN layers and the N-type GaN layers may be repeated four times according to another embodiment. 
         [0035]    According to the second embodiment, the first and second N-type GaN layers  32  and  34  are alternately provided in relation to the first, second, and third Un-GaN layers  31 ,  33 , and  35 , thereby preventing the increase of dislocation density by the first, second, and third Un-GaN layers  31 ,  33 , and  35 . According to the second embodiment, a plurality of Un-GaN layers are provided. In this case, the first, second, and third Un-GaN layers  31 ,  33 , and  35  are thinner than an Un-GaN layer provided in a single layer structure of the Un-GaN layer and an N-type GaN layer according to the related art. Similarly, the first, second, and third N-type GaN layers  32 ,  34 , and  36  may be thin a conventional N-type GaN layer. 
         [0036]    In other words, the increase of dislocation density occurring as the Un-GaN layer becomes thick is prevented by forming a plurality of thin Un-GaN layers. 
         [0037]    For example, the first, second, and third Un-GaN layers  31 ,  33 , and  35  may have thicknesses in the range of 0.3 μm on to 0.6 μm, and the first, second, and third N-type GaN layers  32 ,  34 , and  36  may have thicknesses in the range of 0.5 μm to 1 μm. 
         [0038]    According to the second embodiment, the dislocation density of the N-type GaN layer is reduced as the N-type GaN layer becomes close to the active layer  40 , that is, distant from the buffer layer  20 . 
         [0039]    To this end, the Un-GaN layer and the N-type GaN layer are formed in a chamber having a higher temperature and a lower pressure while reducing an amount of TMGa flowed into the chamber as the Un-GaN layer and the N-type GaN layer are close to the active layer  40 . 
         [0040]    Further, since a dislocation density may be increased as the concentration of impurities is increased in the first, second, and third N-type GaN layers  32 ,  34 , and  36 , the concentration of N-type impurities is decreased as the N-type GaN layers become close to the active layer  40 . 
         [0041]    As described above, in the light emitting diode according to the embodiments, a plurality of thin Un-GaN layers are provided, and the N-type GaN layers are provided between the Un-GaN layers in order to prevent the increase of dislocation density caused by the Un-GaN layers. Accordingly, the increase of the dislocation density in the Un-GaN layer can be prevented due to the N-type GaN layer. 
         [0042]    In addition, the light emitting diode according to the embodiments is provided such that dislocation density is decreased as the N-type GaN layer becomes close to the active layer  40 . 
         [0043]    Accordingly, the dislocation density of the N-type GaN layer in contact with the active layer  40  is decreased so that the light emitting characteristic of the light emitting diode can be improved. 
         [0044]    Hereinafter, a method for manufacturing the light emitting diode according to the embodiment will be described in detail with reference to  FIG. 2 . 
         [0045]    The buffer layer  20  is formed on the substrate  10 . For example, the substrate  10  includes at least one of Al 2 O 3 , Si, SiC, GaAs, ZnO, and MgO. 
         [0046]    The buffer layer  20  is used to reduce a difference between lattice constants of the substrate  10  and the GaN layer stacked on the substrate  10 . For example, the buffer layer  20  may have a stacking structure such as AlInN/GaN, In x Ga 1-x N/GaN, or Al x In y Ga 1-x-y N/In x Ga 1-x N/GaN. 
         [0047]    For example, the buffer layer  20  may be grown by flowing TMGa and TMIn at a flow rate of 3×10 5  Mol/min into the chamber, in which the substrate  10  is positioned, and flowing TMAl at a flow rate of 3×10 6  Mol/min into the chamber together with hydrogen gas and ammonia gases. 
         [0048]    The first Un-GaN layer  31 , the first N-type GaN layer  32 , the second Un-GaN layer  33 , the second N-type GaN layer  34 , the third Un-GaN layer  35 , the third N-type GaN layer  36  are sequentially formed on the buffer layer  20 . The first, second, and third Un-GaN layers  31 ,  33 , and  35  and the first, second, and third N-type GaN layer  32 ,  34 , and  36  may be formed through a metal-organic vapor chemical deposition (MOCVD) process. 
         [0049]    First, the first Un-GaN layer  31  is formed on the buffer layer  20 . For example, the first Un-GaN layer  31  may be formed by flowing NH 3  (3.7×10 −2  Mol/min) and TMGa (2.9×10 −4 -3.1×10 −4  Mol/min) gas in a state in which the chamber is adjusted to have internal pressure of 500 Torr to 700 Torr and the internal temperature in the range of 1040□ to 1050□. 
         [0050]    Then, the first N-type GaN layer  32  is formed on the first Un-GaN layer  31 . For example, the first N-type GaN layer  32  is formed by flowing NH 3  (3.7×10 −2  Mol/min), TMGa (2.9×10 −4 -3.1×10 −4  Mol/min), a SiH 4  gas including N-type impurities such as Si in a state in which a chamber is adjusted to have an internal pressure of 500 Torr to 700 Torr and an internal temperature the temperature in the range of 1040□ to 1050□. 
         [0051]    In this case, the first N-type GaN layer  32  may have a dislocation density of 10 10 /cm 3  or less. In addition, Si may be implanted into the first N-type GaN layer  32  with the concentration of 7×10 18 /cm 3 . 
         [0052]    The second Un-GaN layer  33  is formed on the first N-type GaN layer  32 . The second Un-GaN layer  33  is formed by flowing a less amount of TMGa gas in a chamber with a lower pressure under a higher temperature as compared with the process of performing the first Un-GaN layer  31 . 
         [0053]    For example, the second Un-GaN layer  33  may be formed by flowing NH 3  (3.7×10 −2  Mol/min) and TMGa (1.9×10 −4 -2.1×10 −4  Mol/min) gas in a state in which a chamber is adjusted to have an internal pressure of 300 Torr to 500 Torr and an internal temperature in the range of 1050° C. to 1060° C. 
         [0054]    The second N-type GaN layer  34  is formed on the second Un-GaN layer  33 . The second N-type GaN layer  34  is formed by flowing a less amount of a TMGa gas and an SiH 4  gas in a chamber with a lower pressure under a higher temperature as compared with the process of performing the first N-type GaN layer  32 . 
         [0055]    For example, the second N-type GaN layer  34  may be formed by flowing NH 3  (3.7×10 −2  Mol/min), TMGa (1.9×10 −4 -2.1×10 −4  Mol/min), and a SiH 4  gas including N-type impurities such as Si in a state in which a chamber is adjusted to have an internal pressure of 300 Torr to 500 Torr and an internal in the range of 1050□ to 1060□. 
         [0056]    In this case, the second N-type GaN layer  34  may have the dislocation density of 10 9 /cm 3  or less. In addition, Si may be implanted into the second N-type GaN layer  34  with the concentration of 5×10 18 /cm 3 . 
         [0057]    The third Un-GaN layer  35  is formed on the second N-type GaN layer  34 . The third Un-GaN layer  35  is formed by flowing a less amount of a TMGa gas in a chamber with a lower pressure under a higher temperature as compared with the process of performing the second Un-GaN layer  33 . 
         [0058]    For example, the third Un-GaN layer  35  may be formed by flowing NH 3  (3.7×10 −2  Mol/min) and TMGa (1.4×10 −4 -1.6×10 −4  Mol/min) gas in a state in which a chamber is adjusted to have an internal pressure of 200 Torr to 300 Ton and an internal temperature in the range of 1060° C. to 1070° C. 
         [0059]    The third N-type GaN layer  36  is formed on the third Un-GaN layer  35 . The third N-type GaN layer  36  is formed by flowing a less amount of a TMGa gas and an SiH 4  gas in a chamber with a lower pressure under a higher temperature as compared with the process of performing the second N-type GaN layer  34 . 
         [0060]    For example, the third N-type GaN layer  36  may be formed by flowing NH 3  (3.7×10 −2  Mol/min), TMGa (1.4×10 −4 -1.6×10 −4  Mol/min), and a SiH 4  gas including N-type impurities such as Si in a state in which a chamber is adjusted to have an internal pressure of 200 Torr to 300 Torr and an internal temperature in the range of 1060° C. to 1070° C. 
         [0061]    In this case, the third N-type GaN layer  36  may have the dislocation density of 10 8 /cm 3  or less. In addition, Si may be implanted into the third N-type GaN layer  36  with the concentration of 3×10 18 /cm 3 . 
         [0062]    The active layer  40  is formed on the third N-type GaN layer  36 . For example, the active layer  40  may have a multi-quantum well structure including InGaN/GaN which is grown at a nitrogen gas atmosphere by flowing TMGa and TMIn into the chamber. 
         [0063]    The P-type GaN layer  50  is formed on the active layer  40 . For example, the P-type GaN layer  50  may be grown by supplying TMGa (7×10 −6  Mol/min), TMAl (2.6×10 −5  Mol/min), (EtCp 2 Mg){Mg(C 2 H 5 C 5 H 4 ) 2 } (5.2×10 −7  Mol/min), and NH 3  (2.2×10 −1  Mol/min using hydrogen as a carrier gas. 
         [0064]    The ohmic electrode layer  60  is formed on the P-type GaN layer  50 . For example, the ohmic electrode layer  60  includes at least one of ITO, CTO, SnO 2 , ZnO, RuO x , TiO x , IrO x , and Ga x O x . 
         [0065]    After the above stacking structure is formed, a mask layer (not shown) is formed on the ohmic electrode  60 . The ohmic electrode layer  60 , the P-type GaN layer  50 , the active layer  40 , and the third N-type GaN layer  36  are selectively etched so that a portion of the third N-type GaN layer  36  is exposed upward. 
         [0066]    The first electrode layer  70  is formed on the third N-type GaN layer  36 , and the second electrode layer  80  is formed on the ohmic electrode layer  60 . 
         [0067]    Accordingly, the light emitting diode according to the embodiments can be manufactured. 
         [0068]    In the light emitting diode and the method for manufacturing the same according to the embodiments, the Un-GaN layer and the N-type GaN layer are alternatively stacked, thereby reducing the dislocation density on the N-type GaN layer adjacent to the active layer. 
         [0069]    Further, in the light emitting diode and the method for manufacturing the same according to the embodiments, a plurality of Un-GaN layers and N-type GaN layers are provided. In this case, the Un-GaN layers and the N-type GaN layers are formed by reducing an amount of TMGa flowed into the chamber while increasing the temperature of a chamber and reducing the pressure of the chamber step by step. Accordingly, the dislocation density of the N-type GaN layer adjacent to the active layer may be more reduced. 
         [0070]    In the light emitting diode and the method for manufacturing the same according to the embodiments, a plurality of Un-GaN layers and a plurality of N-type GaN are formed. In this case, the N-type GaN layer is formed by reducing an amount of N-type impurities step by step. Accordingly, the dislocation density of the N-type GaN layer adjacent to the active layer can be more reduced. 
         [0071]    Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
         [0072]    Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.