JP2008226866A - Gallium nitride based light-emitting diode element and light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a GaN-based LED element for providing excellent light emitting output that can be suitably used for the purpose of lighting or the like by reducing a problem of light absorption by a pad electrode. <P>SOLUTION: The GaN-based LED element 100 includes a substrate 101 and a semiconductor laminated body 102 formed of a plurality of GaN-based semiconductor layers formed on the substrate. On a p-type layer 102-3, a light transmitting conductor oxide film 104, a positive pad electrode 105, and a connecting electrode 106 are formed. The conductor oxide film 104 and the positive pad electrode 105 are not overlapped with each other and current is supplied to the p-type layer 102-3 from the positive pad electrode 105 through the conductor oxide film 104. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a GaN-based LED element having a light-emitting element structure using a GaN-based semiconductor, and a light-emitting device using the GaN-based LED element.

A GaN-based semiconductor is a compound semiconductor represented by the chemical formula Al _a In _b Ga _1-ab N (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ a + b ≦ 1), and is a group III nitride semiconductor Also called a nitride-based semiconductor. A GaN-based LED element in which a light-emitting element structure such as a pn junction structure, a double hetero structure, or a quantum well structure is configured by a GaN-based semiconductor can generate green to near-ultraviolet light. It has been put to practical use in applications such as equipment. At present, research and development for applying GaN-based LED elements to lighting applications are actively performed, but higher output is required for practical use.

As a GaN-based LED element according to the prior art, like a GaN-based LED element 10 whose cross-sectional view is shown in FIG. 12, a substrate 11 and a semiconductor laminate 12 composed of a plurality of GaN-based semiconductor layers formed on the substrate, The semiconductor laminate 12 has a p-type layer 12-3 disposed at a position farthest from the substrate 11, and is disposed between the p-type layer 12-3 and the substrate 11. A light-emitting layer 12-2 and an n-type layer 12-1 disposed so as to sandwich the light-emitting layer 12-2 between the p-type layer 12-3 and the p-type layer 12-3. A GaN-based LED element having a configuration in which a translucent conductive oxide film 14 is formed as an ohmic electrode and a positive pad electrode 15 is formed on the conductive oxide film 14 is known. In such a GaN-based LED using a conductive oxide film made of indium tin oxide (ITO) or the like as an electrode, light absorption by the pad electrode formed on the conductive oxide film is high in the LED element. It has been pointed out as one of the factors that hinder output, and as a countermeasure, it has been proposed to form a pad electrode using a metal material having a high reflectance (Patent Document 1). The pad electrode is an electrode to which a material used for connection to an external electrode such as a bonding wire, a conductive paste, a brazing material (solder, eutectic), or the like is bonded.
JP 2005-317931 A

However, as a result of the study by the present inventors, the metal material has a strong effect as a light absorber, no matter how good the reflectance, and only relying on the improvement of the reflectivity of the pad electrode, It has been found that there is a limit to improving the light output of GaN-based LED elements. The present invention has been made in view of such circumstances, and a main object thereof is to provide a GaN-based LED element having a structure capable of reducing light absorption by a pad electrode.

In order to achieve the above object, the present invention provides a GaN-based LED element having the following characteristics.
(1) A p-type layer having a substrate and a semiconductor stacked body formed of a plurality of GaN-based semiconductor layers formed on the substrate, the semiconductor stacked body being disposed at a position farthest from the substrate A GaN-based LED element comprising: a light emitting layer disposed between the p-type layer and the substrate; and an n-type layer disposed so as to sandwich the light emitting layer between the p-type layer A translucent conductive oxide film, a positive pad electrode, and a connection electrode for electrically connecting the conductive oxide film and the positive pad electrode are formed on the p-type layer. The conductive oxide film and the positive pad electrode do not overlap each other, and current is supplied from the positive pad electrode to the p-type layer through the conductive oxide film. A GaN-based LED element.
(2) The GaN-based LED element according to (1), wherein the connection electrode is made of a conductive oxide and has translucency.
(3) The GaN-based LED element according to (2), wherein the connection electrode has a larger film thickness than the conductive oxide film.
(4) The connection electrode is a metal film, part of which overlaps with the conductive oxide film, and the area of the part where the connection electrode which is the metal film overlaps with the conductive oxide film is The GaN-based LED element according to (1), which is 50% or less of the area of the positive pad electrode.
(5) The GaN-based LED element according to any one of (1) to (4), wherein the contact between the positive pad electrode and the p-type layer is non-ohmic.
(6) The GaN-based LED element according to any one of (1) to (4), wherein the surface of the p-type layer in contact with the positive pad electrode is subjected to a high resistance treatment.
(7) The GaN-based LED element according to any one of (1) to (4), wherein the positive pad electrode and the p-type layer are insulated.
(8) The GaN-based LED element according to any one of (1) to (7), wherein the positive pad electrode has a reflective layer mainly composed of Al, Ag, or a platinum group element.
(9) The GaN-based LED element according to any one of (1) to (8), wherein a surface of the p-type layer in contact with the positive pad electrode is a textured surface.
(10) On the p-type layer, a region that is not covered by any of the conductive oxide film, the positive pad electrode, and the connection electrode and has a textured surface is provided. The GaN-based LED element according to any one of (1) to (9).
(11) having a negative electrode connected to the n-type layer and formed on the same side as the positive pad electrode, the negative electrode being in contact with the n-type layer, A translucent lower negative electrode layer made of a conductive oxide, provided with an extension for promoting diffusion, and a connecting material formed on the lower negative electrode layer; A GaN-based LED element according to any one of (1) to (10), comprising an upper negative electrode layer made of a metal material.
(12) The GaN-based LED element according to any one of (1) to (11), wherein the substrate has translucency.
(13) The GaN-based LED element according to any one of (1) to (11), wherein the substrate is made of a metal material.
(14) A light-emitting device obtained by flip-chip mounting the GaN-based LED element according to (12).

Since the GaN-based LED element according to the embodiment of the present invention is excellent in light emission output, it can be suitably used in applications that require high output, such as illumination applications.

In explaining the present invention, when the member constituting the GaN-based LED element is translucent or has translucency, the light-emitting layer when the GaN-based LED element is energized This means that the member exhibits transparency to the light emitted from. Translucency does not mean that the transmittance is 100%, nor does it mean that it is transparent without being clouded.

A GaN-based LED element according to a preferred embodiment of the present invention includes a substrate and a semiconductor stacked body including a plurality of GaN-based semiconductor layers formed on the substrate, and the semiconductor stacked body includes the substrate. A p-type layer disposed farthest from the substrate, a light-emitting layer disposed between the p-type layer and the substrate, and an n-type disposed so as to sandwich the light-emitting layer between the p-type layer A GaN-based LED element including a light-transmitting conductive oxide film, a positive pad electrode, the conductive oxide film, and the positive pad electrode on the p-type layer. And the conductive oxide film and the positive pad electrode do not overlap each other, and a current from the positive pad electrode to the p-type layer is formed. Is supplied through the conductive oxide film. An example of the structure of a GaN-based LED element having such a configuration is shown in FIGS. FIG. 1A is a plan view of the LED element as viewed from the side on which the GaN-based semiconductor layer stack is formed, and FIG. 1B is a cross-sectional view taken along the line XX in FIG. FIG. 2 is a cross-sectional view taken along the line YY in FIG.

The GaN-based LED element 100 includes a substrate 101 and a semiconductor stacked body 102 made of a plurality of GaN-based semiconductors formed thereon, as shown in cross-sectional views in FIGS. . The semiconductor stacked body 102 includes an n-type layer 102-1, a light emitting layer 102-2, and a p-type layer 102-3 in this order from the substrate 101 side. A negative electrode 103 that is an ohmic electrode and also serves as a pad electrode is formed on the partially exposed surface of the n-type layer 102-1. On the p-type layer 102-3, a translucent conductive oxide film 104 that is an ohmic electrode, a positive pad electrode 105, and the conductive oxide film 104 and the positive pad electrode 105 are electrically connected. Connecting electrode 106 to be formed. The conductive oxide film 104 and the positive pad electrode 105 are formed so as not to overlap each other.

In the preferred embodiment, the contact between the positive pad electrode 105 and the p-type layer 102-3 is such that current is supplied from the positive pad electrode 105 to the p-type layer 102-3 through the conductive oxide film 104. , Non-ohmic. For example, if the portion of the positive pad electrode 105 that is in contact with at least the p-type layer 102-3 is formed of a metal such as Al (aluminum), Ti (titanium), W (tungsten), or V (vanadium), a non-ohmic property is obtained. Since the contact is formed, the contact resistance between the positive pad electrode 105 and the p-type layer 102-3 is increased. As a result, the supply of current from the positive pad electrode 105 to the p-type layer 102-3 is mainly conductive. This is performed through the conductive oxide film 104.

In another preferred embodiment, the p-type layer 102 in contact with the positive pad electrode 105 is used so that the current is supplied from the positive pad electrode 105 to the p-type layer 102-3 through the conductive oxide film 104. -3 surface is plasma treated. This plasma treatment includes dry etching treatment using a halogen-based gas (eg, Cl ₂ , SiCl ₄ , BCl _3, etc.). When formed on the surface of a p-type GaN-based semiconductor from which only the natural oxide film on the surface has been removed, an electrode exhibiting a low contact resistance (for example, a Ni / Au electrode) is formed on the p-type GaN-based semiconductor subjected to dry etching. It is known to exhibit high contact resistance when formed on the surface. This is said to be because the surface of the dry-processed p-type GaN-based semiconductor becomes non-ohmic or has a high resistance. Further, this plasma treatment may be exposure to plasma using a gas (Ar, H _2, etc.) that does not have high corrosivity as a raw material. An electrode having a low contact resistance when formed on the surface of a p-type GaN-based semiconductor from which only the natural oxide film has been removed has been exposed to such plasma beyond the extent that the natural oxide film is removed. It is known that when it is formed on the surface of a semiconductor, it exhibits a high contact resistance. This is said to be because a surface layer having a high resistance is formed when the crystal structure is physically damaged. The plasma treatment can be performed using a general RIE (reactive ion etching) apparatus or a plasma etching apparatus.

In another preferred embodiment, the positive pad electrode 105 and the p-type layer 102-are supplied from the positive pad electrode 105 to the p-type layer 102-3 through the conductive oxide film 104. 3 is insulated. This insulation can be performed, for example, by inserting an insulating thin film between the positive pad electrode 105 and the p-type layer 102-3. This insulating thin film may be a thin film of metal oxide, metal nitride, metal oxynitride, metal fluoride, or the like formed by a method such as vacuum deposition, sputtering, or CVD. This insulating thin film can be preferably formed using silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, spinel, aluminum nitride, tantalum oxide, zirconium oxide, hafnium oxide, magnesium fluoride, lithium fluoride, or the like. . This insulating thin film can also have a multilayer structure.

When a light-emitting device is configured using the GaN-based LED element 100, the GaN-based LED element 100 is mounted on a substrate, a slag, a lead frame, so that the surface of the LED element on the semiconductor laminate 102 side faces the light extraction direction of the light-emitting device. It can be fixed on the surface of a mounting substrate such as a unit substrate. When the substrate 101 is a light-transmitting substrate, the GaN-based LED element 100 is fixed on the surface of the mounting substrate so that the surface of the LED element on the substrate 101 side faces the light extraction direction of the light emitting device. You can also. The latter mounting form is called flip chip mounting.

In the GaN-based LED element 100, the conductive oxide film 104 and the positive pad electrode 105 do not overlap each other, and the supply of current from the positive pad electrode 105 to the p-type layer 102-3 is a conductive oxide. Since the process is performed through the film 104, the supply of current to the light emitting layer 102-2 becomes insufficient immediately below the positive pad electrode 105, and thus the generation of light is suppressed. The light generated immediately below the positive pad electrode is strongly absorbed by the positive pad electrode. However, in the GaN-based LED element 100, the generation of this light is suppressed in advance (the current consumed for the generation of this light is reduced). This reduces the loss and improves the light output. The effect of improving the output by suppressing the generation of light that is easily absorbed by the positive pad electrode is particularly noticeable when a light-emitting device in which the GaN-based LED element 100 is flip-chip mounted is configured. Become.

In a light-emitting device configured by mounting the GaN-based LED element 100 so that the surface on the side of the semiconductor laminate 102 faces the light extraction direction, output improvement by suppressing light generation directly under the positive pad electrode 105 It is clear that the effect appears. In such a light emitting device, the light generated immediately below the positive pad electrode cannot be efficiently extracted in the light extraction direction because the positive pad electrode is not only absorbed but also shielded. Therefore, the effect of reducing the loss by suppressing the generation of such light in advance becomes more remarkable.

Further, when an insulating thin film is inserted between the positive pad electrode 105 and the p-type layer 102-3, light generated in the light emitting layer 102-2 and then propagating in the layer direction in the semiconductor stacked body 102 is transmitted. In addition, the effect of being hardly absorbed by the positive pad electrode 106 can be expected.

There is no particular limitation on the material of the connection electrode 106, and the connection electrode 106 can be formed using any conductive material. When the connection electrode 106 is formed of a metal film, sufficient conductivity can be obtained. In this case, the contact portion between the positive pad electrode 105 and the connection electrode 106 may have a configuration in which the positive pad electrode 105 overlaps the connection electrode 106 as in the GaN-based LED element 100. FIG. As shown, the connection electrode 106 may overlap the positive pad electrode 105. Alternatively, as shown in FIG. 4, the positive pad electrode 105 has a two-layer structure including a lower pad electrode layer 105-1 and an upper pad electrode layer 105-2, and the lower pad electrode layer 105-1 and the upper pad electrode 105-2. The connection electrode 106 may be sandwiched between the electrode layer 105-2 and the electrode layer 105-2.

When the connection electrode 106 is a metal film, the area where the connection electrode 106 and the conductive oxide film 104 overlap can be 1% to 80% of the area of the positive pad electrode 105, for example. If this area is too large, the light emission output of the element is lowered due to light absorption by the connection electrode 106. Therefore, when the connection electrode 106 is a metal film, the area where the connection electrode 106 and the conductive oxide film 104 overlap is preferably 50% or less of the area of the positive pad electrode 105, more preferably. Is 25% or less, more preferably 10% or less.

The connection electrode 106 can also be formed to be light-transmitting using a conductive oxide so that light emitted from the light-emitting layer 102-2 is not absorbed. In this case, it is desirable that the thickness of the connection electrode 106 is larger than the thickness of the conductive oxide film 104 so that the operating voltage (forward voltage) of the LED element does not increase due to the series resistance of the connection electrode. .

The planar shape and planar arrangement of the negative electrode 103, the conductive oxide film 104, the positive pad electrode 105, and the connection electrode 106 can be variously modified. As shown in FIG. 5, the connection electrode 106 can have a bent shape. As shown in FIG. 6, the number of connection electrodes 106 may be only one. In the example of FIG. 6, the positive pad electrode 105 is disposed at a corner portion of the square LED element surface. As shown in FIG. 7, the positive pad electrode 105 may be disposed at the corner portion of the square LED element surface, and the two strip-shaped connection electrodes 106 may be formed in directions orthogonal to each other. In the example of FIG. 7, the negative electrode 103 is also arranged at a corner portion of the square LED element surface. In the example shown in FIG. 8, a square positive pad electrode 105 is arranged at the edge of a square LED element surface, and a strip-like connection electrode 106 extends from below the positive pad electrode 105 toward the inside of the LED element surface. Yes. In the example shown in FIG. 9, two positive pad electrodes 105 are formed. As shown in FIG. 10, the connection electrode 106 can be formed in a band shape along the outer peripheral shape of the positive pad electrode 105.

By the way, in the example of FIGS. 8 and 9, the negative electrode 103 is formed of two portions, and the lower negative electrode layer 103− having an elongated extension for promoting diffusion in the surface direction of current is provided. 1 and an upper negative electrode layer 103-2 for bonding a connection material such as a bonding wire. Preferably, the lower negative electrode layer 103-1 provided with the extension is formed to be translucent using a conductive oxide so as not to absorb light emitted from the light emitting layer 102-2. . The upper negative electrode layer 103-2 is formed of a metal material.

If the contact area between the conductive oxide film 104 and the connection electrode 106 or the contact area between the positive pad electrode 105 and the connection electrode 106 is too small, the operation of the GaN-based LED element 100 due to an increase in contact resistance. The voltage (forward voltage) rises. When the cross-sectional area of the connection electrode 106 is too small, the operating voltage of the GaN-based LED element 100 increases due to the increase in series resistance of the connection electrode. Therefore, the contact area between the conductive oxide film and the connection electrode, the contact area between the positive pad electrode and the connection electrode, and the cross-sectional area of the connection electrode may increase the operating voltage of the LED element, which is a practical problem. Make it large enough not to happen.

FIG. 11 shows a structural example of a GaN-based LED element using a conductive substrate according to an embodiment of the present invention. FIG. 11A is a plan view of the LED element as viewed from the side on which the GaN-based semiconductor layer stack is formed, and FIG. 11B is a cross-sectional view taken along the line XX in FIG. It is. As shown in the sectional view of FIG. 11B, the GaN-based LED element 200 includes a substrate 201 and a semiconductor stacked body 202 made of a plurality of GaN-based semiconductor layers formed thereon. The semiconductor stacked body 202 includes an n-type layer 202-1, a light emitting layer 202-2, and a p-type layer 202-3 in this order from the substrate 201 side. A negative electrode 203 is formed on the back surface of the substrate 201. On the p-type layer 202-3, the translucent conductive oxide film 204 and the positive pad electrode 205 are formed so as not to overlap each other, and the connection electrode 206 is electrically connected between them. Connected. The connection electrode 206 is formed of a metal material or a conductive oxide.

Next, a method for manufacturing the GaN-based LED element 100 will be described.
The GaN-based LED element 100 is formed on a substrate 101 using a MOVPE method (organometallic compound vapor deposition method), MBE method (molecular beam epitaxy method), HVPE method (hydride vapor deposition method), or the like. It can be manufactured by epitaxially growing crystals to form the semiconductor stacked body 102. In this case, as the substrate 101, sapphire, spinel, silicon carbide, silicon, GaN-based semiconductor (GaN, AlGaN, etc.), gallium arsenide, gallium phosphide, gallium oxide, zinc oxide, LGO, NGO, LAO, boride A crystal substrate (single crystal substrate, template) made of a material such as zirconium or titanium boride can be preferably used. As the light-transmitting substrate, sapphire, spinel, silicon carbide, GaN-based semiconductor, gallium phosphide, gallium oxide, zinc oxide, LGO, NGO, LAO are used depending on the wavelength of light emitted from the light emitting layer 102-2. A substrate made of a material selected from the above can be preferably used. As the conductive substrate, a substrate made of silicon carbide, silicon, GaN-based semiconductor, gallium arsenide, gallium phosphide, gallium oxide, zinc oxide, zirconium boride, titanium boride, or the like can be preferably used. . When epitaxially growing a GaN-based semiconductor crystal on the substrate 101, it is recommended to use a buffer layer technique. As a preferable buffer layer, a low temperature buffer layer or a high temperature buffer layer formed of a GaN-based semiconductor is exemplified. In order to generate lateral growth of the GaN-based semiconductor crystal, a mask made of silicon oxide or the like is partially formed on the surface of the substrate 101, or the surface of the substrate 101 is processed to be uneven. It can be carried out.

As another method of forming the semiconductor stacked body 102 made of a GaN-based semiconductor on the substrate 101, an n-type layer 102-1, a light emitting layer 102-2, and a p-type layer 102-3 are formed on a growth substrate by an epitaxial growth method. After forming the semiconductor stacked body 102 in this order, the growth substrate is removed from the semiconductor stacked body 102 by using a method such as etching, grinding, polishing, laser lift-off, and the exposed n-type layer 102-1. A method of bonding a separately prepared substrate 101 to the surface can be used. Alternatively, after forming the semiconductor laminate 102 by the same method, removing the growth substrate, and forming a seed layer on the exposed surface of the n-type layer 102-1, the metal layer is formed by electrolytic plating or electroless plating. It is also possible to employ a method in which the metal layer is deposited to a thickness of 50 μm or more and the metal layer is used as the substrate 101. In these methods, the crystal substrate exemplified above can be preferably used as the growth substrate. There is no limitation on the type of the substrate that can be bonded to the surface of the n-type layer 102-1, and the bonding method, and conventionally known techniques can be appropriately referred to. Specifically, examples of the type of substrate include the above-described crystal substrate, metal substrate, and glass substrate. Examples of the bonding method include a method using a conductive adhesive (conductive paste, brazing material), a method using an insulating adhesive, and direct wafer bonding. When the substrate 101 is formed using a plating method, preferable examples of the material include Au (gold), Ni (nickel), Cu (copper), and Ag (silver).

When forming the n-type layer 102-1, it is preferable to add an n-type impurity such as Si or Ge. Further, it is preferable to add a p-type impurity such as Mg or Zn when forming the p-type layer 102-3. After the formation of the p-type layer 102-3, annealing treatment, electron beam irradiation treatment, or the like can be performed in order to promote activation of the added p-type impurity. The light emitting layer 102-2 is not limited by its conductivity type, and may be, for example, a layer with no added impurities, or a layer imparted with n-type or p-type conductivity by the addition of impurities. Alternatively, a laminated body in which an n-type layer and a p-type layer are mixed may be used. There is no limitation on the composition of the GaN-based semiconductor constituting the n-type layer 102-1, the light-emitting layer 102-2, and the p-type layer 102-3, and a GaN-based semiconductor having an arbitrary composition such as GaN, AlGaN, InGaN, or AlInGaN can be used. Can be configured. Preferably, the composition of the GaN-based semiconductor constituting the light emitting layer and the layers sandwiching the light emitting layer is selected so that a double heterostructure is formed. The light emitting layer preferably has a quantum well structure, and particularly preferably has a multiple quantum well structure in which barrier layers and well layers are alternately stacked. Each of the n-type layer 102-1, the light emitting layer 102-2, and the p-type layer 102-3 does not have to be uniform in the thickness direction, and the impurity concentration, crystal composition, and the like are in the thickness direction inside each layer. It may change continuously or discontinuously. Moreover, an additional layer can also be provided between each layer.

For example, the semiconductor stacked body 102 can be configured as follows.
n-type layer 102-1: Si-doped GaN layer having a film thickness of 4 μm and an electron concentration of 5 × 10 ¹⁸ cm ⁻³ .
Light-emitting layer 102-2: a GaN barrier layer having a thickness of 8 nm and an InGaN well layer having a thickness of 2 nm, the uppermost layer and the lowermost layer being barrier layers, and the number of well layers included is 2 to 20 Multiple quantum well layers stacked alternately so that
p-type layer 102-3: a laminate having a two-layer structure comprising a p-type cladding layer in contact with the light-emitting layer 102-2 and a p-type contact layer laminated thereon. The p-type cladding layer is an Mg-doped Al _0.1 Ga _0.9 N layer having a thickness of 100 nm and an Mg concentration of 5 × 10 ¹⁹ cm ⁻³ . The p-type contact layer is an Mg-doped GaN layer having a thickness of 200 nm and an Mg concentration of 1 × 10 ²⁰ cm ⁻³ .

The negative electrode 103 is formed on the surface of the n-type layer 102-1 exposed by partially removing the p-type layer 102-3 and the light-emitting layer 102-2 using a known RIE (reactive ion etching) technique. Can be formed. For the material and the forming method of the negative electrode 103, known techniques can be referred to. In a preferred embodiment, at least a portion of the negative electrode 103 in contact with the n-type layer 102-1 is selected from a simple substance such as Ti (titanium), Al (aluminum), W (tungsten), V (vanadium), or the like. It can form using the alloy containing 1 or more types of metals. The negative electrode 103 has a surface layer of Ag (silver), Au (gold), Sn (tin), In (indium), Bi (bismuth), Cu (copper) so as to facilitate connection to the external electrode. It is preferable to provide a layer made of Zn (zinc) or the like. A thin layer made of a conductive oxide material can be interposed between the negative electrode 103 and the n-type layer 102-1. The film thickness of the negative electrode 103 can be, for example, 0.2 μm to 10 μm, and preferably 0.5 μm to 2 μm. The negative electrode 103 can be formed using a vacuum evaporation method, a sputtering method, a CVD method, or the like. The negative electrode 103 may be formed after the conductive oxide film 104 or the like is formed over the p-type layer 102-3.

The conductive oxide film 104 can be formed using an oxide containing at least one element selected from Zn (zinc), In (indium), Sn (tin), and Mg (magnesium). Specifically, ITO (indium tin oxide), indium oxide, tin oxide, zinc oxide, magnesium oxide and the like are preferably exemplified. Particularly preferred is ITO. The film thickness of the conductive oxide film 104 can be set to 0.1 μm to 1 μm, for example, but is preferably 0.2 μm to 0.5 μm. Furthermore, it is desirable to adjust the film thickness according to the wavelength of the light emitted from the light emitting layer 102-2 so that the antireflection film condition is achieved. The conductive oxide film 104 can have a multilayer structure in whole or in part. The conductive oxide film 104 is preferably formed so that the transmittance at a wavelength of light emitted from the light-emitting layer 102-2 is 80% or more. This transmittance is more preferably 85% or more, and still more preferably 90% or more. The conductive oxide film 104 is desirably formed so as to have a resistivity of 1 × 10 ⁻⁴ Ωcm or less. There is no limitation on the method for forming the conductive oxide film 104, and the conductive oxide film 104 can be formed by using a conventionally known method. Specific examples include sputtering, reactive sputtering, vacuum deposition, ion beam assisted deposition, ion plating, laser ablation, CVD, spray, spin coating, and dip. The conductive oxide film 104 may be heat-treated as necessary after formation. For a method of manufacturing the conductive oxide film 104, Patent Document 1 can also be referred to. The patterning of the conductive oxide film 104 can be performed using a lift-off method. Alternatively, the conductive oxide film 104 can be patterned by being formed over the entire surface of the p-type layer 102-3 and then removing unnecessary portions by using photolithography and etching techniques.

After the formation of the conductive oxide film 104, the connection electrode 106 is formed. As a preferable material when the connection electrode 106 is formed of metal, platinum group (Rh, Pt, Pd, Ir, Ru, Os), Ni (nickel), Ti (titanium), W (tungsten), Ag (silver) And Al (aluminum). In the case where the connection electrode 106 is formed using a conductive oxide, any conductive oxide that can be used for the conductive oxide film 104 can be used. Preferably, the conductive oxide film 104 and the connection electrode 106 are formed of the same type of conductive oxide so that thermal stress is not generated. When the connection electrode is formed of platinum group, Ni, Ag, conductive oxide, etc., the surface of the p-type layer in contact with the connection electrode is subjected to plasma treatment so that the contact resistance between the connection electrode and the p-type layer is increased. It is desirable to insulate between the connection electrode and the p-type layer. The film thickness when the connection electrode is a metal film can be, for example, 0.005 to 0.2 μm. The connection electrode can be formed using a vacuum deposition method, a sputtering method, a CVD method, or the like. The connection electrode may have a multilayer structure.

After the connection electrode 106 is formed, the positive pad electrode 105 is formed. The material of the positive pad electrode 105 is not particularly limited, but in a preferred embodiment, at least a portion of the positive pad electrode 105 in contact with the conductive oxide film 104 is made of a platinum group (Rh, Pt, Pd, Ir, Ru, Os). , Ni (nickel), Ti (titanium), W (tungsten), Ag (silver), Al (aluminum), or the like. However, when platinum group, Ni, Ag, or the like is used, the above-described plasma is applied to the surface of the p-type layer 102-3 in order to increase the contact resistance between the positive pad electrode 105 and the p-type layer 102-3. It is desirable to perform processing or to insulate between the positive pad electrode 105 and the p-type layer 102-3. Otherwise, the current that directly flows from the positive pad electrode 105 to the p-type layer 102-3 increases, and the light emission output improving effect is reduced. In order to reduce light absorption by the positive pad electrode, the portion of the positive pad electrode 105 on the light emitting layer 102-2 side is mainly composed of Al, Ag, or a platinum group element that is a metal with good light reflectance. It is preferable to provide a configured reflective layer. Further, in order to facilitate connection to the external electrode, the positive pad electrode 105 has a surface layer of Ag (silver), Au (gold), Sn (tin), In (indium), Bi (bismuth), Cu as surface layers. It is preferable to provide a layer made of (copper), Zn (zinc), or the like. The film thickness of the positive pad electrode 105 can be, for example, 0.2 μm to 10 μm, and preferably 0.5 μm to 2 μm. The positive pad electrode 105 can be formed using a vacuum deposition method, a sputtering method, a CVD method, or the like.

As an example of plasma processing performed on the surface of the p-type layer 102-3 in order to increase the contact resistance between the positive pad electrode 105 and the p-type layer 102-3, p is performed by RIE (reactive ion etching). A treatment for removing the surface layer portion of the mold layer 102-3 by etching is exemplified. The thickness of the p-type layer removed by this treatment can be set to 1 nm to 100 nm, for example. By the way, although the surface of the polycrystalline conductive oxide film tends to be uneven, for example, by performing RIE treatment on the ITO film having a polycrystalline structure that has been heat-treated at 500 ° C. or higher, When the ITO film is removed to expose the p-type layer, the exposed surface of the p-type layer becomes a textured surface having fine irregularities. If a positive pad electrode is formed on the surface of the textured p-type layer by this method or using another method, the positive pad electrode is firmly adhered to the surface of the p-type layer, and it is difficult to drop off. Is obtained. However, when the positive pad electrode is formed on the textured surface, there is a problem that the light reflectivity of the positive pad electrode is lowered. From the viewpoint of increasing the light reflectivity of the positive pad electrode, the portion of the surface of the p-type layer that contacts the positive pad electrode is a mirror surface having a surface roughness of 0.01 μm or less with the arithmetic average roughness Ra as an index. It is preferable. In the GaN-based LED element 100, the edge of the upper surface of the p-type layer 102-3 is exposed without being covered with the conductive oxide film 104, but the RIE treatment from above the conductive oxide film is performed. Thus, it is also possible to improve the light emission output by texturing the exposed surface.

The planar shape of the positive pad electrode 105 is not particularly limited. However, in the case of wire bonding, it is preferable to use a shape having a small aspect ratio. In addition to a circle, a regular triangle, square, regular pentagon, regular hexagon, or the like A polygon or a combination of these is preferably exemplified. In the current state of the art, it is said that the pad electrode needs to have a size and shape including a circle having a diameter of 60 μm for wire bonding, but in the future, a pad electrode capable of wire bonding will be required. It is almost certain that the size will be smaller. When connecting to an external electrode using a conductive paste or brazing material, the shape and size of the positive pad electrode 105 depends on the shape and size of the external electrode to be connected and the performance of the device used for the connection. Can be set.

Although not shown in FIGS. 1 and 2, the regions on the negative electrode 103 and the positive pad electrode 105 after the formation of the negative electrode 103, the conductive oxide film 104, the connection electrode 106, and the positive pad electrode 105 are completed. It is desirable to cover the surface of the LED element on the side of the semiconductor laminate 102 except for a light-transmitting insulating protective film. This insulating protective film is preferably formed of an insulating metal oxide, metal nitride, or metal oxynitride having high transmittance at the wavelength of light emitted from the light emitting layer. Since a typical emission wavelength range of the GaN-based LED is 350 nm to 600 nm, an insulator having a high transmittance in this wavelength range is a suitable material for the insulating protective film. Specific examples include silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, tantalum oxide, zirconium oxide, and hafnium oxide. The insulating protective film may have a multilayer film structure. There is no limitation on the method for forming the insulating protective film, and a known method such as a sputtering method, a CVD method, or a vacuum evaporation method can be used. As a particularly preferable method, there is a plasma CVD method that can form a film having no pinholes and good adhesion.

After forming an insulating protective film as necessary, the wafer is cut using a wafer division method (for example, dicing, scribing, laser processing) usually used in this field, and the GaN-based LED element 100 is formed. Make a chip. The size of the chip is not particularly limited, and can be, for example, 200 μm square to 2 mm square. The chip shape is not limited to a square (square, rectangle), and may be a parallelogram, a triangle, a pentagon, a hexagon, or the like. Advances in the wafer splitting method using laser processing technology have made it possible to manufacture LED elements having various chip shapes.

The GaN-based LED element 100 can be used for various light emitting devices such as an SMD (surface mount) type LED package, a shell-type lamp, and a chip-on-board (COB) type unit in which the LED element is directly mounted on a unit substrate. The GaN-based LED element 100 may be directly fixed on a mounting substrate such as a substrate, a slag, a lead frame, or a unit substrate, or may be fixed via a submount.

(Appendix)
The present invention further provides a GaN-based LED element having the following characteristics.
(1a) A p-type layer having a substrate and a semiconductor stacked body made of a plurality of GaN-based semiconductor layers formed on the substrate, the semiconductor stacked body being arranged at a position farthest from the substrate A light emitting layer disposed between the p-type layer and the substrate, and an n-type layer disposed so as to sandwich the light-emitting layer between the p-type layer and the p-type layer. A GaN-based LED element having a light-transmitting conductive oxide film and a positive pad electrode electrically connected to the conductive oxide film is connected to the n-type layer. And a negative electrode formed on the same surface side as the positive pad electrode, the negative electrode is in contact with the n-type layer, and an extension for promoting the diffusion of the current in the surface direction is provided. A translucent lower negative electrode layer made of a conductive oxide, and a connection material formed on the lower negative electrode layer Characterized in that it has for engagement, the upper negative electrode layer made of a metal material, a, GaN-based LED element.
The GaN-based LED element (1a) is excellent in light emission output by reducing light absorption by the negative electrode, and is therefore suitable for applications that require high output such as lighting applications. Can be used.

The present invention is not limited to the embodiments explicitly described in the present specification, and various modifications can be made without departing from the spirit of the invention.

It is a figure which shows the structure of the GaN-type LED element which concerns on embodiment of this invention, Fig.1 (a) is a top view, FIG.1 (b) is sectional drawing in the position of the XX line of Fig.1 (a). is there. It is sectional drawing in the position of the YY line of Fig.1 (a) of the GaN-type LED element shown in FIG. It is sectional drawing for demonstrating the electrode shape of the GaN-type LED element which concerns on embodiment of this invention. It is sectional drawing for demonstrating the electrode shape of the GaN-type LED element which concerns on embodiment of this invention. It is a top view for demonstrating the electrode shape of the GaN-type LED element which concerns on embodiment of this invention. It is a top view for demonstrating the electrode shape of the GaN-type LED element which concerns on embodiment of this invention. It is a top view for demonstrating the electrode shape of the GaN-type LED element which concerns on embodiment of this invention. It is a top view for demonstrating the electrode shape of the GaN-type LED element which concerns on embodiment of this invention. It is a top view for demonstrating the electrode shape of the GaN-type LED element which concerns on embodiment of this invention. It is a top view for demonstrating the electrode shape of the GaN-type LED element which concerns on embodiment of this invention. It is a figure which shows the structure of the GaN-type LED element which concerns on embodiment of this invention, Fig.11 (a) is a top view, FIG.11 (b) is sectional drawing in the position of the XX line of Fig.11 (a). is there. It is sectional drawing which shows the structure of the conventional GaN-type LED element.

Explanation of symbols

100, 200 GaN-based LED element 101, 201 Substrate 102, 202 Semiconductor laminate 103, 203 Negative electrode 104, 204 Conductive oxide film 105, 205 Positive pad electrode 106, 206 Connection electrode

Claims (14)

A substrate, and a semiconductor laminate composed of a plurality of GaN-based semiconductor layers formed on the substrate, the semiconductor laminate including a p-type layer disposed at a position farthest from the substrate, In a GaN-based LED element including a light emitting layer disposed between a p-type layer and the substrate, and an n-type layer disposed so as to sandwich the light emitting layer between the p-type layer,
A translucent conductive oxide film, a positive pad electrode, and a connection electrode for electrically connecting the conductive oxide film and the positive pad electrode are formed on the p-type layer. And
The conductive oxide film and the positive pad electrode do not overlap each other,
A GaN-based LED element, wherein current is supplied from the positive pad electrode to the p-type layer through the conductive oxide film. The GaN-based LED element according to claim 1, wherein the connection electrode is made of a conductive oxide and has translucency. The GaN-based LED element according to claim 2, wherein the connection electrode has a larger film thickness than the conductive oxide film. The connection electrode is a metal film, part of which overlaps the conductive oxide film, and the area of the part where the connection electrode, which is the metal film, overlaps the conductive oxide film, The GaN-based LED element according to claim 1, which is 50% or less of the area of the pad electrode. The GaN-based LED element according to claim 1, wherein the contact between the positive pad electrode and the p-type layer is non-ohmic. The GaN-based LED element according to any one of claims 1 to 4, wherein a surface of the p-type layer in contact with the positive pad electrode is subjected to a high resistance treatment. The GaN-based LED element according to claim 1, wherein the positive pad electrode and the p-type layer are insulated. The GaN-based LED element according to claim 1, wherein the positive pad electrode has a reflective layer mainly composed of Al, Ag, or a platinum group element. The GaN-based LED element according to any one of claims 1 to 8, wherein a surface of the p-type layer in contact with the positive pad electrode is a textured surface. 2. The p-type layer is provided with a region that is not covered with any of the conductive oxide film, the positive pad electrode, and the connection electrode, and whose surface is textured. GaN-type LED element in any one of -9. It has a negative electrode connected to the n-type layer and formed on the same side as the positive pad electrode, and the negative electrode is in contact with the n-type layer and promotes the diffusion of the current in the surface direction. A translucent lower negative electrode layer made of a conductive oxide and having an extension for causing a connecting material formed on the lower negative electrode layer to join a connecting material The GaN-based LED element according to claim 1, further comprising an upper negative electrode layer. The GaN-based LED element according to claim 1, wherein the substrate has translucency. The GaN-based LED element according to claim 1, wherein the substrate is made of a metal material. A light-emitting device formed by flip-chip mounting the GaN-based LED element according to claim 12.

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