KR20130014677A - Vertical light emitting diode having light-transmitting material pattern and method of fabricating the same - Google Patents

Abstract

PURPOSE: A vertical light emitting diode with a transmissive material pattern and a manufacturing method thereof are provided to improve luminous efficiency by adopting the transmissive material pattern with an opening part to reduce light absorption in an ohmic electrode layer. CONSTITUTION: A compound semiconductor layer is formed on a conductive substrate(71). The compound semiconductor layer includes a first conductive semiconductor layer(55), an active layer(57), and a second conductive semiconductor layer(59). A transmissive material pattern(60) is interposed between the compound semiconductor layers and the conductive substrate. The transmissive material pattern has an open part to expose the compound semiconductor layers. An ohmic electrode(61) is ohmically contacted with the second conductive semiconductor layer exposed by the open part.

Description

Vertical light emitting diode having a light-transmitting material pattern and a method of manufacturing the same {VERTICAL LIGHT EMITTING DIODE HAVING LIGHT-TRANSMITTING MATERIAL PATTERN AND METHOD OF FABRICATING THE SAME}

The present invention relates to a vertical light emitting diode and a method of manufacturing the same, and more particularly to a vertical light emitting diode having a light-transmitting material pattern between the conductive substrate and the compound semiconductor layer and a method of manufacturing the same.

In general, nitrides of Group III elements, such as gallium nitride (GaN) and aluminum nitride (AlN), have excellent thermal stability and have a direct transition energy band structure. As a lot of attention. In particular, blue and green light emitting devices using gallium nitride (GaN) have been used in various applications such as large-scale color flat panel displays, traffic lights, indoor lighting, high-density light sources, high resolution output systems and optical communication.

The nitride semiconductor layer of such a group III element, in particular, GaN, is difficult to fabricate a homogeneous substrate capable of growing it, and thus, it is difficult to fabricate a homogeneous substrate capable of growing it, such as metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy; MBE) and other processes. A sapphire substrate having a hexagonal system structure is mainly used as a heterogeneous substrate. However, since sapphire is an electrically nonconductive material, it limits the light emitting diode structure and is very stable in terms of mechanics and chemistry, making it difficult to process such as cutting and shaping, and has low thermal conductivity. In recent years, a technology for growing a nitride semiconductor layer on a heterogeneous substrate such as sapphire and then separating the heterogeneous substrate to fabricate a vertical-type LED has been researched.

1 is a cross-sectional view illustrating a conventional vertical light emitting diode.

Referring to FIG. 1, the vertical light emitting diode includes a conductive substrate 31. Compound semiconductor layers including a first conductive semiconductor layer 15, an active layer 17, and a second conductive semiconductor layer 19 are positioned on the conductive substrate 31. In addition, an ohmic electrode layer 21, a metal reflection layer 23, a diffusion barrier layer 25, and an adhesive layer 27 are interposed between the compound semiconductor layers and the conductive substrate 31.

The compound semiconductor layers are generally grown on a sacrificial substrate (not shown) such as a sapphire substrate by using a metal organic chemical vapor deposition method or the like. Thereafter, an ohmic electrode layer 21, a metal reflection layer 23, a diffusion barrier layer 25, and an adhesive layer 27 are formed on the compound semiconductor layers, and the conductive substrate 31 is attached thereto. Subsequently, the sacrificial substrate is separated from the compound semiconductor layers by using a laser lift-off technique or the like, and the first conductivity type compound semiconductor layer 15 is exposed. Thereafter, an electrode pad 17 is formed on the exposed first conductivity type compound semiconductor layer 15. Accordingly, by adopting the conductive substrate 31 having excellent heat dissipation performance, the light emitting efficiency of the light emitting diode can be improved, and the light emitting diode of FIG. 1 having a vertical structure can be provided.

The vertical light emitting diode generally adopts a metal reflection layer 23 to reflect light directed to the conductive substrate 31 to improve luminous efficiency, and also has a contact resistance between the compound semiconductor layers and the metal reflection layer 23. The ohmic electrode layer 21 is adopted to reduce the voltage. Therefore, since the light directed to the conductive substrate 31 is transmitted through the ohmic electrode layer 21, the light is reflected from the metal reflection layer 23, and then is transmitted through the ohmic electrode layer 21 and emitted upward. ) Is formed of a transparent material layer.

However, even when the ohmic electrode layer 21 is formed of a transparent material layer, as the thickness thereof increases, the light transmittance rapidly decreases and the light absorption increases, thereby increasing the light loss caused by the ohmic electrode layer 21. On the other hand, when the ohmic electrode layer 21 is thinly formed to prevent light absorption, stable ohmic contact is not formed between the ohmic electrode layer 21 and the compound semiconductor layer 19, resulting in uneven contact resistance. The problem is that current is concentrated and the forward voltage rises.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a vertical light emitting diode capable of improving light emission efficiency by reducing light absorption by an ohmic electrode layer and a method of manufacturing the same.

Another object of the present invention is to provide a vertical light emitting diode and a method of manufacturing the same, which can ensure stable ohmic contact characteristics.

The present invention provides a conductive substrate, a compound semiconductor layer positioned on the conductive substrate, the compound semiconductor layers including a first conductive compound semiconductor layer, an active layer and a second conductive compound semiconductor layer, and an adhesive layer between the compound semiconductor layers and the conductive substrate. And a plurality of films formed in the order of a diffusion barrier layer, a reflective film, and a translucent material film, wherein the translucent material film is formed of at least one material film selected from the group consisting of silicon oxide film, SOG, aluminum oxide film, silicon nitride film, ITO, and IZO. .

According to embodiments of the present invention, by adopting a light-transmitting material pattern having an opening, it is possible to reduce the light absorption generated by the conventional ohmic electrode layer to improve the luminous efficiency of the vertical light emitting diode. In addition, a thick ohmic electrode interposed between the metal reflection layer and the compound semiconductor layers to be in ohmic contact with the compound semiconductor layer can be formed to ensure stable ohmic contact characteristics.

1 is a cross-sectional view illustrating a vertical light emitting diode according to the prior art.
2 is a cross-sectional view for describing a vertical light emitting diode having a light transmissive material pattern according to an embodiment of the present invention.
3 is a cross-sectional view illustrating a vertical light emitting diode having a light transmissive material pattern according to another exemplary embodiment of the present invention.
4 to 8 are cross-sectional views illustrating a method of manufacturing a vertical light emitting diode having a light transmissive material pattern according to an embodiment of the present invention.

In order to achieve the above technical problem, the present invention provides a vertical light emitting diode having a light transmissive material pattern and a method of manufacturing the same. A vertical light emitting diode according to an aspect of the present invention includes a conductive substrate, and compound semiconductor layers are positioned on the conductive substrate. The compound semiconductor layers include a first conductive compound semiconductor layer, an active layer, and a second conductive compound semiconductor layer. Meanwhile, a light transmissive material pattern is interposed between the compound semiconductor layers and the conductive substrate. The light transmissive material pattern has an opening that exposes the compound semiconductor layers. Meanwhile, an ohmic electrode is in ohmic contact with the exposed semiconductor layers, and a metal reflective layer is interposed between the light transmissive material pattern and the ohmic electrode and the conductive substrate.

According to an aspect of the present invention, an ohmic electrode in ohmic contact with the compound semiconductor layers and a light transmissive material pattern for transmitting light emitted from the compound semiconductor layers are in contact with the compound semiconductor layers. The ohmic electrode is selected in consideration of the ohmic contact property rather than the light transmittance, and the light transmitting material pattern is selected in consideration of the light transmission rather than the ohmic contact property. Accordingly, the light absorption by the ohmic electrode layer formed over the entire surface may be reduced to increase the reflectance of the light, and the thickness of the ohmic electrode may be increased to stabilize the ohmic contact resistance.

The light transmissive material pattern may be formed in various shapes and may be, for example, a matrix pattern of islands, a plurality of lines, or a reticular pattern. These pattern shapes allow the ohmic electrode to be in wide contact with the compound semiconductor layers to prevent current concentration.

On the other hand, the light-transmitting material pattern is not particularly limited, for example, may be formed of a dielectric such as silicon oxide film, SOG, aluminum oxide film or silicon nitride film, or may be formed of a conductive oxide film such as ITO, IZO, or the like. Preferably, the light transmissive material pattern may be formed of a silicon oxide film or a silicon nitride film having a refractive index different from that of the compound semiconductor layers.

The ohmic electrode may be defined in the opening of the light transmissive material pattern. Accordingly, since the light passing through the light transmissive material pattern is reflected by the metal reflective layer, the reflectance is further improved. In this case, the thickness of the ohmic electrode may be further increased. Alternatively, the ohmic electrode may be extended to be interposed between the light transmissive material pattern and the metal reflective layer.

The ohmic electrode may be formed of a metal material including Pt, Pd, Rh, or Ni, and the metal reflective layer may be formed of a metal material including Al or Ag.

Meanwhile, an adhesive layer may be interposed between the metal reflection layer and the conductive substrate, and a diffusion barrier layer may be interposed between the adhesive layer and the metal reflection layer. The adhesive layer allows the compound semiconductor layers to adhere onto the conductive substrate, and the diffusion barrier layer prevents the metal atoms in the adhesive layer from diffusing into the metal reflection layer.

According to another aspect of the present invention, a method of manufacturing a vertical light emitting diode having a light transmissive material pattern is provided. The method includes forming compound semiconductor layers on the sacrificial substrate. A light transmissive material pattern having an opening exposing the compound semiconductor layers is formed on the compound semiconductor layers, and an ohmic electrode is formed in the opening of the light transmissive material pattern. Meanwhile, a metal reflection layer is formed on the compound semiconductor layers having the light transmissive material pattern and the ohmic electrode, and a conductive substrate is formed on the metal reflection layer. In addition, the sacrificial substrate is separated from the compound semiconductor layers. Accordingly, there is provided a vertical light emitting diode in which an ohmic electrode is formed in the light transmissive material pattern and the opening of the light transmissive material pattern.

The light transmissive material pattern may be formed by forming a light transmissive material layer on the compound semiconductor layers and patterning the light transmissive material layer using a photolithography and an etching process. As a result, a light-transmitting material pattern having a shape required for the silicon oxide film or the silicon nitride film can be precisely formed.

The ohmic electrode may be formed using a plating or lift-off technique so as to be defined in the opening of the light transmissive material pattern. Alternatively, the ohmic electrode may be formed to cover the light transmissive material pattern.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples to ensure that the spirit of the present invention can be fully conveyed to those skilled in the art. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, and the like of the components may be exaggerated for convenience. Like numbers refer to like elements throughout.

2 is a cross-sectional view for describing a vertical light emitting diode having a light transmissive material pattern 60 according to an embodiment of the present invention.

Referring to FIG. 2, compound semiconductor layers including a first conductive semiconductor layer 55, an active layer 57, and a second conductive semiconductor layer 59 are positioned on the conductive substrate 71. The conductive substrate 71 is a substrate such as Si, GaAs, GaP, AlGaINP, Ge, SiSe, GaN, AlInGaN or InGaN, but Al, Zn, Ag, W, Ti, Ni, Au, Mo, Pt, Pd, Cu It may be a single metal of Cr or Fe or an alloy thereof. Meanwhile, the compound semiconductor layers are III-N-based compound semiconductor layers, and the first conductive type and the second conductive type represent N type and P type, or P type and N type.

A light transmissive material pattern 60 is interposed between the compound semiconductor layers and the conductive substrate 71. The light transmissive material pattern 60 may be a pattern having various shapes such as a matrix pattern of islands, a plurality of lines or a reticular pattern, and has an opening exposing the compound semiconductor layers. The light transmissive material pattern 60 may be formed of a dielectric such as silicon oxide film, aluminum oxide film, silicon nitride film, or SOG, and may also be formed of a conductive oxide film such as ITO or IZO.

The ohmic electrode 61 is in ohmic contact with the compound semiconductor layers exposed by the opening, for example, the second conductivity type semiconductor layer 59. In the present embodiment, the ohmic electrode 61 is defined in the opening of the light transmissive material pattern 60. The ohmic electrode 61 is preferably distributed over a wide surface of the second conductivity-type semiconductor layer 59 to distribute current, and therefore, the opening of the light transmissive material pattern 60 is preferably distributed widely. The ohmic electrode 61 may be formed of Pt, Pd, Rh, or Ni, and may be formed of a metal material including at least one of them.

On the other hand, a metal reflection layer 63 is interposed between the ohmic electrode 61 and the conductive substrate 71 and between the light transmissive material pattern 60 and the conductive substrate 71. The metal reflection layer 63 may be formed of a metal material having high reflectance, such as silver (Ag) or aluminum (Al), and may be formed of a metal material including at least one of them.

In addition, an adhesive layer 67 may be interposed between the metal reflective layer 63 and the conductive substrate 71, and a diffusion barrier layer 65 may be interposed between the adhesive layer 67 and the metal reflective layer 63. The adhesive layer 67 improves the adhesion between the conductive substrate 71 and the metal reflection layer 63 to prevent the conductive substrate 71 from being separated from the metal reflection layer 63, and the diffusion barrier layer 65 may be formed by the adhesive layer 67 or Metal elements are prevented from diffusing from the conductive substrate 71 into the metal reflection layer 63 to maintain the reflectivity of the metal reflection layer 63.

Meanwhile, the electrode pad 73 is positioned on the upper surface of the compound semiconductor layers to face the conductive substrate 71. The electrode pad 73 may be in ohmic contact with the first conductive semiconductor layer 55. Alternatively, an ohmic electrode layer (not shown) may be interposed between the electrode pad 73 and the compound semiconductor layers. Can be. In addition, extensions (not shown) extending from the electrode pad 73 may be located on the compound semiconductor layers. The extensions may be employed to widely distribute the current flowing into the compound semiconductor layers.

The conventional vertical light emitting diode has an ohmic electrode layer (21 in FIG. 1) between the metal reflection layer (23 in FIG. 1) and the compound semiconductor layers. Therefore, since the light directed to the conductive substrate 31 is transmitted through the ohmic electrode layer 21 and then reflected by the metal reflection layer 23, light loss is generated by light absorption by the ohmic electrode layer 21. In contrast, according to the exemplary embodiment of the present invention, since the ohmic electrode 61 is defined in the opening of the light transmissive material pattern 60, a part of the light directed to the conductive substrate passes through the light transmissive material pattern 60 to allow the metal reflective layer 63 to pass through. Is reflected from. Therefore, the light loss caused by the ohmic electrode 61 can be reduced, and the luminous efficiency can be improved. In addition, since the light absorption by the ohmic electrode 61 can be reduced by forming the light transmissive material pattern 60 in a sufficiently large area, the ohmic electrode 61 can be formed thick to ensure stable ohmic contact characteristics.

3 is a cross-sectional view illustrating a vertical light emitting diode having a light transmissive material pattern according to another exemplary embodiment of the present invention.

Referring to FIG. 3, the vertical light emitting diode according to the present embodiment has substantially the same structure as the vertical light emitting diode described with reference to FIG. 2, except that an ohmic electrode 81 is formed in the opening of the light transmissive material pattern 60. In addition, it extends from the opening and is interposed between the light transmissive material pattern 60 and the metal reflective layer 63.

In this case, the light transmissive material pattern 60 may be formed of a dielectric having a refractive index different from that of the compound semiconductor layers, that is, a relatively low refractive index, such as a silicon oxide film or a silicon nitride film. Accordingly, light emitted from the active layer 57 to the conductive substrate 71 is reflected by internal reflection between the light transmissive material pattern 60 and the compound semiconductor layers, thereby alleviating absorption by the ohmic electrode 81. can do.

4 to 8 are cross-sectional views illustrating a method of manufacturing a vertical light emitting diode having a light transmissive material pattern according to an embodiment of the present invention.

Referring to FIG. 4, compound semiconductor layers are formed on the sacrificial substrate 51. The sacrificial substrate 51 may be a sapphire substrate, but is not limited thereto and may be another hetero substrate. The compound semiconductor layers include a first conductive compound semiconductor layer 55, an active layer 57, and a second conductive compound semiconductor layer 59. The compound semiconductor layers are III-N based compound semiconductor layers, and may be grown by a process such as metal organic chemical vapor deposition (MOCVD) or molecular beam deposition (MBE). The first conductivity type and the second conductivity type represent N-type and P-type, or P-type and N-type.

Meanwhile, before forming the compound semiconductor layers, the buffer layer 53 may be formed. The buffer layer 53 is adopted to mitigate lattice mismatch between the sacrificial substrate 51 and the compound semiconductor layers, and may generally be a gallium nitride-based material layer.

Referring to FIG. 5, a light transmissive material pattern 60 is formed on the compound semiconductor layers. The light transmissive material pattern 60 may be formed of a silicon oxide film, a silicon nitride film, or an SOG using photolithography and etching techniques. That is, the light-transmissive material pattern 60 may be formed by forming a light-transmissive material layer such as a silicon oxide film, a silicon nitride film, or SOG on the compound semiconductor layers, and patterning the light-transmitting material layer using photo and etching techniques. The light transmissive material pattern 60 may be patterned to have various shapes such as a matrix pattern of islands, a plurality of lines or a reticular pattern. In addition, the light transmissive material pattern 60 may be formed of a conductive oxide film such as ITO or IZO.

Referring to FIG. 6, an ohmic electrode 61 is formed on the compound semiconductor layers on which the light transmissive material pattern 60 is formed. The ohmic electrode 61 may be limited in the opening of the light transmissive material pattern 60 as shown, but is not limited thereto. As described with reference to FIG. 3, the ohmic electrode 61 may extend from the opening to transmit the light transmissive material pattern 60. ) May be covered.

The ohmic electrode 61 may be formed at a predetermined position, for example, in an opening of the light transmissive material pattern 60 using, for example, a lift off technique or a plating technique. Alternatively, the light transmissive material pattern 60 may be formed using a front deposition technique. ) May be formed to cover. In addition, after the entire surface deposition, the ohmic electrode material on the light transmissive material pattern 60 may be removed.

 In addition, the ohmic electrode includes a material in ohmic contact with the second conductivity-type semiconductor layer 59. When the second conductivity-type semiconductor layer 59 is a P-type semiconductor, the ohmic electrode 61 is formed of platinum ( It may be formed of a material containing Pt), palladium (Pd), rhodium (Rh) or nickel (Ni). The ohmic electrode is generally heat treated to be in ohmic contact with the second conductivity-type semiconductor layer 59, but the ohmic electrode is formed of platinum (Pt), palladium (Pd), rhodium (Rh), or nickel (Ni), thereby eliminating heat treatment. Can be.

The metal reflection layer 63 is formed on the compound semiconductor layers on which the ohmic electrode 61 is formed. The metal reflection layer 63 covers the ohmic electrode 61 and the light transmissive material pattern 60. The metal reflection layer 63 may be entirely deposited using a plating or deposition technique, or the like, and may be formed of a metal layer including Al or Ag.

Referring to FIG. 7, a conductive substrate 71 is formed on the metal reflection layer 63. The conductive substrate 61 is a substrate such as Si, GaAs, GaP, AlGaINP, Ge, SiSe, GaN, AlInGaN or InGaN, but Al, Zn, Ag, W, Ti, Ni, Au, Mo, Pt, Pd, Cu It may be formed by attaching a single metal of Cr or Fe or an alloy substrate thereof on the compound semiconductor layers. In this case, the conductive substrate 61 may be attached to the metal reflection layer 63 through an adhesive layer 67, and formed on the metal reflection layer 63 before the diffusion barrier layer 65 forms the adhesive layer 67. Can be. On the other hand, the conductive substrate 71 may be formed using a plating technique. That is, the conductive substrate 71 may be formed by plating a metal such as Cu or Ni on the metal reflection layer 63, and for improving the diffusion barrier layer 65 and / or the adhesive force for preventing the diffusion of metal elements. An adhesive layer 67 can be added.

Referring to FIG. 8, the sacrificial substrate 51 is separated from the compound semiconductor layers. The sacrificial substrate 51 may be separated by laser lift off (LLO) technology or other mechanical or chemical methods. In this case, the buffer layer 53 is also removed to expose the first conductivity type compound semiconductor layer 55.

Subsequently, an electrode pad (73 in FIG. 2) is formed on the compound semiconductor layer 55. The electrode pad 73 is in ohmic contact with the first conductive compound semiconductor layer 55. In addition, while the electrode pad 73 is formed, extensions (not shown) extending from the electrode pad 73 may be formed together. Thus, the vertical light emitting diode of FIG. 2 is manufactured.

Meanwhile, an ohmic electrode (not shown) may be formed on the first conductive compound semiconductor layer 55 before forming the electrode pad 73. The ohmic electrode is in ohmic contact with the first conductivity type compound semiconductor layer 55, and the electrode pad 73 is electrically connected to the ohmic electrode.

Claims (9)

Conductive substrates;
Compound semiconductor layers on the conductive substrate and including a first conductivity type compound semiconductor layer, an active layer, and a second conductivity type compound semiconductor layer;
A plurality of films formed between the compound semiconductor layers and the conductive substrate in an order of an adhesive layer, a diffusion barrier layer, a reflective film, and a light transmissive material film;
The light-transmitting material film is a vertical light emitting diode formed of at least one material film selected from the group consisting of silicon oxide film, SOG, aluminum oxide film, silicon nitride film, ITO, IZO. The vertical light emitting diode of claim 1, wherein the light transmissive material layer is formed in a pattern. The vertical light emitting diode of claim 2, wherein the light transmissive material pattern is a matrix pattern of islands, a plurality of lines, or a reticular pattern. The vertical type light emitting diode of claim 1, wherein an ohmic electrode layer having less light transmittance than the light transmissive material layer is formed to contact the semiconductor layers. The vertical type light emitting diode of claim 4, wherein the ohmic electrode layer is formed on a front surface without a pattern. The vertical light emitting diode of claim 4, wherein the light transmissive material layer is a matrix pattern of islands, a plurality of lines or a reticular pattern, and the ohmic electrode layer is positioned between the patterns of the translucent material layer. The vertical type light emitting diode of claim 6, wherein the ohmic electrode layer extends and is interposed between the light transmissive material pattern and the metal reflection layer. The vertical type light emitting diode of claim 6, wherein the reflective film is formed to cover an ohmic electrode layer positioned between the pattern of the light transmissive material film and at least a part of the light transmissive material film. The vertical type light emitting diode of claim 8, wherein the diffusion barrier layer is formed to cover the reflective layer.

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