KR20100036758A - Light emitting diode and method for fabricating the same - Google Patents

Abstract

PURPOSE: A light emitting diode and a method for manufacturing the same are provided to improve external extraction efficiency by effectively emitting photon which is generated from an active layer to the outside. CONSTITUTION: A first conductive semiconductor layer, an active layer and a second conductive semiconductor layer are formed on a conductive substrate(71). A metal reflective layer(61) is formed on the second conductive semiconductor layer. The adhesion layer of an Ag alloy is formed on the second conductive semiconductor layer. An Ag reflective layer is formed on the adhesion layer of the Ag alloy. A metal protection layer(65) is formed on the Ag reflective layer.

Description

LIGHT EMITTING DIODE AND METHOD FOR FABRICATING THE SAME

The present invention relates to a light emitting diode, and more particularly, to a light emitting diode having an improved Ag reflective layer structure and a method of manufacturing the same.

Light emitting diodes, such as flip type light emitting diodes and vertical electrode type light emitting diodes, include a first conductive semiconductor layer (e.g., N-GaN), an active layer, and a second conductive semiconductor layer (e.g., P-GaN) formed on a substrate. And a metal reflective layer formed on the second conductivity-type semiconductor layer to reflect light generated from the active layer toward the substrate.

Silver (Ag) has a high light reflectance (> 90%) in the visible region and a high work function, which can be used as an ohmic contact electrode on the P-GaN layer. However, when silver is deposited on a surface such as a nitride semiconductor and oxide sapphire, the adhesion is poor due to the agglomeration of silver, so that the silver can be easily peeled off. Accordingly, an adhesion enhancing material (for example, Ti, Cr) is inserted between the silver and the P-GaN layer. However, the insertion of such an adhesion enhancing material absorbs photons generated in the active layer, thereby lowering external quantum efficiency. In addition, when silver is exposed to sulfides, nitrides, oxides, and the like, a yellowing occurs, and ohmic contact is changed, and the reliability is very weak.

The problem to be solved by the present invention is a light emitting diode and a method of manufacturing the light emitting diode having a structure of a metal reflective layer to prevent the aggregation of silver when silver (Ag) is used in the metal reflective layer and to suppress the oxidation and yellowing of silver. To provide.

According to one aspect of the invention, the first conductive semiconductor layer, the active layer and the second conductive semiconductor layer; A metal reflective layer formed on the second conductivity type semiconductor layer; The metal reflective layer may include an adhesion medium layer of an Ag alloy formed on the second conductive semiconductor layer; An Ag reflective layer formed on the adhesion medium layer of the Ag alloy; Provided is a light emitting diode comprising a protective metal layer formed on the Ag reflective layer.

Preferably, the adhesion medium layer of the Ag alloy may include at least one of AgCu, AgAl, AgSn.

Preferably, the adhesion medium layer of the Ag alloy may contain Ag as a main component and any one of Cu, Al, and Sn may be 0.5-10 atomic%.

Preferably, the thickness of the adhesion medium layer of the Ag alloy may be greater than 0 and 10 nm or less.

Preferably, the Ag reflecting layer may have a thickness of 50nm-10㎛.

According to another aspect of the invention, forming a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer on a substrate; Forming an adhesion medium layer of Ag alloy on the second conductivity type semiconductor layer; Forming an Ag reflective layer on the adhesion medium layer of the Ag alloy; It provides a light emitting diode manufacturing method comprising the step of forming a protective metal layer on the Ag reflective layer.

Preferably, the adhesion medium layer of the Ag alloy may include at least one of AgCu, AgAl, AgSn.

Preferably, the adhesion medium layer of the Ag alloy may contain Ag as a main component and any one of Cu, Al, and Sn may be 0.5-10 atomic%.

Preferably, the thickness of the adhesion medium layer of the Ag alloy may be greater than 0 and 10 nm or less.

Preferably, the Ag reflecting layer may have a thickness of 50nm-10㎛.

According to the present invention, the metal reflective layer structure formed by sequentially forming an Ag alloy adhesion layer, an Ag reflective layer, and a protective metal layer on a second conductive semiconductor layer, for example, a P-GaN layer, can effectively prevent agglomeration of silver. As a result, the silver adhesion can be enhanced, and the photon emitted from the active layer can be effectively emitted to the outside to improve the external extraction efficiency. In addition, it is possible to implement a device having improved reliability by suppressing oxidation and yellowing of the Ag reflective layer.

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 to those skilled in the art will fully convey. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And, in the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience. Like numbers refer to like elements throughout.

1 is a cross-sectional view illustrating a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 1, compound semiconductor layers including an N-type semiconductor layer 55, an active layer 57, and a P 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 substrate thereof. Meanwhile, the compound semiconductor layers are III-N series compound semiconductor layers. For example, it is a (Al, Ga, In) N semiconductor layer.

A metal reflective layer 61 and an adhesive layer 67 are interposed between the compound semiconductor layers and the conductive substrate 71.

The metal reflective layer 61 is composed of an adhesion medium layer 62 of Ag alloy, an Ag reflective layer 63 and a protective metal layer 65.

The adhesion medium layer 62 of Ag alloy is made of Ag alloy. The Ag alloy may be, for example, any one or combination of AgCu, AgAl, AgSn. The adhesion medium layer 62 of the Ag alloy has Ag as a main component and may contain, for example, 0.5-10 atomic% of Cu, Al, and Sn. The adhesive media layer 62 of the Ag alloy is a media layer for bonding the Ag reflective layer 63 to the P-GaN layer 59 and does not need to be thicker than necessary, and the Ag reflective layer 63 is made of the P-GaN layer 59. It is good to be in the range of the optimum thickness for firmly bonding). The thickness of the adhesion medium layer 62 of the Ag alloy may be, for example, 10 nm or less (not including 0).

Although the Ag alloy used for the adhesion medium layer 62 of the Ag alloy is slightly lower in reflectance than the pure Ag constituting the Ag reflecting layer 63, the adhesion with the P-GaN layer 59 is excellent. Accordingly, the adhesion medium layer 62 of the Ag alloy is formed to perform the function of the adhesion medium layer for strengthening the adhesion between the P-GaN layer 59 and the Ag reflective layer 63.

The Ag alloy that can be used for the adhesion medium layer 62 of the Ag alloy may enhance the adhesion between the P-GaN layer 59 and the Ag reflecting layer 63, and preferably close to the reflectance of pure Ag. Therefore, it is preferable that the adhesion medium layer 62 of the Ag alloy selects an Ag alloy close to the reflectance of pure Ag while having excellent adhesion among various Ag alloys. Here, the excellent adhesive force means that the Ag reflective layer 63 has more than the adhesive force to be deposited on the P-GaN layer 59 so as not to be separated.

The Ag reflective layer 63 uses pure Ag, and is bonded to the P-GaN layer 59 through the adhesion medium layer 62 of Ag alloy. Pure Ag used in the Ag reflective layer 63 has a low direct adhesion to the P-GaN layer 59, but has a higher reflectance than the Ag alloy used in the adhesion medium layer 62 of the Ag alloy. The problem of adhesion is solved by being adhered through the adhesion medium layer 62 of Ag alloy without being directly deposited on the GaN layer 59. The thickness of the Ag reflecting layer 63 may be, for example, 50 nm to 10 μm in consideration of the optimum light efficiency between the reflectance and the thickness of Ag reflecting the light generated in the active layer.

The protective metal layer 65 may maintain the reflectivity of the Ag reflective layer 63 by preventing metal elements from diffusing into the Ag reflective layer 63 from the adhesive layer 67 or the conductive substrate 71. The metal used for the protective metal layer 65 may be selected by focusing on the adhesion to the Ag reflective layer 63 and the yellowing of the Ag reflective layer 63 rather than the light reflection function. The protective metal layer 65 may be formed of, for example, Ni, Ti, Ta, Pt, W, Cr, Pd, or the like. However, the present invention is not limited thereto, and for example, the Ag alloy used in the intermediate metal layer 62 of the Ag alloy may be used as it is. In addition, the protective metal layer 65 has Ag as its main component and Mg, Zn, Sc, Hf, Zr, Te, Se, Ta, W, Nb, Cu, Si, Ni, Co, Mo, Cr, Mn, Hg, Pr And an Ag alloy including at least one selected from the group consisting of La.

The adhesive layer 67 improves the adhesion between the conductive substrate 71 and the metal reflective layer 61 to prevent the conductive substrate 71 from being separated from the metal reflective layer 61.

Meanwhile, the electrode pad 83 is positioned on the upper surface of the compound semiconductor layers to face the conductive substrate 71. Accordingly, light can be emitted by supplying a current through the conductive substrate 71 and the electrode pad 83.

2 to 4 are cross-sectional views illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 2, 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 an N semiconductor layer 55, an active layer 57, and a P-type 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).

Meanwhile, the buffer layer 53 may be formed before forming the compound semiconductor layers. 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. 3, the metal reflective layer 61 is formed on the compound semiconductor layers. The metal reflective layer 61 includes an adhesion medium layer 62 of Ag alloy, a reflective layer 63 of Ag, and a protective metal layer 65. Metal reflective layer 61 may be formed using, for example, plating or deposition techniques.

The adhesion medium layer 62 of the Ag alloy serves to enhance the adhesion between the compound semiconductor layer and the Ag reflective layer 63. The adhesion medium layer 62 of Ag alloy is made of Ag alloy. As the Ag alloy, any one or combination of AgCu, AgAl, AgSn can be used. The adhesion medium layer 62 of the Ag alloy is formed to a thickness of, for example, 10 nm or less (not including 0).

After the adhesion medium layer 62 of Ag alloy is formed, the Ag reflection layer 63 is formed on the adhesion medium layer 62 of Ag alloy. The Ag reflective layer 63 may be, for example, 50 nm-10 μm.

A protective metal layer 65 is formed on the Ag reflective layer 63. The protective metal layer 65 may be formed of, for example, Ni, Ti, Ta, Pt, W, Cr, Pd, or the like. However, the present invention is not limited thereto, and for example, Ag alloy used in the intermediate metal layer 62 of Ag alloy may be used as it is, or Ag may be used as a main component. Ag alloys including at least one selected from the group consisting of W, Nb, Cu, Si, Ni, Co, Mo, Cr, Mn, Hg, Pr, and La can be used.

The conductive substrate 71 is formed on the protective metal layer 65. 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 can be formed by attaching a single metal of Cr or Fe or an alloy substrate thereof onto the compound semiconductor layers. In this case, the conductive substrate 71 may be attached to the protective metal layer 65 through the adhesive layer 67, and 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 protective metal layer 65, and an adhesive layer 67 may be added to improve adhesion.

Referring to FIG. 4, 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. At this time, the buffer layer 53 is also removed to expose the N-type semiconductor layer 59.

Subsequently, an electrode pad 83 is formed on the N-type semiconductor layer 55. Thereafter, the plurality of vertical light emitting diodes shown in FIG. 1 may be manufactured by cutting the conductive substrate 71 and separating them into individual light emitting diode chips. At this time, the conductive substrate 71 is cut along the predefined scribing lines.

The present invention is not limited to the above described embodiments, and various modifications and changes can be made by those skilled in the art, which are included in the spirit and scope of the present invention as defined in the appended claims.

For example, in the exemplary embodiment of the present invention, a vertical light emitting diode among light emitting diodes having a reflective metal layer has been described, but the present invention is not limited thereto, and the first conductive semiconductor layer, the active layer, and the second conductive semiconductor are not limited thereto. Any light emitting diode having a structure of a metal reflective layer for reflecting light generated from the active layer on the structure of the layer may be variously modified without departing from the spirit of the present invention.

In addition, in the exemplary embodiment of the present invention, the light emitting diode having the conductive substrate on the metal reflective layer and having the electrodes above and below the light emitting diode was described. However, the insulating substrate is provided without the conductive substrate and the N-type electrode is formed on one surface. , A P-type electrode may be formed.

1 is a cross-sectional view illustrating a light emitting diode according to an embodiment of the present invention.

2 to 4 are cross-sectional views illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

Claims (6)

A first conductive semiconductor layer, an active layer and a second conductive semiconductor layer; A metal reflective layer formed on the second conductivity type semiconductor layer; The metal reflective layer, An adhesion media layer of Ag alloy formed on the second conductivity type semiconductor layer; An Ag reflective layer formed on the adhesion medium layer of the Ag alloy; A light emitting diode comprising a protective metal layer formed on the Ag reflective layer. The method according to claim 1, The adhesion medium layer of the Ag alloy includes at least one of AgCu, AgAl, AgSn. The method according to claim 2, The adhesion medium layer of the Ag alloy is Ag as a main component and a light emitting diode containing any one of Cu, Al, Sn is 0.5-10 atomic%. The method according to claim 1, The thickness of the adhesive medium layer of the Ag alloy is greater than 0 and less than 10nm. The light emitting diode of claim 1, wherein the Ag reflective layer has a thickness of 50 nm-10 μm. Forming a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer on the substrate; Forming an adhesion medium layer of Ag alloy on the second conductivity type semiconductor layer; Forming an Ag reflective layer on the adhesion medium layer of the Ag alloy; Forming a protective metal layer on the Ag reflective layer.

Images