KR100717258B1 - Luminous element with high efficiency and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a light emitting device. The present invention provides a substrate, an N-type semiconductor layer formed on one surface of the substrate, a P-type semiconductor layer formed in a portion of the N-type semiconductor layer, an ohmic forming conductive film having a mesh structure on the P-type semiconductor layer, It includes an electrode having a transparent conductive oxide film, the ohmic forming conductive film provides a light emitting device comprising a multiple film of an oxide forming material and an oxide non-forming material. The present invention improves light transmittance and improves current diffusion without compromising light efficiency by using a multilayer electrode having a transparent multi-layered first film layer and a transparent conductive oxide film as a second film layer. Can provide.

Light emitting element, electrode, oxide, ohmic, mesh

Description

High efficiency light emitting device and its manufacturing method {LUMINOUS ELEMENT WITH HIGH EFFICIENCY AND METHOD FOR MANUFACTURING THE SAME}

1 is a cross-sectional view of a conventional light emitting device.

2 is a cross-sectional view of a light emitting device according to the present invention;

3A to 3G are cross-sectional views illustrating a method of manufacturing a light emitting device according to the present invention.

<Description of the symbols for the main parts of the drawings>

100a: reflective film 100b: sapphire substrate

100 substrate 200 first semiconductor layer

220: first electrode 240: first bonding pad

300: active layer 400: second semiconductor layer

420a: first film layer 420b: second film layer

420: second electrode 440: second bonding pad

The present invention relates to a light emitting device, and more particularly, to an electrode of a light emitting device.

Nitride semiconductors have recently been spotlighted as materials capable of realizing optical and electronic devices such as light emitting diodes (LEDs), laser diodes (LDs), transistors, and photodetectors. In addition, research is being actively conducted at home and abroad. In the fabrication of nitride light emitting diodes, high-quality ohmic bonding is essential when bonding nitride semiconductors to metals to improve device efficiency and life time. Particularly in the case of P-type gallium nitride (GaN), it is difficult to obtain P-type gallium nitride (GaN) having a high hole concentration, and since there is no metal having a high work function compared to the work function of gallium nitride (GaN), the bonding resistance is very low. It is known that it is difficult to obtain a joint having excellent stability and excellent stability. In addition, gallium nitride (GaN) -based light emitting diodes are generally manufactured in the form of surface light emitting diodes, so that not only the electrical properties of metals used for ohmic contact of the P-type gallium nitride (GaN) layer but also light emitted from the active layer of the light emitting diodes High light transmittance also requires high efficiency of the light emitting diode.

Regarding such an electrode for a light emitting device, Korean Patent No. 10-0452751 discloses a technique using multiple layers of a mesh electrode layer and a transparent electrode layer.

As shown in FIG. 1, the "Korean Patent No. 10-0452751" includes a substrate 11 having a reflective film 50, a buffer layer 12 formed on the substrate 11, and the buffer layer ( 12 formed on the lower contact layer 13, the active layer 14 and the upper contact layer 15 sequentially formed on a portion of the lower contact layer 13, and the upper contact layer 15. The superlattice layer 25, the mesh electrode layer 27 and the translucent electrode layer 26 sequentially formed in a portion of the superlattice layer 25, and a bonding pad formed in the other region of the superlattice layer 25 ( 16). In this case, an ohmic contact layer may be included on the lower contact layer 13.

The conventional light emitting device as described above may obtain an improved light efficiency when forming a front ohmic structure by using a mesh ohmic forming structure and a reflective film. The technique used here deposits a metal transparent electrode film on the entire surface of a material with a large conduction band such as P-type gallium nitride (GaN) because it is difficult to spread current by the electrode. However, since most metals absorb or reflect light, the light efficiency depends largely on the properties of the metal ohmic forming film. Accordingly, the metal ohmic forming film is made into a network structure to minimize absorption of light emitted by the ohmic forming film toward the light emitting device P-type semiconductor layer. In addition, the ohmic forming film is used as a highly reflective material to simultaneously reflect to the lower sapphire substrate to emit light to the outside, thereby improving light efficiency.

In addition, in order to reflect the light emitted to the lower part of the light emitting device, when the light emitting device and the application device are bonded, the device is coated with a metal having good reflection characteristics. The light reflectance is improved by using a silver paste or a transparent paste as a bonding medium. Let's do it.

However, in the above structure, the increase in light efficiency due to the reflective film of the mesh ohmic-forming structure and the reflective film of the lower substrate requires two reflections in the light emitting device, thereby increasing resorption in the light emitting device. In addition, there is no light emission of the reflecting film portion, resulting in poor uniformity, and the reflecting film having to be deposited at a thickness of 200 nm or more is difficult to form and deposit a fine network structure. The mesh ohmic formation structure requires a higher applied voltage than the frontal ohmic structure because the portion where the ohmic formation is not critical is large. In addition, in order to form a front surface ohmic using a transparent conductive oxide (TCO) having good transmissivity, an N-type doping is required in the light emitting device P-type semiconductor layer region, which has an unstable factor of increased cost and still high driving voltage. .

Accordingly, there is a problem that the reflection of light by the reflection characteristics of the mechanism or the reflection of the bonding medium is greater than the degradation of the characteristics of the light emitting device as time passes when the light emitting device is operated.

In order to solve the above problems, the present invention uses a first membrane layer, which is a transparent multiple film, and a multilayer electrode having a transparent conductive oxide film, as a second film layer, to improve light transmittance and improve current diffusion without reducing light efficiency, thereby driving voltage. The purpose is to provide a more efficient light emitting device by lowering the.

In order to achieve the above object, the present invention provides a substrate, an N-type semiconductor layer formed on one surface of the substrate, a P-type semiconductor layer formed in a portion of the N-type semiconductor layer, and a network structure on the P-type semiconductor layer An electrode having an in-omic-forming conductive film and a transparent conductive oxide film is provided, and the ohmic-forming conductive film provides a light emitting device comprising multiple films of an oxide forming material and an oxide non-forming material.

In this case, the oxide forming material may include at least one of nickel (Ni), silver (Ag), magnesium (Mg), zinc (Zn), aluminum (Al), the oxide non-forming material is gold (Au) , At least one of platinum (Pt) and palladium (Pd) and may have an electrical conductivity of 5 × 10 ⁻⁵ (Ωcm) ⁻¹ or less.

In addition, the ohmic forming conductive film has an ohmic contact resistance of 5 × 10 ⁻⁴ (Ω / cm 2) or less, a sheet resistance of 15 (Ω / square) or less, and a light transmittance of 70 to 100%.

In addition, the transparent conductive oxide film may include one of ITO, ZnO, InCe oxide, and InGa oxide.

In this case, the substrate may include a reflective film formed on the other surface of the substrate, and the reflective film may include at least one of aluminum (Al), silver (Ag), rhenium (Re), ruthenium (Ru), and gold (Au).

Moreover, the present invention comprises the steps of preparing a substrate; Forming an N-type semiconductor layer and a P-type semiconductor layer on the substrate; Forming an ohmic forming conductive film of an oxide forming material and an oxide non-forming material on the P-type semiconductor layer in a mesh structure; Forming a transparent conductive oxide film on the ohmic forming conductive film, wherein the ohmic forming conductive film is formed by heat treatment at a temperature of 500 to 600 degrees Celsius in an atmosphere containing oxygen after deposition. To provide.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art, It is provided to inform you. Like reference numerals in the drawings refer to like elements.

2 is a cross-sectional view of a light emitting device according to the present invention.

As shown in FIG. 2, the light emitting device according to the present invention includes a substrate 100, an active layer 300 formed on the first semiconductor layer 200 formed on the substrate 100, and a partial region on the first semiconductor layer. ), A second semiconductor layer 400 formed on the active layer 300, and a second electrode 420 having a multilayer structure formed on the second semiconductor 400 layer. In this case, the substrate 100 includes a sapphire substrate 100b and a reflective film 100a formed under the sapphire substrate 100b, and is formed on the first semiconductor layer 200 and the second semiconductor layer 400. The first pad 240 and the second pad 440 may be formed.

The substrate 100 refers to a conventional wafer for manufacturing a light emitting device. In the present invention, a sapphire substrate 100b having a reflective film 100a formed thereon is used. The sapphire substrate 100b has a light transmitting property and an insulating property.

In the light emitting device of the present invention, and are emitted upwards toward the second semiconductor layer 400. Therefore, in the present invention, the substrate 100 has a reflective film 100a having excellent reflection characteristics, thereby reflecting light transmitted through the sapphire substrate 100b to the upper side to increase the luminous efficiency.

The reflective film 100a is for reflecting light emitted from the active layer 300 to the bottom and transmitted through the sapphire substrate 100b to the top, and includes aluminum (Al), silver (Ag), rhenium (Re), and ruthenium (Ru). ) And gold (Au). That is, such materials may form a single layer or two or more materials may form a multilayer. The reflective film 100a is formed to a thickness of 100 ~ 450nm, and reflects more than 80% of the incident light. In this case, the reflective film 100a mainly considers only the reflective characteristics without considering the electrical characteristics.

The first semiconductor layer 200 is typically an N-type nitride semiconductor layer in which electrons are generated, and is formed of an N-type compound semiconductor layer and an N-type clad layer. In this case, the N-type compound semiconductor layer uses a nitride doped with N-type impurities.

The active layer 300 is a region where a predetermined band gap and a quantum well are made to recombine electrons and holes, and the emission wavelength generated by the combination of electrons and holes is changed according to the type of material constituting the active layer 300. Therefore, it is preferable to use the semiconductor material whose composition was controlled according to the target wavelength as the active layer 300.

The second semiconductor layer 400 is a P-type nitride semiconductor layer in which holes are normally formed, and is formed of a P-type cladding layer and a P-type compound semiconductor layer. In this case, the P-type compound semiconductor layer uses a nitride doped with P-type impurities.

The second electrode 420 is a metal layer formed on the second semiconductor layer 400 to apply an external power source to the nitride semiconductor layer. The second electrode 420 includes an ohmic forming conductive film and a transparent conductive oxide film. In the light emitting device of the present invention, light is emitted upwardly toward the second semiconductor layer 400. At this time, the light emitted from the active layer 300 to the second semiconductor layer 400 and the light emitted to the first semiconductor layer 200 are reflected upward by the lower reflective film 100a and the second electrode 420. ) Is transmitted through and released to the outside. Therefore, the second electrode 420 must be transparent so that light can pass therethrough. That is, the second electrode 420 has a multi-layer structure including a first film layer 420a which is a transparent ohmic forming conductive film and a second film layer 420b which is a transparent conductive oxide film formed on the first film layer 420a. By increasing the light transmittance and lowering the driving voltage of the light emitting device, to provide a light emitting device of high efficiency.

The ohmic formation conductive film, which is the first film layer 420a, of the second electrode 420 may include an oxide including at least one of nickel (Ni), silver (Ag), magnesium (Mg), zinc (Zn), and aluminum (Al). Forming material and oxide non-forming material with high work function such as gold (Au), tin (Pt), palladium (Pd) and high electrical conductivity of about 5 × 10 ^-5 (Ωcm) ^-1 Thin films are deposited in turn to form multiple films. For example, nickel (Ni), silver (Ag), nickel (Ni), and gold (Au) are deposited in the order of 20 Å, 5 Å, 20 Å, 50 각각, respectively, or nickel (Ni), magnesium (Mg), Nickel (Ni) and gold (Au) are sequentially deposited in thicknesses of 20 kV, 5 kV, 20 kV and 50 kV to form the first film layer 420a. However, the present invention is not limited thereto, and multiple films of various combinations may be used as the first film layer 420a.

At this time, the first film layer 420a has a mesh structure and has a contact resistance of 5 × 10 ⁻⁴ Ω / cm 2 or less, a sheet resistance of 15 Ω / Square or less, and a light transmittance of 70 to 80%. In addition, the first film layer 420a forms an ohmic with the second semiconductor layer 400, and preferably 30 to 70% of the upper area of the second semiconductor layer 400.

The second film layer 420b is a transparent conductive oxide film (TCO), for more stable current diffusion of the second semiconductor layer. The second film layer 420b forms ITO (In, Sn, O), ZnO, InCe oxide, InGa oxide, or the like with a thickness of approximately 100 to 400 nm. In this case, the second film layer 420b has a light transmittance of about 80 to 100%, but has a sheet resistance of about 15Ω / Square or less. In addition, the second film layer 420b forms an ohmic with the first film layer 420a so that the current spreading is uniform throughout the light emitting area.

Therefore, the present invention emits most of the light emitted from the active layer 300 to the outside by using the first film layer 420a, which is a transparent ohmic-forming conductive film, and the second film layer 420b, which is a transparent conductive oxide film, as electrodes. . That is, in the conventional light emitting device, an opaque metal layer is formed as the first film layer and is reflected by the opaque metal layer except for light emitted through the mesh. However, according to the present invention, the first film layer is formed of a transparent ohmic forming conductive film having a mesh structure so that light incident to the ohmic forming conductive film can be emitted to the outside without being emitted to the mesh eye. In addition, a small amount of light reflected by the ohmic forming conductive film is also reflected and re-emitted by the reflecting film 100a formed under the sapphire substrate 100b, so that light efficiency is superior to that of the conventional light emitting device.

Hereinafter, a method of manufacturing a light emitting device according to the present invention will be described with reference to the accompanying drawings.

3A to 3G are views for explaining a method of manufacturing a light emitting device according to the present invention.

Referring to FIGS. 3A to 3G, a method of manufacturing a light emitting device according to the present invention may include aluminum (Al), silver (Ag), rhenium (Re), ruthenium (Ru), and gold (1) on one side of a sapphire substrate 100b. A material having excellent light reflection characteristics such as Au) may be used independently or a multilayer may be formed to form a reflective film having excellent contact characteristics with a thickness of 100 to 450 nm.

Thereafter, the N-type semiconductor layer 200, the active layer 300, and the P-type semiconductor layer 400 are sequentially grown on the other side of the sapphire substrate 100b.

A photolithography process using a mask is performed on the grown semiconductor layer to expose the substrate so that each cell is electrically separated. That is, a portion of the P-type semiconductor layer 400, the active layer 300, and the N-type semiconductor layer 200 is removed by an etching process using the mask as an etching mask to expose the substrate 100.

On the other hand, the mask is formed using a photosensitive film. In addition, the etching process may be a wet or dry etching process, it is preferable to perform the dry etching using the plasma in this embodiment.

After the process, the P-type semiconductor layer 400 and the active layer 300 are etched to expose the N-type semiconductor layer 200 of each cell. That is, after the first etching is performed using the first mask exposing the substrate 100, a predetermined region of the P-type semiconductor layer 400 and the active layer 300 is exposed to expose the N-type semiconductor layer 200. Second etching using the second mask is performed. An ohmic metal material is coated on the exposed N-type semiconductor 200 to form an N-type electrode.

Subsequently, each of the materials forming oxides including at least one of nickel (Ni), silver (Ag), magnesium (Mg), zinc (Zn), and aluminum (Al) may be independently used or two or more materials may be used in a predetermined ratio. Materials that have a high work function such as gold (Au), tin (Pt), and palladium (Pd), which form solid solutions and do not form oxides, have high electrical conductivity as high as 5 × 10 ^-5 (Ω㎝) ^-1 Prepare. Multiple layers of the oxide-forming material and the non-oxide-forming material were deposited on an P-type semiconductor layer using an e-beam or a thermal vacuum deposition apparatus in a mesh structure using a mask to include oxygen. The first film layer 420a is formed by annealing at a temperature of 500 to 600 degrees Celsius in an atmosphere.

ITO (In, Sn, O), ZnO, InCe oxide, InGa oxide, etc., which are transparent conductive oxide films (TCO), are deposited on the first film layer 420a in a thickness of 100 to 400 nm and then in an oxygen atmosphere. The heat treatment is performed to form a P-type electrode 420 including the first film layer 420a and the second film layer 420b.

Thereafter, when the light emitting device array substrate manufactured as described above is separated into a unit light emitting device, a light emitting device as shown in FIG. 2 is completed.

In this case, a portion of the transparent electrode on the P-type semiconductor layer 400 may be etched by a photo process to expose the P-type semiconductor layer 400, and a P-type bonding pad 440 may be formed. In addition, an N-type electrode 240 on the N-type semiconductor layer 220 may also be etched to form an N-type bonding pad 220.

The rights of the present invention are not limited to the embodiments described above, but are defined by the claims, and various changes and modifications can be made by those skilled in the art within the scope of the claims. It is self-evident. That is, the N-type electrode 220 on the N-type semiconductor layer 200 and the P-type electrode 420 on the adjacent P-type semiconductor layer 400 may have a predetermined bridge process or step cover. It is also possible to manufacture an AC type light emitting device by electrically connecting using a process.

As described above, the present invention lowers the driving voltage by improving light transmittance and improving current diffusion without lowering light efficiency by using a multilayer electrode having the first film layer of the transparent multiple film and the transparent conductive oxide film as the second film layer. A more efficient light emitting device can be provided.

Claims (7)

Substrate, An N-type semiconductor layer formed on one surface of the substrate, A P-type semiconductor layer formed in a portion of the N-type semiconductor layer, An electrode having an ohmic forming conductive film having a mesh structure and a transparent conductive oxide film on the P-type semiconductor layer, And the ohmic forming conductive film comprises multiple films of an oxide forming material and an oxide non-forming material. The method according to claim 1, The oxide forming material includes at least one of nickel (Ni), silver (Ag), magnesium (Mg), zinc (Zn) and aluminum (Al). The method according to claim 1, The oxide non-forming material comprises at least one of gold (Au), platinum (Pt), palladium (Pd), the light emitting device, characterized in that the electrical conductivity is 5 × 10 ^-5 (Ωcm) ^-1 or less. The method according to any one of claims 1 to 3, The ohmic forming conductive film has an ohmic contact resistance of 5 × 10 ⁻⁴ (Ω / cm 2) or less, a sheet resistance of 15 (Ω / square) or less, and a light transmittance of 70 to 100%. The method according to claim 1, The transparent conductive oxide film is a light emitting device comprising one of ITO, ZnO, InCe oxide, InGa oxide. The method according to claim 1, A reflective film formed on the other surface of the substrate, The reflective film is at least one of aluminum (Al), silver (Ag), rhenium (Re), ruthenium (Ru), gold (Au). Preparing a substrate; Forming an N-type semiconductor layer and a P-type semiconductor layer on the substrate; Forming an ohmic forming conductive film of an oxide forming material and an oxide non-forming material on the P-type semiconductor layer in a mesh structure; Forming a transparent conductive oxide film on the ohmic forming conductive film, wherein the ohmic forming conductive film is formed by heat treatment at a temperature of 500 to 600 degrees Celsius in an atmosphere containing oxygen after deposition. Way.

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