KR100855340B1 - Manufacturing method of light emitting diode device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode device and a manufacturing method thereof, and more particularly, to a structure of a top transparent electrode and a method of forming the same in a gallium nitride (GaN) -based light emitting diode device. A light emitting diode device according to the present invention includes a gallium nitride (GaN) -based light emitting diode device, the gallium nitride semiconductor layer comprising an n-type gallium nitride semiconductor layer and a p-type gallium nitride semiconductor layer; A hole injection layer positioned on the gallium nitride semiconductor layer; And a transparent electrode positioned on the hole injection layer.

Description

Manufacturing Method of Light Emitting Diode Device {MANUFACTURING METHOD FOR LIGHT EMITTING DIODE DEVICE}

1 is a cross-sectional view schematically showing a structure of a general light emitting diode device, and FIG. 2 is a cross-sectional view schematically showing a structure of a light emitting diode device manufactured according to an embodiment of the present invention.

Figure 3 shows the result of comparing the ohmic junction characteristics of the LED device according to the prior art and the LED device manufactured according to the embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a light emitting diode device, and more particularly, to a structure of a top transparent electrode and a method of forming the same in a gallium nitride (GaN) based light emitting diode device.

BACKGROUND ART In general, light emitting diodes used as devices for emitting light have been spotlighted as next-generation lighting replacing incandescent bulbs or fluorescent lamps. In particular, as a blue light emitting diode using gallium nitride (GaN) has been developed, it is possible to realize all colors, and accordingly, demand in various fields is increasing. Light-emitting diodes are considered as next-generation national strategic items because they have the advantages of fast processing speed and low power consumption of semiconductors and environmentally friendly and high energy saving effect.

A general method for producing such a gallium nitride light emitting diode is as follows.

1 is a perspective view schematically showing a structure of a general light emitting diode. As shown in FIG. 1, the first semiconductor layer 11 is formed on the prepared substrate 10. The p-n junction surface 20 may be formed on the first semiconductor layer 11 by forming a second semiconductor layer 12 having a polarity opposite to that of the first semiconductor layer 11. That is, when the first semiconductor layer 11 is doped with p-type, the second semiconductor layer 12 doped with n-type is formed on the first semiconductor layer 11, and the first semiconductor layer 11 is n-type. When doped, the second semiconductor layer 12 doped in a p-type may be formed on the first semiconductor layer 11. The first metal electrode 14 is formed on the surface in contact with the second semiconductor layer 12 to flow current through the p-n junction surface 20 formed as described above. In this case, the current distribution transparent electrode 13 may be formed between the upper surface of the second semiconductor layer 12 and the first metal electrode 14 so that the current flows uniformly to the p-n junction surface 20. In addition, in order to form the second metal electrode 15, etching is performed from the second semiconductor layer 12 at the top of the device structure to a part of the first semiconductor layer 11 using a dry etching method. After etching is completed, a pattern is formed using a photolithography process and the second metal electrode 15 is formed using an electron beam deposition method or the like. A pad (not shown) is then formed for wire contact with an external power source. When current flows through the first metal electrode 14 and the second metal electrode 15 of the light emitting diode manufactured as described above, light is emitted from the p-n junction surface.

The most important factor that determines the electrical properties of the gallium nitride light emitting diode is the ohmic characteristics of the p-type gallium nitride semiconductor layer and the metal electrode. Poor ohmic contact results in a very high voltage required for the operation of the device, reducing the reliability of the device in the long run. Here, the ohmic junction refers to a region in which two materials are bonded to each other and a current flowing in the junction portion is in proportion to the potential difference of the junction portion.

Conventionally, metal thin films have been formed for current diffusion in order to achieve a uniform distribution of current. Metal thin films such as Ni / Au electrodes and Pt are annealed in an oxygen atmosphere to be transparent. However, Ni / Au and Pt have a small specific resistance, but the transparency is not sufficient, and the extraction efficiency of the emitted light is also deteriorated. That is, the light emitted from the light emitting diode is emitted through the transparent electrode, the light transmittance of the Ni / Au electrode is difficult to maintain more than 80%, 20% or more light is lost during the emission process.

In addition, if the thickness of the metal thin film is increased to increase the transmittance of the emitted light, the transparency is increased, but the current spreading effect that is spread evenly throughout the device is remarkably reduced, which does not improve the device characteristics. do.

In addition, when the indium tin oxide (ITO) thin film layer is used for current diffusion, the transparency or current diffusion effect is improved, but since the ITO material belongs to the n-type conductive material, the final thin film layer forming the junction is a p-type gallium nitride semiconductor layer. Since the Schottky bonding characteristic is shown instead of the ohmic bonding, the transparent electrode layer cannot be formed by itself.

As described above, the conventional method has a limit in obtaining desired desired ohmic characteristics. In addition, when heat treatment is performed at high temperature to form an ohmic junction, not only gallium vacancies are generated on the surface of the p-type gallium nitride semiconductor layer, but also nitrogen vacancies occur. Nitrogen vacancies reduce the concentration of holes as opposed to gallium vacancies. Therefore, in order to obtain an optimal ohmic characteristic, a method of increasing the concentration of holes without forming nitrogen vacancies in the p-type gallium nitride semiconductor layer during the heat treatment is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide an electroluminescent device capable of forming an ohmic junction while maximizing a current spreading effect and transparency between a p-type gallium nitride semiconductor layer and an electrode, and a method of manufacturing the same. .

In order to achieve the above technical problem, a light emitting diode device according to the present invention includes a gallium nitride (GaN) -based light emitting diode device, which includes an n-type gallium nitride semiconductor layer and a p-type gallium nitride semiconductor layer, and is stacked on a substrate. Gallium nitride semiconductor layers; A hole injection layer on the gallium nitride semiconductor layer; And a transparent electrode positioned on the hole injection layer.

The gallium nitride semiconductor layer is formed by sequentially stacking an n-type gallium nitride semiconductor layer, an active layer, and a p-type gallium nitride semiconductor layer on a sapphire substrate, and the hole injection layer is positioned directly on the p-type gallium nitride semiconductor layer. It can be done.

The hole injection layer may be formed of a p-type doped transparent conductive oxide, indium-tin oxide (ITO), CuAlO ₂ , CuGaO ₂ , SrCu ₂ O ₂ , ZnO: P, ZnO: N, and In ₂ O _It may include a material selected from the group containing ₃ + Ag ₂ O, the thickness may be within the range of 5 kPa to 100 kPa.

The transparent electrode may be formed of indium tin oxide (ITO), or a mixture of zinc oxide and aluminum (ZnO: Al), and the thickness of the transparent electrode may be within a range of 500 kV to 3000 kV.

In order to achieve the above technical problem, a method of manufacturing a gallium nitride (GaN) -based light emitting diode device according to the present invention includes forming a gallium nitride semiconductor layer including an n-type gallium nitride semiconductor layer and a p-type gallium nitride semiconductor layer on a substrate. step; Forming a hole injection layer on the gallium nitride semiconductor layer; And forming a transparent electrode on the hole injection layer.

The forming of the gallium nitride semiconductor layer may include forming an n-type gallium nitride semiconductor layer on the substrate; Forming an active layer on the n-type gallium nitride semiconductor layer; And forming a p-type gallium nitride semiconductor layer on the active layer, and the hole injection layer may be formed directly on the p-type gallium nitride semiconductor layer.

Hereinafter, a method of manufacturing a light emitting diode according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. When a part of a layer, film, area, plate, etc. is said to be "on" another part, this includes not only the other part "directly" but also another part in the middle. On the contrary, when a part is “just above” another part, there is no other part in the middle.

2 is a cross-sectional view schematically showing the structure of a light emitting diode device manufactured according to an embodiment of the present invention.

In the gallium nitride compound semiconductor light emitting device to which the present invention is applied, similarly to the case of FIG. 1, a buffer layer (not shown) is formed on the substrate 100 made of a material such as sapphire to help the growth of the gallium nitride layer. The gallium nitride layer 110, the active layer (not shown), and the p-type gallium nitride layer 120 are sequentially grown. Subsequently, in the light emitting diode device according to the embodiment of the present invention, unlike the conventional method in which the transparent electrode is formed on the p-type gallium nitride layer 120, the hole injection layer 125 is first formed, and then the hole injection layer is formed. The transparent electrode 130 is formed directly on the 125.

Here, the role of the hole injection layer 125 helps to form an ohmic junction between the p-type gallium nitride layer 120 and the transparent electrode 130 disposed below. That is, when heat treatment is performed at high temperature to form an ohmic junction, a decrease in the concentration of holes due to nitrogen vacancies occurring near the p-type gallium nitride semiconductor layer, particularly near the surface, is prevented or cancelled. Therefore, during the heat treatment, the concentration of holes is maintained or increased in the p-type gallium nitride semiconductor layer.

The hole injection layer 125 having this purpose may be formed of a p-type doped material. That is, the p-type gallium nitride layer 120 is formed of a material doped with a p-type material so as to supply holes, and preferably includes the same doping element as the p-type gallium nitride layer 120, subsequent heat treatment To prevent the loss of the doping element in the process.

In addition, it is important to maintain the light transmittance of the light emitting diode even when the hole injection layer is inserted. For this purpose, a transparent conductive electrode is used. That is, a material that can be doped with a p-type, transparent and excellent in conductivity is required. Representatives for this purpose include conductive oxide materials, preferably indium-tin oxide (ITO), CuAlO ₂ , CuGaO ₂ , SrCu ₂ O ₂ , ZnO: P, ZnO: N, and In ₂ O ₃ + Ag ₂ O It may include a material selected from the group.

In addition, the thickness of the hole injection layer 125 is in the range of 5 kPa to 100 kPa. Since the hole injection layer 125 serves to help form an ohmic junction between the upper transparent electrode 130 and the lower p-type gallium nitride layer 120, subsequent steps such as preventing light loss and patterning processes In consideration of the progress of the process, it is advantageous to form as thin as possible within the range that can serve as the ohmic junction formation.

In general, the p-type gallium nitride layer contains a large amount of hydrogen, which is included during the growth process by organometallic chemical vapor deposition (MOCVD), and forms such as doping element (eg magnesium element) and Mg-H. Are combined. Therefore, only when the hydrogen is removed, the doping element is activated to act as an acceptor to generate holes. In order to remove this hydrogen, a separate rapid heat treatment or heat treatment in an electric furnace is required. Therefore, in the p-type gallium nitride-based device manufacturing method according to an embodiment of the present invention, the hole and / or doping element is diffused from the hole injection layer 125 into the p-type gallium nitride layer 120 by a heat treatment diffusion process , the hole concentration of the p-type gallium nitride can be increased, and the doped element can be activated.

That is, after the hole injection layer 125 is formed on the p-type gallium nitride layer 120, the hole and / or doping elements of the hole injection layer 125 are heat-treated in a vapor deposition apparatus under a nitrogen atmosphere to form the p-type gallium nitride. May diffuse into the interior of layer 120. At this time, it is preferable to maximize the hole injection effect in the middle of rapid thermal treatment (RTA) at a temperature of 400 ° C. to 800 ° C. in a nitrogen atmosphere, while minimizing unnecessary thermal budget. Of course, the method of diffusing the hole and / or doping element into the p-type gallium nitride layer 120 as described above is not limited to the above method, and may be heat-treated in an electric furnace or heat-treated at the same time as the hole injection layer is formed. It may be implemented.

In addition, since the hole injection layer 125 covers the p-type gallium nitride layer 120, it is possible to effectively prevent the nitrogen atoms inside the p-type gallium nitride layer 120 from escaping to the outside during the diffusion process.

The heat treatment process may be performed after the process of forming the transparent electrode 130 on the hole injection layer 125 is completed.

As the transparent electrode 130, indium tin oxide (ITO), which is an n-type transparent electrode material, or a mixture of zinc oxide and aluminum (ZnO: Al) is applicable. In addition, a mixture of zinc oxide and aluminum (ZnO: Al), IrO ₂ , RhO ₂ , RuO ₂ , Co ₃ O ₄ , Fe ₃ O ₄ , Mo ₂ O _3, etc. Oxide-based conductive materials can be used. Since the transparent electrode 130 requires even distribution of current and stable ohmic junction formation, the thickness of the transparent electrode 130 is preferably greater than that of the hole injection layer 125 in a thickness range of 500 kV to 3000 kV.

Subsequent processes are a part of the p-type gallium nitride layer 120 and the n-type gallium nitride layer 110 by a dry etching method in a region where the n-electrode 150 is to be formed, according to a general manufacturing process of a nitride light emitting diode. After removing the n-electrode 150 is formed. The metal material for the p-electrode 140 is deposited on the transparent electrode 130. Thereafter, heat treatment at 400 ° C. to 1000 ° C. may be added to help form the ohmic junction.

The ohmic junction in forming the electrodes 130 and 150 on the n-type and p-type gallium nitride layers 110 and 120, respectively, can be understood from the transport mechanism of the carrier. In general, in order to form an ohmic junction between a low resistance semiconductor and a metal (including conductive oxide) interface, a conductive material having a high work function is employed to tunnel the potential barrier. The materials used for the hole injection layer 125 described above are materials that satisfy these characteristics. For example, the work function of CuAlO ₂ is considerably high as 5.3 eV, compared to that of ITO material of 4.5 eV, which is advantageous for forming ohmic properties. In addition, the optical bandgap is about 4eV, and the visible light transmittance is excellent.

In addition, in order to examine the effect of the hole injection layer introduced in the present invention, the p-type gallium nitride layer prepared according to the conventional technique as shown in Figure 1 and the p-type gallium nitride layer produced in the present invention For each, the electrical characteristics at the interface with the transparent electrode were compared, which is illustrated in the voltage-current relationship graph of FIG. 3.

In FIG. 3, a graph showing a data value in a square form, that is, a graph showing a data value in a square form is for a p-type gallium nitride layer in which a hole injection layer is introduced according to an embodiment of the present invention, and is represented by (b) One graph, a graph showing data values in the form of a circle, is for a p-type gallium nitride layer without a hole injection layer. When the hole injection layer was introduced between the p-type gallium nitride layer and the transparent electrode layer (ITO) and when it was not, a voltage of -0.5 to 0.5V was applied to measure the value of the current flowing between them in 0.05V units. The graph is shown. In the graph (a), that is, when the hole injection layer is introduced between the p-type gallium nitride layer and the transparent electrode layer, the resistance value is about 3.3 ohms, otherwise the resistance value is about 6.7 ohms about 2 times. It was confirmed that the difference in degree. That is, it was confirmed that the ohmic characteristics can be remarkably improved by introducing a hole injection layer between the p-type gallium nitride layer and the transparent electrode layer without changing other conditions.

In the above, the present invention has been described with reference to the presently considered embodiments, but the present invention should not be understood as being limited to the above embodiments. Rather, it should be construed as including all modifications of the range which are easily changed by those skilled in the art from the above-described embodiment of the present invention and considered equivalent.

According to an embodiment of the present invention, an electroluminescence exhibiting excellent ohmic bonding characteristics between a p-type gallium nitride layer and a transparent electrode while using a transparent electrode capable of maximizing a current diffusion effect and transparency in a p-type gallium nitride semiconductor device The device can be manufactured.

The improvement of the above properties can be achieved only by the addition of a relatively simple process step, which is suitable for mass production of electroluminescent devices.

Claims (18)

delete delete delete delete delete delete delete delete In the manufacturing method of a gallium nitride (GaN) series light emitting diode device, Forming an n-type gallium nitride semiconductor layer on the substrate; Forming an active layer on the n-type gallium nitride semiconductor layer; Forming a p-type gallium nitride semiconductor layer on the active layer; Forming a hole injection layer of a p-type doped transparent conductive oxide on the p-type gallium nitride semiconductor layer; Heat treatment by rapid thermal annealing (RTA) at a temperature of 400 to 800 ° C. to reduce contact resistance between the hole injection layer and the gallium nitride semiconductor layer; And Forming a transparent electrode on the hole injection layer Including, The doping element for the hole injection layer is the same as the doping element for the p-type gallium nitride semiconductor layer, The transparent conductive oxide is selected from the group comprising CuGaO ₂ , ZnO: P, ZnO: N, and In ₂ O ₃ + Ag ₂ O. delete delete delete delete delete The method of claim 9, The transparent electrode is formed of indium-tin oxide (ITO), or a mixture of zinc oxide and aluminum (ZnO: Al). The method according to claim 9 or 15, The hole injection layer is a manufacturing method, characterized in that formed to a thickness of 5 ~ 100Å. The method according to claim 9 or 15, The thickness of the transparent electrode is a manufacturing method, characterized in that within the range of 500 kV to 3000 kV. delete

Images