KR100648812B1 - Galium-nitride light emitting diode and method of fabricating the same - Google Patents

Abstract

A gallium nitride-based LED is provided to avoid delamination of a reflection layer and decrease contact resistance by including a connection layer between the reflection layer and a GaN layer and by forming a groove or hole penetrating the connection layer from its upper surface to the lower surface. An active layer(13) is formed on a first GaN layer. A second GaN layer is formed on the active layer. A connection layer(15) is formed on the second GaN layer wherein a groove or a hole(20) is penetrated in the connection layer from its top to its bottom. A reflection layer is formed on the connection layer to fill the inside of the groove or hole. The connection is made of transparent conductive oxide, silicon nitride or silicon oxide.

Description

Gallium nitride-based light emitting diode and a method of manufacturing the same {Galium-nitride Light Emitting Diode And Method Of Fabricating The Same}

1 is a cross-sectional view showing a schematic configuration of a light emitting diode according to the prior art;

2A to 2D are cross-sectional views showing a first embodiment of a gallium nitride based light emitting diode and a method of manufacturing the same according to the present invention;

3 and 4 are plan views illustrating a connection layer in which grooves or holes of a gallium nitride based light emitting diode according to the present invention are formed;

5A to 5E are cross-sectional views showing a second embodiment of a gallium nitride based light emitting diode and a method of manufacturing the same according to the present invention;

6 is a cross-sectional view showing another embodiment of a gallium nitride based light emitting diode according to the present invention.

*** Explanation of the Major Symbols in the Drawings ***

10 substrate 11 undoped U-GaN layer

12: N-GaN layer 13: active layer

14: P-GaN layer 15: connection layer

16 reflection layer 17 N-electrode

18: P-electrode 19: conductive adhesive layer

20: groove or hole 21: InGaN / GaN superlattice layer

30: conductive support

31: Under Bump Metal Layer

The present invention relates to a gallium nitride-based light emitting diode and a method of manufacturing the same, and more particularly, having a connection layer formed between the reflective layer and the GaN layer, and forming a groove or hole penetrating from the upper surface to the lower surface of the connection layer In addition, by allowing a part of the reflective layer to be connected to the P-GaN layer or the conductive adhesive layer through grooves or holes formed in the connection layer, not only the peeling of the reflective layer can be prevented, but also the contact resistance is reduced to reduce the operating voltage and the amount of heat generated. It is to provide a gallium nitride-based light emitting diode and a method for manufacturing the same.

A light emitting diode is a light emitting device that emits light when electrons are transitioned. The light emitting diode emits light in a process in which electrons in a semiconductor conduction band recombine with holes in a valence band. Happens.

Light emitting diodes are smaller than conventional light sources, have a long lifespan, and have low power and good efficiency because electrical energy is directly converted into light energy. In addition, it is used for display devices of automotive instrumentation, display lamps for various electronic devices such as optical communication light sources, numeric display devices, and card readers for calculators.

In recent years, light emitting diodes (LEDs) and laser diodes (LDs) using gallium nitride have applications such as large scale full color flat panel display devices, traffic lights, indoor lighting and high density light sources, high resolution output systems, and optical communication. As a result, many researchers are attracting attention, and attempts for commercialization are ongoing.

The wavelength of light emitted from the light emitting diode is a function of the band gap of the semiconductor material used. Small band gaps require materials with a wider band gap to emit lower energy and longer wavelengths of light, and shorter wavelengths of light.

The light emission wavelength of the light emitting diode is controlled by changing the type of impurities added to the semiconductor. For example, in the case of gallium phosphide, light emission involving zinc and oxygen atoms is red (wavelength 700 nm), and light emission involving nitrogen atoms is green (wavelength 550 nm). On the other hand, silicon carbide (SiC) and group III nitride semiconductors, in particular GaN (gallium nitride), which are semiconductor materials having a relatively large band gap, are used to generate light having a blue or ultraviolet wavelength of the spectrum. In addition to the color itself, the short wavelength light emitting diode has the advantage of increasing the storage space of the optical recording device (about four times larger than the red light).

Among such nitride compound semiconductors for blue light, GaN has no practical technology capable of forming bulk single crystals like other group III nitride systems. Therefore, a substrate suitable for the growth of GaN crystals should be used, typically a sapphire substrate, that is, an aluminum oxide substrate.

1 is a cross-sectional view of a general light emitting diode, in which an N-GaN layer 111, an active layer 112, and a P-GaN layer 113 are sequentially formed on a sapphire substrate 110; Mesa is etched from the P-GaN layer 113 to the N-GaN layer 111; An N-electrode 115 is formed on the mesa-etched N-GaN layer 111; The P-electrode 114 is formed on the P-GaN layer 113.

In this way, when the chip is loaded with a positive load on the P-electrode 114 and a negative load on the N-electrode 115, holes are formed from the P-GaN layer 113 and the N-GaN layer 111, respectively. And electrons gather in the active layer 112 and recombine to emit light in the active layer 112.

The light emitting diode may include a reflective layer to adjust a traveling direction of light in a desired direction. The reflective layer is formed on the opposite side of the direction of travel of the desired light with respect to the active layer. For example, when the illustrated light emitting diode is packaged in the form of a flip chip, a reflective layer is provided between the P-GaN layer and the P-electrode. The reflective layer is made of metal such as silver or aluminum having high reflectance, and the metals are poor in adhesiveness with gallium nitride, and peeling easily occurs. Therefore, it is common to form a connection layer made of a transparent conducting oxide or the like between the P-GaN layer and the reflective layer.

The structure has various problems. First, since the contact resistance between the connection layer and the P-GaN layer is high, there is a problem that the operating voltage is increased and the heat generation of the light emitting diode is increased. Second, since it is necessary to go through a heat treatment process in order to minimize the contact resistance, there is a problem that the process is complicated because the reflective layer is deposited after the deposition of the connection layer, the heat treatment of the connection layer.

Therefore, by solving such a problem, there is a need to develop a light emitting diode having a structure that can not only reduce the operating voltage of the light emitting diode but also can be formed in a relatively simple process.

The present invention is to solve the above problems, and provided with a connection layer formed between the reflective layer and the GaN layer, and forming a groove or hole penetrating from the upper surface to the lower surface of the connection layer, a part of the reflective layer to By connecting to the P-GaN layer or the conductive adhesive layer through the formed grooves or holes, the gallium nitride-based light emitting diode that can not only prevent the peeling of the reflective layer, but also the contact resistance is reduced to reduce the operating voltage and calorific value; It is for providing the manufacturing method.

The present invention is an active layer formed on the first GaN layer; A second GaN layer formed on the active layer; A connection layer formed on the second GaN layer and having a groove or a hole penetrating from an upper surface to a lower surface; And a gallium nitride-based light emitting diode filling the inside of the groove or hole and including a reflective layer formed on the connection layer.

In addition, the connection layer is a gallium nitride-based light emitting diode, characterized in that made of a transparent conductive oxide (Transparent Conducting Oxide), silicon nitride or silicon oxide.

In addition, the thickness of the connection layer is a gallium nitride-based light emitting diode, characterized in that 5 to 5000Å.

The gallium nitride based light emitting diode further comprises a conductive adhesive layer formed between the second GaN layer and the connection layer.

The gallium nitride-based light emitting diode further comprises an InGaN / GaN superlattice layer formed between the second GaN layer and the connection layer.

In addition, the reflective layer is a gallium nitride-based light emitting diode, characterized in that made of aluminum, silver or alloys thereof.

The gallium nitride-based light emitting diode further comprises a support formed under the first GaN layer or on the reflective layer.

The first GaN layer is an N-GaN layer, and the second GaN layer is a P-GaN layer.

The method may further include forming a light emitting structure by sequentially forming a first GaN layer, an active layer, a second GaN layer, a connection layer, a conductive adhesive layer, and a reflective layer on a substrate; Heat-treating the light emitting structure to shrink the connection layer to form a groove or hole penetrating from an upper surface to a lower surface of the connection layer; Forming a conductive support on the reflective layer; Removing the substrate; And forming a first electrode under the first GaN layer from which the substrate is removed, and forming a second electrode on the conductive support.

The method may further include forming a light emitting structure by sequentially forming a first GaN layer, an active layer, a second GaN layer, a connection layer, and a reflective layer on a substrate; Heat-treating the light emitting structure to shrink the connection layer to form a groove or hole penetrating from an upper surface to a lower surface of the connection layer; Mesa etching the light emitting structure to expose a portion of the first GaN layer; And forming a first electrode on the etched top surface of the first GaN layer, and forming a second electrode on the light emitting structure.

Hereinafter, with reference to the accompanying drawings will be described in detail the technical features of the present invention. The invention can be better understood by the examples, the following examples are for illustrative purposes of the invention and are not intended to limit the scope of protection defined by the appended claims.

2A to 2D are cross-sectional views showing a first embodiment of a gallium nitride based light emitting diode and a method of manufacturing the same according to the present invention, wherein an undoped U-GaN layer 11 and an N-GaN layer 12 are formed on the substrate 10. ), Forming an active layer 13, a P-GaN layer 14, a connection layer 15, a reflective layer 16 in order to form a light emitting structure (Fig. 2a); Heat-treating the light emitting structure to shrink the connection layer 15 to form a groove or hole 20 penetrating from an upper surface to a lower surface of the connection layer (FIG. 2B); Mesa etching the light emitting structure to expose a portion of the N-GaN layer 12 (FIG. 2C); And forming an N-electrode 17 on the etched top surface of the N-GaN layer and forming a P-electrode 18 on the light emitting structure (FIG. 2D).

First, an undoped U-GaN layer 11, an N-GaN layer 12, an active layer 13, a P-GaN layer 14, a connection layer 15, and a reflective layer 16 are formed on the substrate 10. Formed in order to form a light emitting structure (Fig. 2a).

The substrate 10 serves as a support for growing a GaN layer. Any one of a sapphire substrate, a silicon (Si) substrate, a zinc oxide (ZnO) substrate, or a nitride semiconductor substrate, or a template substrate in which at least one of GaN, InGaN, AlGaN, and AlInGaN are stacked on the substrate is used. Can be.

As the method for forming the N-GaN layer, the active layer, and the P-GaN layer, any thin GaN layer can be used without limitation, but preferably, an organic metal chemical vapor deposition (MOCVD) method is suitable.

In order to form the N-GaN layer 12, doping with an appropriate dopant is performed during the formation of the GaN layer. As the dopant for N doping, silicon, germanium, selenium, tellurium, carbon, and the like may be used. When silicon is used, the doping concentration is generally about 10 ¹⁷ / cm ³ . The N-GaN layer may be formed in a double layer structure of N ⁺ and N ⁻ by varying the doping concentration.

In this embodiment, an undoped U-GaN layer 11 is first formed on a substrate, and then an N-GaN layer is formed thereon. This is to prevent the occurrence of defects due to the rapid change in the lattice period when the N-GaN layer is formed on the substrate to reduce the thin film characteristics.

The active layer 13 is a part emitting light in the light emitting diode. Al _X Ga _Y In _1-XY N (0≤x <1, 0 <y <1) can be represented by the general formula, binary system such as aluminum nitride, gallium nitride and indium nitride, gallium nitride-indium and gallium nitride Ternary systems such as aluminum. Group III elements may be partially substituted with boron, thallium, and the like, and nitrogen may be partially substituted with phosphorus, arsenic, antimony, and the like.

The active layer can adjust the wavelength of light emitted by changing the component composition. For example, about 22% of indium is included to emit blue light. In addition, about 40% of indium is included to emit green light.

As the dopant of the P-GaN layer 14, magnesium, zinc, beryllium, calcium, strontium, barium, or the like may be used. Like the N-GaN layer, the P-GaN layer can be formed in a two ^- layer structure of P ⁺ and P ⁻ .

The connecting layer 15 is to increase the adhesion so that the reflective layer 16 does not peel off from the P-GaN layer. The connection layer may be made of a transparent conductive oxide such as ITO, ZnO, IZO, ZCO, etc. In addition, the connection layer may be made of an insulating material such as silicon oxide or silicon nitride.

A feature of the present invention is that the portion of the reflective layer is connected to the P-GaN layer by shrinking the connecting layer by a heat treatment process to be described later, so that a part of the reflective layer is connected to the P-GaN layer. It is better not to exceed it. It is preferable that it is 5-5000 microseconds.

A conductive adhesive layer may be formed between the connection layer 15 and the P-GaN layer 14 to improve adhesion. The conductive adhesive layer is preferably made of nickel, aluminum, silver or an alloy thereof.

InGaN / GaN superlattice layers may be formed between the connection layer 15 and the P-GaN layer 14 to further reduce contact resistance. The superlattice structure refers to a structure in which the spatial variation of the semiconductor band gap has one-dimensional or two-dimensional periodicity larger than the lattice constant of the constituent material.

In this embodiment, InGaN and GaN are alternately stacked to form a superlattice structure, and in order to further lower contact resistance, the GaN layer may be N-doped (silicon implanted), in which case the doping concentration is 1 x 10 ¹⁸ / cm. ³ or more are preferable.

When the light emitting diode of the present invention includes both the superlattice layer and the conductive adhesive layer, the light emitting diode is formed in the order of P-GaN layer, superlattice layer, conductive adhesive layer, and connection layer.

The reflective layer 16 reflects light emitted from the active layer toward the N-GaN layer, thereby increasing luminous efficiency. The reflective layer is made of a metal having high reflectance, and specific examples thereof are preferably made of aluminum, silver, or an alloy thereof.

The connection layer and the reflective layer may be formed by sputtering, electron beam deposition, or the like.

Next, the light emitting structure is heat-treated to shrink the connection layer 15 to form a groove or hole 20 penetrating from the top surface to the bottom surface of the connection layer (FIG. 2B). The heat treatment temperature is preferably made at 400 to 800 ℃.

As described above, the connecting layer is formed very thin. Therefore, when shrinkage occurs due to heat treatment, grooves or holes penetrating from the top surface to the bottom surface of the connection layer are formed, so that a part of the reflective layer located on the connection layer is connected to the P-GaN layer or the conductive adhesive layer under the connection layer. .

This structure is connected to the P-GaN layer or the conductive adhesive layer through a groove or a hole formed in the connecting layer to prevent the peeling of the reflective layer, and also reduces the contact resistance, thereby reducing the operating voltage and the amount of heat generated. This has a beneficial effect of decreasing.

3 and 4 are plan views showing grooves or holes formed in the connection layer of the gallium nitride-based light emitting diode according to the present invention. As shown in the drawing, the connection layer contracted by heat treatment penetrates from the top surface to the bottom surface of the connection layer. To form a hole or groove.

In the method of manufacturing a light emitting diode according to the present invention, in forming the above structure, by using a method of forming a thin connection layer and then shrinking the connection layer by heat treatment, the light emitting diode may be damaged by an etching process or the like. There is no.

In addition, in the formation of the connection layer, it is necessary to perform heat treatment in order to reduce the contact resistance. In the manufacturing method of the present invention, a conventional connection layer deposition-heat treatment-reflection layer is deposited by depositing the connection layer and the reflection layer and then performing heat treatment. The process leading to deposition can be simplified.

Next, the light emitting structure is mesa-etched to expose a part of the N-GaN layer 12 (FIG. 2C), and then an N-electrode 17 is formed on the etched top surface of the N-GaN layer. And a P-electrode 18 on the light emitting structure (FIG. 2D).

5A through 5E are cross-sectional views showing a second embodiment of a gallium nitride based light emitting diode and a method of manufacturing the same according to the present invention, wherein an undoped U-GaN layer 11 and an N-GaN layer 12 are formed on the substrate 10. ), Forming an active layer 13, a P-GaN layer 14, a connection layer 15, a reflective layer 16 in order to form a light emitting structure (FIG. 5A); Heat-treating the light emitting structure to shrink the connection layer 15 to form a groove or hole 20 penetrating from an upper surface to a lower surface of the connection layer 15 (FIG. 5B); Forming a conductive support portion 30 on the reflective layer 16 (FIG. 5C); Removing the substrate (10) and undoped U-GaN layer (11) (FIG. 5D); And forming an N-electrode 17 under the N-GaN layer 12 and forming a P-electrode 18 on the conductive support 30 (FIG. 5E).

The embodiment relates to a method of manufacturing a light emitting diode according to the present invention into a vertical light emitting diode.

First, an undoped U-GaN layer 11, an N-GaN layer 12, an active layer 13, a P-GaN layer 14, a connection layer 15, and a reflective layer 16 are formed on the substrate 10. Forming a light emitting structure by forming in order (FIG. 5A), and then heat-treating the light emitting structure, and shrinking the connecting layer 15, the groove or hole 20 penetrating from the upper surface to the lower surface of the connecting layer To form (FIG. 5B). The specific process of the above step is the same as in the above-described embodiment, and as in the above-described embodiment, at least one of a conductive adhesive layer or an InGaN / GaN superlattice layer between the P-GaN layer 14 and the connection layer 15 One can be formed.

Next, the conductive support 30 is formed on the reflective layer (FIG. 5C). The conductive support may be a submount substrate or a plated metal layer. The submount substrate is formed of a conductive base substrate and a metal layer for ohmic contact formed on each of the upper and lower portions of the base substrate, and is bonded to the light emitting structure through conductive solder.

An under bump metal 31 may be formed between the conductive support and the light emitting structure.

Next, the substrate 10 and the undoped U-GaN layer 11 are removed (FIG. 5D). As the removal method, a laser lift-off method or the like may be used. The laser lift-off method will be described in more detail. When a 245-305 nm UV-laser is irradiated through the substrate, the laser passes through the substrate and is absorbed at the interface between the substrate and the GaN layer, whereby GaN is separated into Ga and N ₂ . N ₂ escapes to the outside in a gaseous state, leaving only Ga at the interface. Since Ga has a melting point of about 30 ° C, it is easily melted by heat to remove the substrate.

Since the U-GaN layer in contact with the substrate is damaged by a laser, the N-GaN layer is exposed by removing the U-GaN layer to form an electrode. First, Ga formed in the process of removing the substrate is removed using a dilute hydrochloric acid solution to facilitate the subsequent etching process, and then the U-GaN layer is removed using dry etching. After removing the U-GaN layer, heat treatment is performed to recover crystals damaged during the etching process.

Next, an N-electrode 17 is formed under the N-GaN layer 12, and a P-electrode 18 is formed on the conductive support (FIG. 5E).

6 is a cross-sectional view showing another embodiment of a gallium nitride-based light emitting diode according to the present invention, the active layer 13 formed on the N-GaN layer 12; A P-GaN layer 14 formed on the active layer; An InGaN / GaN superlattice layer 21 formed on the P-GaN layer and a conductive adhesive layer 19 formed on the InGaN / GaN superlattice layer; A connection layer 15 formed on the conductive adhesive layer and having a groove or hole 20 penetrating from an upper surface to a lower surface thereof; A reflection layer 16 filling the inside of the groove or hole and formed on the connection layer; A bonding layer formed on the reflective layer; A conductive support formed on the bonding layer; And a P-electrode 18 formed on the conductive support and an N-electrode 17 formed under the N-GaN layer.

The embodiment is a vertical light emitting diode, further comprising an InGaN / GaN superlattice layer 21 and a conductive adhesive layer 19 between the P-GaN layer 14 and the connection layer 15, thereby reducing contact resistance. The adhesion of the reflective layer is further improved.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

As described above, the gallium nitride based light emitting diode according to the present invention includes a connection layer formed between the reflective layer and the GaN layer, and a groove or a hole penetrating from the top surface to the bottom surface of the connection layer is formed, whereby a part of the reflective layer is formed. It is connected to a P-GaN layer or a conductive adhesive layer through grooves or holes formed in the connection layer. Therefore, not only the peeling of the reflective layer can be prevented, but also the contact resistance is reduced, which has the advantageous effect of reducing the operating voltage and the amount of heat generated.

In addition, in the method for manufacturing a gallium nitride-based light emitting diode according to the present invention, in forming the above-described structure, by forming a connection layer thin, using a method of shrinking the connection layer by heat treatment, light emission by an etching process or the like Not only does the diode have to be damaged, but the process is simplified.

Claims (12)

An active layer formed on the first GaN layer; A second GaN layer formed on the active layer; A connection layer formed on the second GaN layer and having a groove or a hole penetrating from an upper surface to a lower surface; And Gallium nitride-based light emitting diode filling the inside of the groove or hole, and comprising a reflective layer formed on the connection layer. The method of claim 1, The connection layer is a gallium nitride-based light emitting diode, characterized in that consisting of a transparent conductive oxide (Transparent Conducting Oxide), silicon nitride or silicon oxide. The method of claim 1, The thickness of the connection layer is a gallium nitride-based light emitting diode, characterized in that 5 to 5000Å. The method of claim 1, The gallium nitride-based light emitting diode further comprises a conductive adhesive layer formed between the second GaN layer and the connection layer. The method of claim 1, And a gallium nitride-based light emitting diode further comprising an InGaN / GaN superlattice layer formed between the second GaN layer and the connection layer. The method of claim 1, The reflective layer is gallium nitride-based light emitting diode, characterized in that made of aluminum, silver or alloys thereof. The method of claim 1, And a support formed under the first GaN layer or on the reflective layer. The method of claim 1, A gallium nitride-based light emitting diode, characterized in that the first GaN layer is an N-GaN layer, the second GaN layer is a P-GaN layer. Forming a light emitting structure by sequentially forming a first GaN layer, an active layer, a second GaN layer, a connection layer, and a reflective layer on the substrate; Heat-treating the light emitting structure to shrink the connection layer to form a groove or hole penetrating from an upper surface to a lower surface of the connection layer; Forming a conductive support on the light emitting structure; Removing the substrate; And Forming a first electrode under the first GaN layer from which the substrate is removed, and forming a second electrode on the conductive support. Forming a light emitting structure by sequentially forming a first GaN layer, an active layer, a second GaN layer, a connection layer, and a reflective layer on the substrate; Heat treating the light emitting structure to shrink the connection layer to form a groove or hole penetrating from an upper surface to a lower surface of the connection layer; Mesa etching the light emitting structure to expose a portion of the first GaN layer; And And forming a first electrode on the etched upper surface of the first GaN layer, and forming a second electrode on the light emitting structure. The method of claim 9 or 10, The thickness of the connection layer is a manufacturing method of the gallium nitride-based light emitting diode, characterized in that 5 to 5000Å. The method of claim 9 or 10, The method of manufacturing a gallium nitride-based light emitting diode, characterized in that the heat treatment of the connection layer and the reflective layer is made at 400 to 800 ℃.

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