KR20230162568A - Ultraviolet light emitting device and method for manufacturing the same - Google Patents

Abstract

An embodiment includes: a substrate with a plurality of pinholes formed on one surface; a buffer layer disposed on one side of the substrate; and a light-emitting structure disposed on the buffer layer, wherein the buffer layer includes a plurality of cavities formed on the plurality of pinholes. An ultraviolet light-emitting device and a method of manufacturing the same are disclosed.

Description

Ultraviolet light emitting device and method of manufacturing the same {ULTRAVIOLET LIGHT EMITTING DEVICE AND METHOD FOR MANUFACTURING THE SAME}

The embodiment relates to an ultraviolet light-emitting device with good defect density and a method of manufacturing the same.

A light emitting diode (LED) is a type of important solid-state device that converts electrical energy into light, and generally includes an active layer of semiconductor material sandwiched between two opposing doped layers. When a bias is applied to both ends of the two doped layers, holes and electrons are injected into the active layer and then recombine there to generate light. Light generated in the active area is emitted in all directions and escapes out of the semiconductor chip through all exposed surfaces. The packaging of LEDs is typically used to direct the escaping light to the desired output emission form.

Recently, as demand for water treatment and sterilization products has rapidly increased, interest in ultraviolet light-emitting devices is increasing. As the demand for high-output ultraviolet light-emitting devices increases, much research and development is underway to improve light output.

However, ultraviolet light-emitting devices have a problem of reduced luminous efficiency due to relatively high defect density.

The embodiment provides an ultraviolet light-emitting device with improved luminous efficiency by reducing defect density.

The problem to be solved in the embodiment is not limited to this, and also includes purposes and effects that can be understood from the means of solving the problem or the embodiment described below.

An ultraviolet light-emitting device according to an aspect of the present invention includes a substrate having a plurality of pinholes formed on one surface; a buffer layer disposed on one side of the substrate; and a light emitting structure disposed on the buffer layer, wherein the buffer layer includes a plurality of cavities formed on the plurality of pinholes.

Each of the plurality of cavities may be connected to the plurality of pinholes.

The defect density of the area overlapping the plurality of cavities may be lower than the defect density of the area where the plurality of cavities are not formed.

A method of manufacturing an ultraviolet light-emitting device according to an aspect of the present invention includes forming a plurality of pinholes by thermally etching a substrate; forming a buffer layer on the substrate; and forming a light emitting structure on the buffer layer.

According to embodiments, the luminous efficiency of the ultraviolet light-emitting device may be improved by reducing the defect density.

The various and beneficial advantages and effects of the present invention are not limited to the above-described content, and may be more easily understood through description of specific embodiments of the present invention.

1 is a cross-sectional view of an ultraviolet light-emitting device according to an embodiment of the present invention.
Figure 2 is an SEM photo of a light emitting device.
Figure 3 is an AFM (Atomic Force Microscopy) photograph of a buffer layer formed on a portion of the substrate and not yet covering the pinhole.
Figure 4 is a flow chart of manufacturing an ultraviolet light-emitting device according to an embodiment of the present invention.
Figure 5 is a diagram showing the process of forming a cavity in the buffer layer.

The present embodiments may be modified in other forms or various embodiments may be combined with each other, and the scope of the present invention is not limited to each embodiment described below.

Even if matters described in a specific embodiment are not explained in other embodiments, they may be understood as descriptions related to other embodiments, as long as there is no explanation contrary to or contradictory to the matter in the other embodiments.

For example, if a feature for configuration A is described in a specific embodiment and a feature for configuration B is described in another embodiment, the description is contrary or contradictory even if an embodiment in which configuration A and configuration B are combined is not explicitly described. Unless otherwise stated, it should be understood as falling within the scope of the rights of the present invention.

In the description of the embodiment, in the case where one element is described as being formed “on or under” another element, or under) includes both elements that are in direct contact with each other or one or more other elements that are formed (indirectly) between the two elements. Additionally, when expressed as "on or under," it can include not only the upward direction but also the downward direction based on one element.

Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention.

1 is a cross-sectional view of an ultraviolet light-emitting device according to an embodiment of the present invention. Figure 2 is an SEM photo of a light emitting device. Figure 3 is a photograph showing a pinhole formed in a sapphire substrate and a partially formed buffer layer.

Referring to FIG. 1, the light emitting structure 300 according to an embodiment of the present invention can output light in the ultraviolet wavelength range. For example, the light emitting structure 300 may output light in the near-ultraviolet wavelength range (UV-A), light in the far-ultraviolet wavelength range (UV-B), or light in the deep ultraviolet wavelength range (UV-C). ) can be output.

For example, light in the near-ultraviolet wavelength range (UV-A) may have a peak wavelength in the range of 320 nm to 420 nm, and light in the far-ultraviolet wavelength range (UV-B) may have a peak wavelength in the range of 280 nm to 320 nm, Light in the deep ultraviolet wavelength range (UV-C) may have a peak wavelength in the range of 100 nm to 280 nm.

In order for the light emitting structure 300 to emit light in the ultraviolet wavelength range, each semiconductor layer of the light emitting structure 300 contains aluminum (Al) In _x1 Al _y1 Ga _1-x1-y1 N (0≤x1≤1, 0 <y1≤1, 0≤x1+y1≤1). Here, the composition of Al can be expressed as the ratio of the total atomic weight including the In atomic weight, Ga atomic weight, and Al atomic weight to the Al atomic weight. For example, if the Al composition is 40%, the Ga composition may be 60% Al _0.4 Ga _0.6 N.

In addition, in the description of the embodiment, the meaning of low or high composition can be understood as a difference in composition % of each semiconductor layer. For example, if the aluminum composition of the first semiconductor layer is 30% and the aluminum composition of the second semiconductor layer is 60%, the aluminum composition of the second semiconductor layer can be expressed as 30% higher than the aluminum composition of the first semiconductor layer. there is.

The substrate 100 may be formed of a material selected from sapphire (Al ₂ O ₃ ), SiC, GaAs, GaN, ZnO, Si, GaP, InP, and Ge, but is not limited thereto. The substrate 100 may be a light-transmitting substrate that allows light in the ultraviolet wavelength range to pass through. In the following examples, a sapphire substrate will be used.

The buffer layer 200 can alleviate lattice mismatch between the substrate 100 and the semiconductor layers. The buffer layer 200 may be a combination of group III and group V elements or may include any one of AlN, AlGaN, InAlGaN, and AlInN. The buffer layer 200 may be AlN, but is not limited thereto. The buffer layer 200 may include a dopant, but is not limited thereto.

The first conductive semiconductor layer 310 may be implemented as a compound semiconductor such as group III-V or group II-VI, and may be doped with a first dopant. The first conductive semiconductor layer 310 is a semiconductor material with a composition formula of In _x1 Al _y1 Ga _1-x1-y1 N (0≤x1≤1, 0<y1≤1, 0≤x1+y1≤1), e.g. For example, it may be selected from AlGaN, AlN, InAlGaN, etc. And, the first dopant may be an n-type dopant such as Si, Ge, Sn, Se, or Te. When the first dopant is an n-type dopant, the first conductive semiconductor layer 310 doped with the first dopant may be an n-type semiconductor layer.

The active layer 320 may be disposed between the first conductive semiconductor layer 310 and the second conductive semiconductor layer 330. The active layer 320 is a layer where electrons (or holes) injected through the first conductive semiconductor layer 310 and holes (or electrons) injected through the second conductive semiconductor layer 330 meet. The active layer 320 transitions to a low energy level as electrons and holes recombine, and can generate light having an ultraviolet wavelength.

The active layer 320 may have any one of a single well structure, a multi-well structure, a single quantum well structure, a multi quantum well (MQW) structure, a quantum dot structure, or a quantum wire structure. The structure is not limited to this.

The active layer 320 may include a plurality of well layers and a barrier layer. The well layer and the barrier layer may have a composition formula of In _x2 Al _y2 Ga _1-x2-y2 N (0≤x2≤1, 0<y2≤1, 0≤x2+y2≤1). The aluminum composition of the well layer may vary depending on the wavelength of light emission. As the aluminum composition increases, the wavelength emitted from the well layer can become shorter.

The second conductive semiconductor layer 330 is formed on the active layer 320 and may be implemented with a compound semiconductor such as group III-V or group II-VI. Dopants may be doped.

The second conductive semiconductor layer 330 is a semiconductor material with a composition formula of In _x5 Al _y2 Ga _1-x5-y2 N (0≤x5≤1, 0<y2≤1, 0≤x5+y2≤1) or AlInN. , AlGaAs, GaP, GaAs, GaAsP, and AlGaInP may be formed of a selected material. When the second dopant is a p-type dopant such as Mg, Zn, Ca, Sr, Ba, etc., the second conductive semiconductor layer 330 doped with the second dopant may be a p-type semiconductor layer.

An electron-blocking layer (EBL) may be disposed between the active layer 320 and the second conductive semiconductor layer 330. An electron blocking layer (not shown) may reduce electrons from leaving the active layer 320.

A plurality of pinholes 110 may be formed on one side of the substrate 100. A plurality of pinholes 110 may be formed by thermal etching. That is, when hydrogen gas is flowed in the chamber to form a hydrogen atmosphere and heat is applied, the upper surface of the sapphire substrate 100 may be partially decomposed and the pinhole 110 may be formed. However, it is not necessarily limited to this, and the pinhole 110 may be formed by mechanical etching, dry etching, or etching.

The cavity 210 formed in each buffer layer 200 may be connected to the pinhole 110 to form one empty space (UC). This empty space may be defined as one cavity 210.

Referring to FIG. 2, in general light emitting structures, especially ultraviolet light emitting structures, a large number of dislocations DS may be generated due to lattice differences between the substrate and the light emitting structure. Therefore, the defect density of the light emitting structure may increase and its quality may deteriorate.

In an embodiment, random pinholes may be formed in a substrate and a buffer layer may be grown thereon to form a porous cavity inside the buffer layer. In the area where the cavity is formed, even if epi is grown thereon, the generation of dislocations is relatively small, so the defect density can be reduced. Therefore, semiconductor quality can be improved and luminous efficiency can be improved.

Figure 3 is an AFM photograph of a buffer layer formed on a portion of the substrate and not yet covering the pinhole.

Referring to FIG. 3, the shape, size, and depth of the plurality of pinholes 110 may be random. The size of the plurality of pinholes 110 on a plane may be 10 nm to 200 nm in horizontal and/or vertical width.

The pinhole 110 of this size can form a cavity 210 of a predetermined size when the buffer layer 200 is formed thereon. If the horizontal and/or vertical width of the pinhole 110 is less than 10 nm, the cavity 210 may not be created, and if the horizontal and/or vertical width exceeds 200 nm, the cavity 210 may not be created between the buffer layers at the ends of the pinhole. Problems may arise where merging does not occur.

The area in the substrate where a plurality of pinholes are formed may be 10% to 30% of the total area of the substrate. If the pinhole area is less than 10%, the density of the cavity is small, making it difficult to effectively reduce the defect density. If the pinhole area is more than 30%, the uniformity of the pinhole size may be problematic and the size of the pinhole may increase, making it difficult for the buffer layer to form a single layer. there is.

Figure 4 is a manufacturing flowchart of an ultraviolet light-emitting device according to an embodiment of the present invention. FIG. 5 is a diagram showing the process of forming the cavity 210 in the buffer layer 200.

Referring to FIGS. 4 and 5 , the method of manufacturing a light emitting device according to an embodiment includes forming a plurality of pinholes 110 by thermally etching a substrate 100 (S10); Forming a buffer layer 200 on the substrate 100 (S20); And it may include forming the light emitting structure 300 on the buffer layer 200 (S30).

In the step S10 of forming a plurality of pinholes 110, the pinholes 110 may be formed in a hydrogen atmosphere in a chamber and then thermally etched at 1200°C to 1400°C. In this process, a portion of the upper surface of the substrate 100 may be disassembled and a plurality of pinholes 110 may be formed.

The shape, size, and depth of the plurality of pinholes 110 may be random. Some pinholes 110 may be connected to each other to be relatively larger.

The shape, size, and depth of the plurality of pinholes 110 may be random. The size of the plurality of pinholes 110 on a plane may be 10 nm to 200 nm in horizontal and/or vertical width. The pinhole 110 of this size can form a cavity 210 of a predetermined size when the buffer layer 200 is formed thereon.

The area in the substrate where a plurality of pinholes are formed may be 10% to 30% of the total area of the substrate. If the pinhole area is less than 10%, the density of the cavity is small, making it difficult to effectively reduce the defect density. If the pinhole area is more than 30%, the uniformity of the pinhole size may be problematic and the size of the pinhole may increase, making it difficult for the buffer layer to form a single layer. there is.

The step of forming the buffer layer 200 (S20) includes a first step of supplying aluminum gas and nitride gas to the substrate 100 to form an AlN nucleus growth layer in the remaining area except for the plurality of pinholes 110; and a second step in which a cavity 210 is formed inside the plurality of pinholes 110 connected at the top while the AlN nucleus growth layer formed in the remaining area grows.

Referring to (a) of FIG. 5, the first stage may be an initial stage of buffer layer growth. At this time, the island-shaped AlN nucleus growth layer 201 is grown on the upper surface of the sapphire substrate 100 where the pinhole 110 is not formed. The AlN nuclear growth layer 201 is depicted as a single layer, but may be generated as a plurality of particles and grown on the substrate in an island shape. The AlN nuclear growth layer does not grow on the inclined surface inside the pinhole 110.

Referring to Figures 5(b) and 5(c), the second stage may be the middle stage of buffer layer growth. The AlN nucleus growth layer 201 grown on the upper surface of the sapphire substrate 100 gradually grows to form a layer, and as the thickness increases, the gap d1 adjacent to the upper part of the pinhole 110 becomes closer. Afterwards, when further grown, neighboring AlN nuclear growth layers 201 may meet at the top of the pinhole 110 to form one layer. At this time, a cavity 210 in which the buffer layer 200 is not formed may be formed in the upper part of the pinhole 110. The cavity 210 may be connected to the pinhole 110 to form an empty space.

Referring to (d) of FIG. 5, the third stage may be a late stage of buffer layer growth. The buffer layer 200 may gradually grow to a predetermined thickness. For example, the buffer layer 200 may grow to 3㎛, but is not necessarily limited to this.

In the step S30 of forming the light emitting structure 300, the first conductive semiconductor layer 310, the active layer 320, and the second conductive semiconductor layer 330 may be sequentially formed on the buffer layer 200. . The step of forming the light emitting structure 300 can be performed in various ways by applying a general semiconductor layer forming process. Since the embodiment is an ultraviolet light-emitting structure 300, the aluminum composition can be set to be relatively high. As described above, by forming a cavity inside the buffer layer, the defect density of the buffer layer can be reduced and the quality of the ultraviolet light-emitting structure grown thereon can be improved.

These ultraviolet light-emitting devices can be applied to various types of light source devices. For example, the light source device may include a sterilizing device, a curing device, a lighting device, a display device, and a vehicle lamp. In other words, the ultraviolet light-emitting device can be applied to various electronic devices in the form of a light-emitting device package placed in a case (body).

The sterilizing device is equipped with an ultraviolet light-emitting device according to the embodiment and can sterilize a desired area. The sterilizing device may be applied to household appliances such as water purifiers, air conditioners, and refrigerators, but is not necessarily limited thereto. In other words, the sterilization device can be applied to a variety of products that require sterilization (e.g., medical devices).

Exemplarily, a water purifier may be equipped with a sterilizing device according to an embodiment to sterilize circulating water. The sterilizing device may be placed at a nozzle or outlet through which water circulates and irradiate ultraviolet rays. At this time, the sterilizing device may include a waterproof structure.

The curing device is equipped with an ultraviolet light-emitting device according to the embodiment and can cure various types of liquids. Liquid may be the broadest concept that includes all various substances that harden when irradiated with ultraviolet rays. For example, the curing device can cure various types of resin. Alternatively, the curing device may be applied to harden beauty products such as nail polish.

The lighting device may include a light source module including a substrate and an ultraviolet light-emitting device of an embodiment, a heat dissipation unit that dissipates heat from the light source module, and a power supply unit that processes or converts an electrical signal provided from the outside and provides the light source module to the light source module. Additionally, the lighting device may include a lamp, head lamp, or street lamp.

The display device may include a bottom cover, a reflector, a light emitting module, a light guide plate, an optical sheet, a display panel, an image signal output circuit, and a color filter. The bottom cover, reflector, light emitting module, light guide plate, and optical sheet may constitute a backlight unit.

Although the above description focuses on the examples, this is only an example and does not limit the present invention, and those skilled in the art will be able to You will see that various variations and applications are possible. For example, each component specifically shown in the examples can be modified and implemented. And these variations and differences in application should be construed as being included in the scope of the present invention as defined in the appended claims.

100: substrate
110: pinhole
200: buffer layer
210: Cavity
300: Light-emitting structure

Claims (7)

A substrate with a plurality of pinholes formed on one side;
a buffer layer disposed on one side of the substrate; and
Comprising a light emitting structure disposed on the buffer layer,
The buffer layer is an ultraviolet light-emitting device including a plurality of cavities formed on the plurality of pinholes.
According to paragraph 1,
An ultraviolet light-emitting device wherein the plurality of cavities are each connected to the plurality of pinholes.
According to paragraph 1,
An ultraviolet light-emitting device wherein the defect density in an area overlapping with the plurality of cavities is lower than the defect density in an area in which the plurality of cavities are not formed.
According to paragraph 1,
An area where the plurality of pinholes are formed is 10% to 30% of the total area of the substrate.
Forming a plurality of pinholes by thermal etching a substrate;
forming a buffer layer on the substrate; and
A method of manufacturing an ultraviolet light-emitting device, comprising forming a light-emitting structure on the buffer layer.
According to clause 5,
The step of forming the plurality of pinholes includes:
A method of manufacturing an ultraviolet light-emitting device in which the substrate is thermally etched at 1200°C to 1400°C in a hydrogen atmosphere to form a plurality of pinholes.
According to clause 5,
The step of forming the buffer layer is,
A first step of supplying aluminum gas and nitride gas to the substrate to form an AlN layer in the remaining area excluding the plurality of pinholes; and
A method of manufacturing an ultraviolet light-emitting device comprising a second step of forming a cavity inside the plurality of pinholes connected to each other at the top of the plurality of pinholes while growing the AlN layer formed in the remaining area.

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