KR102654365B1 - Light emitting element and manufacturing method thereof - Google Patents

Abstract

A light emitting device according to an embodiment of the present invention includes a substrate; and a plurality of main pillars, each of the plurality of main pillars comprising: a first semiconductor layer formed on the substrate; a second semiconductor layer formed on the first semiconductor; and an active layer disposed between the first semiconductor layer and the second semiconductor layer, wherein the second semiconductor layer includes a photonic crystal structure formed on the second semiconductor layer, and the photonic crystal structure includes a plurality of holes. , the plurality of holes are arranged in a photonic crystal pattern and are filled with air.

Description

Light emitting element and manufacturing method thereof}

The present invention relates to a light-emitting device, and particularly to a light-emitting device having a photonic crystal structure and a method of manufacturing the same.

Recently, the demand for Virtual Reality (VR) and Augmented Reality (AR) devices has been increasing. These VR and Augmented Reality (AR) devices can be equipped with glasses, goggles, helmets, visors or other devices. It can be integrated into a head-mounted display (HMD) device in the form of glasses. The HMD device displays virtual reality images (eg, from at least one virtual environment input) and/or mixed reality (MR) images or augmented reality (AR) images.

The light sources of these AR and VR microdisplays are made of lasers, OLEDs, etc.

However, lasers are an excellent light source with straight-line brightness and fast response speed, but due to the characteristics of lasers, they consume a lot of power and generate a lot of heat, and there are eye safety issues. In addition, OLED consumes a lot of power, does not produce sufficient brightness, and has limitations in realizing high resolution.

Accordingly, interest in micro LED or nano LED to replace laser or OLED is increasing. For example, US Patent No. 10,866,422 proposes a micro LED display system. The micro LED display system includes a plurality of monochrome projectors (e.g., three micro LED projectors) to generate three monochrome images (e.g., red, blue, and green images).

These micro LEDs or nano LEDs are capable of high resolution, low power, and theoretically high brightness, but when manufacturing nano LEDs, external efficiency is low due to side effects during the manufacturing process, and laser ( It has the disadvantage of being less straight than laser.

Despite these drawbacks, Micro LED or ME LED. Because it is possible to achieve high response speed, high brightness, low power consumption, and high resolution, there is a need for a method to improve the optical straightness of micro LED or nano LED and increase external efficiency.

The present invention was made to solve the above problems, and its purpose is to provide a light-emitting device having a photonic crystal structure to improve light propagation and external quantum efficiency, and a method for manufacturing the same.

In order to solve the above problem, a light emitting device according to an embodiment includes a substrate; and a plurality of main pillars, each of the plurality of main pillars comprising: a first semiconductor layer formed on the substrate; a second semiconductor layer formed on the first semiconductor; and an active layer disposed between the first semiconductor layer and the second semiconductor layer, wherein the second semiconductor layer includes a photonic crystal structure formed on the second semiconductor layer, and the photonic crystal structure includes a plurality of holes. , the plurality of holes are filled with air.

The photonic crystal structure may include a plurality of nano pillars installed on the plurality of holes.

The plurality of nano-pillars may be formed of p-GaN or SiO ₂ oxide.

The plurality of nano-fillers may have a refractive index of 1.4 to 2.5.

The plurality of nano-fillers may include either indium tin oxide (ITO) or zinc oxide (ZnO).

The plurality of nano-fillers are formed of any one of a patternable insulating organic material and an oxidized inorganic material, and the insulating organic material and an oxidized inorganic material may include photo resist, polyimide (PI), Su-8, and epoxy. there is.

The main pillar may have any one of a cylindrical shape, a square pillar, or a hexagonal pillar.

A method of manufacturing a light emitting device according to an embodiment of the present invention includes sequentially forming a first semiconductor layer, an active layer, and a second semiconductor layer on a semiconductor substrate; Processing the second semiconductor layer to form a plurality of main pillars; and forming a photonic crystal structure including a plurality of holes on the main pillar.

A method of manufacturing a light emitting device according to another embodiment of the present invention includes sequentially forming a first semiconductor layer, an active layer, and a second semiconductor layer on a semiconductor substrate; Processing the second semiconductor layer to form a plurality of main pillars; forming a filler layer by forming an insulating oxide film or a nitride film on side surfaces of the plurality of main pillars; and forming a photonic crystal structure including a plurality of holes in the filler layer.

The light emitting device manufacturing method may further include installing a plurality of nano pillars in the plurality of holes.

According to the embodiment of the present invention described above, the external QE light efficiency can be improved by eliminating the TM mode lost in the side direction and changing it to the TE mode in the vertical direction, and emitting light in the vertical direction. It is suitable as a display light source, and can produce light-emitting elements especially suitable for producing high-resolution displays for VR, AR, and MR.

FIG. 1 is a diagram showing a light-emitting device having a photonic crystal structure of the present invention. FIG. 1(a) is a perspective view of a light-emitting device according to a first embodiment of the present invention, and FIG. 1(b) is a diagram showing a light-emitting device according to a first embodiment of the present invention. A perspective view of a light emitting device according to an embodiment is shown.
Figure 2 is a diagram for explaining the structure of the main pillar according to the first embodiment of the present invention.
Figure 3 is a diagram for explaining the structure of the main pillar according to the second embodiment of the present invention. FIG. 4 is a cross-sectional view of the light emitting devices of FIG. 1.
Figure 5 shows a number of displays according to the present invention.
6 shows examples of light patterns according to embodiments of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. Like reference numerals refer to substantially the same elements throughout the specification. In the following description, if it is determined that a detailed description of technology or configuration related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. Additionally, the component names used in the following description were selected in consideration of the ease of writing specifications and may be different from the component names of the actual product.

Figure 1 is a diagram showing light-emitting devices according to embodiments of the present invention. Figure 1(a) is a diagram showing a light-emitting device according to a first embodiment of the present invention, and Figure 1(b) is a diagram showing a light-emitting device according to a first embodiment of the present invention. This is a diagram showing a light emitting device according to the second embodiment.

First, referring to FIG. 1(a), the light emitting device according to the first embodiment includes a substrate 200, a plurality of main pillars 100 disposed on the substrate 200, and the plurality of main pillars ( It includes an insulating layer 300 located on the side and top of 100).

The plurality of main pillars 100 may be arranged in a first photonic crystal pattern on the substrate 200. Specifically, the first photonic crystal pattern in which the plurality of main pillars 100 are disposed on the substrate 200 may be determined according to the optical characteristics of the light emitting device. For example, the spacing and size between the plurality of main pillars 100 may be determined according to the emission color of the light emitting device.

In Figure 1, the plurality of main pillars 100 are disclosed as having a cylindrical shape. However, the present invention is not limited to this, and the plurality of main pillars 100 may have other shapes, such as hexagonal pillars or square pillars.

The size of each of the plurality of main pillars 100 may range from 1 μm (micrometer) to 200 μm. Preferably, the size of each of the plurality of main pillars 100 may be within the range of 1㎛ (micrometer) to 100㎛.

If each of the plurality of main pillars 100 has a cylindrical shape, the diameter of the cylindrical shape may be less than 5 μm (micrometer). If each of the plurality of main pillars 100 has a square pillar shape, the length of one side of the square may be 5 μm or less. If each of the plurality of main pillars 100 has a hexagonal pillar shape, the length of the line passing through the center of the hexagon may be 5 μm or less.

Additionally, each of the plurality of main pillars 100 has a photonic crystal structure. Specifically, each of the plurality of main pillars 100 includes a plurality of holes 132 formed on its upper portion. The plurality of holes 132 may be arranged in a second photonic crystal pattern. Additionally, the plurality of holes 132 may be filled with air. The plurality of holes 132 preferably have a circular shape.

Each of the plurality of holes 132 may have a size of 1 μm (micrometer) or less. For example, each of the plurality of holes 132 may have a diameter of ㎛ or less.

Referring to FIG. 1(b), the light emitting device according to the second embodiment has a similar configuration to the light emitting device according to the first embodiment except for the photonic crystal structure formed in the plurality of main pillars 100, so the detailed description thereof is provided. omit.

Each of the plurality of main pillars 100 of the light emitting device according to the second embodiment includes a plurality of holes 132, and includes a plurality of nano pillars 150 formed on the plurality of holes 132. .

The plurality of nano-pillars 150 may be formed of p-GaN or SiO ₂ oxide. The plurality of nano-pillars 150 may have a refractive index of 1.5. The plurality of nano-fillers 150 may be formed of either indium tin oxide (ITO) or zinc oxide (ZnO).

In this case, the insulating layer 300 may be formed to surround the side wall of one of the plurality of nano-pillars 150 with an insulating film or to fill the space between the nano-pillars 150 with an insulating material. In this case, the insulating layer 300 may insulate the nano-pillars 150.

Light-emitting devices having the above configuration have high brightness, laser-like radiation, high resolution, low power consumption, and high response speed.

That is, the main pillars of the light-emitting devices can form a sub-pixel. The light emitting device according to the present invention may have a structure in which pixels composed of the main pillars described above are arranged in a matrix form.

Figure 2 is a diagram for explaining the structure of the main pillar according to the first embodiment of the present invention. Referring to FIG. 2, the main pillar 100 having a photonic crystal structure may be formed on the substrate 200. The main pillar 100 includes a first semiconductor layer 110, a second semiconductor layer 130, an active layer 120 disposed between the first semiconductor layer 110 and the second semiconductor layer 130, and the second semiconductor layer 130. 2 It includes a photonic crystal structure formed in the semiconductor layer 130. A photonic crystal is a material that forms a crystal lattice by regularly arranging particles with different refractive indices from the matrix. It refers to a material that has an optical band gap due to periodic changes in dielectric constant at half the wavelength of light.

The optical bandgap controls photons in a photonic crystal in the same way that the bandgap of electrons controls electrons in a semiconductor. When light with a wide range of spectrum from the outside is incident on the photonic crystal, the wavelength corresponding to the optical bandgap is Only light cannot propagate inside the material and is selectively reflected. When such an optical bandgap exists in the visible light region, selective reflection due to the optical bandgap appears as a reflected color.

The reflected color of a photonic crystal is determined by the refractive index of the matrix material and the colloidal particles dispersed therein, the crystal structure, the size of the colloidal particles, and the spacing between colloidal particles. Therefore, by controlling this, photonic crystals with desired reflection colors can be manufactured.

In this embodiment, the substrate 200 is made of sapphire. In another embodiment, the substrate 200 may be made of gallium nitride (GaN), or a transparent conductive substrate such as silicon carbide (SiC) or zinc oxide (ZnO).

In a preferred embodiment of the present invention, the first semiconductor layer 110 is formed as an n-type semiconductor layer, and the second semiconductor layer 130 is formed as a p-type semiconductor layer, but the reverse case is also possible, of course. .

The n-type semiconductor layer 110 may include n-GaN or un-GaN. Specifically, the n-type semiconductor layer 110 may be formed of a GaN layer or a GaN/AlGaN layer doped with an n-type conductivity impurity (Si).

The p-type semiconductor layer may include p-GaN. Specifically, the p-type semiconductor layer 130 may be formed of a GaN layer doped with a p-type conductivity impurity, or a thin AlGaN layer may be formed on a GaN layer doped with a p-type conductivity impurity. there is.

The active layer 120 has a multi quantum well (MQW) structure in which a plurality of well layers 121 and a plurality of barrier layers 122 are alternately arranged.

Main pillars of 5 micrometers or less are formed in the second semiconductor layer 130. The main pillars can function as micro LED subpixels. And a photonic crystal structure is formed on each main pillar.

The photonic crystal structure may include a plurality of holes 132 formed on the second semiconductor layer 130. The plurality of holes 132 are filled with air. The second semiconductor layer 130 may be formed of the compound GaN. The second semiconductor layer 130 has a refractive index of approximately 2.5, and the air filled in the plurality of holes 130 has a refractive index of approximately 1.

Although the holes 132 in the embodiments of FIGS. 1 and 2 are disclosed as having a circular shape, the holes 132 may have other shapes such as hexagons or squares. The diameter of the holes 132 or the spacing between the holes 132 may be determined according to the optical characteristics of the light emitted by the main pillar 100.

Accordingly, the main pillar 100 has a structure in which the refractive indices of 1 and 2.5 in the second semiconductor layer 130 are arranged (placed) in a predetermined photonic crystal pattern.

In this case, the photonic crystal structure in which the refractive indices of 1 and 2.5 are arranged in a predetermined photonic crystal pattern in the second semiconductor layer 130 has a photonic energy band gap. Accordingly, the part corresponding to the photonic energy band gap of the light emitted from the active layer 120 is hidden and the remaining part is better radiated.

In other words, among the light emitted from the active layer 120 from the second semiconductor layer 130, which has a refractive index of 2.5, into air, light that enters at a certain angle is trapped forever. In other words, forming a photonic crystal structure in the second semiconductor layer 130 (texturing the surface of the second semiconductor layer 130) changes the divergence angle of light emitted from the active layer 120.

In this case, the size and spacing of the holes 132 formed in the second semiconductor layer 130 may be determined through simulation according to the desired optical characteristics of light. Accordingly, a light emitting device having a photonic crystal structure can increase external QE by eliminating the TM mode lost in the side direction and changing it to the TE mode in the vertical direction.

Figure 3 is a diagram for explaining the structure of the main pillar according to the second embodiment of the present invention. Referring to FIG. 3, the main pillar 100 having a photonic crystal structure has a similar structure to the main pillar of FIG. 2, and the similar structure will be briefly described.

The main pillar 100 includes a first semiconductor layer 110, a second semiconductor layer 130, an active layer 120 disposed between the first semiconductor layer 110 and the second semiconductor layer 130, and the second semiconductor layer 130. It may include a photonic crystal structure formed in the two-bit semiconductor layer 130.

The photonic crystal structure is formed in the second semiconductor layer 130. The photonic crystal structure may include a plurality of holes 132. The photonic crystal structure may include a plurality of nano pillars 150 installed in the plurality of holes 132.

The plurality of nano-fillers may be formed of either an insulating organic material or an oxidized inorganic material capable of being patterned. The insulating organic material and oxidized inorganic material may include photo resist, polyimide (PI), Su-8, and epoxy.

According to one embodiment, the plurality of nano-pillars 150 may be formed of p-GaN or SiO ₂ oxide. When the plurality of nano-pillars 150 are made of GaN, they may have a refractive index of 2.5. When the plurality of nano-pillars 150 are formed of SiO ₂ , they may have a refractive index of 1.5.

According to another embodiment, the plurality of nano-fillers 150 may be formed of either indium tin oxide (ITO) or zinc oxide (ZnO). When the plurality of nano-pillars 150 are formed of zinc oxide (ZnO), they may have a refractive index of 2.2.

The plurality of nano-pillars 150 may have a refractive index of 1.4 to 2.5. Preferably, the plurality of nano-pillars 150 may have a refractive index of 1.5.

In this case, since the second semiconductor layer 130 has a refractive index of approximately 2.5, the main pillar 100 has a refractive index of 1 in the second semiconductor layer 130 and a refractive index determined between 1.4 and 2.5 in a predetermined photonic crystal pattern. It has an arranged (arranged) structure.

In this case, the photonic crystal structure in which the refractive index of the second semiconductor layer 130 is determined between 1.4 and 2.5 and the refractive index of 2.5 is arranged in a photonic crystal pattern has a photonic energy band gap. Accordingly, the part corresponding to the photonic energy band gap of the light emitted from the active layer 120 is hidden and the remaining part is better radiated.

In other words, among the light emitted from the active layer 120 from the second semiconductor layer 130 having a refractive index of 2.5 to the nano-pillars 150, light that enters at a certain angle is trapped forever.

In this case, the size and spacing of the holes 132 formed in the second semiconductor layer 130 or the length of the nano pillars 150 may be determined through simulation according to the desired optical characteristics of light.

Accordingly, a light emitting device having a photonic crystal structure can increase external QE by eliminating the TM mode lost in the side direction and changing it to the TE mode in the vertical direction.

FIG. 4 is a cross-sectional view of the light emitting devices of FIG. 1.

FIG. 4(a) shows a cross section of a main pillar including a plurality of holes, and FIG. 4(b) shows a cross section of a main element including a plurality of nano pillars.

Figure 5 shows a number of light-emitting devices according to the invention.

Referring to FIG. 5, the color of the light emitted by the light emitting devices 100 is changed by changing the depth or length of the holes 132 of the main pillar 100 or by changing the thickness and length of the nano pillars installed in the holes 132. It can also change. In Figure 4, the light emitting elements emit red, blue, and green respectively.

The above light-emitting device is a reflective display that displays an image by reflecting external light, does not require a light source such as a backlight, and has the effect of displaying an image at low power, especially outdoors or under bright lighting.

Additionally, since the color of the light emitting device itself changes to display an image, a separate color filter is not required, and all pixels can be used to create a single screen. For example, in a conventional display device composed of R/G/B subpixels, in order to implement one color among R, G, and B, the other two subpixels must display a black image, which lowers the actual resolution. A problem occurred. On the other hand, the display according to the present invention uses all pixels no matter what color it displays, so it has the effect of increasing actual resolution.

The above display displays an image by reflecting external light, does not require a light source such as a backlight, and has the effect of displaying an image with low power, especially outdoors or under bright lighting.

Hereinafter, a method for manufacturing a light emitting device according to an embodiment of the present invention will be described.

First, referring to FIGS. 2 and 3 , first, the first semiconductor layer 110, the active layer 120, and the second semiconductor layer 130 are sequentially formed on the substrate 200. The second semiconductor layer 130 may be formed of a GaN compound.

Next, the second semiconductor layer 130 is processed to form a main pillar 100 having a size of 5 micrometers or less.

If the main pillar 100 is cylindrical, the diameter of the circle in the cross section may be 5 ㎛ or less, and if the main pillar 100 is a square pillar, the length of one side of the square in the cross section may be 5 ㎛ or less.

Next, a photonic crystal structure is formed on the top of the main pillar 100. Specifically, a plurality of holes 132 are formed in the upper part of the main pillar 100. The plurality of holes 132 may be arranged in a predetermined light pattern.

According to another embodiment, before forming the plurality of holes 132, a filler layer is formed by growing an insulating oxide/nitride film such as SiO2, Al2O3, SiN, HfO, WO, etc. on the main pillar 100. Holes 132 may be formed in . In this case, the physical properties of the filler layer and the physical properties of the second semiconductor layer 130 may be different.

The plurality of holes 132 are preferably circular. The diameter of the plurality of holes 132 may be 1 μm or less. The number of plural holes may be 1 to 10.

Specifically, as shown in FIGS. 5(b) and 5(c), a nanopattern with a photonic crystal structure is created on the second semiconductor layer 130. At this time, the depth or width of the hole 132 or nano-pillar 150 in the photonic crystal structure may be determined depending on the color of the displays.

And, an insulating layer 300 may be formed on the main pillar 100. In this case, the main filler may be surrounded or filled with insulating organic and oxidized inorganic materials capable of patterning, such as photo resist, PI, Su-8, and epoxy.

Figure 6 shows examples of light patterns according to embodiments of the present invention. As shown in FIG. 6, different patterns may exist depending on the optical characteristics of the light emitting device. Afterwards, a plurality of nano pillars may be installed in the plurality of holes 132.

According to the embodiment of the present invention described above, light efficiency can be improved by forming a photonic crystal structure in the semiconductor layer. Additionally, a light emitting device with a photonic crystal structure can increase external QE by eliminating the TM mode lost in the side direction and changing it to the TE mode in the vertical direction.

The above description is merely an exemplary description of the present invention, and various modifications may be made by those skilled in the art without departing from the technical spirit of the present invention. Accordingly, the embodiments disclosed in the specification of the present invention do not limit the present invention. The scope of the present invention should be interpreted in accordance with the scope of the patent claims below, and all technologies within the equivalent scope thereof should be interpreted as being included in the scope of the present invention.

100: light emitting device 110: first semiconductor layer
120: active layer 130: second semiconductor layer
132: Hole 150: Nano pillar

Claims (10)

Board; and
Contains a plurality of main fillers,
Each of the plurality of main fillers is
a first semiconductor layer formed on the substrate;
a second semiconductor layer formed on the first semiconductor; and
It includes an active layer disposed between the first semiconductor layer and the second semiconductor layer,
The second semiconductor layer includes a photonic crystal structure formed on the second semiconductor layer,
The photonic crystal structure includes a plurality of holes,
The plurality of holes are filled with air,
A light emitting device wherein the photonic crystal structure includes a plurality of nano pillars installed on the plurality of holes.
delete According to paragraph 1,
A light emitting device, wherein the plurality of nano-pillars are formed of an oxide of p-GaN or SiO ₂ .
According to paragraph 1,
A light emitting device wherein the plurality of nano-fillers include one of ITO (Indium Tin Oxide) and zinc oxide (ZnO).
According to paragraph 1,
A light emitting device characterized in that the plurality of nano-pillars have a refractive index of 1.4 to 2.5.
According to paragraph 1,
The main pillar is a light emitting device characterized in that it has any one of a cylindrical shape, a square pillar, and a hexagonal pillar.
sequentially forming a first semiconductor layer, an active layer, and a second semiconductor layer on a semiconductor substrate;
Processing the second semiconductor layer to form a plurality of main pillars;
forming a photonic crystal structure including a plurality of holes on the main pillar; and
Installing a plurality of nano pillars in the plurality of holes;
A method of manufacturing a light emitting device comprising a.
sequentially forming a first semiconductor layer, an active layer, and a second semiconductor layer on a semiconductor substrate;
Processing the second semiconductor layer to form a plurality of main pillars;
forming a filler layer by forming an insulating oxide film or a nitride film on side surfaces of the plurality of main pillars;
forming a photonic crystal structure including a plurality of holes in the filler layer; and
Installing a plurality of nano pillars in the plurality of holes;
A method of manufacturing a light emitting device comprising a.
delete According to clause 8,
It further includes forming an insulating layer made of any one of a patternable insulating organic material and an oxidized inorganic material on the plurality of nano-fillers,
A method of manufacturing a light emitting device, wherein the insulating organic material and oxidized inorganic material include photo resist, polyimide (PI), Su-8, and epoxy.

Images