KR20210044517A - a high efficiency micro LED device with fixed charge injected - Google Patents

Abstract

The present invention discloses a micro LED device having an area of a light emitting unit, which is equal to or less than 10000 um^2. According to an embodiment of the present invention, the micro LED device comprises a stacked structure in which a P-type semiconductor, the light emitting unit, and an N-type semiconductor are stacked. A doping area, in which a fixed charge is injected within a predetermined distance from an edge of the light emitting unit, is formed.

Description

{A high efficiency micro LED device with fixed charge injected}

The present invention relates to a micro LED device having a relatively small area. In particular, the present invention relates to a micro LED device capable of suppressing the sidewall effect.

In the case of a micro LED chip with a small area, the sidewall area ratio increases sharply compared to the conventional LED chip with a relatively large area, and the relative increase in the sidewall area increases the surface area of the semiconductor with high defect density. As a result, carriers capable of emitting light are non-radiative recombination, resulting in a decrease in internal quantum efficiency.

However, since the area ratio of the sidewall increases as the number of pixels increases, it is necessary to minimize defects in the sidewall to suppress the non-radiative recombination center action to improve the internal quantum efficiency.

Accordingly, hereinafter, a micro LED device having an electrical structure with improved internal quantum efficiency by solving the above-described problems will be described.

Shockley-Read-Hall and Auger non-radiative recombination in GaN based LEDs: A size effect study Appl. Phys. Lett. 111, 022104 (2017); https://doi.org/10.1063/1.4993741

An object of the present invention is to propose a structure capable of suppressing non-emission recombination that may occur in a micro LED device having a relatively small light emitting area.

Specifically, an object of the present invention is to propose a structure capable of suppressing non-emission recombination by generating a repulsive force by forming a doped region at an edge of a light emitting portion of a micro LED device.

The micro LED device according to an embodiment of the present invention includes a stacked structure in which a P-type semiconductor, a light emitting part, and an N-type semiconductor are stacked, and a doped region into which a fixed charge is injected is formed within a predetermined distance from the edge of the light emitting part.

The micro LED device according to an embodiment of the present invention may improve internal quantum efficiency by suppressing non-emission recombination through a doped region.

1 shows the brightness according to the location in the micro LED chip.
2 is a conventional micro LED band diagram.
3 is an experiment result of the relationship between the SRH non-emission recombination constant (A) and the circumference of the LED chip and the area ratio of the top surface.
4 shows a band diagram of a micro LED device according to an embodiment of the present invention.
5 shows a part of a stacked structure of a micro LED device according to an embodiment of the present invention.
6 shows a part of a stacked structure of a micro LED device according to another embodiment of the present invention.
7 shows a part of a stacked structure of a micro LED device according to another embodiment of the present invention.
8 shows a part of a stacked structure of a micro LED device according to another embodiment of the present invention.
9 shows a part of a stacked structure of a micro LED device according to another embodiment of the present invention.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. However, the spirit of the present invention is not limited to the following embodiments, and those skilled in the art who understand the spirit of the present invention can easily add, change, delete, and add components to other embodiments included within the scope of the same idea. It may be suggested, but it will be said that this is also included within the scope of the idea of the present invention.

In the accompanying drawings, in explaining the overall structure in order to easily understand the spirit of the invention, minute parts may not be specifically expressed, and when describing the minute parts, the overall structure may not be specifically reflected. In addition, even if specific parts, such as the installation location, are different, if the action is the same, the same name is given, so that convenience of understanding can be improved. In addition, when there are a plurality of identical configurations, only one configuration will be described, and the same description will be applied to other configurations, and the description will be omitted.

In the case of a micro LED chip with a small area, the sidewall area ratio increases sharply compared to the conventional LED chip with a large area. Here, the micro LED chip generally refers to an LED chip having a minimum area of 10000 um ² or less of the light emitting part. This relative increase in the sidewall area causes an effect of increasing the surface area of a semiconductor having a high defect density, and as a result, carriers capable of emitting light are non-radiatively recombined, thereby reducing internal quantum efficiency.

However, since the area ratio of the sidewall increases as the number of pixels increases, it is necessary to minimize defects in the sidewall to suppress the non-radiative recombination center action to improve internal quantum efficiency.

1 shows the brightness according to the location in the micro LED chip.

Illustratively in FIG. 1 is a PL map of a 7um pixel LED, and it can be seen that the brightness of the edge (0~1 or 7~8um position) corresponding to the sidewall rapidly decreases. As a factor of decreasing edge brightness as illustrated in FIG. 1, shockley-read-hall recombination, which is trap-assited recombination, is an important factor, and particularly, when a small current flows, the effect is large.

2 is a conventional micro LED band diagram.

In FIG. 2, 0 means a sidewall edge, and the farther away from 0 means that the farther away from the side circle surface.

Referring to FIG. 2 to describe the decrease in internal quantum efficiency due to non-radiative recombination, there are many trap levels (Et) on the sidewall surface of the micro LED chip. If the electron 1 exists near the location of the defect level, as shown in FIG. 2, the probability of the electron 1 transitioning to the defect 2 is very high. In addition, the electrons 1 transferred to the defect 2 do not emit light, resulting in a decrease in the internal quantum efficiency of the LED chip.

Equation 1 is an ABC model representing the internal quantum efficiency (IQE) in the above-described micro LED chip. Here, A is an SRH non-luminescence recombination constant, B is a luminescence recombination constant, and C is an Auger non-luminescence recombination constant. And n means carrier concentration. Therefore, the higher the luminescence recombination constant (B) in the molecule, the higher the internal quantum efficiency, and the lower the SRH non-luminescence recombination constant (A) and the Auger non-luminescence recombination constant (C) in the denominator, the higher the internal quantum efficiency. It can be seen from Equation 1 (refer to Prior Technical Document 1).

However, the Auger non-luminescence recombination constant is negligible in a low current (low carrier concentration) state, and is not a constant affected by a trap. In general, it can be regarded as negligible that a low current flows through the micro LED chip due to the physical characteristics of its size. On the other hand, the SRH non-luminescent recombination constant is a non-luminescent recombination constant that is affected by the defect, and as a result, lowering the SRH non-luminescent recombination constant can be a method of increasing the internal quantum efficiency.

3 is an experiment result of the relationship between the SRH non-emission recombination constant (A) and the circumference of the LED chip and the area ratio of the top surface.

As shown in Figure 3, it can be seen that the larger the LED parameter, the larger the non-emission recombination constant (A). In other words, it can be confirmed that the internal quantum efficiency increases only when the sidewall effect decreases.

Accordingly, hereinafter, in order to reduce the sidewall effect, a micro LED device including a structure for inducing a carrier to be difficult to access the sidewall of the light emitting unit of the micro LED chip will be described.

In a specific embodiment, a micro LED device having an electrical structure capable of improving internal quantum efficiency by suppressing the carrier from reaching the non-luminescent recombination center existing near the sidewall by changing the potential state of the sidewall surface is described. Do it.

4 shows a band diagram of a micro LED device according to an embodiment of the present invention.

A repulsive force for repelling carrier electrons is generated by adding immobile minus charges to a number of trap level (Et) regions present on the sidewall surface of the micro LED device according to an embodiment of the present invention. As a result, the surface defect and electrons are isolated from each other by the repulsive force, and the electrons proceed a certain distance away from the sidewall surface. When electrons travel a certain distance away from the sidewall surface, the carrier concentration on the sidewall surface decreases, and non-luminescent recombination occurring in the sidewall decreases, thereby improving the internal quantum efficiency.

In FIG. 4, the distance '0' is the edge of the sidewall of the light emitting part, and it means that as the distance increases, the distance from the sidewall increases.

5 shows a part of a stacked structure of a micro LED device according to an embodiment of the present invention.

As shown in FIG. 5, in the micro LED device according to an embodiment of the present invention, an N-type semiconductor 51, a light emitting part 52, and a P-type semiconductor 53 may be sequentially stacked. Here, an additional layer may be formed between each layer according to a specific embodiment.

The light-emitting unit 52 may use any one of a multi-quantum well structure, a nano structure, or a quantum dot as a light-emitting structure.

In addition, a doped region 54 may be formed up to a predetermined distance from the sidewall of the light emitting part 52. The doped region 54 may be formed through ion implantation, diffusion, and plasma methods.

At this time, the dopant used in the ion implantation process may be at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au. In addition, a gas or liquid or solid containing at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au may be deposited for the diffusion process. have. In addition, the element included in the gas for the plasma process may be at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au.

Here, the doped region 54 may be a region into which a fixed charge is injected. In addition, the doped region 54 may mean a region that is 2 μm or less from the sidewall of the light emitting part 52.

6 shows a part of a stacked structure of a micro LED device according to another embodiment of the present invention.

As shown in FIG. 6, in the micro LED device according to another embodiment of the present invention, an N-type semiconductor 61, a light emitting part 62, and a P-type semiconductor 63 may be sequentially stacked. Here, an additional layer may be formed between each layer according to a specific embodiment.

The light-emitting unit 62 may use any one of a multi-quantum well structure, a nano structure, or a quantum dot as a light-emitting structure.

In addition, a doped region 64 may be formed from the sidewall of the light emitting part 62 to a predetermined distance. The doped region 64 may be formed through ion implantation, diffusion, and plasma methods.

At this time, the dopant used in the ion implantation process may be at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au. In addition, a gas or liquid or solid containing at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au may be deposited for the diffusion process. have. In addition, the element included in the gas for the plasma process may be at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au.

In addition, a doped region 64 doped with a carrier of a type opposite to that of the plurality of carriers of the light emitting part 62 may be formed at the edge of the light emitting part 62. Here, the doped region 64 of the opposite type may be a region into which a fixed charge is injected. In addition, the doped region 64 of the opposite type may mean a region that is 2 μm or less from the sidewall of the light emitting part 62.

7 shows a part of a stacked structure of a micro LED device according to another embodiment of the present invention.

As shown in FIG. 7, in the micro LED device according to another embodiment of the present invention, an N-type semiconductor 71, a light emitting part 72, and a P-type semiconductor 73 may be sequentially stacked. . Here, an additional layer may be formed between each layer according to a specific embodiment.

The light-emitting unit 72 may use any one of a multi-quantum well structure, a nano structure, or a quantum dot as a light-emitting structure.

In addition, a doped region 74 may be formed at a predetermined distance from the sidewall of the light emitting part 72. The doped region 74 may be formed through an ion implantation, diffusion, and plasma method.

At this time, the dopant used in the ion implantation process may be at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au. In addition, a gas or liquid or solid containing at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au may be deposited for the diffusion process. have. In addition, the element included in the gas for the plasma process may be at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au.

In addition, a doped region 74 of the light-emitting part 72 may be formed in a part of the area from the sidewall of the light-emitting part 72 to a predetermined distance. Here, the doped region 74 may be a region into which a fixed charge is injected. In addition, the doped region 74 may mean a region up to a distance of 2 μm or less from the sidewall of the light emitting portion 72.

In the micro LED device according to the exemplary embodiment of FIG. 7, by forming the doped region 74 only at a portion of the edge of the light emitting part 72, the doped region 74 is isolated to reduce a leakage current.

8 shows a part of a stacked structure of a micro LED device according to another embodiment of the present invention.

As shown in FIG. 8, in the micro LED device according to another embodiment of the present invention, an N-type semiconductor 81, a light emitting part 82, and a P-type semiconductor 83 may be sequentially stacked. Here, an additional layer may be formed between each layer according to a specific embodiment.

The light-emitting unit 82 may use any one of a multi-quantum well structure, a nano structure, or a quantum dot as a light-emitting structure.

In addition, a doped region 84 may be formed in a region of the light emitting portion 82 from the sidewall to a predetermined distance. The doped region 84 may be formed through ion implantation, diffusion, and plasma methods.

At this time, the dopant used in the ion implantation process may be at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au. In addition, a gas or liquid or solid containing at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au may be deposited for the diffusion process. have. In addition, the element included in the gas for the plasma process may be at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au.

In the embodiment of FIG. 8, not only the light emitting part 82, but also the doped region 84 may be formed on or below the doped region of the light emitting part 82, or both above and below the light emitting part 82.

8 illustrates that the doped region is formed over the entire region from the edge of the P-type semiconductor 83 to a certain distance, but the doped region is formed only in a portion of the region from the edge of the P-type semiconductor 83 to a certain distance. There may be. In this case, an effect similar to that described in FIG. 7 can be obtained.

Here, the doped region 84 may be a region into which a fixed charge is injected. In addition, the doped region 84 may mean a region up to a distance of 2 μm or less from the sidewall of the light emitting portion 82.

9 shows a part of a stacked structure of a micro LED device according to another embodiment of the present invention.

As shown in FIG. 9, the micro LED device according to another embodiment of the present invention may be in a form in which an N-type semiconductor 91, a light emitting part 92, and a P-type semiconductor 93 are sequentially stacked. . Here, an additional layer may be formed between each layer according to a specific embodiment.

The light-emitting unit 92 may use any one of a multi-quantum well structure, a nano structure, or a quantum dot as a light-emitting structure.

In addition, a doped region 94 may be formed from the sidewall of the light emitting portion 92 to a predetermined distance. The doped region 94 may be formed through ion implantation, diffusion, and plasma methods.

At this time, the dopant used in the ion implantation process may be at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au. In addition, a gas or liquid or solid containing at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au may be deposited for the diffusion process. have. In addition, the element included in the gas for the plasma process may be at least one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au.

In addition, a doped region 94 of the light-emitting part 92 may be formed in all or part of a region from the sidewall of the light-emitting part 92 to a predetermined distance. Here, the doped region 94 may be a region into which a fixed charge is injected. In addition, the doped region 94 may mean a region that is 2 μm or less from the sidewall of the light emitting portion 72.

Additionally, an additional doped region (not shown) may be formed in some of the doped regions 94 to eliminate repulsive force generated by multiple carriers.

In addition, in the micro LED device according to the embodiment of FIG. 9, a layer formed on the light emitting part 92 is smaller than that of the light emitting part 92, or a layer formed under the light emitting part 92 is the light emitting part 92. ), or both layers formed above and below the light emitting part 92 may be formed smaller than that of the light emitting part 92.

In the micro LED device having the structure described with reference to FIGS. 5 to 9 described above, the potential increases in the edge region of the light emitting part, so that electrons are separated from the sidewall surface by a predetermined distance. As such an effect, by suppressing non-luminescent recombination, more electrons are radiative radiation, so that the internal quantum efficiency can be improved.

The above detailed description should not be construed as limiting in all respects and should be considered as illustrative. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

Claims (8)

In a micro LED device having a light emitting area of ^{10000um 2 or less,}
The micro LED device includes a stacked structure in which a P-type semiconductor, a light emitting part, and an N-type semiconductor are stacked,
A doped region into which a fixed charge is injected is formed within a predetermined distance from the edge of the light emitting part.
Micro LED device. The method of claim 1,
The predetermined distance is less than 2um
Micro LED device. The method of claim 2,
The carrier doped in the doped region is of a type opposite to that of the plurality of carriers of the light emitting unit.
Micro LED device. The method of claim 2,
A doped region is formed in a portion of the region from the edge of the light emitting portion to a predetermined distance.
Micro LED device. The method of claim 2,
The doped region is further formed above and/or below the doped region of the light emitting part.
Micro LED device. The method of claim 2,
The layer formed above and/or below the light emitting part is formed smaller than that of the light emitting part.
Micro LED device. The method of claim 6,
The doped region is formed in a portion of the region from the edge of the light emitting portion to a predetermined distance.
Micro LED device. The method of claim 2,
In some of the doped regions of the light emitting part, an additional doped region is formed to remove the repulsive force due to the multiple carriers.
Micro LED device.

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