KR102271031B1 - a high efficiency micro LED device using insulator electron affinity - Google Patents

Abstract

In the present invention, a micro LED device having a light emitting area of ^{10000um 2 or less is disclosed.} In the micro LED device according to an embodiment of the present invention, 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, and an insulating layer is formed on an outer surface of a sidewall of the light emitting part.

Description

A high efficiency micro LED device using insulator electron affinity

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 small-area micro LED chip, the sidewall area ratio rapidly increases compared to a conventional relatively large-area LED chip, and this relative increase in the sidewall area has the effect of increasing the surface area of a semiconductor with high defect density. , and eventually light-emitting carriers undergo non-radiative recombination, reducing the internal quantum efficiency.

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

Therefore, the following describes a micro LED device having an electrical structure with improved internal quantum efficiency by solving the above-described problems.

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.

In particular, an object of the present invention is to propose a structure capable of suppressing non-emission recombination by forming an insulating layer and a metal layer on the outer surface of a sidewall of a light emitting part of a micro LED device.

In the present invention, a micro LED device having a light emitting area of ^{10000um 2 or less is disclosed.} In the micro LED device according to an embodiment of the present invention, 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, and the electronic affinity of the light emitting part is higher than that of the light emitting part on the outer surface of the sidewall of the light emitting part. A low or high insulating layer is formed.

In the micro LED device according to an embodiment of the present invention, by forming an insulating layer and a metal layer that generate a repulsive force against a carrier inside the light emitting unit on the outer surface of the sidewall of the light emitting unit, non-light emitting recombination can be suppressed, and as a result, the internal Quantum efficiency can be improved.

1 shows the brightness according to position in a micro LED chip.
2 is a conventional micro LED band diagram.
3 is an experimental result of the relationship between the SRH non-luminescent recombination constant (A) and the LED chip circumference and top surface area ratio.
4 is 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 change other embodiments included within the scope of the same idea by adding, changing, deleting, and adding components. It may be suggested, but this will also be included within the scope of the present invention.

In the accompanying drawings, in describing the overall structure in order to easily understand the spirit of the invention, minute parts may not be specifically expressed, and in describing the minute parts, the overall structure may not be specifically reflected. In addition, even if specific parts such as an installation location are different, when the action is the same, the same name is assigned to improve the convenience of understanding. 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 thereof will be omitted.

In the case of a micro LED chip having a small area, the sidewall area ratio is rapidly increased compared to a conventional LED chip having a large area. Here, the micro LED chip generally refers to an LED chip having a minimum area of a light emitting part of 10000 um ² or less. Such a relative increase in the sidewall area causes an effect of increasing the surface area of a semiconductor having a high defect density, and eventually, light-emitting carriers non-radiatively recombine, 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 present in the sidewall to suppress the non-radiative recombination center action to improve the internal quantum efficiency.

1 shows the brightness according to position in a micro LED chip.

What is illustrated in FIG. 1 is a PL map of a 7um pixel LED, and it can be seen that the brightness of the edge (0 to 1 or 7 to 8um position) corresponding to the sidewall is sharply lowered. As exemplified in FIG. 1 , as a factor for decreasing edge brightness, Shockley-Read-Hall recombination, which is a rap-assited recombination, is an important factor, and the effect is particularly large when a small current flows.

2 is a conventional micro LED band diagram.

In FIG. 2, 0 means the surface of the sidewall, and the further away from 0, the further away from the surface of the sidewall.

Referring to FIG. 2 , the decrease in internal quantum efficiency due to non-radiative recombination will be described. Many defect levels (trap levels: Et) exist on the sidewall surface of the micro LED chip. When the electron 1 exists near the position of the defect level as shown in FIG. 2 , the probability that the electron 1 transitions 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 the SRH non-luminescent recombination constant, B is the luminescent recombination constant, and C is the Auger non-luminescent recombination constant. And n means carrier concentration. Therefore, the larger the luminescent recombination constant (B) in the molecule, the higher the internal quantum efficiency. It can be seen from Formula 1 (refer to Prior Art Document 1).

However, the Auger non-luminescent recombination constant is negligible under a low current (low carrier concentration) state, and is not a constant affected by a trap. In general, it can be seen that a low current flows in a micro LED chip due to the physical characteristics that come from its size and is negligible. On the other hand, the SRH non-luminescent recombination constant is a non-luminescent recombination constant affected by defects, and consequently, lowering the SRH non-luminescent recombination constant may be a way to increase the internal quantum efficiency.

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

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

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

In a specific embodiment, a micro LED device having an electrical structure that can improve internal quantum efficiency by inhibiting carriers from reaching a non-luminescent recombination center existing near the sidewall by modifying the potential state of the surface of the sidewall is described. let it do

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

4 (a) is a band diagram of a micro LED device according to an embodiment of the present invention, and FIG. 4 (b) is a band diagram of a micro LED device according to another embodiment of the present invention.

(a) will be explained first. (a) is a band diagram when an insulating layer is attached to the light emitting part of the micro LED device. Since band alignment between insulators and semiconductors follows Anderson's rule, a repulsive force that pushes out majority carriers occurs on the sidewall of the semiconductor.

Holes and electrons move due to the energy difference between the insulating layer and the semiconductor in many trap level (Et) regions existing on the surface of the sidewall of the micro LED device according to an embodiment of the present invention, and as a result, they are fixed An immobile minus charge builds up near the surface of the sidewall, creating a repulsive force that repels the carrier electrons. In other words, since the potential near the sidewall surface is high and electrons are difficult to access, as a result, the number of electrons present near the sidewall surface decreases.

And as a result, surface defects and electrons are isolated from each other by the repulsive force, and electrons travel a certain distance away from the surface of the sidewall. When electrons travel a certain distance away from the surface of the sidewall, of course, the carrier concentration on the surface of the sidewall is reduced, so that non-luminescent recombination occurring in the sidewall is reduced, thereby improving the internal quantum efficiency.

(b) is a band diagram when an insulating layer and a metal layer are attached to the light emitting part of the micro LED device.

The micro LED device according to another embodiment of the present invention is provided with a metal layer in addition to the insulating layer, so that, as shown in FIG. 4(b) , the width of the depletion layer can be increased by applying an appropriate bias. Therefore, as a result, it is possible to further increase the energy difference between the insulating layer and the semiconductor. This increase in energy difference may act as a repulsive force that repels electrons, which are carriers, near the surface of the sidewall as described above.

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 , the micro LED device according to an embodiment of the present invention may have an N-type semiconductor 51 , a light emitting unit 52 , and a P-type semiconductor 53 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, the insulating layer 54 may be formed outside the sidewall of the light emitting part 52 . 5 , the insulating layer 54 may be formed to cover all the sidewalls of the light emitting part 52 . In one embodiment, the thickness of the insulating layer 54 may be 0.1nm to 1um.

In addition, a doped region into which a fixed charge is injected may be formed in all or part of the insulating layer 54 . The doped region of the insulating layer 54 may be formed through ion implantation, diffusion, and plasma methods.

Here, the insulating layer 54 may be made of a material having lower electron affinity than the light emitting part 52 when the light emitting part 52 is P-type. In addition, the insulating layer 54 may be made of a material having a higher electron affinity than the light emitting part 52 when the light emitting part 52 is N-type.

In addition, a doped region into which a fixed charge is injected may be formed in part or all of the region up to a predetermined distance from the sidewall of the light emitting unit 52 . Here, the predetermined distance may be 0.2um.

In this case, 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, it is possible to deposit a gas or liquid or solid containing at least any one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au 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.

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 , the micro LED device according to another embodiment of the present invention may have an N-type semiconductor 61 , a light emitting unit 62 , and a P-type semiconductor 63 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, the insulating layer 64 may be formed outside the sidewall of the light emitting unit 62 . 6 , the insulating layer 64 may be formed to partially cover the sidewall of the light emitting unit 62 . In one embodiment, the thickness of the insulating layer 64 may be 0.1nm to 1um.

In addition, a doped region into which a fixed charge is injected may be formed in all or part of the insulating layer 64 . The doped region of the insulating layer 64 may be formed through an ion implantation process, a diffusion method, and a plasma method.

In addition, a doped region into which a fixed charge is injected may be formed in part or all of the region up to a predetermined distance from the sidewall of the light emitting unit 62 . Here, the predetermined distance may be 0.2um.

In this case, 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, it is possible to deposit a gas or liquid or solid containing at least any one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au 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.

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 , the micro LED device according to another embodiment of the present invention may have an N-type semiconductor 71 , a light emitting unit 72 , and a P-type semiconductor 73 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, an insulating layer 74 may be formed outside the sidewall of the light emitting unit 72 . In the embodiment of FIG. 7 , the insulating layer 74 may be formed to cover the entire sidewall of the light emitting unit 72 . In one embodiment, the thickness of the insulating layer 74 may be 0.1nm to 1um.

In addition, a doped region into which a fixed charge is injected may be formed in all or part of the insulating layer 74 . The doped region of the insulating layer 74 may be formed through ion implantation, diffusion, and plasma methods.

In addition, a doped region into which a fixed charge is injected may be formed in part or all of the region up to a predetermined distance from the sidewall of the light emitting unit 72 . Here, the predetermined distance may be 0.2um. In addition, a doped region into which a fixed charge is injected may also be formed inside the semiconductor formed above or below the light emitting unit 72 .

In this case, 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, it is possible to deposit a gas or liquid or solid containing at least any one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au 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, the metal layer 75 may be formed on the other surface of the insulating layer 74 (a surface not in contact with the light emitting part). Metal layers are Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sn, In, Cd, Ag, Pd, Rh, Ru, Tc, Mo, Nb, Zr, Hf, Ta, At least one of W, Re, Os, Ir, Pt, Au, Tl, Y, Sc, Te, Sb, or Se, or a mixture thereof.

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 , the micro LED device according to another embodiment of the present invention may have an N-type semiconductor 81 , a light emitting unit 82 , and a P-type semiconductor 83 stacked in sequence. 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, the insulating layer 84 may be formed outside the sidewall of the light emitting part 82 . In the embodiment of FIG. 8 , the insulating layer 84 may be formed to cover the entire sidewall of the light emitting part 82 . In one embodiment, the thickness of the insulating layer 84 may be 0.1nm to 1um.

In addition, a doped region into which a fixed charge is injected may be formed in all or part of the insulating layer 84 . The doped region of the insulating layer 84 may be formed through ion implantation, diffusion, and plasma methods.

In addition, a doped region into which a fixed charge is injected may be formed in part or all of the region up to a predetermined distance from the edge of the light emitting part 82 . Here, the predetermined distance may be 0.2um.

In this case, 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, it is possible to deposit a gas or liquid or solid containing at least any one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au 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, the metal layer 85 may be formed on the other surface of the insulating layer 84 (a surface that is not in contact with the light emitting part). Metal layers are Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sn, In, Cd, Ag, Pd, Rh, Ru, Tc, Mo, Nb, Zr, Hf, Ta, At least one of W, Re, Os, Ir, Pt, Au, Tl, Y, Sc, Te, Sb, or Se, or a mixture thereof.

Also, as shown in FIG. 8 , the insulating layer 84 and the metal layer 85 may be formed to extend above and/or below the sidewall of the light emitting unit 82 as well as the sidewall of the light emitting unit 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 have an N-type semiconductor 91 , a light emitting unit 92 , and a P-type semiconductor 93 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, an insulating layer 94 may be formed outside the sidewall of the light emitting part 92 . In the embodiment of FIG. 8 , the insulating layer 94 may be formed to cover the entire sidewall of the light emitting unit 92 . In one embodiment, the thickness of the insulating layer 94 may be 0.1nm to 1um.

In addition, a doped region into which a fixed charge is injected may be formed in all or part of the insulating layer 94 . The doped region of the insulating layer 94 may be formed through ion implantation, diffusion, and plasma methods.

In addition, a doped region into which a fixed charge is injected may be formed in part or all of the region up to a predetermined distance from the sidewall of the light emitting unit 92 . Here, the predetermined distance may be 0.2um.

In this case, 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, it is possible to deposit a gas or liquid or solid containing at least any one of Mg, Zn, Be, Al, Ca, Ar, Si, Se, Te, H, S, C, O, or Au 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 metal layer 95 may be formed on the other surface of the insulating layer 94 (a surface not in contact with the light emitting part). Metal layers are Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sn, In, Cd, Ag, Pd, Rh, Ru, Tc, Mo, Nb, Zr, Hf, Ta, At least one of W, Re, Os, Ir, Pt, Au, Tl, Y, Sc, Te, Sb, or Se, or a mixture thereof.

Also, as shown in FIG. 9 , the insulating layer 94 may be formed to extend not only to the sidewall of the light emitting unit 92 but also to the top and/or bottom of the sidewall of the light emitting unit 92 . In addition, the metal layer 95 formed on another surface of the insulating layer 94 may be formed to have a different area from the insulating layer 94 . In an embodiment, the metal layer 95 may be formed to have a smaller area than another surface of the insulating layer 94 .

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

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

Claims (9)

delete delete delete delete In the 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, the light emitting part, and the N-type semiconductor are stacked,
An insulating layer is further formed on the outer surface of the sidewall of the light emitting part, a doped region into which a fixed charge is injected is formed in all or part of the insulating layer, and a bias is applied to another surface of the insulating layer that is not in contact with the light emitting part A micro LED device, characterized in that a metal layer is further formed to increase the width of the depletion layer. 6. The method of claim 5,
The metal layer is formed to have a smaller area than another surface of the insulating layer that is not in contact with the light emitting part.
Micro LED device. 6. The method of claim 5,
The insulating layer is a micro LED device, characterized in that formed above and below the outer surface of the sidewall of the light emitting unit. delete delete

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