KR102514022B1 - Micro led having omnidirectional reflector structure and manufacturing method of the same - Google Patents

Abstract

A micro light emitting device having an omnidirectional reflector structure according to an embodiment of the present invention includes a substrate; a first semiconductor layer disposed on an upper surface of the substrate and including at least one active region; an active layer disposed in the active region; a second semiconductor layer disposed on the upper surface of the active layer to form a semiconductor cell together with the first semiconductor layer and the active layer; a passivation layer disposed to surround an outer surface of the semiconductor cell; and a reflective layer disposed to surround the passivation layer and reflecting light incident from an inner region of the semiconductor cell through the passivation layer toward the inner region of the semiconductor cell.

Description

Micro light emitting device having an omnidirectional reflector structure and its manufacturing method

The present invention relates to a micro light emitting device having an omnidirectional reflector structure and a manufacturing method thereof.

Micro LEDs have an excellent current dissipation effect, so that when current is injected, current is effectively injected to the active layer inside the LED, which has the advantage of increasing light output and current density per unit area compared to conventional large-area LEDs.

In addition, compared to conventional large-area LEDs, the brightness and contrast ratio of light are very excellent and the reaction speed is also very fast, so low power consumption, light weight, and thinness are possible. Since it can have excellent characteristics, it is attracting attention as a next-generation display light source to replace organic light-emitting diodes (OLED).

However, when a conventional micro LED is used as a light source of a display, it has a size of 100 μm or less, and the ratio of the exposed sidewall area to the light emitting area increases rapidly compared to conventional large-area LEDs. There is a problem in that occurrence of non-radiative recombination is rapidly increased due to surface defect states present in the sidewall.

This causes an efficiency droop phenomenon in which the external quantum efficiency (EQE) is reduced as the current density increases, which acts as a very limiting factor in the implementation of high-efficiency micro LEDs.

In order to overcome this, in order to reduce the defect level on the surface, a nitride/oxide-based insulator material having very high transmittance such as SiO _x , SiN _x , Al ₂ O ₃ material is deposited to passivate the existing defect level on the surface. ), research is being conducted, and in order to maximize this effect, research is also being conducted to recover the surface defect level by further proceeding with a heat treatment process after depositing a non-conductive material.

In addition, recent research has been conducted to adjust the thickness of non-conductive materials in consideration of the antireflection effect, which more effectively extracts the light generated from the active layer in the device to the outside of the micro LED device in consideration of the refractive index of the non-conductive material to be deposited.

However, the studies as described above are merely improving the quality of physical properties through a post-process that reduces the probability of non-luminous recombination by combining surface defect levels with oxygen or nitrogen elements, and antireflection effects to improve light extraction of devices. However, the effect is very minimal.

Therefore, the present invention is a new concept that can maximize light extraction by recovering the defect level present on the surface of the sidewall of the micro LED device through a reflective film and at the same time amplifying the light generated inside the micro LED device by using the resonance effect. A micro LED light emitting device and a manufacturing method thereof are proposed.

Embodiments of the present invention have been proposed to solve the above problems, and have a micro light emitting structure having an omnidirectional reflector structure capable of overcoming a decrease in efficiency by immobilizing or restoring surface defect levels existing on the sidewall of a micro LED light emitting device. It is intended to provide a device and a manufacturing method thereof.

In addition, it is intended to provide a micro light emitting device having an omnidirectional reflector structure capable of maximizing a light extraction effect by amplifying light generated from a micro LED light emitting device using a micro-cavity resonance effect and a manufacturing method thereof.

A micro light emitting device having an omnidirectional reflector structure according to an embodiment of the present invention includes a substrate; a first semiconductor layer disposed on an upper surface of the substrate and including at least one active region; an active layer disposed in the active region; a second semiconductor layer disposed on the upper surface of the active layer to form a semiconductor cell together with the first semiconductor layer and the active layer; a passivation layer disposed to surround an outer surface of the semiconductor cell; and a reflective layer disposed to surround the passivation layer and reflecting light incident from an inner region of the semiconductor cell through the passivation layer toward the inner region of the semiconductor cell.

In addition, the passivation layer includes oxide or nitride, and the thickness of the passivation layer is set based on the maximum emission wavelength of light generated from the semiconductor cell and the refractive index of the passivation layer to satisfy the following equation.

는 반도체 셀에서 발생되는 광의 최대 발광 파장,

은 패시베이션층의 굴절율.here,

is the maximum emission wavelength of light generated from the semiconductor cell,

is the refractive index of the silver passivation layer.

The reflective layer may include a vertical reflective layer disposed to surround an outer surface of the passivation layer and reflect the incident light toward an inner region of the semiconductor cell; and an upper electrode layer integrally formed with the vertical reflection layer and electrically connected to the vertical reflection layer.

In addition, a sidewall region of the semiconductor cell includes an omnidirectional reflector structure composed of a portion of the semiconductor cell, the passivation layer, and the reflective layer.

In addition, the omnidirectional reflector structure reflects some of the first light incident from the inner region of the semiconductor cell to the passivation layer toward the inner region of the semiconductor cell, and transmits some of the first light through the passivation layer. Light incident on the reflective layer is reflected toward the inner region of the semiconductor cell by the reflective layer, and constructive interference occurs between the second light reflected by the passivation layer and the third light reflected by the reflective layer. can be designed

In addition, when the reflected light reflected by the omnidirectional reflector structure satisfies the resonance condition defined by the following formula, a micro-cavity resonance phenomenon occurs.

는 반도체 셀에서 발생되는 광의 최대 발광 파장,

은 활성층의 최대 폭,

은 전방위 반사경 구조로 입사되는 광과 반사광 간의 위상 차이,

은 정수임.here,

is the maximum emission wavelength of light generated from the semiconductor cell,

is the maximum width of the active layer,

is the phase difference between the light incident on the omnidirectional reflector structure and the reflected light,

is an integer.

In addition, the light amplified by the micro-cavity resonance is emitted upward from the semiconductor cell, and the maximum width of the active layer is set to satisfy the resonance condition so that the micro-cavity resonance can occur. can

A micro light emitting device having an omnidirectional reflector structure and a manufacturing method thereof according to embodiments of the present invention can passivate or restore surface defect levels present on the sidewall of the micro LED light emitting device, thereby overcoming a decrease in efficiency.

In addition, the light extraction effect can be maximized by amplifying the light generated from the micro LED light emitting device using the micro-cavity resonance effect.

1 is a conceptual diagram for explaining a manufacturing process of a micro light emitting device having an omnidirectional reflector structure according to the present invention.
2 is a view for explaining a resonance effect of a micro light emitting device having an omnidirectional reflector structure according to the present invention.
3 and 4 are views showing in detail the resonance effect of the micro light emitting device having an omnidirectional reflector structure according to the present invention.
5 is a flowchart illustrating a method of manufacturing a micro light emitting device having an omnidirectional reflector structure according to the present invention.
6 is a view showing simulation simulation results of a micro light emitting device having an omnidirectional reflector structure according to the present invention.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

In addition, in describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description will be omitted.

The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art, and the following examples may be modified in many different forms, and the scope of the present invention is as follows It is not limited to the examples.

Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the spirit of the invention to those skilled in the art.

In addition, each component in the following drawings is exaggerated for convenience and clarity of explanation, and the same reference numerals refer to the same elements in the drawings. As used herein, the term "and/or" includes any one and all combinations of one or more of the listed items.

Terms used in this specification are used to describe specific embodiments and are not intended to limit the present invention.

As used herein, the singular form may include the plural form unless the context clearly indicates otherwise. Also, when used herein, "comprise" and/or "comprising" specifies the presence of the recited shapes, numbers, steps, operations, elements, elements, and/or groups thereof. will,

It does not exclude the presence or addition of one or more other shapes, numbers, operations, elements, elements and/or groups.

1 is a conceptual diagram for explaining a manufacturing process of a micro light emitting device having an omnidirectional reflector structure according to the present invention.

Referring to FIG. 1 , a micro light emitting device having an omnidirectional reflector structure according to an embodiment of the present invention includes a substrate 100, a first semiconductor layer 200, an active layer 300, a second semiconductor layer 400, n It may be composed of a -type electrode 500, a current spreading layer 600, a passivation layer 700, and a reflective layer 800.

Referring to FIG. 1 (a), the substrate 100 is a sapphire, silicon, GaN, or SiC substrate generally used for forming a vertical light emitting device, and is not limited thereto as long as it can be used to manufacture a light emitting device.

In addition, the substrate 100 may be a growth substrate on which a semiconductor structure is grown, and may further include a flexible substrate.

The first semiconductor layer 200 may be disposed on the top surface of the substrate 100 and include at least one active region 210 .

Specifically, the first semiconductor layer 200 includes an active region 210 where the unit semiconductor cells 10 are located and an inactive region located between the active regions 210 .

At this time, the semiconductor cell 10 has a size of a micrometer unit, and means a unit structure for generating light in a micro light emitting device. Specifically, the width of the active layer 300 included in the semiconductor cell 10 is 100 It may be less than μm. In addition, the active layer 300 according to an embodiment of the present invention preferably has a width of 2 μm or less, and a micro light emitting device including the semiconductor cell 10 is generally referred to as a micro LED.

In addition, the first semiconductor layer 200 may be formed of a nitride semiconductor thin film known as gallium nitride (GaN), and is an n-type semiconductor thin film doped with an n-type dopant.

As shown in FIG. 1( b ), the active layer 300 may be disposed in the active region of the first semiconductor layer 200 .

In addition, the active layer 300 is a layer in which electrons generated in the first semiconductor layer 200 and holes generated in the second semiconductor layer 400 meet and recombine, and light can be generated by recombination of electrons and holes. . At this time, the generated light may be radiated in all directions.

In addition, the active layer 300 may be implemented as a single quantum well (SQW) structure or a multiple quantum well (MQW) structure having a plurality of quantum well layers.

The second semiconductor layer 400 is disposed on the upper surface of the active layer 300 to form the semiconductor cell 10 together with the first semiconductor layer 200 and the active layer 300 .

In other words, the first semiconductor layer 200, the active layer 300, and the second semiconductor layer 400 may form one semiconductor cell 10, and the maximum emission wavelength of light generated from the semiconductor cell 10 is It can be adjusted according to the material constituting the active layer 300 , and the size of the semiconductor cell 10 is determined by the maximum width of the active layer 300 .

In addition, the maximum width of the active layer 300 may mean an optical path length of the semiconductor cell 10 .

In addition, the second semiconductor layer 400 may be formed of a nitride semiconductor thin film known as gallium nitride (GaN), and is a p-type semiconductor thin film doped with a p-type dopant.

The n-type electrode 500 may be disposed in an inactive region whose surface is exposed in a space between the active regions 210 of the surface of the first semiconductor layer 200 .

The current spreading layer 600 is disposed on the upper surface of the second semiconductor layer 400 .

In addition, the current spreading layer 600 may be a transparent conductive oxide-based material that is a resistance-changing material, and is formed of a material that has a high transmittance to light including the visible ray region and changes its resistance state by an applied electric field. .

In addition, the current spreading layer 600 may exhibit conductivity by changing its resistance state, which is an insulator initially, from a high resistance state to a low resistance state, and may be made of a transparent conductive oxide-based material (SiO ₂ , Ga ₂ O ₃ , Al ₂ O -, ZnO, ITO, etc.), transparent conductive Nitride-based materials (Si ₃ N ₄ , AlN, GaN, InN, etc.), transparent conductive polymer-based materials (polyaniline (PANI)), poly(ethylenedioxythiophene)-polystyrene sulfonate (PEDOT :PSS), etc.), and transparent conductive nanomaterials (CNT, CNT-oxide, Graphene, Graphene-oxide, etc.).

The passivation layer 700 is disposed to surround the outer surface of the semiconductor cell 10 .

Specifically, the passivation layer 700 is formed of the semiconductor cell 10 after the active layer 300, the second semiconductor layer 400, and the n-type electrode 500 are disposed on the first semiconductor layer 200. It may be disposed on the outer surface region, the inactive region of the first semiconductor layer 200 and the entire surface of the n-type electrode 500 .

At this time, the maximum separation distance of the passivation layers 700 disposed on the outer surface of the semiconductor cell 10 and being symmetrical with each other is the same as the maximum width of the active layer 300 included in the semiconductor cell 10 .

Referring to FIG. 1(c) , a reflective layer 800 is disposed to surround the passivation layer 700, and transmits light incident from an inner region of the semiconductor cell 10 through the passivation layer 700 to the passivation layer 700. The reflection may be directed toward the inner region of the semiconductor cell 10 .

Here, the reflective layer 800 may serve as a p-type electrode. For example, when a voltage is applied between the n-type electrode 500 and the reflective layer 800 in the completed micro light emitting device, the current introduced through the reflective layer 800 is applied to the upper surface of the second semiconductor layer 400. Light is injected into the second semiconductor layer 400 through the disposed current spreading layer 600, and light is generated in the active layer 300 by the injected current. Light generated from the active layer 300 may be reflected or emitted to the outside through the current spreading layer 600 .

In addition, the reflective layer 800 is disposed to surround the outer surface of the passivation layer 700, and transmits light incident from an inner region of the semiconductor cell 10 via the passivation layer 700 to the semiconductor cell 10. ) It may include a vertical reflection layer for reflecting toward the inner region and an upper electrode layer integrally formed with the vertical reflection layer and electrically connected to the vertical reflection layer.

In addition, the upper electrode layer is electrically connected to the current spreading layer 600 .

2 is a view for explaining a resonance effect of a micro light emitting device having an omnidirectional reflector structure according to the present invention.

Referring to FIG. 2 , a structure of a micro light emitting device in which light is emitted upward (top emission) is shown.

At this time, the passivation layer 700 includes an oxide or a nitride, and may be specifically composed of a material selected from SiO ₂ , Al ₂ O ₃ , Si _x N _y , SiO _x N _y or a mixture thereof, and (Deposition) method, for example, it may be formed by a low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD) or sputtering (Sputtering) method.

In addition, the thickness T of the passivation layer 700 is set based on the maximum emission wavelength of light generated from the semiconductor cell 10 and the refractive index of the passivation layer 700 so as to satisfy Equation 1.

는 상기 반도체 셀(10)에서 발생되는 광의 최대 발광 파장,

은 상기 패시베이션층(700)의 굴절율이다.here,

Is the maximum emission wavelength of light generated from the semiconductor cell 10,

is the refractive index of the passivation layer 700.

In the micro light emitting device having an omnidirectional reflector structure according to an embodiment of the present invention, the thickness of the passivation layer 700 is preferably in the range of 50 to 90 nm, and the above range is satisfied according to the maximum emission wavelength and refractive index and can be changed.

)은 활성층(300)을 구성하는 물질에 따라 변화될 수 있으며, 상기 활성층(300)은 기본적으로 적색광, 녹색광, 청색광을 발생하도록 설계될 수 있다. In addition, the maximum emission wavelength of the semiconductor cell 10 (

) may change depending on the material constituting the active layer 300, and the active layer 300 may be designed to basically generate red light, green light, and blue light.

Similarly, the refractive index of the passivation layer 700 may change according to the material constituting the passivation layer 700, and for example, if it is composed of SiO ₂ , it may be the refractive index of the SiO ₂ .

The reflective layer 800 includes a metal material that can be a p-type electrode, and specifically includes silver (Ag), gold (Au), aluminum (Al), nickel (Ni), platinum (Pt), and palladium (Pd). It may be composed of a metal material selected from among.

In addition, as shown in FIG. 1 , the reflective layer 800 is electrically connected to the current spreading layer 600 and deposited through a photo process mask pattern to surround the outer surface of the passivation layer 700 .

Thus, in the micro light emitting device having an omnidirectional reflector structure according to the present invention, the sidewall region 20 of the semiconductor cell 10 is composed of a portion of the semiconductor cell 10, the passivation layer 700, and the reflective layer 800. A reflector structure may be included.

Specifically, a reflective film including a passivation layer 700 and a reflective layer 800 is formed on the sidewall of the semiconductor cell 10 , and the thin film includes light having some or all of the wavelengths generated from the semiconductor cell 10 . reflects

That is, the above-described omnidirectional reflector structure is designed to induce constructive interference of light by reflecting light generated from the semiconductor cell 10 in the direction where the sidewall region 20 is located to the inner region of the semiconductor cell 10 again.

More specifically, the omnidirectional reflector structure reflects some of the first light incident from the inner region of the semiconductor cell to the passivation layer 700 toward the inner region of the semiconductor cell 10, and Light incident to the reflective layer 800 via the passivation layer 700 is reflected toward the inner region of the semiconductor cell 10 by the reflective layer 800, and It is designed so that constructive interference occurs between the reflected second light and the third light reflected by the reflective layer 800 .

Also, in the inner region of the semiconductor cell 10, when the reflected light reflected by the omnidirectional reflector structure satisfies the resonance condition defined by Equation 2, a micro-cavity resonance phenomenon may occur.

는 상기 반도체 셀(10)에서 발생되는 광의 최대 발광 파장,

은 활성층(300)의 최대 폭,

은 전방위 반사경 구조로 입사되는 광과 반사광 간의 위상 차이,

은 정수이다.here,

Is the maximum emission wavelength of light generated from the semiconductor cell 10,

is the maximum width of the active layer 300,

is the phase difference between the light incident on the omnidirectional reflector structure and the reflected light,

is an integer.

)은 발생되는 광이 이동하는 광학적 경로 길이를 의미하며, 상기 활성층(300)의 폭이 커질수록 광학적 경로 길이는 증가하게 된다.At this time, the maximum width of the active layer 300,

) means the optical path length through which the generated light moves, and the optical path length increases as the width of the active layer 300 increases.

In addition, the maximum width of the active layer 300 is the same as the distance between reflective films formed parallel to each other so as to be symmetrical with respect to the semiconductor cell 10 .

A phase difference (hereinafter referred to as phase difference) between the light generated from the semiconductor cell 10 and the reflected light is automatically determined when the maximum width of the active layer 300 is set.

Specifically, in one semiconductor cell 10, if the active layer 300 contains a material that generates blue light, the maximum emission wavelength of the active layer 300 is determined, and the phase difference is the maximum of the active layer 300. Since it is determined according to the width, a resonance condition may be satisfied according to the maximum width of the active layer 300, and a micro-cavity resonance phenomenon may occur.

That is, in the micro light emitting device having an omnidirectional reflector structure according to an embodiment of the present invention, the maximum width of the active layer 300 is set to satisfy the resonance condition so that the micro-cavity resonance phenomenon can occur.

In the micro light emitting device having an omnidirectional reflector structure according to an embodiment of the present invention, the maximum width of the active layer 300 is preferably included in the range of 0.1 to 10 μm.

In addition, as the maximum emission wavelength increases, the maximum width of the active layer 300 to satisfy the resonance condition increases.

Thereafter, in the inner region of the one semiconductor cell 10, resonance occurs when the reflected light reflected by the omnidirectional reflector structure satisfies the resonance condition of Equation 2, and the resonant light is amplified to obtain the one It may be emitted to the upper side of the semiconductor cell 10 .

More specifically, the light amplified by the micro-cavity resonance phenomenon is emitted in the direction where the current spreading layer 600 is located.

3 and 4 are views showing in detail the resonance effect of the micro light emitting device having an omnidirectional reflector structure according to the present invention.

Referring to FIG. 3 , the first light generated in the active layer 300 of the semiconductor cell 10 and incident on the passivation layer 700 transmits through the passivation layer 700 or on one side of the passivation layer 700. It may be reflected, and at this time, the first light moves with a waveform as shown in FIG. 3 .

First, when the first light is reflected from the passivation layer 700, the second light that is the reflected light does not undergo a phase change, and the phase difference with the first light may be zero.

만큼 이동하게 되고, 이동하는 동안

만큼의 위상변화가 일어나게 된다.In addition, when the first light passes through the passivation layer 700, the light passing through the passivation layer 700 and incident on the reflective layer is the thickness T of the passivation layer 700.

will move as much as, while moving

As much phase change will occur.

만큼의 위상변화가 일어나게 된다.Thereafter, light incident to the reflective layer via the passivation layer 700 may be reflected on one surface of the reflective layer 800,

As much phase change will occur.

만큼 이동하게 되고, 다시 패시베이션층(700)을 이동하는 동안

만큼의 위상변화가 일어나게 된다.Next, the light reflected from the reflective layer 800 is again the thickness T of the passivation layer 700

while moving the passivation layer 700 again

As much phase change will occur.

As a result, the third light reflected from the reflective layer 800 does not undergo a phase change, and the phase difference with the first light may be zero.

이므로, 최종적으로 2T만큼 이동하였기 때문에 위상변화는

가 된다.For example, the light transmitted through the passivation layer 700 travels as much as the thickness T of the passivation layer 700 and is reflected by the reflective layer 800, and the reflected light is returned to the thickness T of the passivation layer 700. ), it moves to the inner area of the semiconductor cell 10 as the third light. That is, when moving by the thickness T of the passivation layer 700, the phase change

Therefore, since it has finally moved by 2T, the phase change is

becomes

만큼 일어나므로, 상기한 광의 이동거리에 의한 위상변화를 더하며, 상기 제 3 광의 위상변화는

가 되고, 이에 따라 상기 제 1 광과의 위상이 같아져 보강 간섭이 일어나게 될 수 있다. In addition, a phase change in reflection with the reflective layer 800

Since it occurs as much as, the phase change due to the moving distance of the light is added, and the phase change of the third light is

, and accordingly, the phase with the first light is the same, and constructive interference may occur.

As shown in FIG. 4, the light generated from the semiconductor cell 10 is reflected by the passivation layer 700 and the reflective layer 800, and since the reflected light always has the same phase, constructive interference occurs, and the reflected light Light amplification may occur by overlapping with each other.

Accordingly, the micro light emitting device having an omnidirectional reflector structure according to an embodiment of the present invention recovers the surface defect level existing on the sidewall of the semiconductor cell 10 through the passivation layer 700, thereby reducing the occurrence of the micro light emitting device. Light extraction efficiency of the micro light emitting device may be improved by amplifying light emitted from the semiconductor cell 10 while solving the problem of reduced efficiency.

5 is a flowchart illustrating a method of manufacturing a micro light emitting device having an omnidirectional reflector structure according to the present invention.

Referring to FIG. 5 , a method of manufacturing a micro light emitting device having an omnidirectional reflector structure according to an embodiment of the present invention includes forming a first semiconductor layer including at least one active region 210 on an upper surface of a substrate ( S100), disposing the active layer 300 on the active region 210 (S200), the semiconductor cell 10 together with the first semiconductor layer 200 and the active layer 300 on the upper surface of the active layer 300 ) Disposing the second semiconductor layer 400 to form (S300), disposing the current spreading layer 600 on the upper surface of the second semiconductor layer 400 (S400), of the semiconductor cell 10 Disposing a passivation layer 700 so as to surround an outer surface (S500) and a reflective layer for reflecting light incident from an inner region of the semiconductor cell through the passivation layer toward the inner region of the semiconductor cell. and arranging to surround the cells (S600).

Thus, in the method of manufacturing a micro light emitting device having an omnidirectional reflector structure according to an embodiment of the present invention, after disposing the reflective layer (S600), the sidewall region 20 of the semiconductor cell 10 is A part of the omnidirectional reflector structure composed of the passivation layer 700 and the reflective layer 800 may be included.

The step of disposing the active layer in the active region (S200) further includes setting the maximum width of the active layer 300 so that the micro-cavity resonance phenomenon generated by satisfying Equation 2 can occur.

Prior to the step of disposing the passivation layer (S500), the step of disposing the n-type electrode 500 in the inactive region where the surface is exposed in the space between the active regions 210 on the surface of the first semiconductor layer 200 may be further included. can

In the step of disposing the passivation layer (S500), the thickness of the passivation layer 700 is set based on the maximum emission wavelength of light generated from the semiconductor cell 10 and the refractive index of the passivation layer 700 so as to satisfy Equation 1 above. It may further include steps to do.

The disposing of the reflective layer (S600) includes disposing a vertical reflective layer for reflecting the incident light toward an inner region of the semiconductor cell 10 to surround an outer surface of the passivation layer 700; and integrally forming an upper electrode layer electrically connected to the vertical reflection layer with the vertical reflection layer.

In addition, the step of disposing the reflective layer (S600) further includes depositing the reflective layer 800 through a photoprocess mask pattern so as to surround the outer surface of the passivation layer 700 while being electrically connected to the current spreading layer 700. can do.

Specifically, the step of disposing the reflective layer (S600) is generally a step of depositing a metal that can be a p-type electrode on the current spreading layer 600 formed on the second semiconductor layer 400 using a mask, , In the embodiment of the present invention, a metal that can be a p-type electrode is deposited on the outer surface of the passivation layer 700 by partially modifying the pattern of the photo process mask.

< Example 1> Manufacture of micro light emitting device having an omnidirectional reflector structure

Step S100: An n-GaN layer including at least one active region is formed on the substrate.

Step S200: An active layer (Multi-Quatum Well, MQW layer) is disposed in the active region, and after determining a material constituting the active layer, the maximum width of the active layer satisfies Equation 2.

Step S300: A p-GaN layer is disposed on the upper surface of the MQW layer to form a semiconductor cell together with the n-GaN layer and the MQW layer.

Step S400: An ITO layer is disposed on the upper surface of the p-GaN layer.

Step S500: A SiO ₂ layer is deposited to surround the outer surface of the semiconductor cell, and the thickness of the SiO ₂ layer satisfies Equation 1 above.

Step S600: Thereafter, Ag, a metal material that can be a p-type electrode, was electrically connected to the ITO layer and deposited through a photo process mask pattern to surround the outer surface of the SiO ₂ layer to manufacture a micro light emitting device. .

< Experimental example 1> Computational simulation simulation evaluation of micro light emitting device

In order to confirm the electric field intensity of the micro light emitting device manufactured according to the manufacturing method of the micro light emitting device having an omnidirectional reflector structure according to the present invention, the electric field strength of the micro light emitting device manufactured in Example 1 was measured, and the shown in Figure 6.

6 is a view showing simulation simulation results of a micro light emitting device having an omnidirectional reflector structure according to the present invention.

6(a) is a conceptual diagram of computer simulation simulation, and as shown in FIG. No., No. 3) was used to measure the electric field strength in three directions.

6(b) also shows the distribution of the electric field intensity according to the maximum width of the active layer included in the micro light emitting device calculated by the first monitor or the second monitor and the wavelength of light emitted from the light emitting device.

Referring to FIG. 6(b), based on a wavelength of 450 nm (blue light), it can be seen that the intensity of light changes according to the maximum width of the active layer. As a result, when the maximum width of the active layer satisfies the resonance condition, the micro The light intensity is increased by the -cavity resonance phenomenon, and if the resonance condition is not satisfied, the micro-cavity resonance phenomenon does not occur and the light intensity is weakened.

In other words, when the maximum emission wavelength is determined through the result of FIG. 6(b), it can be confirmed that the micro-cavity resonance phenomenon occurs only in a specific width of the active layer included in the micro light emitting device.

FIG. 6(c) is a graph of electric field strength calculated by monitor 1 or monitor 2, and FIG. 6(d) is a graph of electric field strength calculated by monitor 3.

Referring to FIGS. 6(c) and 6(d) , when the maximum width of the active layer satisfies the resonance condition for generating a micro-cavity resonance phenomenon, it can be seen that the light emitted from the light emitting device is amplified.

In other words, through the results of FIGS. 6(c) and 6(d) , the micro light emitting device having the omnidirectional reflector structure can allow emitted light to have enhanced electric field strength.

Thus, the micro light emitting device having the omnidirectional reflector structure according to an embodiment of the present invention has an effect of inducing self-luminous recombination of the micro light emitting device due to a resonance phenomenon caused by the micro-cavity effect.

In addition, the micro light emitting device having an omnidirectional reflector structure according to an embodiment of the present invention has an effect of improving light extraction efficiency because light is amplified and emitted by the micro-cavity effect.

In addition, the micro light emitting device having an omnidirectional reflector structure according to an embodiment of the present invention has an effect of improving the color purity of the display by reducing color interference between adjacent semiconductor cells when used in displays such as general smartphones and TVs. there is.

In addition, the micro light emitting device having an omnidirectional reflector structure according to an embodiment of the present invention uses a separate photo process mask pattern in the process of depositing a metal that can be a conventional p-type electrode without adding a process to the omnidirectional reflector. structure can be formed.

Although the micro light emitting device having an omnidirectional reflector structure and its manufacturing method according to an embodiment of the present invention have been described as specific embodiments, this is only an example, and the present invention is not limited thereto, and the basic ideas disclosed herein should be construed as having the widest scope that follows. A person skilled in the art may implement a pattern of a shape not indicated by combining or substituting the disclosed embodiments, but this also does not deviate from the scope of the present invention. In addition, those skilled in the art can easily change or modify the disclosed embodiments based on this specification, and it is clear that such changes or modifications also fall within the scope of the present invention.

100: substrate
200: first semiconductor layer
300: active layer
400: second semiconductor layer
500: n-type electrode
600: current dissipation layer
700: passivation layer
800: reflective layer

Claims (12)

In the micro light emitting device that emits light in a direction opposite to the direction toward the substrate,
Board;
a first semiconductor layer disposed on an upper surface of the substrate and including at least one active region;
an active layer disposed in the active region;
a second semiconductor layer disposed on the upper surface of the active layer to form a semiconductor cell together with the first semiconductor layer and the active layer;
a passivation layer disposed to surround an outer surface of the semiconductor cell; and
a reflective layer disposed to surround the passivation layer and reflecting light incident from an inner region of the semiconductor cell through the passivation layer toward the inner region of the semiconductor cell;
The reflective layer is designed such that light reflected by the reflective layer causes constructive interference with light incident on the reflective layer.
According to claim 1,
The passivation layer,
contain oxides or nitrides;
The thickness of the passivation layer is set based on the maximum emission wavelength of light generated from the semiconductor cell and the refractive index of the passivation layer to satisfy the following formula.

here,

is the maximum emission wavelength of light generated from the semiconductor cell,

is the refractive index of the silver passivation layer.
According to claim 1,
The reflective layer,
a vertical reflection layer disposed to surround an outer surface of the passivation layer and to reflect the incident light toward an inner region of the semiconductor cell; and
A micro light emitting device comprising an upper electrode layer integrally formed with the vertical reflection layer and electrically connected to the vertical reflection layer.
According to claim 3,
The sidewall region of the semiconductor cell includes an omnidirectional reflector structure composed of a portion of the semiconductor cell, the passivation layer, and the reflective layer.
According to claim 4,
The omnidirectional reflector structure,
Reflecting some of the first light incident on the passivation layer from an inner region of the semiconductor cell toward the inner region of the semiconductor cell;
Among the first lights, the light passing through the passivation layer and incident on the reflective layer is reflected toward an inner region of the semiconductor cell by the reflective layer;
A micro light emitting device designed so that constructive interference occurs between the second light reflected by the passivation layer and the third light reflected by the reflective layer.
According to claim 5,
In the inner region of the semiconductor cell,
Micro-cavity resonance occurs when the reflected light reflected by the omnidirectional reflector structure satisfies the resonance condition defined by the following formula.

here,

is the maximum emission wavelength of light generated from the semiconductor cell,

is the maximum width of the active layer,

is the phase difference between the light incident on the omnidirectional reflector structure and the reflected light,

is an integer.
According to claim 6,
The light amplified by the micro-cavity resonance is emitted upward from the semiconductor cell,
The maximum width of the active layer is set so that the micro-cavity resonance phenomenon generated by satisfying the resonance condition may occur.
A method for manufacturing a micro light emitting device that emits light in a direction opposite to a direction toward a substrate,
forming a first semiconductor layer including at least one active region on an upper surface of a substrate;
disposing an active layer in the active region;
disposing a second semiconductor layer on an upper surface of the active layer to form a semiconductor cell together with the first semiconductor layer and the active layer;
disposing a passivation layer to surround an outer surface of the semiconductor cell; and
disposing a reflective layer surrounding the semiconductor cell to reflect light incident from an inner region of the semiconductor cell through the passivation layer toward the inner region of the semiconductor cell;
The reflective layer is designed such that light reflected by the reflective layer causes constructive interference with light incident on the reflective layer.
According to claim 8,
After disposing the reflective layer,
The method of claim 1 , wherein the sidewall region of the semiconductor cell includes an omnidirectional reflector structure composed of a portion of the semiconductor cell, the passivation layer, and the reflective layer.
According to claim 8,
Disposing an active layer in the active region,
A method of manufacturing a micro light emitting device comprising the step of setting a maximum width of the active layer so that a micro-cavity resonance phenomenon occurs by satisfying the following formula.

here,

is the maximum emission wavelength of light generated from the semiconductor cell,

is the maximum width of the active layer,

is the phase difference between the light incident on the omnidirectional reflector structure and the reflected light,

is an integer.
According to claim 8,
The step of disposing the passivation layer,
and setting a thickness of the passivation layer based on a maximum emission wavelength of light generated from the semiconductor cell and a refractive index of the passivation layer to satisfy the following equation.

here,

is the maximum emission wavelength of light generated from the semiconductor cell,

is the refractive index of the silver passivation layer.
According to claim 8,
The step of disposing the reflective layer,
disposing a vertical reflection layer for reflecting the incident light toward an inner region of the semiconductor cell to surround an outer surface of the passivation layer; and
A method of manufacturing a micro light emitting device comprising the step of integrally forming an upper electrode layer electrically connected to the vertical reflection layer and the vertical reflection layer.

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