KR100960762B1 - Laser emitting diode, and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a laser light emitting diode and a method of manufacturing the same, wherein the surface of the transparent electrode where the p-pad electrode is not formed and the p-nitride layer, the active layer, and the n-pad electrode, which are exposed to the outside, are not formed. By forming a reflective insulating film on the surface of each of the nitride layers, when the device emits light, a substantial amount of light emitted from the active layer in the upper direction is reflected in the lower direction to improve the luminous efficiency of the device.

Laser, light emitting diode, diode, reflective insulating film

Description

Laser light emitting diode, and method for manufacturing the same

1 is a view showing a general laser light emitting diode,

2A to 2E are process flowcharts illustrating a method of manufacturing a laser light emitting diode according to the present invention;

3 is a view showing an embodiment of a laser light emitting diode according to the present invention;

4 is a view for showing that the reflectivity is improved when the reflective insulating film used in the present invention is formed of a multilayer film.

Explanation of symbols on the main parts of the drawings

20: dissimilar substrate 21: n-nitride layer

22 active layer 23 p-nitride layer

24: transparent electrode 25: n pad electrode

26: p pad electrode 27: reflective insulating film

According to the present invention, a reflective insulating film is formed on a surface of a transparent electrode on which a p-pad electrode is not formed, and on a surface of each of the p-nitride layer, an active layer, and an n-nitride layer on which an n-pad electrode is not formed. Accordingly, the present invention relates to a laser light emitting diode and a method of manufacturing the same, which can improve the luminous efficiency of the device by reflecting a substantial amount of light emitted from the active layer in the upper direction in the downward direction when the device emits light.

Recently, as the demand for high efficiency short wavelength optical devices increases, research into nitride semiconductors that are known to be suitable for such applications is being actively conducted. In particular, by adding phosphors in addition to the blue violet short wavelength optical devices, With the ability to produce white light, interest in this field is growing day by day.

On the other hand, light emitting devices such as nitride-based laser light emitting diodes mainly use sapphire as a substrate, and nitride and sapphire have a high density when a nitride layer is formed on the sapphire substrate due to a difference in lattice constant and thermal expansion coefficient. Crystal defects occur, and FIG. 1 is a diagram illustrating a general laser light emitting diode using such a sapphire substrate.

As shown in the drawing, a conventional laser light emitting diode includes a nitride layer 11 (hereinafter, abbreviated as " n-nitride layer ") and an active layer doped n-type on the top surface of the sapphire substrate 10 by MOCVD method. (12), a p-type doped nitride layer 13 (hereinafter, abbreviated as " p-nitride layer ") is sequentially stacked, and then a transparent electrode 14 is formed on the top surface of the p-nitride layer 13. The p-pad electrode 15 and the n-pad electrode 16 are formed on the transparent electrode 14 and the n-nitride layer 11, respectively. When current is applied through the light, light is generated in the active layer, and the light is emitted to the outside through the sapphire substrate.

In the conventional laser light emitting diode, light is emitted from the active layer, and the emitted light travels up and down the active layer, and particularly, the light propagated upward generates light absorption in the pad electrode region, thereby lowering the luminous efficiency of the device. There is this.

Accordingly, the present invention has been developed to solve the above problems, the laser light emitting diode and its manufacture to increase the light emitting efficiency of the device by reducing the light that is unnecessarily absorbed in the pad electrode region, etc. at the time of light emission of the laser light emitting diode The purpose is to provide a method.

To this end, the present invention provides a reflective insulating film on the surface of the transparent electrode on which the p-pad electrode is not formed, on the surfaces of the p-nitride layer, the active layer, and the n-nitride layer on which the n-pad electrode is not formed. By forming the light emitting device, a large amount of light emitted from the active layer in the upper direction is reflected in the lower direction, thereby improving the light emitting efficiency of the device.

First, the nitride used in the present invention is defined as a compound of the group III-V element containing Ga, such as GaN, GaAlN, InGaN, InAlGaN, the chemical formula is as follows.

<< chemical formula >>

In _x Al _y Ga _1-y (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ x + y ≤ 1)

Hereinafter, with reference to the accompanying Figures 2a to 2e look at the present invention.

First, as shown in FIG. 2A, the n-nitride layer 21, the active layer 22, and the p-nitride layer 23 are sequentially formed on the upper surface of the substrate 20.

That is, an n-doped nitride is deposited on the entire upper surface of the substrate 20, and grown by a predetermined thickness using a side growth method (LEO) to form the n-nitride layer 21, and then the n-nitride The active layer 22 is formed by depositing a specific light emitting material on the upper surface of the layer 21, and the p-nitride layer 23 is formed by depositing and growing a p-type doped nitride on the entire upper surface of the active layer 22. .

In this case, the substrate 20 may be any one selected from among sapphire substrates and silicon carbide substrates, and the active layer 22 may be a single quantum well structure or a multi-layer quantum well structure. It is preferable to form a quantum well structure.

Subsequently, when the n-nitride layer 21, the active layer 22, and the p-nitride layer 23 are sequentially formed on the upper surface of the substrate 20, the n− in the vertical direction from the p-nitride layer 23. The nitride layer 21 is etched to expose a portion of the n-nitride layer 21 (FIG. 2B).

Then, a thin metal is deposited and patterned on a portion of the upper surface of the p-nitride layer 23 remaining without etching to form a transparent electrode 24 (FIG. 2C). Since the related technology is a known technology, a detailed description thereof will be omitted.                     

Meanwhile, when the transparent electrode 24 is formed on the upper surface of the p-nitride layer 23, as shown in FIG. 2D, metal is deposited on the transparent electrode 24 and patterned to bond the wire. A p pad electrode 25 to be used as a sea pad is formed.

At the same time as the p pad electrode formation 25 or respectively, the n-nitride layer exposed by mesa etching in a vertical direction from the p-nitride layer 23 to a part of the n-nitride layer 21 is exposed. A n pad electrode 26 is formed by depositing and patterning a metal on the upper surface of the 21, wherein the metal is any one selected from Cr, Ni, Au, Al, Ti, Pt, or It is preferable to use what consists of combinations.

Finally, the surface of the transparent electrode 24 on which the p-pad electrode 25 is not formed, the exposed p-nitride layer 23, the active layer 22, and the n-pad electrode 26 are not formed. By forming a reflective insulating film 27 on the surface of each of the n-nitride layers 21, the passivation function can be minimized, and the light generated in the active layer 22 can be prevented from being emitted upward. .

In addition, the reflective insulating layer 27 is preferably formed by applying an insulator for HR coating (High Reflective coating), the insulator for HR coating (High Reflective coating) is selected from TiO ₂ , SiO ₂ , Al ₂ O ₃ Use either one.

In addition, as the following equation, the thicker the thickness of the reflective insulating film 27, the higher the refractive index, and accordingly increases the reflectance of the light emitted from the active layer 22, so that the reflective insulating film in order to make the thickness as thick as possible It is preferable to form in a multi-layer.

《Mathematical formula》

Thickness = λ / (4 × n) {n: refractive index of material used for reflective insulating film}

As shown in FIG. 2E, the laser light emitting diode manufactured according to the above-described manufacturing method of the present invention includes the substrate 20 and the n-nitride layer 21, the active layer 22, and p sequentially formed on the upper surface of the substrate. The nitride layer 23, the transparent electrode 24, the p-pad electrode 25 formed on a part of the upper surface of the transparent electrode 24, and the n- in the vertical direction from a part of the p-nitride layer 23; The n-pad electrode 26 formed on the upper surface of the n-nitride layer 21 exposed by mesa etching to the nitride layer 21 and the transparent electrode 24 on which the p-pad electrode 25 is not formed Reflective insulating film 27 formed on the surface of each of the n-nitride layer 21 on which the p-nitride layer 23, the active layer 22, and the n-pad electrode 26 are not exposed. )

In this laser light emitting diode, the reflective insulating layer 27 is one that is not modulated and has a high reflectance even at a high temperature such as a lateral growth temperature of nitride, and particularly, any one selected from TiO ₂ , SiO ₂ , and Al ₂ O ₃ . Preference is given to using.

In addition, as shown in FIG. 3, it is preferable to form the reflective insulating film 27 in a multi-layer as possible and to increase the thickness thereof so as to improve the reflectance.                     

For example, the first reflective insulating film and the second reflective insulating film which are made of different materials are alternately formed, or the first reflective insulating film, the second reflective insulating film, and the third reflective insulating film, in which three different materials are selectively used, respectively. Are alternately formed, the above-described multi-layer aspect is merely one example and various modifications thereof are possible.

As described above, the laser light emitting diode of the present invention includes a surface of the transparent electrode on which the p-pad electrode is not formed, an p-nitride layer exposed to the outside, an active layer, and an n-nitride layer on which the n-pad electrode is not formed. By forming a reflective insulating film on each surface, it is possible to improve the luminous efficiency of the device by reflecting a substantial amount of light emitted from the active layer in the upward direction downward when the device emits light.

On the other hand, Figure 4 is a view for showing that the reflectivity is improved when the reflective insulating film is formed of a multilayer film through the following experimental example.

<< experimental example >>

1. A reflective insulating film was formed on the outer circumferential surface of each of the transparent electrode, p-nitride layer, and n-nitride layer on which no p-pad electrode or n-pad electrode was formed.

In addition, the reflective insulating layer was formed by alternately depositing TiO ₂ and SiO ₂ to form a multilayer of 11 layers or 5 layers, and the bare glass shown in FIG. 4 is a case where the reflective insulating layer is not formed.

2. GaN was used as the nitride, and the wavelength of light used in the experiment was 420 nm.                     

As a result of the experiment through the above-described reaction example, when the reflective insulating film is a multilayer film of 11 layers, the reflectivity is 0.957, the reflectivity is 0.512 when the multilayer film is 5 layers, and 0.078 when the reflective insulating film is not formed. As the reflective insulating layer is formed in multiple layers, the reflectivity is improved.

As described in detail above, the laser light emitting diode and the method of manufacturing the same of the present invention include a surface of the transparent electrode on which the p-pad electrode is not formed, the p-nitride layer exposed to the outside, the active layer, and the n-pad. By forming a reflective insulating film on the surface of each of the n-nitride layers on which electrodes are not formed, there is an effect of improving the luminous efficiency of the device by reflecting a substantial amount of light emitted upward from the active layer in the downward direction when the device emits light. .

Although the invention has been described in detail only with respect to the specific examples described, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

Claims (6)

A first step of sequentially forming an n-nitride layer, an active layer, and a p-nitride layer on the upper surface of the substrate; A second step of etching from the p-nitride layer to a portion of the n-nitride layer in a vertical direction to expose a portion of the n-nitride layer; A third step of forming a transparent electrode on an upper surface of the p-nitride layer remaining without etching; Forming a p pad electrode on a portion of an upper surface of the transparent electrode and forming an n pad electrode on an upper surface of the exposed n-nitride layer; A reflective insulating film is formed on a surface of the transparent electrode on which the p-pad electrode is not formed, on each of the surfaces of the p-nitride layer, the active layer, and the n-nitride layer on which the n-pad electrode is not formed; A laser light emitting diode manufacturing method comprising five steps. The method of claim 1, wherein the fifth step; And forming the reflective insulating film in a multi-layer. The method of claim 1 or 2, wherein the reflective insulating film; HR coating (High Reflective) on the surface of the transparent electrode without the p-pad electrode, the surface of the p-nitride layer, the active layer, and the n-nitride layer where the n-pad electrode is not formed. A method for manufacturing a laser light emitting diode, characterized by coating and forming an insulator for coating). The method of claim 3, wherein The insulator for HR coating (High Reflective coating); TiO ₂ , SiO ₂ , Al ₂ O _{3 It} characterized in that any one selected from, laser light emitting diode manufacturing method. An n-nitride layer, an active layer, and a p-nitride layer are sequentially formed on the substrate; Etching from the p-nitride layer to a portion of the n-nitride layer in a vertical direction to expose a portion of the n-nitride layer; A transparent electrode is formed on an upper surface of the p-nitride layer remaining without etching; P-pad electrodes and n-pad electrodes are formed on a portion of the top surface of the transparent electrode and the top surface of the exposed n-nitride layer, respectively; The reflective insulating film is formed on the surface of the transparent electrode where the p-pad electrode is not formed, and the surfaces of the p-nitride layer, the active layer, and the n-nitride layer where the n-pad electrode is not formed. Laser light emitting diode The method of claim 5, wherein the reflective insulating film; A laser light emitting diode, characterized in that formed in a multi-layer.

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