KR101182189B1 - Iii-nitride semiconductor light emitting device - Google Patents

Abstract

PURPOSE: An III group nitride semiconductor light emitting diode is provided to improve current spreading by forming a light absorption blocking layer into insulating material. CONSTITUTION: A buffer layer(320), a first semiconductor layer(330), an active layer(340), and a second semiconductor layer(350) are formed on a substrate(310). The first semiconductor layer and the second semiconductor layer have different conductivity. A transparent conductive layer(360) is formed on the second semiconductor layer. A first pad electrode(370) is formed on the transparent conductive layer. A first light absorption blocking layer(305) is formed between the second semiconductor layer and the first pad electrode. The first light absorption blocking layer has a refractive index lower than the second semiconductor layer.

Description

 Group III nitride semiconductor light emitting device {III-NITRIDE SEMICONDUCTOR LIGHT EMITTING DEVICE}

The present disclosure generally relates to a group III nitride semiconductor light emitting device, and more particularly, to a group III nitride semiconductor light emitting device having improved light extraction efficiency to the outside of the light emitting device.

Here, the group III nitride semiconductor light emitting element is a group III nitride of Al (x) Ga (y) In (1-xy) N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). Means a light emitting device such as a light emitting diode including a semiconductor layer, and additionally excludes the inclusion of a material consisting of elements of other groups such as SiC, SiN, SiCN, CN or a semiconductor layer made of these materials. no.

Herein, the background art relating to the present disclosure is provided, and these are not necessarily meant to be known arts.

1 is a view showing an example of a conventional group III nitride semiconductor light emitting device. The group III nitride semiconductor light emitting device includes a substrate 10 (eg, a sapphire substrate), a buffer layer 20 grown on the substrate 10, an n-type group III nitride semiconductor layer 30 grown on the buffer layer 20, and an n-type 3 The current diffusion electrode formed on the active layer 40 grown on the group nitride semiconductor layer 30, the p-type group III nitride semiconductor layer 50 grown on the active layer 40, and the p-type group III nitride semiconductor layer 50 ( 60, the n-type group III nitride semiconductor layer 30 in which the p-side pad electrode 70 formed on the current spreading electrode 60, the p-type group III nitride semiconductor layer 50 and the active layer 40 are mesa-etched and exposed. ) And an n-side pad electrode 80 and a passivation layer 90.

The current spreading electrode 60 is provided so that the current is well supplied to the entire p-type group III nitride semiconductor layer 50. The current spreading electrode 60 is formed over almost the entire surface of the p-type group III nitride semiconductor layer, for example, formed of a transmissive conductive film using ITO or Ni and Au, or as a reflective conductive film using Ag. Can be formed.

The p-side pad electrode 70 and the n-side pad electrode 80 are metal electrodes for supplying current and wire bonding to the outside, for example, nickel, gold, silver, chromium, titanium, platinum, palladium, and rhodium. And iridium, aluminum, tin, indium, tantalum, copper, cobalt, iron, ruthenium, zirconium, tungsten, molybdenum, or any combination thereof.

The passivation layer 90 is formed of a material such as silicon dioxide and may be omitted.

As the semiconductor light emitting device becomes larger in size and consumes higher power, branch electrodes and a plurality of electrodes are introduced to smoothly spread current in the semiconductor light emitting device. For example, according to the Group III nitride semiconductor light emitting device having a large area (eg, 1000 μm / 1000 μm in width and length), branch electrodes are provided at the p-side pad electrode 70 and the n-side pad electrode 80. As a result, current spreading is improved, and in addition, a plurality of p-side pad electrodes 70 and n-side pad electrodes 80 may be provided for sufficient current supply.

Metal-like electrodes such as the p-side pad electrode 70 and the n-side pad electrode 80 have a thick thickness and a large light absorption loss, thereby degrading light extraction efficiency of the light emitting device.

This will be described later in the Specification for Implementation of the Invention.

SUMMARY OF THE INVENTION Herein, a general summary of the present disclosure is provided, which should not be construed as limiting the scope of the present disclosure. of its features).

According to one aspect of the present disclosure, an according to one aspect of the present disclosure includes: a first semiconductor layer having a first conductivity, a second semiconductor layer having a second conductivity different from the first conductivity, and a first semiconductor layer; An active layer disposed between the second semiconductor layers and generating light through recombination of electrons and holes; A transmissive conductive film positioned on the second semiconductor layer; A first pad electrode positioned on the light transmissive conductive film; And a first light absorption prevention layer formed to cover at least a portion of the second semiconductor layer and the first pad electrode by the light-transmissive conductive film, and having a lower refractive index than the second semiconductor layer. A nitride semiconductor light emitting device is provided.

According to another aspect of the present disclosure, a first semiconductor layer having a first conductivity, a second semiconductor layer having a second conductivity different from the first conductivity, and positioned between the first semiconductor layer and the second semiconductor layer, An active layer generating light through recombination of holes; A conductive film on the second semiconductor layer; A first pad electrode positioned on the conductive film; A second pad electrode on the exposed first semiconductor layer, the second semiconductor layer and the active layer being etched in a mesa form, and electrically connected to the first semiconductor layer; and between the first semiconductor layer and the second pad electrode Located in, and a light absorption prevention layer having a lower refractive index than the first semiconductor layer; Group III nitride semiconductor light emitting device comprising a.

This will be described later in the Specification for Implementation of the Invention.

1 is a view showing an example of a conventional group III nitride semiconductor light emitting device,
2 is a view showing an example of a group III nitride semiconductor light emitting device according to the present disclosure;
3 is a cross-sectional view taken along the line II ′ in FIG. 2;
4 is a simulation result showing the relationship between the thickness and the reflectance of the light absorption prevention layer,
5 is a view showing another example of the group III nitride semiconductor light emitting device according to the present disclosure;
6 is a view showing still another example of the group III nitride semiconductor light emitting device according to the present disclosure;
7 is a view showing still another example of the group III nitride semiconductor light emitting device according to the present disclosure.

The present disclosure will now be described in detail with reference to the accompanying drawing (s).

FIG. 2 is a diagram illustrating an example of a group III nitride semiconductor light emitting device according to the present disclosure, and FIG. 3 is a cross-sectional view taken along line II ′ of FIG. 2.

The group III nitride semiconductor light emitting device 300 includes a substrate 310, a buffer layer 320, a first semiconductor layer 330, an active layer 340, a second semiconductor layer 350, a light absorption prevention layer 305, and a transparent conductive material. The film 360, the first pad electrode 370, and the second pad electrode 380 are included.

The buffer layer 320, the first semiconductor layer 330, the active layer 340, and the second semiconductor layer 350 are formed on the substrate 310. The semiconductor layers epitaxially grown on the substrate 310 are mainly grown by organometallic vapor phase growth (MOCVD), and each layer may further include sublayers as necessary.

The substrate 310 may be a GaN-based substrate as a homogeneous substrate, and a sapphire substrate, a SiC substrate, or a Si substrate may be used as the heterogeneous substrate. Any substrate may be used as long as the group III nitride semiconductor layer can be grown.

The first semiconductor layer 330 and the second semiconductor layer 350 are provided to have different conductivity. In the present disclosure, the first semiconductor layer 330 is an n-type nitride semiconductor layer 330 (eg, an n-type GaN layer), and the second semiconductor layer 350 is a p-type nitride semiconductor layer 350 (eg, p-type GaN layer), the first pad electrode 370 is used as the p-side pad electrode 370, and the second pad electrode 380 is used as the n-side pad electrode 380, for example.

After the n-type nitride semiconductor layer 330, the active layer 340, and the p-type nitride semiconductor layer 350 are formed, the p-type nitride semiconductor layer 350 and the active layer 340 are etched in a mesa form to form n. The type nitride semiconductor layer 330 is exposed. As a method of removing a plurality of semiconductor layers, a dry etching method, for example, an inductively coupled plasma (ICP) may be used.

Next, a light absorption prevention layer (PCVD) is formed on a portion of the p-type nitride semiconductor layer 350 by a method such as plasma enhanced chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD), sputtering, e-beam evaporation, or thermal evaportation. 305). The light absorption prevention layer 305 is formed of a material which the light absorption prevention layer 305 is in contact with, in this embodiment, a material having a refractive index lower than that of the p-type nitride semiconductor layer 350. For example, SiO ₂ , SiN, AlO _x , SiON and TiO _{2 It} may be made of at least one selected from the group consisting of.

Subsequently, the sputtering method, the E-beam evaporation method, the thermal evaporation method, and the like, as shown in FIGS. 2 and 3, almost the front surface and the light absorption of the p-type nitride semiconductor layer 350. The transmissive conductive film 360 is formed on the prevention layer. The transparent conductive film 360 improves the uniformity of light. The transparent conductive film 360 is mainly formed of an ITO or Ni / Au oxide film. If the translucent conductive film 360 is too thin, the driving voltage is increased due to the current diffusion, and if it is too thick, the light extraction efficiency may be reduced due to light absorption.

Next, the n-side pad electrode 380 and the p-side pad electrode 370 are formed by using a method such as sputtering, electron beam evaporation, and thermal evaporation. For example, the n-side pad electrode 380 and the p-side pad electrode 370 may be formed by stacking chromium, nickel, and gold.

The n-side pad electrode 380 is formed on the n-type nitride semiconductor layer 330 exposed by mesa etching, and the p-side pad electrode 370 is formed on the transparent conductive film 360 on the light absorption prevention layer 305. have. For example, as shown in FIG. 2, the n-side pad electrode 380 and the p-side pad electrode 370 are located at opposite sides, and the n-side pad electrode 380 and the p-side pad electrode 370 are located. The shape and arrangement of the can be changed in various ways.

The light absorption prevention layer 305 may be formed of an insulator and has a very high resistance to cut off current to the active layer 340 under the p-side pad electrode 370, thereby reducing light loss by the p-side pad electrode 370. There are advantages to it. At this time, the current is diffused through the transparent conductive film 360.

The refractive index of GaN constituting the p-type nitride semiconductor layer 350 is 2.4, and the refractive index of SiO ₂ constituting the light absorption prevention layer 305 is about 1.5. Therefore, the light generated in the active layer 340 is reflected at the interface between the p-type nitride semiconductor layer 350 and the light absorption prevention layer 305 has the advantage of reducing the absorption of light by the p-side pad electrode 370. The reason for this is as follows.

The critical angle is determined by the difference in refractive index between the p-type nitride semiconductor layer 350 and the light absorption prevention layer 305. Light entering the critical angle is reflected only a certain amount at the interface, and light entering at an angle larger than the critical angle is totally reflected. Therefore, the amount of light absorbed by the p-side pad electrode 370 may be reduced.

To be affected by the refractive index of the medium where light meets, the thickness of the medium must be at least as thick as the wavelength of light. Therefore, since the refractive index of ITO is 1.8 to 2.0, when the thickness of the light absorption prevention layer 305 is too thin, the effect of preventing light from being absorbed by the p-side pad electrode 370 may be small. Therefore, the thickness T10 of the light absorption prevention layer 305 is preferably sufficiently thick, with the current blocking function of the light absorption prevention layer 305, and the reflectance between the p-type nitride semiconductor layer 350 and the light absorption prevention layer 305. The larger the value is, the better the external quantum efficiency is.

For example, the light absorption prevention layer 305 is formed in an island shape under the p-side pad electrode 370. If the width of the light absorption prevention layer 305 is too wide, the area where the current is cut off may become too large, and the efficiency of the device may be reduced. Also, light generated by the active layer 340 and incident on the light absorption prevention layer 305 is more than necessary. The light absorbing layer 305 may be reflected back toward the substrate 310. If the light absorbing layer 305 is narrow, the light absorbing layer 305 may not be effectively reflected to the p-side pad electrode 370. The width of the side pad electrode 370 is preferably equal to or slightly wider.

4 is a simulation result showing the relationship between the thickness and the reflectance of the light absorption prevention layer.

In FIG. 4, the horizontal axis represents an incident angle of light to the light absorption prevention layer 305, and the vertical axis represents a reflectance. The light absorption prevention layer 305 is made of SiO ₂ , and the thickness is simulated by changing the thickness. Representatively, a graph for the case where the thickness is 2500 mV and 3000 mV is shown.

If the incident angle is very small or large, it can be seen that the reflectance does not have a large difference depending on the thickness of the light absorption prevention layer 305. However, when the light is incident at an oblique angle of about 25 degrees to 70 degrees, the reflectance varies greatly depending on the thickness of the light absorption prevention layer 305. When the thickness of the light absorption prevention layer is thinner than 3000Å, the reflectance decreases rapidly. In addition, when the thickness of the light absorption prevention layer is 3000Å or more, it can be seen that it has a high reflectance regardless of the incident angle. In addition, although not shown in FIG. 4, the simulation result of increasing the thickness indicates that the reflectance improvement effect is saturated when the thickness is about 20000 μs.

Therefore, the thickness T10 of the light absorption prevention layer 305 may affect the reflection efficiency of light, and in order to effectively reflect the light, the light absorption prevention layer 305 preferably has a thickness of 3000 kPa or more and 20000 kPa or less.

5 is a view showing another example of the group III nitride semiconductor light emitting device according to the present disclosure.

The group III nitride semiconductor light emitting device 600 is substantially the same as the group III nitride semiconductor light emitting device 300 described with reference to FIGS. 2 and 3 except for further including a distributed Bragg reflective layer 606. Therefore, the same elements are given the corresponding reference numerals and duplicate descriptions are omitted.

In FIG. 5, the dispersed Bragg reflective layer 606 is formed between the light absorption prevention layer 605 and the transparent conductive film 660. For example, TiO ₂ and SiO ₂ may be repeatedly stacked one to three times on the light absorption prevention layer 605 to form a distributed Bragg reflector 606 (DBR). In the distributed Bragg reflective layer 606, the thicknesses of TiO ₂ and SiO ₂ may be uniform, and the Distributed Bragg reflective layer 606 may receive light incident on the p-side pad electrode 670 without being reflected by the light absorbing reflective layer 605. There is an advantage that the reflection efficiency is further increased because of reflection.

6 is a view showing still another example of the group III nitride semiconductor light emitting device according to the present disclosure.

The group III nitride semiconductor light emitting device 700 is a group III nitride semiconductor light emitting device described with reference to FIGS. 2 and 3 except that the second light absorption preventing layer 707 is further provided on the bottom surface of the n-side pad electrode 780. Substantially the same as 300). Therefore, the same elements are given the corresponding reference numerals and duplicate descriptions are omitted.

In FIG. 6, a first light absorption preventing layer 705 is formed on the p-type nitride semiconductor layer 750 under the p-side pad electrode 770. In addition, a second light absorption preventing layer 707 is formed on the n-type nitride semiconductor layer 730 below the n-side pad electrode 780. The n-side pad electrode 780 covers the second light absorption preventing layer 707 and is in contact with the n-type nitride semiconductor layer 730.

The second light absorption prevention layer 707 may be formed of at least one selected from the group consisting of SiO ₂ , SiN, AlO _x , SiON, and TiO ₂ , and the thickness of the second light absorption prevention layer 707 may be 3000 kPa or more and 20000 kPa or less. .

When the amount of light absorption by the n-side pad electrode 780 cannot be ignored, the second light absorption prevention layer 707 may be formed to improve external quantum efficiency.

7 is a view showing still another example of the group III nitride semiconductor light emitting device according to the present disclosure.

In the group III nitride semiconductor light emitting device 900, the light absorption prevention layer under the p-side pad electrode 970 is removed, and the light absorption prevention layer 907 is provided on the bottom surface of the n-side pad electrode 980. And substantially the same as the group III nitride semiconductor light emitting device 300 described with reference to FIG. 3. Therefore, the same elements are given the corresponding reference numerals and duplicate descriptions are omitted.

In FIG. 7, the light absorption prevention layer 907 may be formed of at least one selected from the group consisting of SiO ₂ , SiN, AlO _x , SiON, and TiO ₂ , and the thickness T20 of the light absorption prevention layer 907 may be 3000 kPa or more and 20000 kPa or less. desirable.

When the conductive film 960 is a reflective conductive film, there is a small need to provide a light absorption prevention layer below the p-side pad electrode 970 to reflect light. In this case, the light is reflected by the reflective conductive film 960 to be reflected toward the substrate 910, so that the amount of light incident on the n-side pad electrode 980 may be insignificant. In this case, as described above, the light absorption prevention layer 907 may be formed on the n-type nitride semiconductor layer 930 under the n-side pad electrode 980, thereby reducing light absorption and improving external quantum efficiency.

Hereinafter, various embodiments of the present disclosure will be described.

(1) A group III nitride semiconductor light emitting device, characterized in that the first light absorption preventing layer is made of an insulating material.

(2) The first semiconductor layer, the active layer and the second semiconductor layer are made of Al (x) Ga (y) In (1-xy) N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1 And a first light absorption preventing layer comprises at least one selected from the group consisting of SiO ₂ , SiN, AlO _x , SiON, and TiO ₂ .

(3) A group III nitride semiconductor light emitting element, wherein the thickness of the first light absorption preventing layer is 3000 kPa or more and 20000 kPa or less.

(4) The group III nitride semiconductor light emitting device, wherein the first light absorption preventing layer is formed in an island shape and has a width equal to or larger than that of the first pad electrode.

(5) a Group III nitride further comprising: a distributed Bragg Reflector positioned between the first light absorption preventing layer and the first pad electrode and having a repeatedly stacked TiO ₂ / SiO ₂ layer; Semiconductor light emitting device.

(6) The first semiconductor layer, the active layer and the second semiconductor layer are made of Al (x) Ga (y) In (1-xy) N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1 The first light absorption prevention layer is composed of at least one selected from the group consisting of SiO ₂ , SiN, AlO _x , SiON and TiO ₂ , and the thickness of the first light absorption prevention layer is 3000 kPa or more and 20000 kPa or less. Group III nitride semiconductor light emitting device.

(7) a second pad electrode disposed on the exposed first semiconductor layer in which the second semiconductor layer and the active layer are etched in the form of mesa; and is positioned between the first semiconductor layer and the second pad electrode, The group III nitride semiconductor light emitting device of claim 3, further comprising a second light absorption preventing layer having a lower refractive index than the semiconductor layer.

In the present disclosure, the group III nitride semiconductor light emitting device includes a case in which the n-type nitride semiconductor layer is electrically bonded directly on the lead electrode by omitting the second pad electrode.

(8) The conductive film is a reflective conductive film that reflects light, and the first semiconductor layer, the active layer and the second semiconductor layer are Al (x) Ga (y) In (1-xy) N (0 ≦ x ≦ 1, 0 ≤ y ≤ 1, 0 ≤ x + y ≤ 1), the light absorption prevention layer is composed of at least one selected from the group consisting of SiO ₂ , SiN, AlO _x , SiON and TiO ₂ , A group III nitride semiconductor light-emitting device having a thickness of 3000 kPa or more and 20000 kPa or less.

According to the group III nitride semiconductor light emitting device according to the present disclosure, since light absorption is reduced due to the light absorption prevention layer under the pad electrode, light extraction efficiency is improved.

In addition, it is possible to further improve the light extraction efficiency by selecting the material and thickness of the light absorption prevention layer suitable for light reflection.

In addition, according to the group III nitride semiconductor light emitting device according to the present disclosure, the light absorption prevention layer may be formed of an insulating material to improve current spreading.

300: group III nitride semiconductor light emitting device 310: substrate
305: light absorption prevention layer 320: buffer layer
330 n-type nitride semiconductor layer 340 active layer
350 p-type nitride semiconductor layer 360 translucent conductive film
370: p-side pad electrode 380: n-side pad electrode

Claims (10)

delete delete delete delete delete Located between the first semiconductor layer having a first conductivity, the second semiconductor layer having a second conductivity different from the first conductivity, and the first semiconductor layer and the second semiconductor layer to generate light through recombination of electrons and holes Active layer;
A transmissive conductive film positioned on the second semiconductor layer;
A first pad electrode positioned on the light transmissive conductive film; And
And a first light absorption prevention layer formed to cover at least a portion of the second semiconductor layer and the first pad electrode by the light transmissive conductive film, and having a lower refractive index than the second semiconductor layer.
A Group 3 nitride semiconductor light emitting device further comprising: a distributed Bragg reflector positioned between the first light absorption preventing layer and the first pad electrode and having a repeatedly stacked TiO ₂ / SiO ₂ layer; . The method of claim 6,
The first semiconductor layer, the active layer and the second semiconductor layer are made of Al (x) Ga (y) In (1-xy) N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). 3, wherein the first light absorption prevention layer is formed of at least one selected from the group consisting of SiO ₂ , SiN, AlO _x , SiON, and TiO ₂ , and the thickness of the first light absorption prevention layer is 3000 kPa or more and 20000 kPa or less. Group nitride semiconductor light emitting device. Located between the first semiconductor layer having a first conductivity, the second semiconductor layer having a second conductivity different from the first conductivity, and the first semiconductor layer and the second semiconductor layer to generate light through recombination of electrons and holes Active layer;
A transmissive conductive film positioned on the second semiconductor layer;
A first pad electrode positioned on the light transmissive conductive film; And
And a first light absorption prevention layer formed to cover at least a portion of the second semiconductor layer and the first pad electrode by the light transmissive conductive film, and having a lower refractive index than the second semiconductor layer.
A second pad electrode on the exposed first semiconductor layer, the second semiconductor layer and the active layer being etched in the form of mesa; and
And a second light absorption preventing layer disposed between the first semiconductor layer and the second pad electrode and having a lower refractive index than the first semiconductor layer. Located between the first semiconductor layer having a first conductivity, the second semiconductor layer having a second conductivity different from the first conductivity, and the first semiconductor layer and the second semiconductor layer to generate light through recombination of electrons and holes Active layer;
A conductive film on the second semiconductor layer;
A first pad electrode positioned on the conductive film;
A second pad electrode on the exposed first semiconductor layer, the second semiconductor layer and the active layer being etched in the form of mesa, and electrically connected to the first semiconductor layer; and
And a light absorption preventing layer having a refractive index lower than that of the first semiconductor layer and positioned between the first semiconductor layer and the second pad electrode. The method according to claim 9,
The conductive film is a reflective conductive film that reflects light, and the first semiconductor layer, the active layer, and the second semiconductor layer are made of Al (x) Ga (y) In (1-xy) N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), wherein the light absorption prevention layer is formed of at least one selected from the group consisting of SiO ₂ , SiN, AlO _x , SiON, and TiO ₂ , and has a thickness of 3000 Å. A group III nitride semiconductor light-emitting device, characterized in that it is 20000 GPa or more.

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