KR100706949B1 - High brightness nitride semiconductor light emitting device - Google Patents

Abstract

The present invention relates to a high brightness nitride-based semiconductor light emitting device, comprising: an n-type nitride semiconductor layer formed on a substrate, an active layer formed in a predetermined region on the n-type nitride semiconductor layer, a p-type nitride semiconductor layer formed on the active layer, A p-type electrode formed on the p-type nitride semiconductor layer, a p-type bonding metal formed on the p-type electrode, an n-type nitride semiconductor layer on which the active layer is not formed, and a current diffusion layer made of TCO; It provides a high brightness nitride-based semiconductor light emitting device comprising an n-type electrode formed on the current diffusion layer.

Nitride system, light emitting device, current diffusion, light emitting area, TCO, high brightness

Description

High Brightness Nitride Semiconductor Light Emitting Device {HIGH BRIGHTNESS NITRIDE SEMICONDUCTOR LIGHT EMITTING DEVICE}

1 is a plan view showing the structure of a horizontal type nitride semiconductor light emitting device according to the prior art.

FIG. 2 is a cross-sectional view taken along line II-II ′ of FIG. 1. FIG.

3 is a plan view showing the structure of a vertical nitride-based semiconductor light emitting device according to the prior art.

4 is a cross-sectional view taken along line IV-IV ′ of FIG. 3.

5 is a plan view showing the structure of a high-brightness nitride-based semiconductor light emitting device according to a first embodiment of the present invention.

6 is a cross-sectional view taken along the line VI-VI 'of FIG. 5.

7 is a plan view showing a high brightness nitride-based semiconductor light emitting device according to a second embodiment of the present invention.

8 is a cross-sectional view taken along the line VII-VII 'of FIG. 7.

9 is a plan view showing a high luminance nitride-based semiconductor light emitting device according to a first modification of the second embodiment.

10 is a plan view showing a high brightness nitride-based semiconductor light emitting device according to a second modification of the second embodiment.

<Explanation of symbols for the main parts of the drawings>

110 substrate 120 n-type nitride semiconductor layer

130: active layer 140: p-type nitride semiconductor layer

150: p-type electrode 160: p-type bonding metal

170: n-type electrode 180, 190, 220: current diffusion layer

210: structural support layer

The present invention relates to a nitride-based semiconductor light emitting device, and more particularly to a nitride-based semiconductor light emitting device to maximize the light emitting area, improve the current diffusion effect to ensure a high luminous efficiency.

In general, nitride semiconductors are actively employed in optical devices for generating short wavelength light such as blue or green as materials having relatively high energy band gaps (for example, about 3.4 eV in GaN semiconductors). As the nitride semiconductor, a material having an Al _x In _y Ga _(1-xy) N composition formula (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1) is widely used.

However, since the nitride semiconductor has a relatively large energy band gap, it is difficult to form an ohmic contact with the electrode. In particular, since the n-type nitride semiconductor layer has a larger energy band gap, the contact resistance is increased at the contact portion with the n-type electrode, which causes a problem that the operating voltage of the device is increased and the heat generation amount is increased.

Accordingly, in order to prevent the nitride-based semiconductor light emitting device from increasing the operating voltage of the device due to the high energy band gap of the n-type nitride semiconductor layer, various researches have recently been conducted.

Such nitride-based semiconductor light emitting devices are classified into horizontally structured light emitting diodes and vertically structured light emitting diodes.

Next, a nitride based semiconductor light emitting device according to the related art will be described in detail with reference to the accompanying drawings.

First, a horizontal nitride semiconductor light emitting device among the nitride semiconductor light emitting devices according to the related art will be described with reference to FIGS. 1 and 2.

1 is a plan view showing the structure of a horizontal nitride semiconductor light emitting device according to the prior art, Figure 2 is a cross-sectional view taken along the line II-II 'of FIG.

As shown in FIGS. 1 and 2, the horizontal nitride semiconductor light emitting device 100 according to the related art includes an n-type nitride semiconductor layer 120 sequentially formed on a sapphire substrate 110 and GaN having a multi-well structure. / InGaN active layer 130 and a p-type nitride semiconductor layer 140, the p-type nitride semiconductor layer 140 and GaN / InGaN active layer 130 is a partial region of the portion by the etching (mesa etching) process. As a result, the upper portion of the n-type nitride semiconductor layer 120 is exposed.

The n-type electrode 170 made of Au / Cr is formed on the n-type nitride semiconductor layer 120, and the p-type electrode 150 made of ITO and Au / Cr are formed on the p-type nitride semiconductor layer 140. A p-type bonding metal 160 is formed.

Since the n-type nitride semiconductor layer 120 has a larger energy band gap, when the n-type electrode 170 is in contact with the n-type electrode 170, the contact resistance is increased, thereby increasing the operating voltage of the device and increasing the amount of heat generated. have.

Accordingly, as shown in FIG. 1, the n-type nitride semiconductor layer 120 on which the n-type electrode 170 is not formed among the n-type nitride semiconductor layers 120 exposed by some etching is formed. A current diffusion layer 190 made of Au / Cr is provided to increase the current diffusion effect of the n-type nitride semiconductor layer 120 to reduce the operating voltage of the device.

However, the current diffusion layer 190 as described above has the advantage of reducing the operating voltage of the device by increasing the current diffusion effect of the n-type nitride semiconductor layer 120, but because of the Au / Cr part of the light emitted from the active layer There is a problem of lowering the overall luminous efficiency of the device by absorbing.

Next, a vertical nitride semiconductor light emitting device according to the related art will be described with reference to FIGS. 3 and 4.

3 is a plan view showing the structure of a vertical nitride semiconductor light emitting device according to the prior art, Figure 4 is a cross-sectional view taken along the line IV-IV 'of FIG.

3 and 4, the vertical nitride semiconductor light emitting device 200 according to the related art has an n-type electrode 170 and an n-type nitride semiconductor formed on the bottom surface of the n-type electrode 170. The layer 120, the active layer 130 formed on the bottom surface of the n-type nitride semiconductor layer 120, the p-type nitride semiconductor layer 140 formed on the bottom surface of the active layer 130, and the p-type nitride. The p-type electrode 150 is formed on the lower surface of the semiconductor layer 140 and the structural support layer 210 formed on the lower surface of the p-type electrode 150.

However, since the n-type nitride semiconductor light emitting device 120 also has a high energy band gap, the contact resistance increases when the n-type electrode 170 contacts the n-type electrode 170, thereby operating the device. There is a problem in that the heat generation increases the voltage increases.

Accordingly, as shown in FIG. 2, the n-type nitride semiconductor layer 120 further includes a transparent electrode layer 180 made of ITO between the n-type nitride semiconductor layer 120 and the n-type electrode 160. The operating voltage of the device was reduced by increasing the current diffusion effect of the device.

On the other hand, the light emitting device (LED) using the conventional nitride-based semiconductor as described above has a low external quantum efficiency (efficiency of the light extracted from the LED of the current put into the LED), resulting in a power conversion efficiency (input) compared to the fluorescent lamp Among the powers, there is a problem that the efficiency of extractable light output) is low.

Accordingly, there is a continuous demand for development of a light emitting device related technology capable of further improving external light emitting efficiency and quantum efficiency of the light emitting device.

Accordingly, an object of the present invention is to maximize the light emitting area, improve the current diffusion effect to lower the operating voltage in order to solve the above problems, the nitride-based semiconductor light emitting device that can improve the external light emission efficiency and quantum efficiency To provide.

In order to achieve the above object, the present invention provides an n-type nitride semiconductor layer formed on a substrate, an active layer formed in a predetermined region on the n-type nitride semiconductor layer, a p-type nitride semiconductor layer formed on the active layer, and the p A p-type electrode formed on the type nitride semiconductor layer, a p-type bonding metal formed on the p-type electrode, and an n-type nitride semiconductor layer on which the active layer is not formed, and a current diffusion layer made of TCO and the current A high brightness nitride-based semiconductor light emitting device including an n-type electrode formed on a diffusion layer is provided.

In addition, in the high brightness nitride-based semiconductor light emitting device of the present invention, the TCO, preferably having a sheet resistance and specific resistance lower than or equal to ITO, which is selected from the group consisting of tin, zinc, silver, magnesium, copper and aluminum It consists of a mixture formed by adding the above elements to indium oxide. At this time, the addition element is preferably added in an amount of 1 to 20% by weight based on the weight of the entire mixture.

In the high brightness nitride-based semiconductor light emitting device of the present invention, the current spreading layer preferably has a thickness of 800 to 8000 800.

Further, in the high brightness nitride semiconductor light emitting device of the present invention, it is preferable to further include an adhesive layer at the interface between the n-type nitride semiconductor layer and the current diffusion layer.

In addition, in the high brightness nitride-based semiconductor light emitting device of the present invention, the adhesive layer is made of transparent Ni / Au, or by adding one or more elements selected from the group consisting of tin, zinc, silver, magnesium, copper and aluminum to indium oxide It is made of a mixture formed, and made by varying the element added with the TCO, or a mixture formed by adding one or more elements selected from the group consisting of tin, zinc, silver, magnesium, copper and aluminum to the indium oxide, It is preferable to make it by changing the addition amount of TCO and the element to add.

In addition, in the high brightness nitride-based semiconductor light emitting device of the present invention, since the adhesive layer decreases as the thickness increases, the adhesive layer preferably has a thickness of 1 to 200 kPa.

In addition, in the high brightness nitride-based semiconductor light emitting device of the present invention, it is preferable to further include a reflective electrode at the interface between the current diffusion layer and the n-type electrode.

In order to achieve the above object, the present invention comprises an n-type electrode, a TCO, a first current spreading layer having a predetermined shape extending outwardly about the n-type electrode in contact with the n-type electrode, and ITO. A second current spreading layer formed on the bottom surface of the first current spreading layer, an n-type nitride semiconductor layer on the bottom surface of the second current spreading layer, an active layer formed on the bottom surface of the n-type nitride semiconductor layer, and a p-type formed on the bottom surface of the active layer A high brightness nitride-based semiconductor light emitting device comprising a nitride semiconductor layer, a p-type electrode formed on the bottom surface of the p-type nitride semiconductor layer, and a structure support layer formed on the bottom surface of the p-type electrode.

In the high brightness nitride-based semiconductor light emitting device of the present invention, a reflection electrode is further included at an interface between the n-type electrode and the second current spreading layer, and at the interface between the first current spreading layer and the second current spreading layer. It is preferable to further include an adhesive layer.

In the high brightness nitride-based semiconductor light emitting device of the present invention, the first current spreading layer preferably has a thickness of 800 to 8000 Å.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like reference numerals designate like parts throughout the specification.

Now, a high brightness nitride-based semiconductor light emitting device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[ Example  One]

First, the high brightness nitride-based semiconductor light emitting device according to the first embodiment of the present invention will be described in detail with reference to FIGS. 5 and 6.

FIG. 5 is a plan view showing the structure of a high-brightness nitride semiconductor light emitting device according to a first exemplary embodiment of the present invention, and FIG. 6 is a cross-sectional view taken along the line VI-VI 'of FIG. 5.

5 and 6, the high brightness nitride-based semiconductor light emitting device 100 according to the first embodiment of the present invention may include a buffer layer (not shown) and an n-type nitride semiconductor layer (not shown) on the substrate 110. 120, the active layer 130 and the p-type nitride semiconductor layer 140 are sequentially stacked.

The substrate 110 is preferably formed using a transparent material including sapphire. In addition to sapphire, the substrate 110 may be formed of zinc oxide (ZnO), gallium nitride (GaN), silicon carbide (SiC), and aluminum nitride (AlN).

The buffer layer (not shown) is formed of GaN and may be omitted.

The n-type or p-type nitride semiconductor layers 120 and 140 are formed of GaN layers or GaN / AlGaN layers doped with conductive impurity, respectively, and the active layer 130 is composed of a multi-well structure composed of InGaN / GaN layers. Quantum Well).

Meanwhile, the active layer 130 may be formed of one quantum well layer or a double hetero structure. In addition, the active layer 130 determines whether the diode is a green light emitting device or a blue light emitting device by the amount of indium (In) constituting it. More specifically, about 22% of indium is used for light emitting devices having blue light, and about 40% of indium is used for light emitting devices having green light. That is, the amount of indium used to form the active layer 130 varies depending on the required blue or green wavelength.

A portion of the active layer 130 and the p-type nitride semiconductor layer 140 are removed by mesa etching, exposing a portion of the n-type nitride semiconductor layer 120 on the bottom.

The p-type electrode 150 made of ITO is formed on the p-type nitride semiconductor layer 140. In this case, the p-type electrode 150 may be formed not only of a conductive metal oxide such as indium tin oxide (ITO) but also a metal thin film having high conductivity and low contact resistance if the transmittance of the light emitting device is high. have.

A p-type bonding electrode 160 made of Cr / Au or the like is formed on the p-type electrode 150, and a reflection role and an electrode role are formed on a predetermined portion of the n-type nitride semiconductor layer 120 exposed by the mesa etching. An n-type electrode 170 is formed at the same time. Here, the n-type electrode 170 is made of Cr / Au.

However, as described above, when the n-type electrode 170 is in contact with the n-type nitride semiconductor layer 120, due to the high energy band gap of the n-type nitride semiconductor layer 120, the contact resistance is high, thereby There was a problem that the heat generation amount of the device increases as the operating voltage increases.

Accordingly, in order to solve the above problem, the present invention provides a current diffusion layer 190 made of transparent conducting oxide (TCO) on the n-type nitride semiconductor layer 120 where the n-type electrode 170 is not formed. Equipped. In this case, when the thickness of the current diffusion layer 190 has a thickness of about 800 mA or less, it is difficult to obtain a sufficient current diffusion effect, and when the thickness of the current diffusion layer 190 is about 8000 mA or more, the light transmittance is lowered. Do.

In addition, the TCO constituting the current spreading layer 190 is a transparent layer, it is preferable to have a sheet resistance and resistivity lower than or equal to ITO in order to maximize the current spreading effect.

Therefore, TCO according to the present embodiment is selected from the group consisting of tin (Sn), zinc (Zn), silver (Ag), magnesium (Mg), copper (Cu), and aluminum (Al) in indium oxide. A mixture formed by adding one or more elements is used. On the other hand, the addition element is added in an amount of substantially 1 to 20% by weight based on the total weight of the mixture because there is a problem that can lower the flow of current if more than 20% by weight is added It is preferable.

That is, since the current spreading layer 190 according to the present embodiment is made of transparent TCO, the current spreading layer 190 has the same or more current spreading effect as compared to the current spreading layer made of Au / Cr according to the prior art, thereby reducing the operating voltage. At the same time, the light emitting area of the device may be maximized to maximize external quantum efficiency and light emitting efficiency.

In the present embodiment, the n-type nitride semiconductor layer 120 and the current diffusion layer further include an adhesive layer (not shown) at an interface between the n-type nitride semiconductor layer 120 and the current diffusion layer 190. The adhesive force of 190 is being firm. Here, since the transmittance decreases when the thickness increases to 200 kPa or more, it is preferable to have a thickness of 1 to 200 kPa.

On the other hand, the adhesive layer (not shown) may be formed of transparent Ni / Au, or the composition and combination of the TCO constituting the current spreading layer 190 and the added elements may be formed of different TCO. In this case, the TCO constituting the current spreading layer 190 and the TCO having a different composition and combination of added elements are more specifically, at least one element selected from the group consisting of tin, zinc, silver, magnesium, copper, and aluminum in indium oxide. It consists of a mixture formed by the addition of the TCO and in addition to the TCO and indium oxide different from the element to be added to the mixture formed of one or more elements selected from the group consisting of tin, zinc, silver, magnesium, copper and aluminum And TCO which changed the addition amount of the said TCO and the element added. For example, when TCO constituting the current diffusion layer 190 is added to indium oxide, the adhesive layer is formed of TCO added with zinc to indium oxide, and the TCO constituting the current diffusion layer 190 is indium oxide. When 5 wt% tin is added to the adhesive layer, the adhesive layer is formed of TCO in which 9 wt% tin is added to indium oxide.

In addition, the present embodiment may further include a reflective electrode (not shown) at the interface between the current diffusion layer 190 and the n-type electrode 170 to obtain a high brightness. On the other hand, the n-type electrode 170 can be omitted when the role can be sufficiently reflected.

[ Example  2]

Next, the high brightness nitride-based semiconductor light emitting device according to the second embodiment of the present invention will be described in detail with reference to FIGS. 7 and 8.

As shown in FIGS. 7 and 8, the n-type electrode 170 made of Cr / Au or the like is formed on the top of the high-brightness nitride-based semiconductor light emitting device 200 according to the second embodiment of the present invention.

An n-type gallium nitride layer 120 is formed on the bottom surface of the n-type electrode 170.

Meanwhile, in the present exemplary embodiment, first and second electrodes are disposed at one side of the n-type electrode 170 and the interface between the n-type electrode 170 and the n-type gallium nitride layer 120 to maximize the current diffusion efficiency of the device. Current diffusion layers 220 and 180 are formed. In this case, the second current spreading layer 180 is made of transparent ITO, and the first current spreading layer 220 is made of TCO having a sheet resistance and specific resistance lower than or equal to ITO.

Therefore, TCO, which is the first current spreading layer 220 according to the present embodiment, includes tin (Sn), zinc (Zn), silver (Ag), magnesium (Mg), copper (Cu), and aluminum in indium oxide. A mixture formed by adding one or more elements selected from the group consisting of (Al) is used. On the other hand, the addition element is added in an amount of substantially 1 to 20% by weight based on the total weight of the mixture because there is a problem that can lower the flow of current if more than 20% by weight is added It is preferable.

In addition, when the thickness of the first current spreading layer 220 has a thickness of about 800 mA or less, it is difficult to sufficiently obtain a current diffusion effect, and when the thickness of the first current spreading layer 220 has a thickness of about 8000 mA or more, the light transmittance is lowered. It is preferable.

That is, since the second current spreading layer 220 according to the present embodiment has a sheet resistance and specific resistance lower than or equal to ITO, the second current spreading layer 220 includes only the first current spreading layer 220 made of conventional ITO. Compared with this, an improved current spreading effect can be obtained, and therefore, external quantum efficiency and luminous efficiency can also be maximized.

Meanwhile, as illustrated in FIGS. 9 and 10, the first current spreading layer 220 includes not only a straight line (refer to FIG. 7) extending around the n-type electrode but also a straight line having a bent portion and a straight line having a cross shape. It is possible. That is, it is possible to have various types of lines depending on the characteristics of the device and the process conditions. In addition, in the embodiment of the present invention, the end side shape of the line is shown as a rectangle, but this is not limited to the rectangle can be implemented in various shapes such as hemispherical or triangular.

9 is a plan view illustrating a high brightness nitride semiconductor light emitting device according to the first modified example of the second embodiment, and FIG. 10 is a plan view illustrating a high brightness nitride semiconductor light emitting device according to the second modified example of the second embodiment.

In addition, in the present exemplary embodiment, a reflective electrode (not shown) may be further included at an interface between the n-type electrode 170 and the second current spreading layer 180 to obtain high luminance. On the other hand, the n-type electrode 170 can be omitted when the role can be sufficiently reflected.

In the present embodiment, the first current spreading layer 220 and the second further include an adhesive layer (not shown) at an interface between the first current spreading layer 220 and the second current spreading layer 180. The adhesive force of the current spreading layer 180 is firm. Here, the adhesive layer also, as in the adhesive layer according to the first embodiment, since the transmittance decreases when the thickness increases to 200 kPa or more, it is preferable to have a thickness of 1 to 200 kPa.

On the other hand, the adhesive layer (not shown) may be formed of transparent Ni / Au, or the composition and combination of the TCO constituting the first and second current spreading layers (220, 180) and the added elements may be formed of other TCO. have. For example, in the case where TCO is added to indium oxide in the first current spreading layer 220 and TCO forming the second current spreading layer 180 is added to zinc indium oxide, the adhesive layer is formed on indium oxide. Manganese is formed with added TCO.

The active layer 130 and the p-type nitride semiconductor layer 140 are sequentially stacked on the bottom surface of the n-type nitride semiconductor layer 120.

The n-type or p-type nitride semiconductor layers 120 and 140 may be GaN layers or GaN / AlGaN layers doped with a conductive impurity, and the active layer 130 may be a multi-well structure composed of InGaN / GaN layers. Well).

The p-type electrode 120 is formed on the bottom surface of the p-type nitride semiconductor layer 140. Although not shown, the p-type gallium nitride layer 140 may have a structure in which a p-type electrode 160 and a reflective film (not shown) are sequentially stacked downward, and as in the present embodiment, a reflective film When not provided, the p-type electrode 160 serves as a reflective film.

The structural support layer 210 is bonded to the lower surface of the p-type electrode 160 by a conductive bonding layer (not shown). In this case, the structural support layer 210 serves as a supporting layer and an electrode of the final LED element, and is made of a silicon (Si) substrate, a GaAs substrate, a Ge substrate, or a metal layer. The metal layer may be formed by electrolytic plating, electroless plating, thermal evaporator, e-beam evaporator, sputter, chemical vapor deposition (CVD), or the like.

Although the preferred embodiments of the present invention have been described in detail above, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Accordingly, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

As described above, the present invention increases the light emitting area of the n-type electrode side by using a TCO having a sheet resistance and specific resistance lower than or equal to ITO to maximize the overall light emitting area of the device, and improves the current diffusion efficiency to increase the driving voltage. Minimization may improve external quantum efficiency and luminous efficiency.

Therefore, the present invention has the effect of improving the characteristics and reliability of the high brightness nitride-based semiconductor light emitting device.

Claims (22)

delete delete delete delete delete delete delete delete delete delete delete n-type electrode; A first current spreading layer formed of a TCO, the first current spreading layer having a predetermined shape extending outwardly from the n-type electrode in contact with the n-type electrode; A second current spreading layer formed of ITO and formed on a lower surface of the first current spreading layer; An n-type nitride semiconductor layer on a lower surface of the second current spreading layer; An active layer formed on a bottom surface of the n-type nitride semiconductor layer; A p-type nitride semiconductor layer formed on the lower surface of the active layer; A p-type electrode formed on the lower surface of the p-type nitride semiconductor layer; And A high brightness nitride-based semiconductor light emitting device comprising a structure support layer formed on the lower surface of the p-type electrode. The method of claim 12, And a reflective electrode at an interface between the n-type electrode and the second current spreading layer. The method of claim 12, The TCO is a high brightness nitride-based semiconductor light emitting device, characterized in that it has a sheet resistance and specific resistance lower than or equal to ITO. The method of claim 14, The TCO is a high brightness nitride-based semiconductor light emitting device, characterized in that the mixture formed by adding at least one element selected from the group consisting of tin, zinc, silver, magnesium, copper and aluminum to indium oxide. The method of claim 15, The addition element is a high brightness nitride-based semiconductor light emitting device, characterized in that added in an amount of 1 to 20% by weight based on the weight of the entire mixture. The method of claim 12, The first current spreading layer has a thickness of 800 to 8000 Å, high brightness nitride-based semiconductor light emitting device. The method of claim 12, The high brightness nitride-based semiconductor light-emitting device of claim 1, further comprising an adhesive layer on the interface between the first current diffusion layer and the second current diffusion layer. The method of claim 18, The adhesive layer is a high brightness nitride-based semiconductor light emitting device, characterized in that made of transparent Ni / Au. The method of claim 18, The adhesive layer is made of a mixture formed by adding one or more elements selected from the group consisting of tin, zinc, silver, magnesium, copper, and aluminum to indium oxide, and has a high brightness, characterized in that the TCO and the added elements are different. Nitride semiconductor light emitting device. The method of claim 18, The adhesive layer is made of a mixture formed by adding at least one element selected from the group consisting of tin, zinc, silver, magnesium, copper, and aluminum to indium oxide, wherein the amount of TCO and the added element is different. A high brightness nitride-based semiconductor light emitting device. The method of claim 18, The adhesive layer has a thickness of 1 to 200 GPa, high brightness nitride-based semiconductor light emitting device.

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