KR100831713B1 - Nitride semiconductor light emitting diode - Google Patents

Abstract

The present invention relates to a nitride semiconductor light emitting diode, comprising: a substrate, an n-type nitride semiconductor layer formed on the substrate, an active layer formed on a portion of the n-type nitride semiconductor layer, a p-type nitride semiconductor layer formed on the active layer; And a p ⁺⁺ type nitride semiconductor layer formed on the p type nitride semiconductor layer, a p type electrode formed on the p ⁺⁺ type nitride semiconductor layer and an n type nitride semiconductor layer on which the active layer is not formed. A nitride-based semiconductor light emitting diode comprising an n-type electrode.

LED, ITO, p-type electrode, ohmic characteristics

Description

Nitride semiconductor light emitting diodes {NITRIDE SEMICONDUCTOR LIGHT EMITTING DIODE}

1 is a cross-sectional view showing the structure of a nitride-based semiconductor light emitting diode according to the prior art.

2 is a cross-sectional view showing the structure of a nitride-based semiconductor light emitting diode according to an embodiment of the present invention.

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

100 substrate 110 buffer layer

120: n-type nitride semiconductor layer 130: active layer

140: p-type nitride semiconductor layer 150: p-type electrode

170: n-type electrode 200: p ⁺⁺ type nitride semiconductor layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride semiconductor light emitting diode, and more particularly to a nitride based semiconductor light emitting diode for improving ohmic characteristics of a p-type electrode made of a transparent oxide material.

In general, a light emitting diode (LED) is used to send and receive an electric signal by converting an electric signal into an infrared, visible or light form using a property of a compound semiconductor called recombination of electrons and holes. It is a semiconductor device.

Usually, the use range of LED is used for home appliances, remote controllers, electronic signs, indicators, various automation devices, optical communications, and the types are largely divided into Infrared Emitting Diode (IRD) and Visible Light Emitting Diode (VLED).

In LEDs, the frequency (or wavelength) of light emitted is a function of the band gap of the material used in the semiconductor device. When using a semiconductor material having a small band gap, low energy and long wavelength photons are generated, and a wide band gap When using a semiconductor material having a photon of a short wavelength is generated. Therefore, the semiconductor material of the device is selected according to the kind of light to be emitted.

For example, AlGaInP materials are used for red LEDs, and silicon carbide (SiC) and group III nitride semiconductors, especially gallium nitride (GaN), are used for blue LEDs. In recent years, nitride semiconductors used as blue light emitting diodes include (Al _x In _{1 -x} ) _y Ga _{1 - y} N (where 0≤x≤1, 0≤y≤1, and 0≤x + y≤1). GaN-based materials with) are widely used.

Next, a nitride based semiconductor LED according to the prior art will be described in detail with reference to FIG. 1.

1 is a cross-sectional view showing the structure of a nitride semiconductor light emitting diode according to the prior art.

As shown in FIG. 1, the nitride-based semiconductor LED according to the related art includes a buffer layer 110 made of GaN, an n-type nitride semiconductor layer 120, and a single quantum well on a sapphire substrate 100, which is a light transmissive substrate. The active layer 130 and the p-type nitride semiconductor layer 140 of a multi-quantum well (MQW) structure containing InGaN or InGaN having an SQW) structure are sequentially stacked.

In addition, since some regions of the p-type nitride semiconductor layer 140 and the active layer 130 are removed by some mesa etching process, a part of the upper surface of the n-type nitride semiconductor layer 120 is exposed. . In addition, an n-type electrode 170 is formed on the exposed n-type nitride semiconductor layer 120, and a p-type electrode made of a transparent oxide material (eg, ITO) is formed on the p-type nitride semiconductor layer 160. The 150 and the p-type bonding electrode 160 are sequentially stacked.

On the other hand, currently commercially available nitride-based semiconductor LED is a white LED that is mixed with a phosphor that emits yellow (yellow) in a blue LED chip based mainly on GaN-based materials. There are two ways to increase the brightness of the white LED, which is to increase the brightness of the blue LED chip or improve the light conversion efficiency of the yellow phosphor.

Therefore, as described above, in order to increase the brightness of the blue LED chip, the p-type electrode 150 is formed of a transparent oxide material instead of a conventional translucent metal material.

However, when the p-type electrode 150 is formed of a transparent oxide-based material, the transmittance of the electrode may be increased to minimize absorption of blue light, thereby improving luminance, but in general, the transparent oxide-based material may be n-type nitride semiconductor and ohmic. As a material for forming a junction, ohmic contact between the p-type electrode 150 and the p-type nitride semiconductor layer 140 is not performed, resulting in high ohmic contact resistance. In particular, in the case of an LED device, an operating voltage V _f ) Is high.

However, as described above, when the operating voltage of the LED device is increased, since the blue-shift of the center wavelength of the LED device is shortened due to the concentration of the current density, there is a problem that the luminous efficiency is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a nitride-based semiconductor LED to implement a high brightness by improving the ohmic characteristics of the p-type electrode made of a transparent oxide (oxide) material.

In order to achieve the above object, the present invention provides a substrate, an n-type nitride semiconductor layer formed on the substrate, an active layer formed on a portion of the n-type nitride semiconductor layer, a p-type nitride semiconductor layer formed on the active layer and And a p ⁺⁺ type nitride semiconductor layer formed on the p type nitride semiconductor layer, a p type electrode formed on the p ⁺⁺ type nitride semiconductor layer and an n type nitride semiconductor layer on which the active layer is not formed. Provided is a nitride-based semiconductor LED comprising an n-type electrode.

In the nitride semiconductor LED of the present invention, the p ⁺⁺ type nitride semiconductor layer is formed of an In _X Al _Y Ga ₁ -X _{- Y} N (0≤X, 0≤Y, X + Y≤1) composition. It is preferred that the p-type conductive impurity is doped in high concentration to have n-type electrical conductivity.

In addition, in the nitride semiconductor LED of the present invention, the p ^{+ +} nitride semiconductor layer, it is preferable that the p-type conductive impurity is doped with a high concentration of 5E20 cm ^-3 or more in order to have an n-type electrical conductivity.

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.

A nitride semiconductor device according to an embodiment of the present invention will now be described in detail with reference to FIG. 2. 2 is a cross-sectional view illustrating a structure of a nitride based semiconductor light emitting diode according to an embodiment of the present invention.

As shown in FIG. 2, a nitride based semiconductor LED according to an embodiment of the present invention includes a substrate 100, a buffer layer 110, an n-type nitride semiconductor layer 120, and an active layer on the substrate 100. 130, the p-type nitride semiconductor layer 140 includes a light emitting structure formed by sequentially stacking.

The substrate 100 is a substrate suitable for growing a nitride semiconductor single crystal, and may be a heterogeneous substrate such as a sapphire substrate and a silicon carbonate (SiC) substrate or a homogeneous substrate such as a nitride substrate.

The buffer layer 110 is a layer for improving lattice matching with the substrate 100 before growing the n-type nitride semiconductor layer 120, and generally includes a nitride including GaN or Ga, for example, SiC / It is formed of InGaN, which can be omitted depending on the characteristics of the device and the process conditions.

The n-type and p-type nitride semiconductor layers 120 and 140 and the active layer 130 have an In _X Al _Y Ga _{1 -X- Y} N composition formula (where 0 ≦ X, 0 ≦ Y, and X + Y ≦ 1). It may be made of a semiconductor material having. More specifically, the n-type nitride semiconductor layer 120 may be formed of a GaN layer or a GaN / AlGaN layer doped with n-type conductivity impurities, for example, Si, Ge, Sn Etc. are used, and preferably Si is mainly used. In addition, the p-type nitride semiconductor layer 140 may be formed of a GaN layer or a GaN / AlGaN layer doped with a p-type conductive impurity, for example, Mg, Zn, Be, etc. It is used, Preferably Mg is mainly used. The active layer 130 may be formed of an InGaN / GaN layer having a multi-quantum well structure.

In particular, in the present invention, the p-type nitride semiconductor layer 140 and the p ^{+ +} nitride semiconductor layer 140 is formed. This is to make an ohmic junction between the p-type electrode made of a transparent oxide-based material and the p-type nitride semiconductor layer 140 which will be described later.

In more detail, the p ⁺⁺ type nitride semiconductor layer 140 is a semiconductor material having an In _X Al _Y Ga _{1 -X- Y} N composition formula (where 0 ≦ X, 0 ≦ Y, and X + Y ≦ 1). And p-type conductive impurities Mg, Zn, Be, and the like have high concentration and n-type characteristics, that is, n-type electrical conductivity. In this embodiment, Mg was used as the p-type conductive impurity, which is doped with 5E20 cm ⁻³ or more to show n-type electrical conductivity.

The p-type electrode 150 is formed on the p ⁺⁺ type nitride semiconductor layer 200. In this case, the p-type electrode 150 is made of a transparent oxide material having a high transmittance with respect to the light emission wavelength of the light emitting device in order to increase the current diffusion effect to improve the brightness, for example, ITO (Indium Tin Oxide), TO (Tin Oxide), Indium Zinc Oxide (IZO), Indium Tin Zinc Oxide (ITZO), Zinc Oxide (ZnO), etc. are used, and preferably ITO is mainly used.

That is, the present invention is the p-type nitride semiconductor layer 140 a in the p-type electrode 150 made of a transparent oxide material and having a p ⁺⁺ type nitride semiconductor layer 200 having n-type conductivity is p The ohmic contact resistance of the p-type electrode 150 may be lowered by contacting the p ^++- type nitride semiconductor layer 200 having the n-type electrical conductivity instead of the p-type nitride semiconductor layer 140 having the conductivity. As such, when the ohmic contact resistance of the p-type electrode 150 is lowered and the ohmic characteristic is improved, the operating voltage of the nitride-based semiconductor LED is lowered, thereby improving the characteristics and reliability of the LED.

The p-type bonding electrode 160 made of Cr / Au or the like is formed on the p-type electrode 150.

A portion of the p ⁺⁺ type and p type nitride semiconductor layers 200 and 140 and the active layer 130 are removed by mesa etching to expose a portion of the n type nitride semiconductor layer 120 on the bottom surface. .

A portion of the n-type nitride semiconductor layer 120 exposed by mesa etching is formed of Cr / Au or the like to form an n-type electrode 170.

Although a preferred embodiment of the present invention has 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 can improve the ohmic characteristics of the p-type electrode by forming a p-type electrode made of a transparent oxide-based material on the p ⁺⁺ type nitride semiconductor layer having n-type electrical conductivity.

As such, the present invention has an advantage of providing a highly reliable nitride-based semiconductor LED by lowering the operating voltage V _f due to the improved ohmic characteristics of the p-type electrode.

Claims (3)

Board; An n-type nitride semiconductor layer formed on the substrate; An active layer formed on a portion of the n-type nitride semiconductor layer; A p-type nitride semiconductor layer formed on the active layer; A p ⁺⁺ type nitride semiconductor layer formed on the p type nitride semiconductor layer; A p-type electrode formed on the p ⁺⁺ type nitride semiconductor layer; And And an n-type electrode formed on the n-type nitride semiconductor layer on which the active layer is not formed. The method of claim 1, The p ⁺⁺ type nitride semiconductor layer is composed of In _X Al _Y Ga _{1 -X- Y} N (0≤X, 0≤Y, X + Y≤1) composition, and the p-type conductive impurity is heavily doped A nitride-based semiconductor light emitting diode having an n-type electrical conductivity. delete

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