KR101013724B1 - Nitride compound light emitting device - Google Patents

Abstract

The present invention relates to a nitride compound light emitting device, in which a buffer layer, an n-type GaN layer, an active layer and a p-type GaN layer are sequentially stacked on a substrate; An In _x Ga _1-x N layer is formed on the p-type GaN layer; Mesa is etched from the In _x Ga _1-x N layer to a portion of the n-type GaN layer; An uneven light extraction layer is formed on a portion of the In _x Ga _1-x N layer; A transparent electrode is formed on the light extracting layer and on the In _x Ga _1-x N layer; A p-type metal layer is formed on the transparent electrode on which the light extraction layer is not formed; An n-type metal layer is formed on the mesa-etched n-type GaN layer.

Accordingly, the present invention forms an In _x Ga _1-x N layer on the p-type GaN layer and a light extraction layer having an uneven shape on the upper portion thereof, whereby light outside the critical angle is trapped inside the device. By reducing the external quantum efficiency can be improved.

Emission, element, light, extraction layer, irregularities, total reflection

Description

 Nitride compound light emitting device

1 is a cross-sectional view of a nitride compound light emitting device according to the prior art

2 is a conceptual view illustrating a phenomenon in which light emitted from a nitride compound light emitting device according to the related art is totally reflected and trapped inside

3 is a cross-sectional view of the nitride compound light emitting device according to the present invention

4a to 4c show planar shapes of openings and protrusions of the light extraction layer according to the invention;

5 is a conceptual diagram showing a state in which light emitted from the nitride compound light emitting device according to the present invention is emitted to the outside by the light extraction layer having an uneven shape.

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

100 substrate 110 buffer layer

120: n-type GaN layer 130: active layer

140: p-type GaN layer 150: In _x Ga _1-x N layer

160: light extraction layer 161: opening

162: protrusion 170: transparent electrode

180: p-type metal layer 190: n-type metal layer                 

201: Stripe 202: Circle

203 polygon

The present invention relates to a nitride compound light emitting device, and more particularly, to form an In _x Ga _1-x N layer on the p-type GaN layer, and to form an uneven light extraction layer (light extraction layer) Accordingly, the present invention relates to a nitride compound light emitting device capable of improving external quantum efficiency by reducing light trapped outside the critical angle inside the device.

Since the group III nitride compound light emitting device has a wide band gap, it is more reliable than the device using other semiconductors, and the light emitting spectrum can be developed in a wide range of light emitting devices from ultraviolet rays to infrared rays.

Recently, the Group III nitride compound semiconductor technology has been applied in many commercial areas.

The group III nitride compound light emitting device is grown by MOCVD, and sapphire, silicon carbide, and the like are used as the substrate.

1 is a cross-sectional view of a nitride compound light emitting device according to the prior art, in which a buffer layer 11, an n-type GaN layer 12, an active layer 13, and a p-type GaN layer 14 are sequentially formed on an sapphire substrate 10. Stacked; Mesa is etched from the p-type GaN layer 14 to a portion of the n-type GaN layer 12; A transparent electrode 15 is formed on the p-type GaN layer 14; A p-type metal layer 16 is formed on the transparent electrode 15; An n-type metal layer 17 is formed on the mesa-etched n-type GaN layer 12.

The transparent electrode 15 on the p-type GaN layer 14 is made by heat-treating a thin metal such as NiAu for diffusion of current and ohmic contact.

However, this transparent electrode 15 is not high transmittance, there is a problem that only a part of the generated light is transmitted through.

In order to solve such a problem, there has been an attempt to use TCO (transparent conductive oxide) having good transmittance as a transparent electrode, but direct adhesion on the p-type GaN layer has a problem that the driving voltage becomes high, so there is little practicality.

Recently, by forming a thin n-type In _x Ga _1-x N layer on the p-type GaN layer, it is possible to lower the driving voltage even when using a TCO-based transparent electrode.

This uses the principle of tunnel junction, which brings some improvement in luminous efficiency.

However, even this case does not transmit all the light.

FIG. 2 is a conceptual diagram illustrating a phenomenon in which light emitted from a nitride compound light emitting device according to the prior art is totally reflected and trapped therein. First, light passing between two media having different refractive indices is reflected and transmitted at an interface thereof. If the angle of incidence is greater than any angle, transmission does not occur and total reflection occurs. The angle is called a critical angle.

When the light emitted from the active layer 13 of the nitride compound light emitting device according to the prior art has an angle greater than or equal to the critical angle and proceeds to the transparent electrode 15 by the total reflection phenomenon, the light is totally reflected at the transparent electrode 15. As a result of being trapped inside the device and being absorbed by the epi layer and the sapphire substrate of the device, the external quantum efficiency of the device is lowered.

In order to solve the problems described above, the present invention forms an In _x Ga _1-x N layer on the p-type GaN layer and a light extraction layer having an uneven shape on the upper portion thereof, thereby providing a critical angle. It is an object of the present invention to provide a nitride-based compound light emitting device capable of improving external quantum efficiency by reducing light trapped inside the device.

According to a preferred aspect of the present invention, a buffer layer, an n-type GaN layer, an active layer and a p-type GaN layer are sequentially stacked on a substrate;

An In _x Ga _1-x N layer is formed on the p-type GaN layer;

Mesa is etched from the In _x Ga _1-x N layer to a portion of the n-type GaN layer;

An uneven light extraction layer is formed on a portion of the In _x Ga _1-x N layer;

A transparent electrode is formed on the light extracting layer and on the In _x Ga _1-x N layer;

A p-type metal layer is formed on the transparent electrode on which the light extraction layer is not formed;

A nitride-based compound light emitting device is characterized in that an n-type metal layer is formed on the mesa-etched n-type GaN layer.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

3 is a cross-sectional view of a nitride compound light emitting device according to the present invention, in which a buffer layer 110, an n-type GaN layer 120, an active layer 130, and a p-type GaN layer 140 are sequentially formed on a substrate 100. Stacked; An In _x Ga _1-x N layer 150 is formed on the p-type GaN layer 140; Mesa is etched from the In _x Ga _1-x N layer 150 to a portion of the n-type GaN layer 120; A light extraction layer 160 having an uneven shape is formed on a portion of the In _x Ga _1-x N layer 150; A transparent electrode 170 is formed on the light extraction layer 160 and on the In _x Ga _1-x N layer 150; A p-type metal layer 180 is formed on the transparent electrode 170 on which the light extraction layer 160 is not formed; An n-type metal layer 190 is formed on the mesa-etched n-type GaN layer 120.

At this time, the substrate 100 is preferably a sapphire substrate.

Here, the light extracting layer 160 is on the top a plurality of apertures (161) film or the In _x Ga _1-x N layer 150 having exposing the In _x Ga _1-x N layer 150 The film may be formed of a plurality of protrusions 162 spaced apart from each other.

In addition, the planar shape of the openings 161 and the protrusions 162 may be a stripe 201, as illustrated in FIG. 4A, or a circle 202, as shown in FIG. 4B, as shown in FIG. It is preferable that it is any one selected from among.

In addition, the light extraction layer 160 may be formed of any one selected from GaN, ITO, ZnO, IZO, AZO, CdO, and MgO, and the refractive index of the light extraction layer 160 may be In _x Ga ₁ It is desirable to be larger than 0.2 times the refractive index of the _-x N layer 150 and smaller than 1.2 times the refractive index of the In _x Ga _1-x N layer.

In addition, the transparent electrode 170 is formed of any one material selected from ITO, ZnO, IZO, AZO, CdO, and MgO of TCO (transparent conductive oxide) series.

On the other hand, as in the prior art, since the driving voltage of the light emitting device is increased when the light extraction layer of the TCO series is formed on the p-type GaN layer 140, In _x Ga on the p-type GaN layer 140 in the present invention _After forming the _1-x N layer 150, the light extraction layer 160 is formed.

5 is a conceptual view showing a state in which light emitted from the nitride compound light emitting device according to the present invention is emitted to the outside by the uneven shape light extraction layer, the light extraction layer is formed in the uneven shape, the angle above the critical angle The light proceeding in the above can be emitted well in the upward direction, and the external quantum efficiency can be improved by improving the light output.

As described above, the present invention forms an In _x Ga _1-x N layer on the p-type GaN layer and a light extraction layer having an uneven shape on the upper portion thereof, thereby preventing light from escaping the critical angle. By reducing the trapped inside the device it is possible to improve the external quantum efficiency.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (6)

A buffer layer, an n-type GaN layer, an active layer and a p-type GaN layer are sequentially stacked on the substrate; An In _x Ga _1-x N layer is formed on the p-type GaN layer; Mesa is etched from the In _x Ga _1-x N layer to a portion of the n-type GaN layer; An uneven light extraction layer is formed on a portion of the In _x Ga _1-x N layer; A transparent electrode is formed on the light extracting layer and on the In _x Ga _1-x N layer; A p-type metal layer is formed on the transparent electrode on which the light extraction layer is not formed; The nitride-based compound light emitting device, characterized in that the n-type metal layer is formed on the mesa-etched n-type GaN layer. The method of claim 1, The light extraction layer And a film including a plurality of openings exposing the In _x Ga _1-x N layer or a plurality of protrusions spaced apart from each other on top of the In _x Ga _1-x N layer. The method of claim 2, The planar shape of the openings and protrusions, Stripe, nitride-based compound light-emitting device, characterized in that any one selected from circles and polygons. 4. The method according to any one of claims 1 to 3, The light extraction layer A nitride compound light emitting device, characterized in that formed of any one selected from GaN, ITO, ZnO, IZO, AZO, CdO and MgO. 4. The method according to any one of claims 1 to 3, The refractive index of the light extraction layer, A nitride-based compound light emitting device, characterized in that greater than 0.2 times the refractive index of the In _x Ga _1-x N layer, and less than 1.2 times the refractive index of the In _x Ga _1-x N layer. 4. The method according to any one of claims 1 to 3, The transparent electrode, A nitride compound light emitting device, characterized in that formed of any one material selected from ITO, ZnO, IZO, AZO, CdO and MgO.

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