KR100687527B1 - Light emitting diode and method for forming thereof - Google Patents

Abstract

A light emitting diode and its fabricating method are provided to relieve concentration of a current on an end of an active layer and an second semiconductor layer by using a conductive pattern as a current diffusion layer. A light emitting structure is formed on a substrate(110) and has a first semiconductor layer(121), an active layer(122), and a second semiconductor layer(123). A portion of the first semiconductor layer is not covered by the active layer and the second semiconductor layer is exposed. A first electrode(141) is positioned on the exposed first semiconductor layer, and a second electrode(143) is positioned on the second semiconductor layer. A first conductive pattern is interposed between the first electrode and the second electrode.

Description

LIGHT EMITTING DIODE AND METHOD FOR FORMING THEREOF

1 is a cross-sectional view of a GaN based light emitting diode according to the prior art.

FIG. 2 is a diagram illustrating the intensity of an electric field according to the position of the light emitting diode of FIG. 1.

3 is a plan view illustrating a light emitting diode according to an exemplary embodiment of the present invention.

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

5A to 5C are diagrams illustrating the intensity of an electric field according to the position of the light emitting diode of FIG. 4.

6 is a plan view illustrating a light emitting diode according to another embodiment of the present invention.

FIG. 7 is a cross-sectional view taken along the line II ′ of FIG. 6.

8A to 8C are diagrams illustrating the intensity of an electric field according to the position of the light emitting diode of FIG. 7.

9 to 12 are cross-sectional views taken along the line II ′ of FIG. 3 to explain the method of forming the light emitting diode of FIG. 3.

FIG. 13 is a cross-sectional view taken along the line II ′ of FIG. 6 to explain the method of forming the light emitting diode of FIG. 6.

14 schematically illustrates the function of a floating guard pattern in accordance with embodiments of the present invention.

The present invention relates to a semiconductor device, and more particularly, to a light emitting diode and a manufacturing method thereof.

In general, a light emitting diode (LED) is a semiconductor device that emits light based on recombination of electrons and holes, and is widely used as a light source of various types in optical communication and electronic devices.

The frequency (or wavelength) of light generated at the light emitting diodes is a function of the band gap of the semiconductor material used. That is, in the small band gap, photons of relatively low energy and long wavelength are generated, and in the large band gap, photons of shorter wavelength are generated. For example, group III nitride semiconductors, in particular gallium nitride (GaN), which are semiconductor materials with relatively large band gaps, produce light having blue or ultraviolet wavelengths. Short wavelength LEDs have the advantage of increasing storage space in optical storage.

GaN generating such short wavelength blue light cannot form a bulk single crystal like other group III nitride semiconductors. Therefore, an appropriate substrate should be used for the growth of GaN crystals. As a substrate for growing such GaN crystals, a sapphire substrate is typical. However, since the sapphire substrate is insulating, the structure of the GaN-based light emitting diode formed on the sapphire substrate is limited.

1 is a cross-sectional view of a GaN based light emitting diode according to the prior art.

Referring to FIG. 1, the light emitting diode includes a sapphire substrate 10 and a light emitting structure 20 formed on the sapphire substrate 10. The light emitting structure 20 includes an n-type GaN layer 21 and an active layer 22 and a p-type GaN layer 23 having a multi-quantum well (MQW) structure sequentially formed on the sapphire substrate 10. It is composed.

A portion of the p-type GaN layer 23 and the active layer 22 is dry etched to expose a portion of the n-type GaN layer 21. The n-type electrode 41 and the p-type electrode 43 are formed on the exposed n-type GaN layer 21 and the p-type GaN layer 23, respectively. In general, a transparent electrode 30 is formed between the p-type GaN layer 23 and the p-type electrode 43 to increase the current injection area but not adversely affect the luminance.

As described above, since the GaN-based light emitting diode uses a sapphire substrate 10 that is an insulating material, two electrodes 41 and 43 are formed on a substantially horizontal surface. Therefore, when voltage is applied, current flow from the p-type electrode 43 toward the n-type electrode 41 through the active layer is inevitably concentrated at the A portion. Due to such a narrow current flow, GaN-based light emitting diodes have a problem in that the forward voltage increases and current efficiency decreases. In addition, the electric field generated between the p-type electrode 43 and the n-type electrode 41 increases rapidly at the A portion.

FIG. 2 is a diagram showing the intensity of an electric field according to the position of the light emitting diode of FIG. 1. In Figure 2, the horizontal axis represents the position in the light emitting diodes, and the vertical axis represents the intensity of the electric field at the position. The position represents a distance from the left side with respect to the left side of the light emitting diode in FIG. 1. Referring to FIG. 2, the intensity of the electric field is rapidly increased to 136 V / cm at the point where the position is 200 μm (that is, the portion A where current flow is concentrated in FIG. 1). As a result, the light emitting diode can be reduced in resistance due to electrostatic discharge.

 As described above, the reliability of the light emitting diode may be degraded due to a decrease in resistance due to electrostatic discharge and a current concentration phenomenon.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a light emitting diode having improved reliability and a method of forming the same.

A light emitting diode according to embodiments of the present invention includes: a first semiconductor layer, an active layer, and a second semiconductor layer positioned on a substrate, wherein a portion of the first semiconductor layer is formed by the active layer and the second semiconductor layer. A light emitting structure exposed without being covered; A first electrode on the exposed first semiconductor layer; A second electrode on the second semiconductor layer; And a first conductive pattern spaced apart from the first electrode and the second electrode on the light emitting structure between the first electrode and the second electrode.

The second electrode may include a transparent electrode in contact with the second semiconductor layer. The first conductive pattern may be located on the first semiconductor layer or on the exposed second semiconductor layer. An insulating pattern may be interposed between the first semiconductor layer or the second semiconductor layer and the first conductive pattern. The first conductive pattern may be made of a metal material. The first conductive pattern may surround the first electrode or the second electrode such that a direction of a current flowing between the first electrode and the second electrode crosses the first conductive pattern. The first semiconductor layer may include a second conductive pattern extending in the direction of the first electrode and the second electrode under the first electrode and the second electrode.

A method of forming a light emitting diode according to embodiments of the present invention includes: a first semiconductor layer, an active layer, and a second semiconductor layer on a substrate, wherein a portion of the first semiconductor layer is formed on the active layer and the second semiconductor layer. Forming a light emitting structure that is not covered by the light emitting structure; Forming a first electrode on the exposed first semiconductor layer, and forming a second electrode on the second semiconductor layer; And forming a first conductive pattern spaced apart from the first electrode and the second electrode on the light emitting structure between the first electrode and the second electrode.

The forming of the second electrode may include forming a transparent electrode in contact with the second semiconductor layer. The first conductive pattern may be formed on the first semiconductor layer or on the exposed second semiconductor layer. The forming of the first conductive pattern may include forming an insulating film on the light emitting structure including the second electrode and the first electrode, forming a conductive film on the insulating film, and forming the conductive film on the insulating film. Patterning the film. The first conductive pattern may be formed of a metal material. The forming of the first semiconductor layer may include forming a lower semiconductor layer on the substrate, and forming a second conductive pattern extending in the directions of the first electrode and the second electrode on the lower semiconductor layer. And forming an upper semiconductor layer covering the second conductive pattern on the lower semiconductor layer.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosure may be made thorough and complete, and to fully convey the spirit of the present invention to those skilled in the art.

Although terms such as first, second, etc. are used herein to describe various elements, the elements should not be limited by such terms. These terms are only used to distinguish the elements from one another. In addition, when it is mentioned that a film is on another film or substrate, it means that it may be formed directly on another film or substrate or a third film may be interposed therebetween. In the drawings, the thickness or the like of the film or regions may be exaggerated for clarity.

(Structure of Light Emitting Diode)

3 is a plan view illustrating a light emitting diode according to an exemplary embodiment of the present invention, and FIG. 4 is a cross-sectional view taken along the line II ′ of FIG. 3.

3 and 4, the light emitting structure 120 is positioned on the substrate 110. The substrate 110 may be a substrate capable of growing a crystal of a nitride semiconductor such as GaN, for example, a sapphire substrate. The light emitting structure 120 may include a first semiconductor layer 121, an active layer 122, and a second semiconductor layer 123. The first semiconductor layer 121 may include n-type GaN, the second semiconductor layer 123 may include p-type GaN, and the active layer 122 may have a multi-quantum well (MQW) structure. Can have A portion of the first semiconductor layer 121 is exposed without being covered by the active layer 122 and the second semiconductor layer 123. A buffer layer (not shown) may be interposed between the substrate 110 and the first semiconductor layer 121 to relieve stress.

The first semiconductor layer 121 may include a lower semiconductor layer 121_1 and an upper semiconductor layer 121_2, and the conductive pattern 125 may be interposed between the lower semiconductor layer 121_1 and the upper semiconductor layer 121_2. Can be. The lower semiconductor layer 121_1 may include undoped or doped GaN. The conductive pattern 125 may function as a spreading layer for diffusing current and may include a material having a lower bandgap than the first semiconductor layer 121. For example, the conductive pattern 125 may include InGaN having a low concentration of In, and the InGaN may be evenly spread after the carrier is confined. The conductive pattern 125 may occupy 10% to 90% of the area of the lower semiconductor layer 121_1. In addition, the conductive pattern 125 may extend in the direction of the first electrode 141 and the second electrode 143 under the first electrode 141 and the second electrode 143. For example, the planar shape of the conductive pattern 125 may be a mesh or a line, and may be variously modified.

The first electrode 141 is positioned on the exposed first semiconductor layer 121, and the transparent electrode 130 and the second electrode 143 are positioned on the second semiconductor layer 123. The first electrode 141 and the second electrode 143 may be n-type electrodes and p-type electrodes, respectively. The first electrode 141 and the second electrode 143 may include a metal material such as Cr / Au, and the transparent electrode 130 may include a transparent conductive material such as Ni / Au or indium tin oxide (ITO). can do.

A floating guard pattern 150 is positioned on the second semiconductor layer 123 between the transparent electrode 130 and the second electrode 143. The floating guard pattern 150 is disposed to be spaced apart from the first and second electrodes 141 and 143 and the transparent electrode 130. In addition, the floating guard pattern 150 is formed so that the direction of the current flowing between the first electrode 141 and the second electrode 143 (or the transparent electrode 130) may intersect the floating guard pattern 150. The first electrode 141 may be surrounded. The floating guard pattern 150 may include an upper conductive pattern 151 and a lower insulating pattern 152. For example, the conductive pattern 151 may be a metal material, and the insulating pattern 152 may be silicon oxide.

14 schematically illustrates the function of a floating guard pattern in accordance with embodiments of the present invention. Referring to FIG. 14, the floating guard pattern 150 may reduce the electric field concentrated at the ends of the active layer 122 and the second semiconductor layer 123 between the first electrode 141 and the second electrode 143. . Thereby, the light emitting diode can enhance resistance by electrostatic discharge. In addition, since the conductive pattern 125 disposed on the first semiconductor layer 121 is used as a current diffusion layer, concentration of current at the ends of the active layer 122 and the second semiconductor layer 123 can be alleviated, External quantum efficiency can be increased by extending the region. In addition, the effect of the floating guard pattern 150, that is, resistance to electrostatic discharge may be further enhanced by the conductive pattern 125.

5A to 5C are diagrams illustrating the intensity of an electric field according to the position of the light emitting diode of FIG. 4. 5A to 5C illustrate a distance Dp between the floating guard pattern 150 and the transparent electrode 130 of 5 μm, 10 μm, and 20 μm, respectively, and the width of the floating guard pattern 150 is 10 μm. The case is shown. 5A to 5C, the horizontal axis represents a position in the light emitting diode, and the vertical axis represents the intensity of the electric field at the position. The position represents a distance from the left side with respect to the left side of the light emitting diode in FIG. 4. Therefore, the position of the left side of the light emitting diode is 0 mu m, and the position of the right side thereof is 320 mu m.

5A to 5C, the electric fields concentrated at the ends of the active layer 122 and the second semiconductor layer 123 between the first electrode 141 and the second electrode 143 are 75, 66, and 57V /, respectively. It is greatly reduced by cm than without the floating guard pattern. In addition, it can be seen that as the distance between the floating guard pattern 150 and the transparent electrode 130 increases, the intensity of the electric field decreases further.

6 is a plan view illustrating a light emitting diode according to another exemplary embodiment of the present invention, and FIG. 7 is a cross-sectional view taken along the line II ′ of FIG. 6.

6 and 7, the floating guard pattern 150 is positioned on the exposed first semiconductor layer 141 unlike the above-described embodiment, but may have the same effect as the above-described embodiment. have.

8A to 8C are diagrams illustrating the intensity of an electric field according to the position of the light emitting diode of FIG. 7. 8A to 8C show that the distance Dn between the floating guard pattern 150 and the transparent electrode 130 is 5 μm, 10 μm, and 20 μm, respectively, and the width of the floating guard pattern 150 is 10 μm in FIG. 7. The case is shown.

8A through 8C, the electric fields concentrated at the ends of the active layer 122 and the second semiconductor layer 123 between the first electrode 141 and the second electrode 143 are 54, 42, and 37V /, respectively. It is greatly reduced by cm than without the floating guard pattern. In addition, it can be seen that as the distance between the floating guard pattern 150 and the transparent electrode 130 increases, the intensity of the electric field decreases further.

(Formation method of light emitting diode)

9 to 12 are cross-sectional views taken along the line II ′ of FIG. 3 to explain the method of forming the light emitting diode of FIG. 3.

9, a light emitting structure 120 is formed on a substrate 110. The substrate 110 may be a substrate capable of growing a crystal of a nitride semiconductor such as GaN, for example, a sapphire substrate. The light emitting structure 120 may include a first semiconductor layer 121, an active layer 122, and a second semiconductor layer 123, and the first semiconductor layer 121 may include a lower semiconductor layer 121_1 and an upper semiconductor layer. It may include (121_2).

First, the lower semiconductor layer 121_1 is formed on the substrate 110. For example, the lower semiconductor layer 121_1 may be formed of undoped or doped GaN by performing an epitaxial process. Before forming the lower semiconductor layer 121_1, a buffer layer (not shown) may be further formed to relieve stress between the substrate 110 and the lower semiconductor layer 121_1. For example, the buffer layer may be formed of AlN.

The conductive pattern 125 is formed on the lower semiconductor layer 121_1. The conductive pattern 125 may be formed of a material having a lower band gap than the first semiconductor layer 121, for example, InGaN including a low concentration of In. The conductive pattern 125 may be formed to occupy 10% to 90% of the area of the lower semiconductor layer 121_1. That is, the conductive pattern 125 may expose 10% to 90% of the area of the lower semiconductor layer 121_1, and the exposed surface of the lower semiconductor layer 121_1 may have a seed layer for growing the upper semiconductor layer 121_2. seed layer). The conductive pattern 125 may be formed to extend in the direction of the first electrode 141 and the second electrode 143 under the first electrode 141 and the second electrode 143. In addition, the conductive pattern 125 may be formed in various forms such as a mesh or a line. Although not shown, an insulating pattern covering the top surface and / or the sidewall of the conductive pattern 125 may be further formed.

An upper semiconductor layer 121_2 is formed on the lower semiconductor layer 121_1 to cover the conductive pattern 125. The upper semiconductor layer 121_2 may be formed of n-type GaN by performing an epitaxial process using the lower semiconductor layer 121_1 exposed by the conductive pattern 125 as a seed layer.

The active layer 122 and the second semiconductor layer 123 are sequentially formed on the lower semiconductor layer 121_1. The active layer 122 may be formed of a material having a multi-quantum well (MQW) structure. For example, the active layer 122 may be formed to include an InGaN film or an InGaN film doped with zinc or silicon. The upper semiconductor layer 123 may be formed of, for example, p-type GaN.

The first semiconductor layer 121, the active layer 122, and the second semiconductor layer 123 including the lower semiconductor layer 121_1 and the upper semiconductor layer 121_2 are respectively grown in liquid phase growth (LPE) and vapor phases. Epitaxial techniques such as vapor phase epitaxy (VPE), metal organic chemical vapor deposition (MOCVD), and molecular beam epitaxy (MBE).

Referring to FIG. 10, the active layer 122 and the second semiconductor layer 123 are patterned to expose the first semiconductor layer 121. In this case, the upper semiconductor layer 121_2 of the first semiconductor layer 121 may also be patterned to reduce its thickness.

Referring to FIG. 11, a first electrode 141 is formed on the exposed first semiconductor layer 121, and a transparent electrode 130 and a second electrode 143 are formed on the second semiconductor layer 123. do. The first and second electrodes 141 and 143 may be formed of a metal material. For example, the first and second electrodes 141 and 143 may be formed of a Cr / Au film. The transparent electrode 130 may be formed of a transparent conductive material such as Ni / Au or indium tin oxide (ITO).

Referring to FIG. 12, a floating gaurd pattern 150 is formed on the second semiconductor layer 123 between the transparent electrode 130 and the second electrode 143. The floating guard pattern 150 may be formed by forming an insulating film and a conductive film on the light emitting structure 120 and then patterning the floating guard pattern 150. Accordingly, the floating guard pattern 150 may include an upper conductive pattern 151 and a lower insulating pattern 152. In addition, the floating guard pattern 150 may be formed to be spaced apart from the first and second electrodes 141 and 143 and the transparent electrode 130 and to surround the first electrode 141. For example, the conductive layer may be formed of a metal material, and the insulating layer 152 may be formed of silicon oxide.

FIG. 13 is a cross-sectional view taken along the line II ′ of FIG. 6 to explain the method of forming the light emitting diode of FIG. 6. 9 to 11 in the above-described embodiment may be equally applicable to this embodiment. Referring to FIG. 13, in the present exemplary embodiment, the floating guard pattern 150 may be formed on the exposed first semiconductor layer 141, unlike the above-described exemplary embodiment. Alternatively, the floating guard pattern 150 may be formed on both the first semiconductor layer 121 and the second semiconductor layer 123.

Accordingly, one or more floating guard patterns 150 may be formed at appropriately selected positions in consideration of the degree of integration, luminous efficiency, resistance to electrostatic discharge, and current spreading.

So far, specific embodiments of the present invention have been described. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

According to embodiments of the present invention, the light emitting diodes can enhance resistance to electrostatic discharge and can prevent current concentration. Therefore, the reliability of the light emitting diode is improved.

Claims (15)

A light emitting structure including a first semiconductor layer, an active layer, and a second semiconductor layer on the substrate, wherein a portion of the first semiconductor layer is exposed without being covered by the active layer and the second semiconductor layer; A first electrode on the exposed first semiconductor layer; A second electrode on the second semiconductor layer; And And a first conductive pattern spaced apart from the first electrode and the second electrode on the light emitting structure between the first electrode and the second electrode. The method of claim 1, The second electrode includes a transparent electrode in contact with the second semiconductor layer. The method of claim 1, The first conductive pattern is a light emitting diode on the first semiconductor layer. The method of claim 1, The first conductive pattern is on the exposed second semiconductor layer. The method according to claim 3 or 4, A light emitting diode in which an insulating pattern is interposed between the first semiconductor layer or the second semiconductor layer and the first conductive pattern. The method of claim 1, The first conductive pattern is a light emitting diode made of a metal material. The method of claim 1, The first conductive pattern surrounds the first electrode or the second electrode such that a direction of a current flowing between the first electrode and the second electrode crosses the first conductive pattern. The method of claim 1, The first semiconductor layer includes a second conductive pattern extending in the direction of the first electrode and the second electrode under the first electrode and the second electrode. Forming a light emitting structure including a first semiconductor layer, an active layer, and a second semiconductor layer on a substrate, wherein a portion of the first semiconductor layer is exposed without being covered by the active layer and the second semiconductor layer; Forming a first electrode on the exposed first semiconductor layer, and forming a second electrode on the second semiconductor layer; And Forming a first conductive pattern on the light emitting structure between the first electrode and the second electrode, the first conductive pattern being spaced apart from the first electrode and the second electrode. The method of claim 9, The forming of the second electrode includes forming a transparent electrode in contact with the second semiconductor layer. The method of claim 9, And the first conductive pattern is formed on the first semiconductor layer. The method of claim 9, The first conductive pattern is formed on the exposed second semiconductor layer. The method of claim 9, Forming the first conductive pattern, Forming an insulating film on the light emitting structure including the first electrode and the second electrode; Forming a conductive film on the insulating film; And And patterning the insulating film and the conductive film. The method of claim 9, The first conductive pattern is a method of forming a light emitting diode formed of a metal material. The method of claim 9, Forming the first semiconductor layer, Forming a lower semiconductor layer on the substrate; Forming a second conductive pattern extending in the direction of the first electrode and the second electrode on the lower semiconductor layer; And Forming an upper semiconductor layer covering the second conductive pattern on the lower semiconductor layer.

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