KR101747732B1 - Light emitting device - Google Patents

Abstract

The present invention relates to a light emitting device capable of lowering current density, comprising: a substrate; A photoelectric layer including a first semiconductor layer, an active layer, and a second semiconductor layer which are sequentially stacked on the substrate; An ohmic contact layer formed on the second semiconductor layer with a transparent conductive material; A first electrode pad formed on a portion of the first semiconductor layer exposed by removing the ohmic contact layer, the second semiconductor layer, and a part of the active layer; At least one first electrode extending from the first electrode pad on a partial region of the first semiconductor layer and having a cross-sectional area gradually increasing as the length extending from the first electrode pad is increased; A second electrode pad formed on the ohmic contact layer; And a second electrode pad formed on the ohmic contact layer and extending from the second electrode pad so as to alternate with the at least one first electrode and having a cross sectional area gradually increasing as the length extending from the second electrode pad is increased, And two electrodes.

Description

[0001] LIGHT EMITTING DEVICE [0002]

The present invention relates to a light emitting device, and more particularly to a light emitting device including a photoelectric layer made of a nitride semiconductor.

A light emitting device (LED) is a type of photoelectric device including a photoelectric layer including a plurality of p-n junction semiconductor layers, and is an element that converts electric energy into light energy to emit light.

Such a light emitting device is advantageous in that it can emit light of a high luminance at a low voltage and has a high energy efficiency as compared with other devices that emit light. In particular, a light emitting device in which a photoelectric layer is formed of a gallium nitride (GaN) based nitride semiconductor can emit light in a wide wavelength range including infrared rays or infrared rays. Accordingly, the light emitting device can be applied to various automation devices such as a backlight unit of a liquid crystal display device, an electric sign board, a display device, a home appliance, and the like, and can be applied to various environmentally harmful substances such as arsenic (As) It is popular as a next generation light source.

Generally, the light emitting element includes a photoelectric layer comprising a plurality of semiconductor layers including an n-type semiconductor layer, an active layer and a p-type semiconductor layer, a first electrode for injecting electrons into the n- type semiconductor layer, A second electrode for injecting holes into the p-type semiconductor layer; and a second electrode pad connecting the second electrode and the outside.

When a forward voltage is applied between the first electrode and the second electrode, holes and electrons injected through the first electrode and the second electrode in the photoelectric layer are recombined to generate an exciton And the excitons at this time emit extra energy as light comes to the base state from the excited state.

However, holes and electrons have a tendency to move along the path of minimum resistance, and a phenomenon (hereinafter referred to as "current densification phenomenon ") in which current is concentrated in the shortest distance region between the first electrode and the second electrode is generated . In particular, the resistance of each of the first electrode and the second electrode gradually increases in proportion to the increased length as the distance from the first electrode pad and the second electrode pad increases. Accordingly, a large amount of electrons and holes are diffused and concentrated in the region adjacent to the first electrode pad and the second electrode pad in the photoelectric layer, and a first electrode pad and a second electrode pad are formed in a region spaced apart from the first electrode pad and the second electrode pad, A very small amount of electrons and holes are diffused as compared with the region adjacent to the second electrode pad. That is, current confluence is intensified by the resistances of the first electrode and the second electrode.

Due to such a current confluence phenomenon, the charge (here, "charge" refers to a positive charge and a negative charge carried by each of holes and electrons) does not spread widely within the photoelectric layer, (Hereinafter referred to as "luminous efficiency") at which the charges injected from the outside are converted into light is lowered.

As described above, electric charges accumulated in some regions are converted into heat energy, and heat of high temperature is generated in the device, so that there is a problem that deterioration leads to decrease in the life of the device and deterioration of reliability.

The present invention is to provide a light emitting device capable of improving the luminous efficiency by lowering the current density.

In order to solve the above problems, the present invention provides a semiconductor device comprising: a substrate; A photoelectric layer including a first semiconductor layer, an active layer, and a second semiconductor layer which are sequentially stacked on the substrate; An ohmic contact layer formed on the second semiconductor layer with a transparent conductive material; A first electrode pad formed on a portion of the first semiconductor layer exposed by removing the ohmic contact layer, the second semiconductor layer, and a part of the active layer; At least one first electrode extending from the first electrode pad on a partial region of the first semiconductor layer and having a cross-sectional area gradually increasing as the length extending from the first electrode pad is increased; A second electrode pad formed on the ohmic contact layer; And a second electrode pad formed on the ohmic contact layer and extending from the second electrode pad so as to alternate with the at least one first electrode and having a cross sectional area gradually increasing as the length extending from the second electrode pad is increased, And two electrodes.

A light emitting device according to the present invention includes at least one first electrode formed on a first semiconductor layer extending from a first electrode pad and a second electrode extended from a second electrode pad to alternate with at least one first electrode on a second semiconductor layer And at least one second electrode formed on the substrate. At least one of the first electrodes has a cross-sectional area that gradually increases as a length extending from the first electrode pad increases, and each of the at least one second electrode has a cross-sectional area that gradually increases as the length extending from the second electrode pad becomes longer . That is, at least one of the first and second electrodes is formed to have a cross-sectional area widened along the longer length of the first and second electrode pads. Since at least one of the first and second electrodes has a length that increases in proportion to the distance between the first and second electrode pads and an increased cross-sectional area, the spacing distance between the first and second electrode pads The increase of the resistance due to the increase of the resistance of the first and second electrodes can be minimized and the decrease of the movement of the charges due to the increase of the resistance of the first and second electrodes can be minimized.

In addition, the light emitting device according to the present invention further includes a plurality of diffusion holes formed through at least one of the first and second electrodes, respectively, wherein the plurality of diffusion holes arranged along at least one of the first and second electrodes The diffusion holes of the first and second electrode pads have a smaller distance from the first and second electrode pads. Through this plurality of diffusion holes, the diffusion of holes and electrons toward the photoelectric layer at at least one of the first and second electrodes can be promoted.

As described above, the light emitting device according to the present invention has at least one first and second electrodes having a cross-sectional area that gradually increases as the distance from the first and second electrode pads increases, The plurality of diffusion holes formed to penetrate each of the first and second electrodes to promote the charge transfer from the first and second electrodes to the photoelectric layer can reduce the current density. Therefore, the charge can be diffused in the photoelectric layer more widely than before, so that the luminous efficiency of the device can be improved and the lifetime of the device caused by the deterioration due to the high current density can be prevented and the reliability can be prevented from lowering.

1 is a plan view of a light emitting device according to an embodiment of the present invention.
2 is a cross-sectional view taken along the line A-A 'in FIG. 1 according to the first embodiment of the present invention.
3 is a cross-sectional view taken along the line B-B 'in FIG. 1 according to the first embodiment of the present invention.
4A and 4B show diffusion of electrons and holes in the light emitting device according to the first embodiment of the present invention.
5 illustrates various cross-sectional views of a diffusion hole according to a first embodiment of the present invention.
6 is a cross-sectional view taken along the line B-B 'in FIG. 1 according to the second embodiment of the present invention.
7 is a cross-sectional view taken along the line B-B 'in Fig. 1 according to the third embodiment of the present invention.

Hereinafter, a light emitting device according to each embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, referring to FIGS. 1 to 5, a light emitting device according to a first embodiment of the present invention will be described.

1 is a plan view of a light emitting device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line A-A 'in FIG. 1 according to the first embodiment of the present invention, and FIG. 3 is a cross-sectional view taken along the line B-B' in FIG. 1 according to the first embodiment of the present invention. 4A and 4B show diffusion of electrons and holes in the light emitting device according to the first embodiment of the present invention. 5 shows various cross-sectional views of the diffusion holes according to the first embodiment of the present invention.

First, a cross section of the light emitting device according to the first embodiment of the present invention is as follows.

2 and 3, the light emitting device according to the first exemplary embodiment of the present invention includes a substrate 110, a buffer layer 121 sequentially stacked on the substrate 110, a first semiconductor layer 122, An active layer 123 and a second semiconductor layer 124; an ohmic contact layer 130 formed of a transparent conductive material on the second semiconductor layer; an ohmic contact layer 130; At least one first electrode 140 formed on a portion of the first semiconductor layer 122 exposed by removing a part of each of the semiconductor layer 124 and the active layer 123, And at least one second electrode (150) formed through at least one second electrode (150) and at least one first electrode (140) formed on the substrate And a plurality of second diffusion holes 151 formed in the second diffusion holes 151.

1, the light emitting device according to the first embodiment of the present invention includes a first electrode pad 142 and an ohmic contact layer (not shown) formed on a part of the exposed first semiconductor layer 122 And a second electrode pad 152 formed on the first electrode pad 130.

The substrate 110 may be selected from GaN based materials similar to GaN and Al ₂ O ₃ (sapphire), SiC, and AlN having a crystal structure similar to GaN. Particularly, the substrate 110 can be selected as a sapphire (Al ₂ O ₃ ) substrate having advantages of low cost, low alkali or acid-induced deformation rate, and low heat distortion rate.

The buffer layer 121 is a buffer layer for reducing crystal defects generated in the photoelectric layer 120 due to a difference in lattice constant and a thermal expansion coefficient between the substrate 110 and the semiconductor material forming the photoelectric layer 120. The buffer layer 121 may be formed of an undoped nitride semiconductor or an n-type nitride semiconductor which is grown in an atmosphere containing low-temperature heat for growing a semiconductor material horizontally on a growth surface.

The first semiconductor layer 122 is formed on the buffer layer 121 by an n-type nitride semiconductor which is doped with an n-type impurity to increase electron mobility. At this time, the n-type impurity may be Si.

The active layer 123 is formed on the first semiconductor layer 122 with a nitride semiconductor of a quantum well structure. The active layer 123 generates light by using energy generated when electrons and holes injected through the first electrode 140 and the second electrode 150 meet and recombine to generate excitons falling to the atmospheric state .

For example, if the semiconductor material forming the photoelectric layer 120, gallium nitride (GaN) sealed, the active layer 123 is In _x (Al _y Ga _(1-y)) barrier layers of N and In _x (Al _y Ga _(1-y) ) N, or a multiple quantum well structure (MQW). At this time, the wavelength region of the light emitted from the light emitting device is freely determined from a long wavelength to a short wavelength having an AlN (~ 6.4 eV) band gap according to the composition ratio of the nitride semiconductor (InGaN, GaN) of the barrier layer and the well layer.

The second semiconductor layer 124 is formed on the active layer 123 with a p-type nitride semiconductor doped with a p-type impurity to increase the hole mobility. At this time, the p-type impurity may be Mg.

Meanwhile, the plurality of semiconductor layers 121 to 124 constituting the photoelectric layer 120 may be formed by growing a semiconductor material using a MOCVD (Metal Organic Chemical Vapor Deposition) method.

The ohmic contact layer 130 is formed of a transparent conductive material on the second semiconductor layer 124 for diffusing holes injected into the second electrode 150 into the second semiconductor layer 124 as widely as possible. At this time, the transparent conductive material forming the ohmic contact layer 130 is a metal oxide selected from the group consisting of SnO ₂ , ZnO, In ₂ O ₃ and TiO ₂ , and a metal oxide such as F, Sn, Al, Fe, Ga, and Nb At least one may be selected as the doped material.

At least one of the first electrode 140 and the first electrode pad 142 may be formed by removing portions of the ohmic contact layer 130, the second semiconductor layer 124, and the active layer 123, (Not shown). At this time, each of the at least one first electrodes 140 extends like a branch at the first electrode pad 142. 1, according to the first embodiment of the present invention, each of the at least one first electrodes 140 has a cross-sectional area (width) gradually widening as the length extending from the first electrode pad 142 becomes longer, Respectively.

At least one second electrode 150 and a second electrode pad 152 are formed on the ohmic contact layer 130. Each of the at least one second electrodes 150 may be alternated with at least one first electrode 140 in the light emitting surface (here, the "light emitting surface" means the top surface in which light is mainly emitted from the light emitting device) And extends like a branch at the second electrode pad 152. In particular, as shown in FIG. 1, according to the first embodiment of the present invention, each of the at least one second electrodes 150 has a cross-sectional area (width) gradually widening as a length extending from the second electrode pad 152 becomes longer, Respectively.

The at least one first electrode 140, the first electrode pad 142, the at least one second electrode 150, and the second electrode pad 152 are formed of the same or different conductive materials. In particular, Ni, Au, Pt, Ti, Al, and Cr, or an alloy containing two or more metals.

The plurality of first diffusion holes 141 are formed to penetrate the first electrode 140 and are arranged in parallel along each of the at least one first electrode 140. At this time, in the plurality of first diffusion holes 141 arranged in each first electrode 140, the distance between two neighboring first diffusion holes 141 becomes longer as the distance from the first electrode pad 142 Becomes smaller.

The plurality of second diffusion holes 151 are formed to penetrate the second electrode 150 and are arranged in parallel along each of the at least one second electrode 150. At this time, in the plurality of second diffusion holes 151 arranged in each second electrode 150, the distance between the adjacent two second diffusion holes 151 becomes longer from the second electrode pad 152 Becomes smaller.

Alternatively, a plurality of first and second diffusion holes 141 and 151 arranged in each of the at least one first and second electrodes 140 and 150 may be separated from the first and second electrode pads 142 and 152 May be formed in a gradually increasing number, or may be formed in an increasingly large cross-sectional area, spaced at a certain interval or gradually narrowing interval.

As described above, according to the first embodiment of the present invention, at least one of the first electrode 140 and the at least one second electrode 150 includes the first electrode pad 142 and the second electrode pad 152, And has a cross-sectional area that becomes wider as it extends.

As shown in the following equation (1), the resistance R is proportional to the length L and inversely proportional to the cross-sectional area A. At least one first electrode 140 and at least one second electrode 150 each having a cross-sectional area that gradually widens in accordance with an elongated extension length may be formed of a first electrode pad 142 and a second electrode pad 150, Lt; RTI ID = 0.0 > 152 < / RTI >

Therefore, as shown by the arrows in FIG. 4A, the charge is also close to the first electrode pad 142 and the second electrode pad 152 in a region far from the first electrode pad 142 and the second electrode pad 152 The current densification phenomenon due to the resistance of the electrodes 140 and 150 can be mitigated.

The light emitting device according to an embodiment of the present invention includes a plurality of first and second diffusion holes 141 and 142 formed to pass through at least one first electrode 140 and at least one second electrode 150, 151). Electrons and holes moving through at least one first electrode 140 and at least one second electrode 150 through the plurality of first and second diffusion holes 141 and 151 pass through the photoelectric layer 120 And can be more easily diffused. In particular, the spacing distance between the plurality of diffusion holes 141 and 151 arranged side by side along the electrodes 140 and 150 becomes smaller as the distance from the electrode pads 142 and 152 increases.

Thus, as shown in FIG. 4B, the diffusion of electric charge becomes easier through the plurality of first and second diffusion holes 141 and 151, and the current densification phenomenon can be alleviated.

1, the first and second diffusion holes 141 and 151 have a circular cross section, but the first embodiment of the present invention is not limited thereto.

5 (a), the first and second diffusion holes 141 and 151 may have an elliptical cross-section, or may have a cross section as shown in Figs. 5 (b) and 5 (c) As described above, it may have a circular or elliptical cross section having a ridge-shaped edge. As described above, when the cross-section of the diffusion holes 141 and 151 has an outline shape, the contact area between the diffusion holes 141 and 151 and the electrodes 140 and 150 is widened, , It becomes easier to diffuse the current.

Next, the light emitting device according to the second and third embodiments of the present invention will be described.

6, the light emitting device according to the second embodiment of the present invention further includes a plurality of second diffusion holes 153 formed through the second electrode 150 and the ohmic contact layer 130 1 to 3, and therefore, a duplicate description will be omitted below.

7, the light emitting device according to the third embodiment of the present invention includes a plurality of first and second diffusion holes 143 and 154 filled with a metal material. The first embodiment shown in FIGS. 1 to 3 and the second embodiment shown in FIG. 6, and a description thereof will be omitted below. At this time, the metal material filling the inside of the plurality of first and second diffusion holes 143 and 154 can be selected to be the same as the first and second electrodes 140 and 150, or a different material having higher conductivity May be selected.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and various substitutions, modifications, and changes may be made without departing from the technical spirit of the present invention.

110: substrate 120: photoelectric layer
121: buffer layer 122: first semiconductor layer
123: light emitting layer 124: second semiconductor layer
130: ohmic contact layer 140: first electrode
142: first electrode pad 150: second electrode
152: second electrode pad 141, 151, 153, 154: diffusion hole

Claims (7)

Board;
A photoelectric layer including a first semiconductor layer, an active layer, and a second semiconductor layer which are sequentially stacked on the substrate;
An ohmic contact layer formed on the second semiconductor layer with a transparent conductive material;
A first electrode pad formed on a portion of the first semiconductor layer exposed by removing the ohmic contact layer, the second semiconductor layer, and a part of the active layer;
At least one first electrode extending from the first electrode pad on a partial region of the first semiconductor layer and having a cross-sectional area gradually increasing as the length extending from the first electrode pad is increased;
A second electrode pad formed on the ohmic contact layer; And
And a second electrode pad formed on the ohmic contact layer and extending from the second electrode pad so as to alternate with the at least one first electrode and having a cross sectional area gradually increasing as a length extending from the second electrode pad is increased, A light emitting device comprising an electrode. The method according to claim 1,
And a plurality of diffusion holes formed through the at least one first electrode and the at least one second electrode, respectively. 3. The method of claim 2,
Wherein a distance between the plurality of diffusion holes formed through any one of the at least one first electrode decreases as the distance from the first electrode pad increases. 3. The method of claim 2,
Wherein a distance between the plurality of diffusion holes formed through any one of the at least one second electrode decreases as the distance from the second electrode pad increases. 3. The method of claim 2,
Wherein the plurality of diffusion holes formed through any one of the at least one second electrode are formed to further penetrate the ohmic contact layer. 6. The method according to claim 2 or 5,
Wherein the plurality of diffusion holes include an interior filled with a metal material. 3. The method of claim 2,
And each of the plurality of diffusion holes has a circular or elliptical cross section or a circular or elliptical cross section having a concave-convex edge.

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