KR101300495B1 - Led having a reflection layer - Google Patents

Abstract

The present invention relates to an LED having a high reflectance reflective layer to minimize light loss and excellent light quality.
N-type semiconductor layer,
A P-type semiconductor layer, and
An active layer formed between the N-type semiconductor and the P-type semiconductor,
A reflection layer for reflecting the light emitted from the active layer on the opposite side of the light exit surface of the light emitting diode to the light exit surface;
The reflective layer includes a reflective structure for reflecting light reaching the reflective layer within a predetermined angle range.

Description

Light Emitting Diode with Reflective Layer {LED HAVING A REFLECTION LAYER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to light emitting diodes, and more particularly, to a LED having a high reflectance reflective layer to minimize light loss.

Light emitting diodes are solid state devices that convert electrical energy into light and generally comprise an active layer of one or more semiconductor materials formed between conversely doped N-type and P-type layers. When a bias is applied across the doped N-type and P-type layers, holes and electrons are injected into the active layer and recombined to produce light, which is emitted to the active layer and the entire surface of the LED.

1 is a view showing the structure of a conventional LED 10. As shown in FIG. 1, the structure of a conventional LED 10 includes an LED layer 12, 13, 14, and a current spreading layer 15, and includes a first and second means for operating the LEDs 12, 13, 14. It may be formed by further including a second electrode (11a, 11b). The LED 10 generally includes an N-type semiconductor layer 12, a P-type semiconductor layer 14, and an active layer 13 formed between the N-type semiconductor layer 12 and the P-type semiconductor layer 14.

In the structure shown in FIG. 1, when voltage is applied to the first and second electrodes 11a and 11b, the electrical signal transmitted from the first electrode 11 passes through the N-type semiconductor layer 12 to the active region ( 13, the electrical signal transmitted from the second electrode 16 is diffused through the current diffusion layer 15 through the P-type semiconductor layer 14 to the active layer 13. At this time, the light generated from the active layer is emitted to the front of the LED, as shown in Figure 1 part of the light is emitted to the exit surface (S1) while a part of the light is emitted to the opposite side of the exit surface, such LED internal structure The optical loss due to this is also called TIR (Total Internal Reflection) loss.

In the structure of the conventional LED shown in FIG. 1, it is proposed to reflect through the surface of the reflective layer 19 to the exit surface S1 by further forming a metal reflective layer 19 on the opposite side of the exit surface to suppress total internal reflection (TIR) loss. However, according to this method, light reflected by the light reflected from the reflecting layer 19 in the LED is present a plurality of times, resulting in a change in the wavelength of the final output light, which is used in the precision measurement industry such as biotechnology. There is a problem that the following is not suitable and the efficiency of light reflected from the reflecting surface is not good.

<Prior Art Literature>
Korean Publication 10-2011-0138563 (2011.12.28)

An object of the present invention is to provide an LED that can achieve stability of the wavelength of light output while suppressing the loss of light generated from the LED to the invention.

In order to solve the above problems, the light emitting diode according to the first aspect of the present invention includes an N-type semiconductor layer, a P-type semiconductor layer, and an active layer formed between the N-type semiconductor and the P-type semiconductor, the light emitted from the active layer And a reflecting layer for reflecting light emitted to the light emitting surface opposite to the light emitting surface of the light emitting diode, wherein the reflecting layer includes a reflecting structure for reflecting the light reaching the reflecting layer within a predetermined angle range. Include as.

The reflective structure may be formed by stacking a plurality of materials having different refractive indices, and may also be a DBR structure in which a high refractive index material and a low refractive index material are alternately stacked.

In addition, a light emitting diode according to a second aspect of the present invention includes an LED layer including an N-type semiconductor layer, a P-type semiconductor layer, and an active layer formed between the N-type semiconductor and the P-type semiconductor, and a submount on which the LED layer is mounted. And a reflecting layer disposed between the LED layer and the submount and reflecting the light emitted toward the submount of the light emitted from the LED active layer toward the light emitting surface side, wherein the reflecting layer preliminarily lights the light reaching the reflecting layer. And a reflective structure for reflecting within a predetermined angle range, wherein the reflective layer is formed of a conductive material to transfer current from an electrode to an adjacent semiconductor layer to activate the semiconductor layer.

In addition, the light emitting diode may further include a metal reflective layer between the reflective layer and the submount, wherein the metal reflective layer is formed to re-reflect light passing through the reflective structure of the reflective layer.

In addition, a light emitting diode according to another aspect of the present invention is an LED layer including an N-type semiconductor layer, a P-type semiconductor layer, and an active layer formed between the N-type semiconductor and the P-type semiconductor, and a submount on which the LED layer is mounted, And a metal reflective layer formed on the submount, wherein the metal reflective layer includes a reflective structure for reflecting the light emitted toward the submount among the light emitted from the LED active layer toward the light exit surface side.

In addition, the reflective structure of the light emitting diode may be formed by stacking a plurality of materials having different refractive indices, or the reflective structure may be a DBR structure in which a high refractive index material and a low refractive index material are alternately stacked.

According to the present invention, the stability of the wavelength of the output light can be improved while suppressing the loss of the light generated from the LED as much as possible.

1 is a cross-sectional view of a LED having a conventional reflective layer.
2 shows a cross section of an LED with a reflective layer according to an embodiment of the invention.
3 is an enlarged view partially showing the reflective structure of the reflective layer;
4 shows a modification of the reflective structure.
5 is a view showing the LED mounted on the submount of the present invention.
6 illustrates an LED according to a second embodiment of the present invention.
7 illustrates an LED according to a third embodiment of the present invention.
7 illustrates an LED according to a fourth embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent by reference to the embodiments described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below, but may be embodied in various forms.

The present embodiments are provided so that the disclosure of the present invention is thoroughly disclosed and that those skilled in the art will fully understand the scope of the present invention. And the present invention is only defined by the scope of the claims. Accordingly, in some embodiments, well known components, well known operations, and well-known techniques are not specifically described to avoid an undesirable interpretation of the present invention.

Like reference numerals refer to like elements throughout the specification. Moreover, terms used herein (to be referred to) are intended to illustrate embodiments and are not intended to limit the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. Also, components and acts referred to as &quot; comprising (or comprising) &quot; do not exclude the presence or addition of one or more other components and operations.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless they are defined.

Hereinafter, the technical features of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating an example of an LED 100 according to an embodiment of the present invention. The LED 100 illustrated in FIG. 2 includes LED layers 120, 130, and 140 and a current spreading layer 150. In addition, the LED layer includes an N-type semiconductor layer 120, a P-type semiconductor layer 140, an active layer 130 formed between the N-type semiconductor layer 120 and the P-type semiconductor layer 140. In addition, the LED 100 according to the present invention includes a reflective layer 160 made of a P-type metal (P-metal) to suppress the loss of light due to total internal reflection, and the reflective layer 160 includes a plurality of reflective structures 161. Is formed.

Manufacturing and operation of the LED layers 120, 130 and 140 are generally well known in the art, so a detailed description thereof will be omitted. In one example, the LED layers 120, 130 and 140 may be manufactured using a known technique such as MOCVD. Typically, the LED layers 120, 130 and 140 comprise an active layer 130 between the oppositely doped N-type semiconductor layers 120 and P-type semiconductor layers 140 and typically all of them are formed continuously on a growth substrate (not shown). . The active layer 130 may include a single quantum well (SQW), a plurality of quantum wells (MQW), a double heterostructure, or a superlattice structure.

The active layer 130 and vice versa doped semiconductor layers 120 and 140 may be fabricated from different material systems, and group III nitride based material systems may be used. Group III nitrides may be semiconductor compounds formed between nitrogen and group III elements of the periodic table of elements, typically aluminum (Al), gallium (Ga) and indium (In), and also aluminum gallium nitride (AlGaN) and aluminum indium gallium Ternary compounds such as nitrides (AlInGaN) and quaternary compounds.

In one embodiment, the N-type semiconductor layer 120 and the P-type semiconductor layer 140 is gallium nitride (GaN), and the active layer 130 includes InGaN. In another embodiment, the N-type semiconductor layer 120 and the P-type semiconductor layer 140 may be AlGaN, aluminum gallium arsenide (AlGaAs0, or aluminum gallium indium arsenide phosphide (AlGaInAsP), and related compounds.

Different embodiments of the LED layers 120, 130, and 140 may emit light of different wavelengths depending on the composition of the N-type semiconductor layer 120, the P-type semiconductor layer 140, and the active layer 120. LED 100 may also be covered with one or more light converting materials, such as phosphors, whereby at least some of the light from the LEDs passes through one or more phosphors and is converted into light of one or more different wavelengths. Preferably, the LEDs 100 may be combined such that the light from the active layer 130 of the LEDs emits white light via one or more phosphors.

In the case of the group III nitride device, since the current does not normally diffuse effectively through the P-type semiconductor layer 140, the current diffusion layer 150 of the thin film is formed to cover all or part of the P-type semiconductor layer 140. It is good. The current spreading layer 150 functions to spread the current from the P-type contact or the second electrode 110b over the surface of the P-type semiconductor layer 140, and correspondingly the active layer 130 from the P-type semiconductor layer 140. Improves the possibility of current injection into The current spreading layer 150 is typically a transparent conductive oxide such as indium tin oxide (ITO) or a metal such as platinum (Pt), although other materials may be used. The current spreading layer 150 can have a number of different thicknesses. In embodiments in which current spreading is not important, the current spreading layer may be omitted.

Next, the reflective layer 160 will be described. The reflective layer 160 is formed of a conductive material on the top of the current spreading layer 150 and configured to transfer current from the electrode to the adjacent semiconductor layer. 3 is an enlarged view of the structure of the reflective layer 160 according to the present invention. The reflective layer 160 serves to reflect light emitted from the active layer 130 to the rear surface as described in the related art. For this purpose, the reflective layer 160 includes a plurality of reflective structures 161.

Each reflective structure 161 is formed in a hemispherical shape to reflect the light generated from the LED active layer 130 and emitted to the rear surface of the light toward the light emitting surface (S1) when using a conventional metal reflective film It is possible to suppress a change in wavelength of the output light due to diffuse reflection (or plural reflections) that may occur.

The reflective structure 161 may be formed of a distributed bragg reflector (DBR) structure formed of a plurality of thin films. For example, the reflective structure 161 may have a structure in which materials such as silicon nitride, silicon oxide, and potassium nitride are stacked in multiple layers. Specifically, examples of materials having a relatively high refractive index include ITO (refractive index about 2.0), TiO2 (refractive index about 2.3), ZrO2 (refractive index about 2.05), and Si3N4 (refractive index about 2.02). Examples of Al 2 O 3 (refractive index of about 1.68), SiO 2 (refractive index of about 1.46), and MgO (refractive index of about 1.7) may be mentioned. At this time, the material of high refractive index or low refractive index is not limited to the above-mentioned materials, but in the method of lamination, it is preferable that different materials having different refractive indices are alternately laminated.

3 shows an example formed of four thin films, in which case the first reflective film 161a may be made of a first material having a high refractive index, and the second reflective film 162a has a relatively lower refractive index than the first reflective film. It may be made of a second material having a low refractive index. In addition, any one material including the first material having a high refractive index may be selected as the third reflective film 162c, and another material having a low refractive index may be selected as the fourth reflective film. In contrast, the first reflective film 161a is made of a material having a low refractive index, the second reflective film 161b is made of a material having a high refractive index, and the third reflective film 161c is made of a material having a low refractive index, and a fourth reflective film 161d is used. ) May be sequentially stacked materials having a high refractive index.

4 is a view showing a modification of the reflective structure 161 according to the present invention. As shown in FIG. 4, the reflective structure 161 according to the present invention is formed to have a curvature or an inclined surface to reflect the light reaching the reflective structure 161 within a range of angles. The structure of the reflective structure is preferably formed of an uneven structure having a circular, triangular, trapezoidal cross section. However, the shape of the reflective structure 161 according to the present invention is not limited thereto, and may include any geometric shape capable of reflecting the reached light within a predetermined range.

FIG. 5 illustrates the LED 100 according to the present invention, which is formed in a flip chip method on the sub-mount layer 170 so that the p-side is down (P-side down method) and the active layer 130 is activated. It is a figure which shows the example which formed the 2nd electrode 110a. The submount 170 can be composed of a number of different materials, can have a number of different thicknesses, and the preferred submount 170 can be an electrical signal applied to the active area of the LED via the submount 170. So that it is electrically conductive.

The first electrode 110a may be formed on the N-type semiconductor layer 120, and the second electrode 110b may be formed on the submount 170. The first electrode 110a and the second electrode 110b may comprise a number of different materials, such as Au, Cu, Ni, In, Al, Ag, or compositions thereof. In another embodiment, the first electrode 110a and the second electrode 110b include ITO, nickel oxide, zinc oxide, cadmium tin, indium oxide, tin oxide, magnesium oxide, ZnGa 2 O 4, ZnO 2 / Sb, Ga 2 O 3 / Sn, Transparent conductive oxides and conductive oxides such as AgInO 2 / Sn, In 2 O 3 / Zn, CuAlO 2, LaCuOS, CuGaO 2 and SrCu 2 O 2. The choice of material used may depend on the location of formation of the electrode as well as the required electrical properties such as transparency, junction resistivity and sheet resistance and is preferably chosen for the application.

In the operation of the LED, power is applied to both ends of the first electrode 110a and the second electrode 110b. The electrical signal on the first electrode 110a diffuses through the N-type semiconductor layer 120 to the active layer 130. The signal on the second electrode 110b passes through the submount 170 and diffuses through the current diffusion layer 150 through the reflective layer 160, through the P-type semiconductor layer 140, and to the active layer 130. As a result, electrons and holes are combined in the active layer 130 and light is emitted as much as the bandgap energy. The reflective structure 161 of the reflective layer 160 is emitted from the active layer 130 toward the submount 170 or inside thereof. The light reflected by the total reflection to the submount 170 side is reflected back toward the upper surface, which is the exit surface of the LED 100. Reflective layer 160 facilitates the emission of light towards the exit surface of LED 100 and reduces the loss during reflection due to improved reflectivity by reflective layer 160, and to the curvature or inclined reflective surface of reflective structure 161. Therefore, as the light is reflected within a predetermined range, the reflected light may be reflected back to minimize the change in the wavelength generated.

6 is a view showing another embodiment according to the present invention. This embodiment is the same as the previously described embodiment except that it further includes a P-type metal reflective layer 190 between the reflective layer 160 and the submount 170, and the same reference numerals are assigned to the same components. The description is omitted.

The P-type metal reflective layer 190 is formed to reflect the light passing through the reflective layer 160 back toward the emission surface, and is preferably formed to have a reflectance of 70% or more. In addition, the reflective metal layer 190 may be formed of one or a plurality of layers made of a material selected from the group consisting of Ag, Al, Pd, and combinations thereof. The reflective metal layer 190 may be formed by a deposition method or a sputtering process, which is a conventional metal layer growth method.

7 shows an embodiment of another LED according to the invention. This embodiment shows that the reflective structure 161 is formed in the P-type metal reflective layer 190. Except that the reflective structure 161 is formed in the P-type metal reflective layer is the same as in the previously described embodiment and a description thereof will be omitted.

8 shows an embodiment of another LED according to the invention. This embodiment is the same as the previously described embodiment except that the reflective structure 161 is formed on the second electrode 110b as the lower electrode. In this embodiment, however, the second electrode 110b includes a reflective material such that the second electrode 110b applies power to the P-type semiconductor layer 140 while reflecting light reflected downward from the active layer 130 toward the upper emission surface S1. It is formed to. In this case, as the reflective material included, any one of Ag, Al, Pd, or one or more thereof may be used in combination.

The foregoing description is merely illustrative of the technical idea of the present invention and various changes and modifications may be made without departing from the essential characteristics of the present invention by those skilled in the art. Therefore, the embodiments disclosed in the present invention are not intended to limit the scope of the present invention but to limit the scope of the present invention. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

100: LED
110a, 110b: electrode
120: N-type semiconductor layer
130: active layer
140: P-type semiconductor layer
150: current diffusion layer
160: reflective layer
161: reflective structure
170: submount
190: metal reflective layer
S1: light exit surface

Claims (9)

In the light emitting diode,
N-type semiconductor layer,
A P-type semiconductor layer, and
An active layer formed between the N-type semiconductor and the P-type semiconductor,
A reflection layer for reflecting the light emitted from the active layer on the opposite side of the light exit surface of the light emitting diode to the light exit surface;
And the reflective layer includes a reflective structure having a curvature reflective surface or an inclined reflective surface to reflect light reaching the reflective layer within a predetermined angle range.
The method of claim 1,
And the reflective structure is formed by stacking a plurality of materials having different refractive indices.
The method of claim 2,
The reflective structure is a light emitting diode having a reflective layer, characterized in that the high refractive index material and the low refractive index material is a DBR structure laminated alternately.
In the light emitting diode,
An LED layer comprising an N-type semiconductor layer, a P-type semiconductor layer, and an active layer formed between the N-type semiconductor and the P-type semiconductor, and a submount on which the LED layer is mounted,
A reflection layer disposed between the LED layer and the submount and reflecting the light emitted toward the submount among the light emitted from the LED active layer toward the light exit surface;
The reflective layer includes a reflective structure having a curvature reflective surface or an inclined reflective surface to reflect light reaching the reflective layer within a predetermined angle range, the reflective layer transferring current from an electrode to a P-type semiconductor layer adjacent to the reflective layer A light emitting diode having a reflective layer, characterized in that formed of a conductive material to activate the P-type semiconductor layer.
5. The method of claim 4,
And a metal reflective layer between the reflective layer and the submount, wherein the metal reflective layer is formed to re-reflect light passing through the reflective structure of the reflective layer.
In the light emitting diode,
An LED layer including an N-type semiconductor layer, a P-type semiconductor layer, and an active layer formed between the N-type semiconductor and the P-type semiconductor, a submount on which the LED layer is mounted, and a metal reflective layer formed on the submount; ,
The metal reflecting layer includes a reflecting structure having a curvature reflecting surface or an inclined reflecting surface to reflect the light emitted toward the submount of the light emitted from the LED active layer within a predetermined angle range toward the light emitting surface side. A light emitting diode having a reflective layer.
The method according to claim 4 or 6,
The reflective structure is a light emitting diode having a reflective layer, characterized in that formed by stacking a plurality of materials having different refractive index.
The method according to claim 4 or 6,
The reflective structure is a light emitting diode having a reflective layer, characterized in that the high refractive index material and the low refractive index material is a DBR structure laminated alternately.
In the light emitting diode,
An LED layer comprising an N-type semiconductor layer, a P-type semiconductor layer, and an active layer formed between the N-type semiconductor layer and the P-type semiconductor layer, an N-type electrode for applying power to the N-type semiconductor layer, and the P-type semiconductor layer. P-type electrode for applying power,
The P-type electrode may include a reflective structure having a curvature reflecting surface or an inclined reflecting surface to reflect light emitted toward the P-type electrode among the light emitted from the LED active layer within a predetermined angle range toward the light emitting surface side. A light emitting diode having a reflective layer.

Images