KR100809508B1 - Light emitting device having plane fresnel lens and fabrication method thereof - Google Patents

Abstract

A light emitting device having a planar Fresnel lens and a manufacturing method thereof are provided to improve the light efficiency by easily integrating the planar Fresnel lens having a vertical profile through an etching process. Compound semiconductor layers(210,230) are formed on a substrate(100), and have a light emitting region. A planar Fresnel lens layer(300) is formed over the compound semiconductor layers to focus or diffuse the light emitted from the compound semiconductor layers. The planar Fresnel lens layer has concentric circle patterns having the same height which are formed by etching and are spaced apart from each other. The Fresnel lens layers have the same pitch, and are made of single transmissive material.

Description

LIGHT EMITTING DEVICE HAVING PLANE FRESNEL LENS AND FABRICATION METHOD THEREOF}

1 is a cross-sectional view of a vertical light emitting device having a flat Fresnel lens according to an embodiment of the present invention.

2 is a plan view of a vertical light emitting device having a flat Fresnel lens according to an embodiment of the present invention.

3 shows the structure and principle of convex and concave lenses;

4 shows the shapes of convex and concave lenses;

Fig. 5 is a virtual divided view of the convex lens for explaining the planar design of the convex lens.

FIG. 6 is a schematic plan view of the convex lens shown in FIG. 5; FIG.

FIG. 7 is a schematic plan view of the convex lens of FIG. 6.

8 is an exemplary view of applying a planar lens pattern to a light emitting device according to an embodiment of the present invention.

9 is an exemplary view of applying a planar lens pattern to a light emitting device according to another embodiment of the present invention.

10 is a pattern of a focusing flat Fresnel lens according to an embodiment of the present invention.

Figure 11 is a pattern of the diffuse planar Fresnel lens in accordance with an embodiment of the present invention.

12 is a cross-sectional view of a horizontal light emitting device having a flat Fresnel lens according to another embodiment of the present invention.

13 is a plan view of a horizontal light emitting device having a flat Fresnel lens according to another embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device having a planar Fresnel lens. Specifically, a planar Fresnel lens for improving light extraction rate by forming a convex lens for condensing light or a concave lens for diffusing light in a light emitting device It relates to a light emitting device having a and a method of manufacturing the same.

Gallium nitride devices grown by deposition methods such as organometallic vapor deposition methods have low light output efficiency, which may increase the internal quantum efficiency by changing the film quality of gallium nitride and increase the external quantum efficiency by modifying the external appearance. Method is used to increase the light efficiency.

Recently, in the light emitting diode of a vertical structure manufactured by separating sapphire or substrate by laser technology, the light output is increased through the bottom reflective metal and upper unevenness treatment.

In particular, the upper concave-convex treatment uses a method of easily concave-convex treatment by wet and dry etching, and uses a method of increasing light output by applying an antireflective coating using a transparent thin film such as SiO ₂ .

Although it is preferable to form a lens in order to increase the light output more, spherical lenses are not easy to manufacture, and most of them do not integrate into the element and often depend on an external package.

US Pat. No. 6,987,613 (January 1, 2006) discloses a technique in which a Fresnel lens is formed on a light emitting device in "FORMING AN OPTICAL ELEMENT ON THE SURFACE OF LIGHT EMITTING DEVICE FOR IMPROVED LIGHT EXTRACTION".

However, the Fresnel lens introduced in US 6,987,613 has a jagged shape, so the manufacturing process is difficult.

The technical problem to be achieved by the present invention is to improve the light output of the light emitting device and to simplify the pattern process for forming the lens by forming a convex lens or a concave lens in a planar design and integrated in the light emitting device to solve the conventional problems.

According to an aspect of the present invention for achieving the above technical problem, a compound, a compound semiconductor layer formed on the substrate having a light emitting region, and formed on the compound semiconductor layer to focus light emitted from the compound semiconductor layer or And a flat Fresnel lens layer for diffusing, wherein the flat Fresnel lens layer has at least one concentric circle pattern formed at the same height and spaced apart from each other by a groove formed by etching, and the pitch between the concentric circle patterns is the same. Provided is a light emitting device having a flat Fresnel lens, which is made of a light transmitting material.

Preferably, the width of each concentric pattern provided in the planar Fresnel lens layer may be reduced or increased at a constant rate toward the radially outward direction.

Preferably, the bottom of the groove formed between each of the concentric circle patterns is increased as the width of the adjacent concentric circle patterns increases, and may have a shape that is increased or decreased at a constant ratio toward the radially outward direction.

Preferably, the planar Fresnel lens layer is an insulating material consisting of SiOx, SixNy, SixONy, SrF ₂ , HF ₂ O ₃ , TiOx, Al ₂ O ₃ , AlN, GaN, AlInGaN, GaAs, Ge, Si, InP A semiconductor material consisting of one of the following, an insulating film material consisting of one of Polyimide, BCB, and Epoxy, a metal oxide made of one of ITO and Cu-doped tin oxide (CIO), Ni, Al, Au, Pt, Ru, Ti, Cr It may be any one material selected from a metal material consisting of one, and lithium niobate.

Preferably, the bottom of the groove formed between each concentric circle pattern may be formed with irregularities.

According to another aspect of the present invention, a step of preparing a substrate, forming a compound semiconductor layer having a light emitting region on the substrate, and a planar focusing or diffusing light emitted from the compound semiconductor layer on the compound semiconductor layer Forming a Fresnel lens layer, wherein the planar Fresnel lens layer has at least one concentric circle pattern formed at the same height and spaced apart from each other by grooves formed by etching, and one having the same pitch between the concentric circle patterns It provides a method for manufacturing a light emitting device having a flat Fresnel lens, characterized in that made of a light-transmitting material.

Preferably, the planar Fresnel lens layer forming step includes forming a light-transmitting material having a predetermined thickness on the compound semiconductor layer, and having at least one concentric circle pattern on the light-transmitting material, and having a same pitch between the concentric circle patterns. And etching the translucent material so that the compound semiconductor layer is exposed between the concentric circles using the mask pattern.

Preferably, the width of each concentric pattern provided in the mask pattern may be reduced or increased at a constant rate toward the radially outward direction.

Preferably, the planar Fresnel lens layer forming step includes forming a light-transmissive material having a predetermined thickness on the compound semiconductor layer, and having at least one concentric circle pattern on the light-transmissive material, wherein the pitch between the concentric circle patterns is the same The width of the concentric circles includes forming a mask pattern that decreases or increases at a constant rate toward the outer side of the concentric circle, and etching the translucent material such that grooves are formed between the concentric circle patterns using the mask pattern. The bottom of the groove formed between each of the concentric patterns by the etching may increase in width as the width of the adjacent concentric patterns increases, and may increase or decrease at a constant ratio toward the radially outward direction.

Preferably, the planar Fresnel lens layer is an insulating material consisting of SiOx, SixNy, SixONy, SrF ₂ , HF ₂ O ₃ , TiOx, Al ₂ O ₃ , AlN, GaN, AlInGaN, GaAs, Ge, Si, InP A semiconductor material consisting of one of the following, an insulating film material consisting of one of Polyimide, BCB, and Epoxy, a metal oxide made of one of ITO and Cu-doped tin oxide (CIO), Ni, Al, Au, Pt, Ru, Ti, Cr It may be any one material selected from a metal material consisting of one, and lithium niobate.

Preferably, the bottom of the groove formed between the concentric patterns by the etching may be uneven.

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

1 is a cross-sectional view of a vertical light emitting device having a flat Fresnel lens according to an embodiment of the present invention, Figure 2 is a plan view of a vertical light emitting device having a flat Fresnel lens.

1 and 2, a vertical light emitting device having a planar Fresnel lens includes a substrate 100, an N-type semiconductor layer 210, a light-emitting layer 220, a P-type semiconductor layer 230, and a flat Fresnel The lens layer 300 is included.

The planar Fresnel lens layer 300 includes a plurality of concentric circle patterns 300a formed by etching and grooves 300b formed between the concentric circle patterns 300a.

The substrate 100 prepares a substrate having conductivity.

N-type semiconductor layer 210 may be formed of N-type _{Al x In y Ga 1 -x- y} N (0≤x, y, x + y≤1), may include an N-type clad layer. The N-type semiconductor layer 210 may be formed by doping silicon (Si).

The emission layer 220 is an area where electrons and holes are recombined and includes InGaN. The emission wavelength emitted from the light emitting diode is determined according to the type of material constituting the light emitting layer 220. The light emitting layer 220 may be a multilayer film in which a quantum well layer and a barrier layer are repeatedly formed. The barrier layer and the well layer may be a semiconductor layer 2-to 4 won the compounds represented by the general formula _{Al x In y Ga 1 -x- y} N (0≤x, y, x + y≤1).

P-type semiconductor layer 230 may be formed of P-type _{Al x In y Ga 1 -x- y} N (0≤x, y, x + y≤1), may include a P-type clad layer. The P-type semiconductor layer 230 may be formed by doping zinc (Zn) or magnesium (Mg).

The planar Fresnel lens layer 300 is formed on the P-type semiconductor layer 230 to surround portions except the electrode pad 400.

The planar Fresnel lens layer 300 is formed of an insulating film material such as SiOx, SixNy, SixONy, SrF2, HF ₂ O ₃ , TiOx, Al ₂ O ₃ , and a semiconductor such as AlN, GaN, AlInGaN, GaAs, Ge, Si, InP. Materials, insulating films such as Polyimide, BCB, Epoxy, metal oxides such as ITO, Cu-doped tin oxide (CIO), and metals such as Ni, Al, Au, Pt, Ru, Ti, Cr, etc. Can be used. In addition, materials such as lithium niobate used in the optical communication portion are also possible.

That is, the planar Fresnel lens layer 300 may be any material that can transmit light. This is because the metal also transmits within a certain thickness.

The electrode pad 400 is connected to a lead (not shown) by a wire to receive power from an external power source.

Although not illustrated, a transparent electrode may be formed between the P-type semiconductor layer 230 and the planar Fresnel lens layer 300. The transparent electrode has a plate shape and transmits light emitted from the light emitting layer 220 to the outside. The transparent electrode may be formed of a transparent material such as Ni / Au or indium tin oxide (ITO). The transparent electrode may also play a role of increasing luminous efficiency by evenly distributing the current input through the electrode pad 400.

The vertical light emitting device in which the flat Fresnel lens is formed may be manufactured by the following process.

First, the conductive substrate 100 is prepared.

An N-type semiconductor layer 210, a light emitting layer 220, and a P-type semiconductor layer 230 are formed on the substrate 100. The P-type electrode 400 is formed on the P-type semiconductor layer 230.

A light-transmitting material 300 having a predetermined thickness is formed on the P-type semiconductor layer 230 except for the P-type electrode 400.

A mask pattern (not shown) is formed on the light transmissive material 300.

In this case, the mask pattern has a plurality of concentric circle patterns, and the pitch between each concentric circle pattern is the same, but the width of each concentric circle has a pattern form that decreases or increases at a constant rate toward the radially outward direction.

In the state in which the mask pattern is formed on the light transmissive material 300, the light transmissive material is etched using the mask pattern so that the P-type compound semiconductor layer is exposed between the concentric circles.

In this case, the bottom surface of the groove formed between each pattern of the planar Fresnel lens through the etching process can be easily processed without the need for a separate photolithography.

After removing the mask pattern, a vertical light emitting device in which the planar Fresnel lens shown in FIG. 1 is formed is completed.

In this case, when etching is performed in a state where a mask pattern is formed on the light transmissive material 300, etching may be performed using a partial etching technique.

In this case, the bottom of the groove formed between the concentric patterns by the partial etching increases as the width of the adjacent concentric patterns increases.

At this time, depending on the shape of the mask pattern toward the outside of the diameter may be adjusted to a higher or lower shape at a constant ratio.

3 is a view showing the structure and principle of the lens.

As shown, the convex lens 1 serves to collect light, and the concave lens 2 diffuses the light.

4 to 7 are views for explaining the principle of manufacturing a flat Fresnel lens.

4 shows the shapes of convex and concave lenses. Referring to Fig. 4, the convex lens 3 and the concave lens 4 have a refractive index N1, and the refractive index N0, such as the atmosphere, is in contact with a lower media than the lens.

At this time, in order for the light to be transmitted without being reflected, the refractive index condition must satisfy N1≥N0. However, there are exceptional cases in which the refractive index is N1≤N0 depending on the medium.

FIG. 5 is a virtual divided view of the convex lens for explaining the planar design of the convex lens, and FIG. 6 is a schematic plan view of the convex lens shown in FIG. 5.

Referring to FIG. 5, by dividing a plurality of zones A1-A5 by imagining a rectangle (dotted line) including a lens and dividing them vertically, the lens area 300a having a refractive index N1 and a refractive index in A1, for example, within each zone. It can be seen that the areas of the standby area 300b which is N0 are different. That is, the effective refractive index N_eff, which is the ratio of the lens region 300a having the refractive index N1 and the atmospheric region 300b having the refractive index N0, is changed in each zone A1-A5.

Therefore, when the lens region 300a having the refractive index N1 and the atmospheric region 300b having the refractive index N0 are unfolded and arranged in one plane, the shape becomes as shown in FIG. 6. That is, the lens region 300a having the same pitch and the refractive index N1 and the refractive index are arranged. It exists between the waiting areas 300b which are N0. As described above, in a structure in which media having different refractive indices are arranged by a constant ratio, diffraction of light is generated to perform a lens function of focusing or diffusing light. The lens principle by this structure is the principle of Fresnel lens.

The planar Fresnel lens is found when the lens region 300a having the refractive index N1 and the atmospheric region 300b having the refractive index N0 become smaller or larger at a constant ratio.

FIG. 7 is a schematic plan view of the convex lens of FIG. 6.

Referring to FIG. 7, the pitch P, which is the sum of the lens region 300a having the refractive index N1 and the atmospheric region 300b having the refractive index N0, is a constant in each zone A1-A5.

However, the ratios of the lens region 300a having the refractive index N1 and the standby region 300b having the refractive index N0 are changed differently. That is, it has a vertical pattern structure in which the width X of the lens region 300a having the refractive index N1 gradually increases from A1 to A5.

The vertical pattern structure simplifies the fabrication process in implementing flat Fresnel lenses. When the vertical pattern structure is used, the planar Fresnel lens may be formed through one etching process or a patterning process in a state where a mask pattern is formed.

In this case, the relationship must be as follows.

P: pitch (0 ≤ P≤ chip diagonal length)

X: length having main refractive index N1 (0≤X≤P)

D: Height of material made of lens (0 ≤ D)

Preferably P is adapted to the antireflective coating conditions as a function of wavelength.

8 is an exemplary diagram in which a planar lens pattern is applied to a light emitting device according to an embodiment of the present invention. When applying the lens pattern, it is possible to form a convex lens or a concave lens by adjusting the relief or the relief structure.

A thin film such as SiO ₂ , BCB, ITO, or a semiconductor material such as GaN, GaAs is etched according to a designed pattern.

9 is an exemplary view of fabricating a highly efficient planar lens using a partial etching technique according to another embodiment of the present invention.

Referring to FIG. 9, it can be seen that the plane is designed to be closer to the spherical lens.

After the mask pattern is formed, etching is performed to use different etching times depending on the area to be etched when the portion between the pattern and the pattern is removed by etching.

In other words, the narrower the open space, the later the etching is performed. If the area to be etched is equal to or greater than a predetermined area, the same etching depth can be obtained.

That is, the height of the bottom 300c of the groove gradually increases from A1 to A5 in the groove 330b formed between the lens regions 300a of the refractive index N1.

Using this phenomenon, the lens shape as shown in FIG. 9 can be easily manufactured. In FIG. 6, the planar lens may be designed to simplify the pattern and to have characteristics more similar to those of the spherical lens than in FIG. 7.

10 shows a pattern shape of a concentrated planar Fresnel lens according to an embodiment of the present invention.

Referring to FIG. 10, the pitch between concentric circles in the planar Fresnel lens layer 300 is the same, and the converging pattern can focus light by decreasing the width of each concentric pattern in a constant ratio toward the radially outward direction. The lens function will be performed.

FIG. 11 shows the pattern shape of a diffused planar Fresnel lens according to an embodiment of the present invention. FIG.

Referring to FIG. 11, if the pitch between concentric circles is the same in the flat Fresnel lens layer 300, and the width of each concentric circle pattern is increased at a constant ratio toward the radially outward direction, the diffusion type may diffuse light. The lens function will be performed.

Thus, when manufacturing the lens pattern, it is possible to manufacture a focused flat Fresnel lens that performs a focused lens function to focus light by selecting an embossed or intaglio, and to produce a diffused flat Fresnel lens that can diffuse light. Can be.

12 is a cross-sectional view of a horizontal light emitting device with a flat Fresnel lens according to another embodiment of the present invention, Figure 13 is a horizontal light emitting device with a flat Fresnel lens according to another embodiment of the present invention Top view.

12 and 13, a horizontal light emitting device including a planar Fresnel lens according to another embodiment of the present invention includes a substrate 100, an N-type semiconductor layer 210, a light-emitting layer 220, and a P-type semiconductor layer. The transparent electrode 500 is formed on the 230.

The P-type electrode 410 is formed on the transparent electrode 500, and the N-type electrode 420 is formed in the N-type semiconductor layer 210.

The planar Fresnel lens layer 300 is formed on the transparent electrode 500.

In this case, the planar Fresnel lens layer 300 is formed in such a manner that the width of each concentric pattern decreases at a constant ratio toward the outside of the diameter in the state where the pitch between the patterns forming the concentric circles is the same, thereby performing the function of the focused lens.

The present invention is not limited to the embodiments described above, and various modifications and changes can be made by those skilled in the art, which are included in the spirit and scope of the present invention as defined in the appended claims.

For example, in the embodiment of the present invention, the first conductive semiconductor layer is an N-type semiconductor layer and the second conductive semiconductor layer is a P-type semiconductor layer, but the first conductive semiconductor layer is a P-type semiconductor layer and the second Even if the conductive semiconductor layer is an N-type semiconductor, it can be applied to any number.

In addition, although the embodiment of the present invention has been described in that the planar Fresnel lens layer formed on the upper portion of the light emitting device, the planar Fresnel lens layer may be formed on the lower portion of the light emitting device to increase the light extraction efficiency.

In addition, although the embodiment of the present invention has described the formation of a flat Fresnel lens layer on the light emitting device having a substrate, the vertical light emitting device from which the substrate is removed through the substrate separation process is also disposed on the light emitting device. The planar Fresnel lens layer may be formed to increase light extraction efficiency.

According to the present invention, the planar Fresnel lens having a vertical cross section can be easily integrated into the light emitting device through an etching process instead of the sawtooth planar Fresnel lens which is difficult to integrate into the light emitting device.

In addition, the light output efficiency can be improved by combining the spherical lens and the Fresnel lens by using the principle that the smaller the open part is, the later the etching when etching the transparent material to be the lens layer, and the pattern of the flat Fresnel lens Since the bottom surface of the groove formed therebetween can be easily processed without the need for a separate photolithography, it is possible to increase more light output efficiency.

Claims (11)

Substrate, A compound semiconductor layer formed on the substrate and having a light emitting region; A planar Fresnel lens layer formed on the compound semiconductor layer to focus or diffuse light emitted from the compound semiconductor layer, The planar Fresnel lens layer has at least one concentric circle pattern formed at the same height and spaced apart from each other by a groove formed by etching, the planar Fresnel characterized in that made of one translucent material with the same pitch between the concentric circle pattern A light emitting device having a lens. The method according to claim 1, The width of each concentric pattern provided in the planar Fresnel lens layer is a light emitting device having a planar Fresnel lens, characterized in that the width decreases or increases at a constant rate toward the radially outward direction. The method according to claim 2, The bottom of the groove formed between each of the concentric circle pattern is a light emitting device having a flat Fresnel lens, characterized in that the width of the adjacent concentric pattern increases as the width increases, and the shape is increased or lowered at a constant ratio toward the radially outward direction. The method according to claim 1, wherein the Fresnel lens layer, An insulating film made of one of SiOx, SixNy, SixONy, SrF ₂ , HF ₂ O ₃ , TiOx, Al ₂ O ₃ , a semiconductor material made of one of AlN, GaN, AlInGaN, GaAs, Ge, Si, InP, and Polyimide, BCB , An insulating material made of one of epoxy, a metal oxide made of one of ITO and Cu-doped tin oxide (CIO), a metal material made of one of Ni, Al, Au, Pt, Ru, Ti, Cr, and lithium niobate A light emitting device comprising a planar Fresnel lens of any one selected from. The method according to claim 1, The bottom of the groove formed between each concentric pattern is a light emitting device having a flat Fresnel lens, characterized in that the irregularities are formed. Preparing a substrate; Forming a compound semiconductor layer having a light emitting region on the substrate; Forming a planar Fresnel lens layer on the compound semiconductor layer to focus or diffuse light emitted from the compound semiconductor layer, The planar Fresnel lens layer has at least one concentric circle pattern formed at the same height and spaced apart from each other by a groove formed by etching, the planar Fresnel characterized in that made of one translucent material with the same pitch between the concentric circle pattern A method of manufacturing a light emitting device having a lens. The method of claim 6, wherein the planar Fresnel lens layer forming step, Forming a light-transmitting material having a predetermined thickness on the compound semiconductor layer; Forming at least one concentric circle pattern on the light-transmitting material, wherein pitches between the concentric circle patterns form the same mask pattern; And etching the translucent material such that the compound semiconductor layer is exposed between the concentric patterns by using the mask pattern. The method according to claim 7, The width of each concentric pattern provided in the mask pattern is reduced or increased at a constant rate toward the radially outward direction, the manufacturing method of a light emitting device having a flat Fresnel lens. The method of claim 6, wherein the Fresnel lens layer forming step, Forming a light-transmitting material having a predetermined thickness on the compound semiconductor layer; Forming a mask pattern having at least one concentric circle pattern on the light-transmitting material, the pitch of each concentric circle pattern being the same, but the width of each concentric circle decreasing or increasing at a constant rate toward the radially outward direction; Etching the translucent material such that a groove is formed between the concentric patterns using the mask pattern, The bottom of the groove formed between the concentric patterns by the etching is increased as the width of the adjacent concentric patterns increases, and the light emission having the flat Fresnel lens, characterized in that the shape is increased or decreased at a constant ratio toward the radially outward direction. Method of manufacturing the device. The method according to claim 6, wherein the Fresnel lens layer, An insulating film made of one of SiOx, SixNy, SixONy, SrF ₂ , HF ₂ O ₃ , TiOx, Al ₂ O ₃ , a semiconductor material made of one of AlN, GaN, AlInGaN, GaAs, Ge, Si, InP, and Polyimide, BCB , An insulating material made of one of epoxy, a metal oxide made of one of ITO and Cu-doped tin oxide (CIO), a metal material made of one of Ni, Al, Au, Pt, Ru, Ti, Cr, and lithium niobate Method of manufacturing a light emitting device having a flat Fresnel lens of any one selected from. The method according to claim 6, The bottom of the groove formed between the concentric patterns by the etching is a method of manufacturing a light emitting device having a flat Fresnel lens, characterized in that the irregularities are formed.

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