KR20100003013A - Light emitting diode and method for fabricating the same - Google Patents

Abstract

A compound semiconductor layer comprising at least a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer formed on the substrate; There is provided a light emitting diode, characterized in that the reflection structure for reflecting the light emitted in the lateral direction from the light generated in the active layer is formed in the direction perpendicular to the semiconductor layer growth direction inside the at least one compound semiconductor layer. do.

Description

LIGHT EMITTING DIODE AND METHOD FOR FABRICATING THE SAME}

The present invention relates to a light emitting diode and a method of manufacturing the same, and more particularly, to a light emitting diode having a reflection structure for reflecting light emitted to at least one side of the light emitting diode therein to improve the light extraction efficiency and its manufacturing method It is about.

A light emitting diode, which is a typical light emitting device, is a photoelectric conversion semiconductor device having a structure in which an N-type semiconductor and a P-type semiconductor are bonded to each other, and are configured to emit light by recombination of electrons and holes.

As such a light emitting diode, a GaN-based light emitting diode is known. GaN-based light emitting diodes are manufactured by sequentially stacking GaN-based N-type semiconductor layers, active layers (or light-emitting layers), and P-type semiconductor layers on a substrate made of a material such as sapphire or SiC.

Recently, high-efficiency light emitting diodes are expected to replace fluorescent lamps. In particular, the efficiency of white light emitting diodes has reached a level similar to that of conventional fluorescent lamps. However, the efficiency of the light emitting diode is further improved, and therefore, continuous efficiency improvement is further required.

Two major approaches have been attempted to improve the efficiency of light emitting diodes. The first is to increase the internal quantum efficiency, which is determined by the crystal quality and the epilayer structure, and the second is that the light generated in the light emitting diode is not emitted to the whole outside but is lost inside. This increases the light extraction efficiency.

In the conventional case, light extraction from the inside is made by forming irregularities on the surface of the sapphire substrate before epi growth, roughening the surface of the P-type semiconductor layer, which is the final stage of epi growth, or depositing a highly reflective metal or oxide on the back side of the substrate. To improve the efficiency.

However, in order to make a pattern on a sapphire substrate, expensive photo equipment is required and productivity is a problem because of low yield, and when the surface of the P-type semiconductor layer is roughened, operating voltage and contact resistance increase, which causes problems in reliability. . In addition, when the metal is deposited on the back side of the substrate, discoloration deterioration or peeling, such as oxidation / sulfurization, may occur in an environment such as high temperature and high humidity.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light emitting diode and a method of manufacturing the same, which reflect light emitted to at least one side of the light emitting diode to improve light extraction efficiency.

According to one aspect of the present invention, there is provided a compound semiconductor layer including at least a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer formed on a substrate; A light emitting diode having a reflective structure for reflecting light emitted in a lateral direction among light generated in the active layer is formed in the at least one compound semiconductor layer in a direction perpendicular to the growth direction of the semiconductor layer.

Preferably, the reflective structure comprises at least one material selected from Al, Ag, Pt, Pd, Au, Rh or Al alloy, Ag alloy, Pt alloy, Pd alloy, Au alloy, Rh alloy; It may further include an insulating film surrounding the at least one material.

Preferably, the reflective structure is a distributed bragg reflector (DBR) formed by alternately stacking two or more insulating layers having different refractive indices.

Preferably, the light emitting diode may further include a TiN buffer layer formed between the substrate and the first conductivity type semiconductor layer.

Preferably, the reflective structure may have a curved surface or irregularities.

Preferably, the light emitting diode may expose a portion of the upper portion of the first conductivity type semiconductor layer, and the reflective structure may be formed inside the exposed first conductivity type semiconductor layer.

Preferably, in the light emitting diode, a portion of an upper portion of the first conductivity type semiconductor layer is exposed, and the active layer and the second conductivity type semiconductor layer are disposed on another portion of the upper portion of the first conductivity type semiconductor layer. The reflective structure may be formed inside another portion of the first conductive semiconductor layer, the active layer, and the second conductive semiconductor layer.

Preferably, in the light emitting diode, a portion of an upper portion of the first conductivity type semiconductor layer is exposed, and the active layer and the second conductivity type semiconductor layer are formed on another portion of the upper portion of the first conductivity type semiconductor layer. The reflective structure may include a portion of an upper portion of the first conductive semiconductor layer, the active layer, the inside of the second conductive semiconductor layer; It may be formed in a portion of the exposed first conductive semiconductor layer.

According to another aspect of the invention, forming a compound semiconductor layer comprising at least a first conductive semiconductor layer, an active layer, a second conductive semiconductor layer formed on a substrate; Etching an inner portion of the at least one compound semiconductor layer; And forming a reflective structure on the etched portion of the at least one compound semiconductor layer to reflect light emitted in the lateral direction from the light generated in the active layer in a direction perpendicular to the growth direction of the semiconductor layer. A manufacturing method is provided.

Preferably, the reflective structure comprises at least one material selected from Al, Ag, Pt, Pd, Au, Rh or Al alloy, Ag alloy, Pt alloy, Pd alloy, Au alloy, Rh alloy; It may further include an insulating film surrounding the at least one material.

Preferably, the reflective structure is a distributed bragg reflector (DBR) formed by alternately stacking two or more insulating layers having different refractive indices.

Advantageously, the light emitting diode manufacturing method includes forming a first conductivity type semiconductor layer on a substrate; The method may further include forming a TiN buffer layer between the substrate and the first conductive semiconductor layer.

Preferably, the reflective structure may have a curved surface or irregularities.

Preferably, the light emitting diode may expose a portion of the upper portion of the first conductivity type semiconductor layer, and the reflective structure may be formed inside the exposed first conductivity type semiconductor layer.

Preferably, in the light emitting diode, a portion of an upper portion of the first conductivity type semiconductor layer is exposed, and the active layer and the second conductivity type semiconductor layer are formed on another portion of the upper portion of the first conductivity type semiconductor layer. The reflective structure may be formed inside another part of the first conductive semiconductor layer, the active layer, and the second conductive semiconductor layer.

Preferably, in the light emitting diode, a portion of an upper portion of the first conductivity type semiconductor layer is exposed, and the active layer and the second conductivity type semiconductor layer are formed on another portion of the upper portion of the first conductivity type semiconductor layer. The reflective structure may include a portion of an upper portion of the first conductive semiconductor layer, the active layer, the inside of the second conductive semiconductor layer; It may be formed in a portion of the exposed first conductive semiconductor layer.

According to an embodiment of the present invention, by forming a reflection structure near the edge of the light emitting diode so that the light generated in the active layer is reflected by the reflection structure and emitted to the upper side, as a result, the electrical characteristics of the light emitting diode are not degraded. The light generated in the active layer can be emitted to the outside effectively. In addition, it is possible to easily manufacture using the general equipment and processes of the semiconductor process can improve the light extraction efficiency of the light emitting diode without affecting the reliability and yield reduction.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples to ensure that the spirit of the present invention can be fully conveyed to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And, in the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience. Like numbers refer to like elements throughout.

1 is a cross-sectional view illustrating a light emitting diode according to an embodiment of the present invention, and FIG. 2 is a plan view of FIG. 1.

1 and 2, an LED according to an embodiment of the present invention includes an N-type semiconductor layer 55, an active layer 57, and a P-type semiconductor layer on a substrate 51 via a buffer layer 53. Compound semiconductor layers comprising (59) are positioned. The substrate 51 may be an insulating or conductive substrate. The substrate 51 includes sapphire (Al ₂ O ₃ ), silicon carbide (SiC), zinc oxide (ZnO), silicon (Si), gallium arsenide (GaAs), gallium phosphorus (GaP), lithium-alumina (LiAl ₂ O _3). ), Boron nitride (BN), aluminum nitride (AlN) or gallium nitride (GaN) substrate, but is not limited thereto. Meanwhile, the compound semiconductor layers are III-N series compound semiconductor layers. For example, it is a (Al, Ga, In) N semiconductor layer. The P electrode 83 is formed in the P-type semiconductor layer 59, and the N electrode 85 is formed in a portion of the N-type semiconductor layer 55. Therefore, light can be emitted by supplying current through the P electrode 83 and the N electrode 85.

In some regions (preferably the edges) of the N-type semiconductor layer 55, a reflective structure 60 is formed in the vertical direction from the top of the N-type semiconductor layer 55 to the buffer layer 53, and in the horizontal direction. As illustrated in FIG. 2, the P-type electrode 83 and the N-type electrode 85 of the light emitting diode are surrounded.

The reflective structure 60 is preferably used for a material having high reflectance. For example, the reflective structure 60 may use an insulating material or a conductive material having high reflectance. In the case of the conductive structure, the reflective structure 60 may be formed in the N-type semiconductor layer 55 through an insulating film. For example, the reflective structure 60 may be formed such that two or more insulating layers having different refractive indices are alternately stacked in multiple layers to perform a function of a distributed bragg reflector (DBR). Distributed Bragg Reflectors (DBRs) are used when high reflectivity is required in various light emitting devices including light emitting functions, light detection functions, light modulation functions, and the like. DBR is a reflecting mirror which laminates | stacks two types of media from which refractive indices differ, and reflects light using the difference in refractive index. The insulating material that can be used for the reflective structure 60 may be selected from, for example, SiO _x , SiN _x , Si _x N _y , and SiON _x , and may be formed, for example, by chemical vapor deposition or sputtering. The conductive material that can be used for the reflective structure 60 may be selected from, for example, Al, Ag, Pt, Pd, Au, Rh or Al alloy, Ag alloy, Pt alloy, Pd alloy, Au alloy, Rh alloy. It is selectable and can be formed in the N-type semiconductor layer 55 via an insulating film such as SiO _x , SiN _x , Si _x N _y , SiON _x , TiO ₂ .

Among the light generated in the active layer 57, the light directed toward the substrate 51 rather than toward the P-type semiconductor layer 59 is reflected by the reflective structure 60 and is emitted toward the upper portion of the P-type semiconductor layer 59.

3 to 5 are cross-sectional views illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 3, compound semiconductor layers are formed on a substrate 51. The substrate 51 may be a sapphire substrate, but is not limited thereto, and may be another hetero substrate. The compound semiconductor layers include an N-type semiconductor layer 55, an active layer 57, and a P-type semiconductor layer 59. The compound semiconductor layers are III-N-based compound semiconductor layers, and may be grown by a process such as metal organic chemical vapor deposition (MOCVD) or molecular beam deposition (MBE).

Meanwhile, before forming the compound semiconductor layers, a buffer layer 53 may be formed on the substrate 51. The buffer layer 53 is adopted to mitigate lattice mismatch between the substrate 51 and the compound semiconductor layers, and may generally be a gallium nitride-based material layer.

Referring to FIG. 4, a portion of the N-type semiconductor layer 55 is exposed by mesa etching some regions of the compound semiconductor layers 55, 57, and 59. An N electrode 85 is formed in a portion of the N-type semiconductor layer 55 exposed through mesa etching, and a P electrode 83 is formed in a portion of the P-type semiconductor layer 59.

Referring to FIG. 5, etching is performed to form an open region 55a surrounding the P electrode 83 and the N electrode 85 in a horizontal direction in an edge region of the N-type semiconductor layer 55. The N-type semiconductor layer 55 is exposed through the open region 55a formed through etching.

When the reflective structure 60 is formed by filling a reflective material in the open region 55a of the N-type semiconductor layer 55, the light emitting diode shown in FIG. 1 is completed. The reflective structure 60 is formed _by depositing an insulating film such as, for example, SiO _x , SiN _x , Si _x N _y , SiON _x in the open region 55a by, for example, chemical vapor deposition or sputtering. At least one of Al, Ag, Pt, Pd, Au, Rh or an Al alloy, Ag alloy, Pt alloy, Pd alloy, Au alloy, Rh alloy may be formed by filling. In contrast, the reflective structure 60 alternately stacks insulating materials having different refractive indices, for example, SiO _x , SiN _x , Si _x N _y , SiON _x , and TiO ₂ , in the open region 55a. By doing this, a DBR can be formed. The width of the reflective structure 60 may be, for example, 10 nm or more and 100 μm or less, but considering the etching depth, an aspect ratio of about 1.5 or less may be appropriate.

6 and 7 are a cross-sectional view and a plan view for explaining a light emitting diode according to another embodiment of the present invention.

In the light emitting diode according to the exemplary embodiment of the present invention illustrated in FIGS. 1 to 5, the reflective structure 60 is limited to the N-type semiconductor layer 55, but the present invention illustrated in FIGS. In the light emitting diode according to another embodiment, the N-type semiconductor layer 55, the active layer 57, and the P-type semiconductor layer 59 are formed in a stacked portion. Therefore, after performing the processes described with reference to FIGS. 3 and 4, the N-type semiconductor layer 55, the active layer 57, and the P-type semiconductor layer 59 are sequentially stacked on the edge of the portion where they are stacked. After forming an open region (not shown) surrounding the P electrode 83, the reflective structure 60 is formed by filling the open region with the above-described reflective material. The reflective structure 60 may be formed from the top of the P-type semiconductor layer 59 where the P electrode 83 is formed in the vertical direction to the buffer layer 53. As the reflective structure 60 is formed over the N-type semiconductor layer 55, the active layer 57, and the P-type semiconductor layer 59, the light directed toward the side and the bottom of the light generated in the active layer 57 Reflected by the reflective structure 60 may be emitted toward the top of the light emitting diode.

8 and 9 are a cross-sectional view and a plan view for explaining a light emitting diode according to another embodiment of the present invention.

In the light emitting diode according to the exemplary embodiment of the present invention illustrated in FIGS. 1 to 5, the reflective structure 60 is limited to the N-type semiconductor layer 55 and is illustrated in FIGS. 6 and 7. In the light emitting diode according to another embodiment, the N-type semiconductor layer 55, the active layer 57 and the P-type semiconductor layer 59 are formed to be limited to the stacked portion, but the present invention shown in Figs. In the light emitting diode according to another exemplary embodiment of the present invention, the reflective structure 60 is formed to surround a portion of the N-type semiconductor layer 55 on which the P electrode 83 is formed and the N electrode 85 is formed. have.

Therefore, after performing the process described with reference to FIGS. 3 and 4, the P electrode (at the edge of the portion where the N-type semiconductor layer 55, the active layer 57, and the P-type semiconductor layer 59 are sequentially stacked) is formed. An open region (not shown) is formed to surround 83 and surround the N electrode 85 formed in the N-type semiconductor layer 55, and then fill the open region with a reflective material to form the reflective structure 60. The reflective structure 60 may be formed from the top of the P-type semiconductor layer 59 to the buffer layer 53 in the portion where the P electrode 83 is formed in the vertical direction, and the N electrode 85 is formed. In the portion of the N-type semiconductor layer 55 to the buffer layer 53 can be formed. The reflective structure 60 surrounds the P electrode 83 in the horizontal direction and is formed over the N-type semiconductor layer 55, the active layer 57, and the P-type semiconductor layer 59 in the vertical direction, and N in the horizontal direction. As formed in the N-type semiconductor layer 55 surrounding the electrode 85, the light directed toward the side and the bottom of the light generated by the active layer 57 is reflected by the reflecting structure 60 so that the top of the light emitting diode Can be released to the side.

Although the present invention has been described in detail with reference to preferred embodiments, the scope of the present invention is not limited to the specific embodiments, it should be interpreted by the appended claims. In addition, those of ordinary skill in the art will understand that many modifications and variations are possible without departing from the scope of the present invention.

For example, in the embodiments of the present invention, in forming the buffer layer 53 on the substrate 51, a gallium nitride-based material layer may be employed to mitigate lattice mismatch between the substrate 51 and the compound semiconductor layers. For example, the light directed toward the substrate is deposited by mitigating lattice mismatch between the substrate 51 and the compound semiconductor layers, and depositing a material having excellent reflective properties, such as TiN (but the present invention is not limited thereto). May be further reflected from the buffer layer 53 and sent back to the upper side.

In addition, in forming the reflective structure 60, it is possible to improve the reflective characteristics of the reflective structure 60 by changing the shape, such as giving a curved surface or irregularities.

Further, in the embodiments of the present invention, the structure of the substrate, the N-type semiconductor layer, the active layer, and the P-type semiconductor layer has been described. However, the present invention is not limited thereto, and the structure of the substrate, the P-type semiconductor layer, the active layer, and the N-type semiconductor layer is described. Applicable to

In addition, in the embodiments of the present invention, the reflective structure is formed perpendicularly to the semiconductor layer growth direction from the top of the N-type semiconductor layer or the top of the P-type semiconductor layer to the buffer layer, but the present invention is not limited thereto. The first conductive semiconductor layer, the active layer, the second conductive semiconductor layer, and the buffer layer may be formed in at least a portion of at least one layer. For example, it may be formed on only part of the active layer, or may be formed throughout, or may be formed on part or all of the first conductivity type semiconductor layer, or may be formed on part or all of the second conductivity type semiconductor layer, It may be formed in part or all of the buffer layer, and various combinations thereof may be possible.

Further, in the embodiments of the present invention, the reflective structure is formed to surround the light emitting diode, but may be formed only in at least one side direction.

1 and 2 are a cross-sectional view and a plan view for explaining a light emitting diode according to an embodiment of the present invention.

3 to 5 are cross-sectional views illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

6 and 7 are a cross-sectional view and a plan view for explaining a light emitting diode according to another embodiment of the present invention.

8 and 9 are a cross-sectional view and a plan view for explaining a light emitting diode according to another embodiment of the present invention.

Claims (13)

A compound semiconductor layer comprising at least a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer formed on the substrate; A reflective structure for reflecting light emitted in the lateral direction among the light generated in the active layer is formed in the direction perpendicular to the semiconductor layer growth direction in the at least one compound semiconductor layer. The method according to claim 1, wherein the reflective structure, At least one material selected from Al, Ag, Pt, Pd, Au, Rh or an Al alloy, Ag alloy, Pt alloy, Pd alloy, Au alloy, Rh alloy; And an insulating film surrounding the at least one material. The method according to claim 1, wherein the reflective structure, A light emitting diode, which is a distributed bragg reflector (DBR) formed by alternately stacking two or more insulating layers having different refractive indices. The method according to claim 1, wherein the light emitting diode, And a TiN buffer layer formed between the substrate and the first conductivity type semiconductor layer. The method according to claim 1, wherein the reflective structure, A light emitting diode having a curved surface or irregularities. The method according to claim 1, wherein the light emitting diode, A portion of the upper portion of the first conductivity type semiconductor layer is exposed, The reflective structure is formed in the interior of the exposed first conductive semiconductor layer. The method according to claim 1, wherein the light emitting diode, A portion of the upper portion of the first conductivity type semiconductor layer is exposed, The active layer and the second conductive semiconductor layer are formed on the other upper portion of the first conductive semiconductor layer, And the reflective structure is formed inside another part of the first conductive semiconductor layer, the active layer, and the second conductive semiconductor layer. The method according to claim 1, wherein the light emitting diode, A portion of the upper portion of the first conductivity type semiconductor layer is exposed, The active layer and the second conductivity type semiconductor layer are formed on another portion of the upper portion of the first conductivity type semiconductor layer, The reflective structure may include a part of another upper portion of the first conductive semiconductor layer, the active layer, the inside of the second conductive semiconductor layer; The light emitting diode of claim 1, wherein the light emitting diode is formed in a portion of the exposed first conductive semiconductor layer. Forming compound semiconductor layers comprising at least a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer formed on the substrate; Etching an inner portion of the at least one compound semiconductor layer; And forming a reflective structure on the etched portion of the at least one compound semiconductor layer to reflect light emitted in the lateral direction among the light generated in the active layer in a direction perpendicular to the growth direction of the semiconductor layer. Light emitting diode manufacturing method. The method of claim 9, wherein the reflective structure, At least one material selected from Al, Ag, Pt, Pd, Au, Rh or an Al alloy, Ag alloy, Pt alloy, Pd alloy, Au alloy, Rh alloy; And an insulating film surrounding the at least one material. The method according to claim 9, wherein the reflective structure, A method of manufacturing a light emitting diode, characterized in that the DBR (Distributed Bragg Reflector) formed by alternately stacking two or more insulating layers having different refractive indices. The method according to claim 9, The light emitting diode manufacturing method, Forming a first conductivity type semiconductor layer on the substrate; The method of claim 1, further comprising forming a TiN buffer layer between the substrate and the first conductive semiconductor layer. The method of claim 9, wherein the reflective structure, The light emitting diode manufacturing method characterized by having a curved surface or uneven | corrugated.

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