KR20070097906A - A light emitting device having a patterned transparent electrode layer and a method of manufacturing the same - Google Patents

Abstract

A light emitting device having a patterned transparent electrode layer and a method of manufacturing the same are disclosed. This light emitting device includes a zinc oxide substrate having a bottom surface and a top surface. The lower surface of the zinc oxide substrate is defined in the lower region of the upper surface, and the upper surface has a larger cross-sectional width than the lower surface. On the other hand, the N-type semiconductor layer is located on the upper surface of the zinc oxide substrate, and the P-type semiconductor layer is located on the N-type semiconductor layer. In addition, an active layer is interposed between the N-type semiconductor layer and the P-type semiconductor layer. In addition, a zinc oxide transparent electrode layer is located on the P-type semiconductor layer. The zinc oxide transparent electrode layer has a lower surface facing the P-type semiconductor layer and an upper surface defined in the upper region of the lower surface. The lower surface of the zinc oxide transparent electrode layer has a larger cross-sectional width than its upper surface. By adopting the above transparent electrode layer and the substrate, a light emitting device having improved light extraction efficiency and light uniformity is provided.

Description

LIGHT EMITTING DEVICE HAVING PATTERNED TRASPARENT ELECTRODE LAYER AND METHOD OF FABRICATING THE SAME}

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

3 and 4 are cross-sectional views illustrating a method of manufacturing a light emitting device according to an embodiment of the present invention.

5 and 6 are plan and cross-sectional views for describing a light emitting device according to another exemplary embodiment of the present invention, and FIG. 7 is an equivalent circuit diagram of FIG. 6.

8 to 10 are cross-sectional views illustrating a method of manufacturing a light emitting device according to another embodiment of the present invention.

The present invention relates to a light emitting device and a method of manufacturing the same, and more particularly to a light emitting device having a patterned transparent electrode layer and a method of manufacturing the same.

Gallium nitride (GaN) series light emitting diodes have been applied and developed for more than 10 years. GaN-based LEDs have changed the LED technology considerably and are currently used in a variety of applications, including color LED displays, LED traffic signals and white LEDs. Recently, high-efficiency white LEDs are expected to replace fluorescent lamps. In particular, the efficiency of white LEDs has reached a level similar to that of conventional fluorescent lamps.

Two major approaches are being attempted to improve LED efficiency. The first is to increase the internal quantum efficiency determined by the crystal quality and epilayer structure, and the second is to increase the light extraction efficiency. Internal quantum efficiency is currently 70-80%, so there is not much room for improvement, but light extraction efficiency has much room for improvement. Improving light extraction efficiency has been a major problem to remove internal light loss due to internal reflection and to improve heat dissipation performance.

Meanwhile, the GaN-based compound semiconductor is epitaxially grown on a substrate having a similar crystal structure and lattice constant to reduce the occurrence of crystal defects. In general, sapphire has been used as the substrate. However, since sapphire is an insulating material, electrode pads of the light emitting diode are formed on the growth surface of the epi layer. The formation of the electrode pads leads to a reduction in the light emitting area, and consequently the chip area is increased to obtain the required light output per unit chip. An increase in chip area leads to an increase in manufacturing cost per chip. Therefore, there is a need for a new light emitting diode capable of increasing light output in the same unit chip area.

In addition, sapphire has a low thermal conductivity, and thus does not easily release heat generated from the light emitting diodes to the outside. This low heat dissipation performance makes it difficult to apply light emitting diodes in applications requiring high power.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a light emitting device having improved light extraction efficiency.

Another object of the present invention is to provide a light emitting device capable of increasing light output per unit area.

Another object of the present invention is to provide a method of manufacturing a light emitting device capable of increasing light extraction efficiency and light output per unit area.

In order to achieve the above technical problem, the present invention provides a light emitting device having a patterned transparent electrode layer and a method of manufacturing the same. The light emitting device according to the embodiment of the present invention includes a zinc oxide substrate having a lower surface and an upper surface. The lower surface is defined in a lower region of the upper surface, and the upper surface has a larger cross-sectional width than the lower surface. Meanwhile, an N-type semiconductor layer is located on the upper surface of the zinc oxide substrate, and a P-type semiconductor layer is located on the N-type semiconductor layer. In addition, an active layer is interposed between the N-type semiconductor layer and the P-type semiconductor layer. In addition, a zinc oxide transparent electrode layer is located on the P-type semiconductor layer. The zinc oxide transparent electrode layer has a lower surface facing the P-type semiconductor layer and an upper surface defined in an upper region of the lower surface. The lower surface of the zinc oxide transparent electrode layer has a larger cross-sectional width than the upper surface.

In the present embodiment, the zinc oxide transparent electrode layer and the zinc oxide substrate have sloped side surfaces to prevent light loss due to internal reflection. In addition, the inclined side surfaces of the zinc oxide transparent electrode layer prevent light from being concentrated at the edges, thereby uniformly emitting light to the outside. Accordingly, by adopting the patterned zinc oxide transparent electrode layer and the zinc oxide substrate, it is possible to provide a light emitting device having improved light extraction efficiency and uniformity of light.

The N-type semiconductor layer, the P-type semiconductor layer and the active layer may be formed of a gallium nitride-based compound semiconductor, that is, (B, Al, In, Ga) N.

The method of manufacturing the light emitting device according to the embodiment of the present invention includes forming an N-type semiconductor layer, an active layer, a P-type semiconductor layer, and a ZnO transparent electrode layer on a ZnO substrate. The ZnO transparent electrode layer is patterned. As a result, a patterned ZnO transparent electrode layer is formed having a lower surface facing the P-type semiconductor layer and an upper surface defined in an upper region of the lower surface, the lower surface having a larger cross-sectional width than the upper surface. In addition, the ZnO substrate is patterned. As a result, a patterned ZnO substrate is formed having an upper surface facing the N-type semiconductor layer and a lower surface defined in the lower region of the upper surface, the upper surface having a larger cross-sectional width than the lower surface.

The ZnO substrate may be patterned using photo and etching processes. Alternatively, the ZnO substrate may be patterned by a dicing process using a diamond blade.

The light emitting device according to another embodiment of the present invention includes a zinc oxide substrate having a lower surface and an upper surface. The lower surface is defined in a lower region of the upper surface, and the upper surface has a larger cross-sectional width than the lower surface. Meanwhile, a lower N-type semiconductor layer is located on the upper surface of the zinc oxide substrate, a P-type semiconductor layer is located on the lower N-type semiconductor layer, and an upper N-type semiconductor layer is on one region of the P-type semiconductor layer. Located in In addition, a lower active layer is interposed between the lower N-type semiconductor layer and the P-type semiconductor layer, and an upper active layer is interposed between the P-type semiconductor layer and the upper N-type semiconductor layer. In addition, a zinc oxide transparent electrode layer is located on the upper N-type semiconductor layer. The zinc oxide transparent electrode layer has a lower surface facing the upper N-type semiconductor layer and an upper surface defined in an upper region of the lower surface. The lower surface of the zinc oxide transparent electrode layer has a larger cross-sectional width than the upper surface. Accordingly, the light emitting diodes sharing the P-type semiconductor layer are stacked on each other to provide a light emitting device having improved light output per unit area.

The lower N-type semiconductor layer, the lower active layer, the P-type semiconductor layer, the upper active layer, and the upper N-type semiconductor layer may be formed of a gallium nitride-based compound semiconductor.

The light emitting device manufacturing method according to another embodiment of the present invention includes forming a lower N-type semiconductor layer, a lower active layer, a P-type semiconductor layer, an upper active layer, an upper N-type semiconductor layer and a ZnO transparent electrode layer on a ZnO substrate. . Thereafter, the ZnO transparent electrode layer, the upper N-type semiconductor layer, and the upper active layer are patterned. As a result, the P-type semiconductor layer is exposed, and has a lower surface facing the upper N-type semiconductor layer and an upper surface defined within an upper region of the lower surface, the lower surface being patterned having a larger cross-sectional width than the upper surface. A ZnO transparent electrode layer is formed. In addition, the ZnO substrate is patterned. As a result, a patterned ZnO substrate is formed having an upper surface facing the lower N-type semiconductor layer and a lower surface defined in the lower region of the upper surface, the upper surface having a larger cross-sectional width than the lower surface.

The ZnO substrate may be patterned using photo and etching processes. Alternatively, the ZnO substrate may be patterned by a dicing process using a diamond blade.

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 plan view illustrating a light emitting device 20 according to an exemplary embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line I-I of FIG. 1.

1 and 2, the light emitting device 20 includes a zinc oxide (ZnO) substrate 21. The ZnO substrate 21 has a lower surface 21a and an upper surface 21b. The lower surface 21a is defined in the lower region of the upper surface 21b, and the upper surface 21b has a larger cross-sectional width than the lower surface 21a. Therefore, the zinc oxide (ZnO) substrate 21 has an inclined side toward the lower surface 21a from the upper surface 21a.

The N-type semiconductor layer 23 is positioned on the upper surface 21b of the ZnO substrate 21. In addition, a P-type semiconductor layer 27 is positioned on the N-type semiconductor layer 23, and an active layer 25 is interposed between the N-type semiconductor layer 23 and the P-type semiconductor layer 27. The N-type semiconductor layer 23, the active layer 25, and the P-type semiconductor layer 27 constitute a light emitting diode 26.

The N-type semiconductor layer 23, the active layer 25, and the P-type semiconductor layer 27 may be formed of gallium nitride (GaN) -based semiconductor layers formed of (B, Al, Ga, In) N, respectively. . In general, the gallium nitride-based N-type semiconductor layer may be formed by doping Si, the P-type semiconductor layer may be formed by doping Mg. The active layer 25 may be a single quantum well or multiple quantum wells.

The ZnO transparent electrode layer 29 is positioned on the P-type semiconductor layer 27. The ZnO transparent electrode layer 29 has a lower surface 29a facing the P-type semiconductor layer 27 and an upper surface 29b defined in the upper region of the lower surface 29a. The lower surface 29a of the ZnO transparent electrode layer 29 has a larger cross-sectional width than the upper surface 29b.

According to the present embodiment, the ZnO substrate 21 and the ZnO transparent electrode layer 29 are disposed below and above the light emitting diode 26, respectively. The substrate 21 and the transparent electrode layer 29 have a predetermined shape, and this shape reduces light loss due to internal reflection, thereby improving light extraction efficiency.

For example, as shown, when the cross section of the ZnO transparent electrode layer 29 has a trapezoidal shape, the amount of light generated in the light emitting diodes 26 is totally reflected at the upper surface 29b of the transparent electrode layer 29 and is greatly reduced. You can. In addition, by forming the side of the transparent electrode layer 29 to be inclined, it is possible to prevent the phenomenon that light is concentrated in the edge region due to total reflection and light refraction. Meanwhile, the ZnO substrate 21 has an inverted trapezoidal shape, and a reflective film (not shown) is coated on the lower surface 21a and the side surface of the ZnO substrate 21. Light incident from the light emitting diode 26 to the ZnO substrate 21 is reflected at the lower surface 21a and the side surface. Since the ZnO substrate 21 has an inclined side surface, the light reflected from the side surface is relatively directed toward the transparent electrode layer 29. Accordingly, light incident on the ZnO substrate 21 experiences less internal reflection, thus reducing light loss.

Meanwhile, an electrode pad (not shown) for connecting a bonding wire may be formed on the ZnO transparent electrode layer 29. In addition, a tunnel layer or a metal layer (not shown) is formed between the ZnO transparent electrode layer 29 and the P-type semiconductor layer 27 to ohmic-bond the ZnO transparent electrode layer 29 and the P-type semiconductor layer 27. You can.

3 and 4 are cross-sectional views illustrating a method of manufacturing a light emitting device according to an embodiment of the present invention.

3, an N-type semiconductor layer 23, an active layer 25, a P-type semiconductor layer 27 and a ZnO transparent electrode layer 29 are formed on a ZnO substrate 21. The N-type semiconductor layer 23 ), The active layer 25 and the P-type semiconductor layer 27 are (B, Al, In, Ga) N compound semiconductors using metalorganic chemical vapor deposition, molecular beam growth (MBE) or hydride vapor phase growth (HVPE) techniques. It can be formed as.

The ZnO transparent electrode layer 29 may be formed using a molecular beam growth method, a metal organic chemical vapor deposition technique, or the like. The ZnO transparent electrode layer 29 is ohmic contacted to the P-type semiconductor layer 27, and a highly doped tunnel layer or metal layer (not shown) is formed between the ZnO transparent electrode layer 29 and the P-type semiconductor layer 27. Can be formed on.

ZnO materials are metal oxides with excellent etchability and good light transmission and electrical properties. Accordingly, the ZnO transparent electrode layer 29 may be formed relatively thicker than Ni / Au and indium tin oxide (ITO). For example, Ni / Au and ITO are limited to a thickness of about 0.005 to 0.2 μm due to the light transmittance limitation, but the ZnO transparent electrode layer 29 may be formed to a thickness of several to several tens of microns.

Referring to FIG. 4, the ZnO transparent electrode layer 29 is patterned. Since the ZnO transparent electrode layer 29 may be formed thicker than Ni / Au or ITO, the ZnO transparent electrode layer 29 may be patterned using photo and etching processes to form various shapes. For example, the patterned ZnO transparent electrode layer 29 has a lower surface 29a facing the P-type semiconductor layer 27 and an upper surface 29b defined in an upper region of the lower surface 29a. 29a) has a larger cross-sectional width than the upper surface 29b. While the ZnO transparent electrode layer 29 is patterned, the P-type semiconductor layer 27, the active layer 25, and the N-type semiconductor layer 23 are patterned together to separate the light emitting diodes 26. Separating the light emitting diodes 26 may be performed before or after patterning the ZnO transparent electrode layer 29.

Subsequently, the ZnO substrate 21 is patterned. As shown in FIG. 2, the patterned ZnO substrate 21 has an upper surface 21b facing the N-type semiconductor layer 23 and a lower surface 21a defined in a lower region of the upper surface. The upper surface 21b has a larger cross-sectional width than the lower surface 21a.

The ZnO substrate 21 may be patterned using photolithography and etching processes. Alternatively, the ZnO substrate 21 may be performed using a dicing process for separating chips using a diamond blade. That is, the ZnO substrate 21 is cut using a blade whose cross section width is narrowed toward the end. As a result, as shown in FIG. 2, a ZnO substrate 21 having a patterned inclined side surface is formed.

5 is a cross-sectional view illustrating a light emitting device 50 according to another exemplary embodiment of the present invention, FIG. 6 is a cross-sectional view taken along the line II-II of FIG. 5, and FIG. 7 is an equivalent circuit diagram of FIG. 6.

5 and 6, the light emitting device 50 includes a ZnO substrate 51. The ZnO substrate 51 has an upper surface and a lower surface of the same structure as the ZnO substrate 21 of FIG. 2.

A lower N-type semiconductor layer 53, a lower active layer 55, and a P-type semiconductor layer 57 are positioned on the ZnO substrate 51. The lower N-type semiconductor layer 53, the lower active layer 55, and the P-type semiconductor layer 57 constitute a lower light emitting diode 56. Meanwhile, an upper N-type semiconductor layer 61 is positioned on one region of the P-type semiconductor layer 57, and an upper active layer 59 is disposed between the P-type semiconductor layer 57 and the upper N-type semiconductor layer 61. ) Is interposed. The P-type semiconductor layer 57, the upper active layer 59, and the upper N-type semiconductor layer 61 constitute an upper light emitting diode 60. Another region of the P-type semiconductor layer 57 is exposed adjacent to the upper N-type semiconductor layer 61. The P-type electrode pad 65 is formed on another exposed region of the P-type semiconductor layer 57.

 As described with reference to FIG. 2, the lower N-type semiconductor layer 53, the lower active layer 55, the P-type semiconductor layer 57, the upper active layer 59, and the upper N-type semiconductor layer 61, respectively, (B, Al, Ga, In) N.

Meanwhile, the ZnO transparent electrode layer 63 is positioned on the upper N-type semiconductor layer 61. The ZnO transparent electrode layer 63 has a lower surface 63a facing the upper N-type semiconductor layer 61 and an upper surface 63b defined in the upper region of the lower surface 63a. The lower surface 63a of the ZnO transparent electrode layer 63 has a larger cross-sectional width than the upper surface 63b.

According to the present embodiment, the substrate 51 and the transparent electrode layer 63 have a predetermined shape, and this shape reduces the light loss due to internal reflection to improve the light extraction efficiency.

Referring to FIG. 7, the light emitting device 50 according to the present exemplary embodiment has a lower light emitting diode 56 and an upper light emitting diode 60 facing each other. Therefore, the positive terminal of the external power source (not shown) is connected to the P-type electrode pad 65, and the negative terminal of the external power source is connected to the ZnO substrate 51 and the ZnO transparent electrode layer 63 to emit light. Diodes 56 and 60 can be driven. Therefore, two light emitting diodes 56 and 60 can be driven simultaneously on a single chip, thereby improving light output.

8 to 10 are cross-sectional views illustrating a method of manufacturing a light emitting device 50 according to another embodiment of the present invention.

Referring to FIG. 8, the lower N-type semiconductor layer 53, the lower active layer 55, the P-type semiconductor layer 57, the upper active layer 59, and the upper N-type semiconductor layer 61 are formed on the ZnO substrate 51. And a ZnO transparent electrode layer 63. The N-type semiconductor layers 53 and 61, the active layers 55 and 59, and the P-type semiconductor layer 57 use metalorganic chemical vapor deposition, molecular beam growth (MBE), or hydride vapor phase (HVPE) technology. Can be formed of a (B, Al, In, Ga) N compound semiconductor. Meanwhile, the ZnO transparent electrode layer 63 may be formed using a molecular beam growth method, a metal organic chemical vapor deposition technique, or the like.

Referring to FIG. 9, the P-type semiconductor layer 57 is exposed by patterning the ZnO transparent electrode layer 63, the upper N-type semiconductor layer 61, and the upper active layer 59.

Meanwhile, the ZnO transparent electrode layer 63 positioned on the upper N-type semiconductor layer 61 is patterned into a predetermined shape. As described with reference to FIG. 4, the ZnO transparent electrode layer 63 may be patterned using photo and etching processes to form various shapes. Patterning the ZnO transparent electrode layer 63 to form a predetermined shape may be performed after exposing the P-type semiconductor layer 57, but is not limited thereto.

Meanwhile, before or after the P-type semiconductor layer 57 is exposed, the semiconductor layers 53, 55, 57, 59, and 61 and the ZnO transparent electrode layer 29 are patterned to form a portion on the ZnO substrate 51. The light emitting diodes 56 may be separated.

Accordingly, the vertically stacked light emitting diodes 56 and 60 are formed, a portion of the P-type semiconductor layer 57 is exposed, and a ZnO transparent electrode layer patterned in a predetermined shape on the upper N-type semiconductor layer 61. 63 is formed. The P-type electrode pad 65 may be formed on the exposed P-type semiconductor layer 57.

Subsequently, as described with reference to FIG. 4, the ZnO substrate 51 is patterned. The patterned ZnO substrate 51 has an upper surface 51b facing the lower N-type semiconductor layer 53 and a lower surface 51a defined in the lower region of the upper surface, as shown in FIG. 6. The upper surface 51b has a larger cross-sectional width than the lower surface 51a.

According to the present embodiment, since the lower and upper light emitting diodes 56 and 60 are provided with the light emitting device 50 having a vertically stacked structure, the light output per unit area of the substrate is higher than that of the light emitting device having a conventional single light emitting diode structure. Can be increased.

According to embodiments of the present invention, by using a patterned ZnO substrate and a ZnO transparent electrode layer, it is possible to provide a light emitting device capable of preventing light loss due to internal reflection and improving light extraction efficiency. In addition, the light emitting diodes may be stacked vertically to provide a light emitting device having increased light output per unit area.

Claims (6)

A ZnO substrate having a lower surface and an upper surface, the lower surface being defined within a lower region of the upper surface, the upper surface having a larger cross-sectional width than the lower surface; An N-type semiconductor layer on an upper surface of the ZnO substrate; A P-type semiconductor layer located on the N-type semiconductor layer; An active layer interposed between the N-type semiconductor layer and the P-type semiconductor layer; And A ZnO transparent electrode layer disposed on the P-type semiconductor layer, the ZnO transparent electrode layer having a lower surface facing the P-type semiconductor layer and an upper surface defined in an upper region of the lower surface, the lower surface having a larger cross-sectional width than the upper surface; Light emitting element. The method according to claim 1, The N-type semiconductor layer, the P-type semiconductor layer and the active layer is a light emitting device formed of a gallium nitride-based compound semiconductor. Forming an N-type semiconductor layer, an active layer, a P-type semiconductor layer, and a ZnO transparent electrode layer on the ZnO substrate, Patterning the ZnO transparent electrode layer to form a patterned ZnO transparent electrode layer having a lower surface facing the P-type semiconductor layer and an upper surface defined in an upper region of the lower surface, the lower surface having a larger cross-sectional width than the upper surface; , Patterning the ZnO substrate to form a patterned ZnO substrate having an upper surface facing the N-type semiconductor layer and a lower surface defined in a lower region of the upper surface, the upper surface having a larger cross-sectional width than the lower surface; Light emitting device manufacturing method. A ZnO substrate having a lower surface and an upper surface, the lower surface being defined within a lower region of the upper surface, the upper surface having a larger cross-sectional width than the lower surface; A lower N-type semiconductor layer on an upper surface of the ZnO substrate; A P-type semiconductor layer on the lower N-type semiconductor layer; An upper N-type semiconductor layer on one region of the P-type semiconductor layer; A lower active layer interposed between the lower N-type semiconductor layer and the P-type semiconductor layer; An upper active layer interposed between the upper N-type semiconductor layer and the P-type semiconductor layer; And A ZnO transparent electrode layer disposed on the upper N-type semiconductor layer, having a lower surface facing the upper N-type semiconductor layer and an upper surface defined in an upper region of the lower surface, the lower surface having a cross-sectional width greater than that of the upper surface; Light emitting device comprising. The method according to claim 4, And the lower N-type semiconductor layer, the lower active layer, the P-type semiconductor layer, the upper active layer, and the upper N-type semiconductor layer are formed of a gallium nitride-based compound semiconductor. Forming a lower N-type semiconductor layer, a lower active layer, a P-type semiconductor layer, an upper active layer, an upper N-type semiconductor layer, and a ZnO transparent electrode layer on a ZnO substrate, The P-type semiconductor layer is exposed by patterning the ZnO transparent electrode layer, the upper N-type semiconductor layer, and the upper active layer, and has a lower surface facing the upper N-type semiconductor layer and an upper surface defined in an upper region of the lower surface. Forming a patterned ZnO transparent electrode layer, the lower surface having a larger cross-sectional width than the upper surface, Patterning the ZnO substrate to form a patterned ZnO substrate having an upper surface facing the lower N-type semiconductor layer and a lower surface defined in a lower region of the upper surface, wherein the upper surface has a larger cross-sectional width than the lower surface. Light emitting device manufacturing method comprising.

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