KR20070097642A - Vertical type light emitting diode with electrode layer made of zn compound and method for fabricating the same - Google Patents

Abstract

A vertical type light emitting diode with an electrode layer and a manufacturing method thereof are provided to emit the light having high brightness at uniform distribution by forming a transparent electrode layer with Zn compound on an N-type semiconductor layer. A porous silicon substrate is prepared as a sacrificial substrate. An N-type semiconductor layer(160), an active layer(140) and a P-type semiconductor layer(120) are sequentially deposited on the porous silicon substrate. The porous silicon substrate is removed to expose the N-type semiconductor layer. A conductive reflection layer(122) is formed on the P-type semiconductor layer, and a transparent electrode layer(170) made of Zn compound is formed on the N-type semiconductor layer.

Description

Vertical type light emitting diode having an electrode layer made of a compound and a method of manufacturing the same {Vertical type light emitting diode with electroluminescent diode made of Zn compound and metal compound for FABRICATING THE SAME}

1 is a cross-sectional view showing a vertical light emitting diode according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a light emitting diode package including the vertical light emitting diode shown in FIG.

3 is a cross-sectional view showing a vertical light emitting diode having a rough surface on the transparent electrode layer according to another embodiment of the present invention.

Figure 4 is a flow chart schematically showing a sacrificial substrate manufacturing process for manufacturing a vertical light emitting diode according to the present invention.

5 to 9 are cross-sectional views illustrating a process of manufacturing a vertical light emitting diode using a sacrificial substrate manufactured by the manufacturing process of FIG. 4.

10 (a) and 10 (b) are cross-sectional views illustrating a vertical light emitting diode according to a modified embodiment of the present invention.

<Code Description of Main Parts of Drawing>

120: P-type semiconductor layer 122: reflective layer

140: active layer 160: N-type semiconductor layer

170: transparent electrode layer 182: fluorescent material

184: encapsulant

The present invention relates to a vertical light emitting diode and a method of manufacturing the same, and more particularly, to a vertical light emitting diode having a transparent electrode layer of a Zn compound, such as ZnO or ZnS, and a method of manufacturing the same.

The light emitting diode 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. For example, a gallium nitride (GaN) -based light emitting diode is known as the light emitting diode.

In general, a gallium nitride-based light emitting diode is manufactured by growing an N-type semiconductor layer, an active layer (or a light emitting layer), and a P-type semiconductor layer in order on a sapphire substrate as a sacrificial substrate. That is, the sapphire substrate in contact with the N-type semiconductor layer is removed by, for example, a laser, whereby a vertical type light emitting diode (or VLED) with improved brightness can be manufactured.

The vertical light emitting diode as described above has a metal reflective layer formed on the surface where the sapphire substrate is removed, that is, an N-type semiconductor layer, and a transparent electrode layer made of Ni / AU or ITO is formed on the opposite P-type semiconductor layer. In addition, electrode pads for all causes are formed on the metal reflective layer and the transparent electrode layer.

In general, the thickness of the Ni / Au transparent electrode layer and the ITO transparent electrode layer is limited to about 0.005 to 0.2 μm due to light transmission characteristics and / or current characteristics. Such thickness limitations make it difficult to design various shapes of the transparent electrode layer, thereby causing problems of scattering light emission and / or light emission with uniform distribution.

That is, when the thickness of the transparent electrode layer is large, it is possible to design the shape of the transparent electrode layer to make the light emission distribution more wide and uniform or to reduce the total internal reflection of light according to the critical angle principle, whereas the thickness of the Ni / Au transparent electrode layer or the ITO transparent electrode layer is Because of this limitation, it is difficult to design such a shape.

In addition, the conventional light emitting diode has a problem that light emitted from the active layer passes through the P-type semiconductor layer more than the N-type semiconductor layer, causing relatively high light loss. This is due to the fact that the P-type semiconductor layer has more defects causing loss of light as compared to the N-type semiconductor layer. In addition, the conventional vertical light emitting diode has a problem that it is uneconomical and difficult to mass produce because a sapphire substrate, which is expensive and unsuitable for mass production, is used as a sacrificial substrate.

Accordingly, an object of the present invention is to use a cheap sacrificial substrate to replace the existing sapphire substrate, to form a transparent electrode layer made of Zn compound, which is economical and easy to design optical properties, on the N-type semiconductor layer, thereby further improving light emission performance. It is to provide a vertical light emitting diode and a method of manufacturing the same.

Another object of the present invention is to use a cheap sacrificial substrate and to use a transparent electrode layer made of a Zn compound, and also to allow the Zn compound transparent electrode layer to emit light more broadly toward the fluorescent material surrounding the same. It is to provide a vertical light emitting diode formed and a method of manufacturing the same.

According to one aspect of the invention, (a) preparing a porous silicon substrate as a sacrificial substrate; (b) growing an N-type semiconductor layer, an active layer, and a P-type semiconductor layer in order on the porous silicon substrate; (c) removing the porous silicon substrate to expose the N-type semiconductor layer located thereon; (d) forming a conductive reflective layer on the P-type semiconductor layer and forming a transparent electrode layer made of a Zn compound on the N-type semiconductor layer; Provided is a method of manufacturing a vertical light emitting diode comprising the same.

In the method of manufacturing a vertical light emitting diode according to an embodiment of the present invention, the step (a) includes: (a1) preliminarily defining a pore forming site by KOH etching a non-porous silicon substrate; (a2) It is preferred to include the step of forming a porous silicon substrate by treating the KOH etched nonporous silicon substrate by anodization.

According to another aspect of the invention, semiconductor layers having an N-type semiconductor layer, a P-type semiconductor layer and an active layer therebetween grown using a porous silicon substrate as a sacrificial substrate; A conductive reflective layer formed on a bottom surface of the P-type semiconductor layer; A transparent electrode layer formed on the N-type semiconductor layer and made of a Zn compound for improving light emission characteristics from the semiconductor layer; A vertical light emitting diode is provided.

In this case, the transparent electrode layer is preferably made of a ZnO layer or a ZnS layer doped with Pb and Cu. In addition, the transparent electrode layer is preferably formed in a pyramid cross section having inclined surfaces on both sides, or is formed in a domed cross section convex in the light emission direction. Furthermore, it is preferable that a portion of the N-type semiconductor layer is exposed to the outside of the transparent electrode layer.

Hereinafter, exemplary 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.

<Example>

1 is a view illustrating a vertical light emitting diode according to an embodiment of the present invention.

As shown in FIG. 1, the light emitting diode 100 according to the present embodiment has a structure in which a P-type semiconductor layer 120, an active layer 140, and an N-type semiconductor layer 160 are sequentially stacked. The layers 120, 140, and 160 are layers grown on a sacrificial substrate, which will be described below. The order of growth may include the N-type semiconductor layer 160, the active layer 140, and the P-type semiconductor layer 120 from the sacrificial substrate. In order. As the sacrificial substrate is removed, the N-type semiconductor layer 160 is exposed, thereby forming the layers 120, 140, and 160 as shown in FIG. 1.

The active layer 140 is a layer providing a region where electrons and holes are coupled between the P-type semiconductor layer 120 and the N-type semiconductor layer 160. In the present embodiment, the active layer 140 includes InGaN. In addition, the emission wavelength extracted from the light emitting diodes 100 is determined according to the type of material constituting the active layer 140. In this case, the active layer 140 may be a multilayer film in which a quantum well layer and a barrier layer are repeatedly formed, and the barrier layer and the well layer may be Al _x In _y Ga _{1 −x− y} N (0 ≦ x, y). It may be a binary to four-membered compound semiconductor layers represented by, x + y ≤ 1).

The P-type semiconductor layer 120 is formed in a direction opposite to the N-type semiconductor layer 160, and a conductive metal reflective layer 122 is formed on the bottom thereof. The metal reflective layer 122 serves to reflect upwardly the light generated in the active layer 140 and directed downward through the P-type semiconductor layer 120. The P-type semiconductor layer 120 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 . In this case, forming the metal reflective layer 122 on the P-type semiconductor layer 120 is advantageous in improving luminance than forming the metal reflective layer on the N-type semiconductor layer 160, which is a P-type semiconductor layer 120. This is caused by an increase in the amount of light emitted immediately through the N-type semiconductor layer 160 with fewer internal defects and a decrease in light loss.

N-type semiconductor layer 160 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. At this time, the transparent electrode layer 170 made of a Zn compound is formed on the upper surface of the N-type semiconductor layer 160. The transparent electrode layer 170 is made of a Zn compound having a free design of light transmission performance and excellent etching ability compared to the ITO forming the transparent electrode layer.

Among them, ZnO is an excellent ZnO compound with excellent etching properties and excellent light transmittance and electrical properties. It is excellent in light transmittance to thickness to form a transparent electrode layer of sufficient thickness. It enables the shape design of various transparent electrode layers.

The transparent electrode layer 170 made of ZnO described above has an advantage of forming a desirable ohmic contact with the N-type semiconductor layer 160 while forming an N-type without doping N-type impurities. That is, when a ZnO layer is bonded to a general P-type semiconductor layer, a tunnel structure for ohmic contact is required, whereas when the ZnO transparent electrode layer is formed on the N-type semiconductor layer 160, the tunnel structure described above is necessary. Eliminates

The ZnO transparent electrode layer 170 according to the present exemplary embodiment is formed in a pyramidal cross-sectional shape in which cross-sectional shapes are gradually narrowed along the emission direction of light, that is, slopes are formed on both sides. This cross-sectional shape can be easily implemented by etching due to the nature of ZnO. In addition, the cross-sectional shape of the transparent electrode layer 170 as described above enables light to be emitted in a wide and uniform distribution, so that the light can be applied to the fluorescent material more broadly and uniformly in the LED package including the fluorescent material. Help For example, the light emitting diode 100 including the ZnO transparent electrode layer 170 as described above, when applied to a white light emitting diode package, helps to realize white light with high luminance.

In addition, the width of the transparent electrode layer 170 is located at a substantially center of the N-type semiconductor layer 160 and the width thereof is predetermined so that a portion of the N-type semiconductor layer 160 is exposed to the outside thereof. This increases the lateral directivity of the light on the inclined surface 171 of the transparent electrode layer 170 and increases the straightness of the light on the top surface 172 of the transparent electrode layer 170 and the exposed surface 162 of the N-type semiconductor layer 160. It allows for a wide and uniform light emission throughout (see Figure 2).

Meanwhile, Zn compounds that can be used as transparent electrode layer materials in place of ZnO include Pb and Cu. That is doped with ZnS (ZnS co-doped with Pb ^{+ 2} and Cu ^{+ 2).} Pb and Cu of the ZnS The doping of is very useful in that it improves the optical properties of ZnS which is lower than ZnO at room temperature, and the fluorescence intensity can be controlled by controlling the relative doping amount of Pb and Cu. Cu, Pb-doped ZnS has a light emission peak in a range of approximately 500 to 550 μm and has a relatively wide emission band, and has an optical characteristic similar to that of ZnO at room temperature, and may be used as a transparent electrode layer to replace the ZnO. will be.

2 is a schematic view of a light emitting diode package including the vertical light emitting diode 100 shown in FIG. 1 and a main part thereof in an enlarged view. Referring to FIG. 2, the above-described vertical light emitting diode 100 is surrounded by a resin encapsulant 184 formed by a molding method. In addition, the encapsulant 184 includes a powdery fluorescent substance 182 in a uniform distribution.

At this time, the directional light is emitted through the inclined surface 171 of the transparent electrode layer 170, and the flat surface 172 on the top of the transparent electrode layer 170 and the exposed surfaces 162 on the left and right sides of the N-type semiconductor layer 160. Through this, a large amount of linear light is emitted. Accordingly, the vertical light emitting diode 100 emits a wide and uniform light toward the fluorescent material 182 scattered around the vertical light emitting diode 100, and the emitted light acts on the fluorescent material 182 in a wider manner, thereby providing more luminance. High light (especially white light) can be emitted.

Meanwhile, according to another embodiment of the present invention, a rough surface 173 may be formed on the light emitting surface of the transparent electrode layer 170, which is illustrated in FIG. 3. The rough surface 173 as described above reduces the total internal reflection of light according to the light extraction critical angle principle and contributes to improving the light extraction efficiency of the light emitting diode. The rough surface 173 is preferably formed by etching the surface of the transparent electrode layer 170. The transparent electrode layer 170 may be formed to a sufficient thickness on the N-type semiconductor layer due to the Zn compound, in particular, ZnO. In addition, it is excellent in etching and the formation of the rough surface 173 by etching is easy.

Hereinafter, the above-described vertical light emitting diode manufacturing method will be described with reference to FIGS. 4 to 9.

<Manufacture of sacrificial substrates>

Looking at the manufacturing process of the porous silicon substrate to be a sacrificial substrate with reference to Figure 4 as follows.

First, a non-porous silicon substrate is prepared (S102). As the non-porous silicon substrate, a P-type Si substrate having a (100) planar orientation is used. In addition, the non-porous silicon substrate is cleaned with a cleaning solution comprising T.C.E (Trichloroethylane), acetone and methanol and then prepared for the next step. At this time, in order to obtain a sufficient cleaning effect, the non-porous silicon substrate is kept in the cleaning liquid at a temperature of approximately 100 to 200 ° C. for about 10 to 20 minutes.

Next, a KOH etching process is performed as a preliminary step for forming pores in the silicon substrate (S103). In this embodiment, the KOH etching is performed by immersing the non-porous silicon substrate in order of 1 to 5 minutes each in containers containing 1.5 mole, 3 mol, and 5 mol of potassium hydroxide solution, wherein the potassium hydroxide solution is The temperature is maintained at about 60-80 ° C.

By the KOH etching process as described above, a rough surface having a roughly pyramid shape is formed on the surface of the non-porous silicon substrate, and the rough surface serves to define a pore forming site of the porous silicon substrate, It allows porous silicon substrates to have uniform and dense pores.

Then, a process of forming an anode electrode on the non-porous silicon substrate is performed (S104). This process is to form an electrode for applying power to the non-porous silicon substrate in a subsequent process, in this embodiment , Al is deposited on one surface of the non-porous silicon substrate. In addition, the non-porous silicon substrate on which the anode electrode is formed may be heat treated at a temperature of about 400 ° C. for 1 minute.

Finally, a process of forming the non-porous silicon substrate into the porous silicon substrate by anodization is performed (S105). In this step, a solution in which a 50 wt% HF solution and ethanol (C ₂ H ₅ OH) is mixed at a ratio of 1.5: 1 is used as the electrolyte. At this time, ethanol helps to form a uniform pore in the silicon substrate by minimizing the generation of hydrogen bubbles during anodization. When the electrolytic solution is prepared, the non-porous silicon substrate as an anode was positioned a non-porous silicon substrate prepared from the above step in the electrolytic solution is filled electrolytic cell, and platinum (Pt) metal to the current density 10cm / m ² to a cathode of Turn on the power. As a result, an anodization reaction occurs actively in the electrolyte to form a porous silicon substrate 101 (see FIG. 5) having pores.

The process of heat-treating the porous silicon substrate through the above process at a temperature of approximately 400 to 700 ° C. for about 30 minutes may be additionally performed, and this heat treatment process is to impart thermal stability to the porous silicon substrate.

Although the manufacturing process of the porous silicon substrate used as the sacrificial substrate has been described as an example, it is also possible to manufacture the porous silicon substrate by a method or condition different from the above.

<Formation of Semiconductor Layer and Transparent Electrode Layer>

A process of manufacturing a vertical light emitting diode using the porous silicon substrate manufactured as described above as a sacrificial substrate is well illustrated in FIGS. 5 to 9.

Referring to FIG. 5, an N-type semiconductor layer 160, an active layer 140, and a P-type semiconductor layer 120 are sequentially formed on the porous silicon substrate 101. Formation of such layers 160, 140, 120 may be accomplished by metalorganic chemical vapor deposition (MOCVD), molecular beam growth (MBE) or hydride vapor phase growth (HVPE). Each of the layers 160, 140, and 120 may be formed continuously in the same process chamber. In this case, a buffer layer may be formed between the porous silicon substrate 101 and the N-type semiconductor layer 160 to reduce lattice mismatch.

Next, as shown in FIG. 6, the porous silicon substrate 101 facing the N-type semiconductor layer 160 is removed. Since the porous silicon substrate used as the sacrificial substrate is in a flexible state by the porous structure, it is easy to remove it from the N-type semiconductor layer 160. In FIG. 6, it is removed from the N-type semiconductor layer 160 for convenience of understanding. The sacrificial substrate 101 is shown as a virtual line. In the following description, a combination of the semiconductor layers from which the sacrificial substrate 101 has been removed will be referred to as a "diode chip."

Next, as shown in FIG. 7, the P-type semiconductor layer 120 of the diode chip has a conductive metal reflective layer, more preferably, a metal reflective layer 122 made of silver (Ag) material formed by plating or vapor deposition. do. Here, the reflective layer 122 is generated in the active layer 140 serves to reflect the light passing through the P-type semiconductor layer 120 back to the active layer 140.

Next, after the inversion of the diode chip, a process of forming the ZnO transparent electrode layer 170 to a predetermined thickness on the surface of the N-type semiconductor layer 160 from which the porous silicon substrate 101 is removed is performed as shown in FIG. 8. do. At this time, the ZnO transparent electrode layer 170 is formed to a thickness sufficient for shape design to improve the light emission characteristics.

According to the exemplary embodiment of the present invention, the ZnO transparent electrode layer 170 is formed by bonding ZnO of a predetermined thickness to the surface of the N-type semiconductor layer 160 at high temperature and high pressure. However, the ZnO transparent electrode layer 170 ) May be formed. And, in this embodiment, the formation of the ZnO transparent electrode layer 170 is made after the formation of the metal reflective layer 122, but this is not a limitation of the present invention, the metal reflective layer 122 after the formation of the ZnO transparent electrode layer 170 It is also within the scope of the present invention to form.

Next, a process of etching the ZnO transparent electrode layer 170 into the shape shown in FIG. 9 is performed. By such a process, the ZnO transparent electrode layer 170 has a pyramid-shaped cross section, and the cross-sectional shape of the ZnO transparent electrode layer 170 allows the light emitting diode to emit light in a wide and uniform distribution as mentioned above. Makes it possible. In addition, the N-type semiconductor layer 160 is exposed toward the light emission direction outside the ZnO transparent electrode layer 170. In addition, after the above process, a rough surface for reducing total internal reflection of light may be formed on the surface of the transparent electrode layer 170.

After bonding the transparent electrode layer 170 to the N-type semiconductor layer 160 as described above, it is preferable to etch the transparent electrode layer 170 to have a pyramidal cross-sectional shape. Alternatively, the transparent electrode layer 170 may be prepared in advance to have a pyramid cross-section or any other shape. It is also possible to directly bond the transparent electrode layer 170 to the N-type semiconductor layer 160.

Although not shown, after completion of the above-described process, electrode pads are formed on the metal reflective layer 122 and the ZnO transparent electrode layer 170, respectively, and electrical wiring is connected to each of the electrode pads. Next, an encapsulant 184 including the fluorescent material 182 is formed to surround the above-described light emitting diode 100 to manufacture a light emitting diode package.

As described above, although ZnO is used as the material of the transparent electrode layer 170 in this embodiment, for example, Pb and Cu A Zn compound such as ZnS doped together may be used as a material of the transparent electrode layer. In particular, Pb and Cu ZnS doped together with the luminescent property at room temperature is almost similar to ZnO, and thus may be preferably used for the transparent electrode layer to replace ZnO.

10 is a cross-sectional view illustrating a vertical light emitting diode according to various embodiments of the present disclosure. Referring to FIG. 10, a transparent electrode layer 170 made of a Zn compound, such as ZnO or ZnS, may be formed on a N-type semiconductor layer. It is formed with a plurality of dome-shaped cross sections. Since the transparent electrode layers 170 also disperse and emit light at the convex curved surface, the light emitting diodes can emit light with a wide and uniform distribution.

The vertical light emitting diode according to the present invention has a structure in which a transparent electrode layer made of a Zn compound, such as ZnO or ZnS, having excellent light transmittance and etching properties, is formed on an N-type semiconductor layer from which a sacrificial substrate is removed, thereby providing high brightness. Can be emitted in a uniform distribution.

In addition, the present invention can contribute to the economical mass production of light emitting diodes by using a porous silicon substrate as a sacrificial substrate which is inexpensive and can reduce lattice mismatch with a semiconductor layer (especially, a GaN semiconductor layer). Provide effect.

In addition, the present invention has the effect of eliminating a separate means for forming ohmic contacts, such as tunnel structure, by the structure in which the two layers that can form ohmic contacts, that is, the ZnO layer and the N-type semiconductor layer directly contact each other, Has

In addition, the present invention can reduce the loss of light caused by the light passing through the P-type semiconductor layer by the arrangement in which the reflective layer is formed in the P-type semiconductor layer and the transparent electrode layer is formed in the N-type semiconductor layer. This is realized by the arrangement of the above-described layers, which increases the amount of light passing through the N-type semiconductor layer where the internal defects are less than the P-type semiconductor layer.

In addition, the present invention, the transparent electrode layer is formed in a shape capable of emitting light in a wide and uniform distribution, in particular, pyramid shape, which allows the light to act widely on the fluorescent material contained in the encapsulant, for example For example, high brightness white light can be realized. In addition, the present invention also provides the effect that it is easy to shape the transparent electrode layer in a shape that reduces the total internal reflection.

Claims (15)

(a) preparing a porous silicon substrate as a sacrificial substrate; (b) growing an N-type semiconductor layer, an active layer, and a P-type semiconductor layer in order on the porous silicon substrate; (c) removing the porous silicon substrate to expose the N-type semiconductor layer located thereon; (d) forming a conductive reflective layer on the P-type semiconductor layer and forming a transparent electrode layer made of a Zn compound on the N-type semiconductor layer; Vertical light emitting diode manufacturing method comprising a. The method of claim 1, wherein the transparent electrode layer is a ZnO layer. The method of claim 1, wherein the transparent electrode layer is a ZnS layer doped with Pb and Cu. The method of claim 1, wherein the transparent electrode layer further comprises forming a pyramid cross section having inclined surfaces on both sides thereof. The method of claim 1, further comprising forming the transparent electrode layer in a convex domed cross section in a light emission direction. The method of claim 4, wherein the N-type semiconductor layer is partially exposed to both sides of the transparent electrode layer. 6. The method of claim 1, further comprising forming a rough surface on the light emitting surface of the transparent electrode layer to reduce total internal reflection. 7. The method according to claim 1, wherein step (a), (a1) KOH etching the non-porous silicon substrate to define a pore forming site in advance; (a2) treating the KOH-etched non-porous silicon substrate by anodizing to form a porous silicon substrate; Vertical light emitting diode manufacturing method comprising a. Semiconductor layers having an N-type semiconductor layer, a P-type semiconductor layer, and an active layer therebetween, grown using a porous silicon substrate as a sacrificial substrate; A conductive reflective layer formed on the P-type semiconductor layer; A transparent electrode layer formed on the N-type semiconductor layer and made of a Zn compound for improving light emission characteristics from the semiconductor layer; Vertical light emitting diode comprising. 10. The vertical light emitting diode of claim 9, wherein the transparent electrode layer is a ZnO layer. 10. The vertical light emitting diode of claim 9, wherein the transparent electrode layer is a ZnS layer doped with Pb and Cu. The vertical type light emitting diode of claim 9, wherein the transparent electrode layer has a pyramid cross section having inclined surfaces on both sides thereof. The vertical type light emitting diode of claim 9, wherein the transparent electrode layer has a domed cross section convex in the light emission direction. The vertical type light emitting diode of claim 12 or 13, wherein a portion of the N-type semiconductor layer is exposed to both sides of the transparent electrode layer. The vertical type light emitting diode of any one of claims 9 to 13, wherein a rough surface that reduces total internal reflection is formed on the light emitting surface of the transparent electrode layer.

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