KR200379693Y1 - Vertical electrode structure of white light emitting diode - Google Patents

Abstract

The present invention discloses a white light emitting diode manufactured by combining a GaN series diode and a photoconversion layer substrate of ZnTe or ZnSe using a transparent conductive adhesive layer. While the GaN emitting diode emits a blue wavelength, a portion of the blue is absorbed by the light converting layer of ZnTe or ZnSe to emit another yellow wavelength. After the yellow light and the blue light are mixed together, white light is produced.

Description

Vertical electrode structure of white light emitting diodes {VERTICAL ELECTRODE STRUCTURE OF WHITE LIGHT EMITTING DIODE}

The present invention relates to a vertical electrode structure of a white light emitting diode, and in particular, the structure of the present invention has achieved an innovative improvement over the previous design due to the vertical structure. In addition, a vertical GaN LED and an optical wavelength conversion substrate are used in combination. An optical wavelength conversion substrate that absorbs a portion of blue light and emits yellow light is also used. Finally, yellow light and blue light are mixed together to produce white light.

1 (a) shows a conventional use of the horizontal electrode structure of a GaN LED shown in cross section. The light emitting diode 1 'comprises a first cladding layer, for example an N-type GaN layer 11' positioned over sapphire 10 '. A buffer layer is typically included between the substrate and the first cladding layer; It is not shown in this figure. The active layer is InGaN 12 'on the first cladding layer as an example. The second cladding layer is, for example, a P-type GaN layer 13 'on the active layer. As shown in the figure, the first cladding layer 15 'and the second cladding layer 14' are each other having two different polarities, such as the N-type electrode 15 'and the P-type electrode 14'. Other electrode layers. In conventional white LED technology, what is shown in US Pat. No. 5,998,925 is the most common white LED structure. The packaging resin comprises phosphorus, for example YAG phosphor 16 ', during packaging in the laminate structure described above. Referring to FIG. 1B, light, for example, blue light, is emitted from the active layer of the laminated layer described above. Some of the light, for example, is absorbed by the YAG phosphor and converted into yellow light of different wavelengths. Subsequently, the color light is mixed to form white light.

However, the above-mentioned horizontal electrode white LED uses an insulating material and sapphire in the substrate, its thermal conductivity coefficient is low and heat dissipation is poor. As a result, the YAG phosphor 16 'is easily depleted by heat while a larger drive current is applied during long term operation. In addition, the conversion efficiency is lowered and the chrominance is shifted. In addition, as the insulating material sapphire substrate 10 'is used, horizontal electrode fabrication is required and the extra required chip area is increased. In other words, it reduces the chip production capacity per unit area. In addition, this increases manufacturing costs because wire bonding becomes more complex in the packaging process.

In order to improve the above-described horizontal electrode LED, a non-insulating material is used for the lower substrate. In addition, as shown in FIG. 2, a vertical electrode is used as a design of an LED that provides an optical wavelength conversion substrate underneath. As shown in Fig. 2, the lower substrate is an N-type ZnSe material 22 '. N-type ZnSe buffer layer 23 ', N-type ZnMgSSe cladding layer 24', ZnCdSe / ZnSeMQW active layer 25 ', P-type ZnMgSSe cladding layer 26' and P-type ZnTe contact layer 27 'are sequentially Disposed on the substrate. The N-type ZnSe buffer layer 23 'is mainly used to reduce lattice mismatching between the substrate 22' and the N-type ZnMgSSe cladding layer 24 '. Both sides of the ZnCdSe / ZnSeMQW 25 ', the N-type ZnMgSSe cladding layer 24' and the P-type ZnMgSSe cladding layer 26 'have a wider bandgap than the active layer 25' and increase the carrier limiting effect.

In addition, the upper and lower portions of the above-described laminated structure include an N-type electrode 21 'and a P-type electrode 28'. When an appropriate voltage is provided to the N-type electrode 21 'and the P-type electrode 28', the ZnCdSe / ZnSe MQW active layer 25 'between the P-N contact layers emits blue light. Part of the blue light is absorbed by the N-type ZnSe substrate and then forms yellow light. By mixing blue light and yellow light, white light is formed.

Comparing the horizontal electrode fabrication described first and the vertical LED fabrication described later, the latter not only has a simpler process, but also avoids the complexity and thermal conductivity issues required during the packaging process. However, the lifetime of the latter component is described in the journal JPN. J. Appl. Phys. Vol. 43 (2004) pp. Although 10000 hours can be achieved as disclosed in 1287, the luminous efficiency is not as good as the GaN series, so the quality of the epitaxial layer of the ZnSe series is still not ideal. In addition, the journal JPN by M. Tamsda et al. J. Appl. Phys. Vol. 41 (2002) pp. The journal JPN on L246 and by B. Damilano et al. J. Appl. Phys. Vol. 40 (2001) pp. As shown in the L918, each mentions a mixed LED and presents an InGaN quantum well emitting layer that emits multiple color light. One emitting layer may emit shorter blue wavelengths and mix with longer green wavelengths emitted from another emitting layer. Therefore, it is possible to emit a specific color difference of mixed light or white light. However, in order to achieve a longer emission wavelength, the composition of In of the InGaN layer and the thickness of the InGaN layer must be adjusted, so that the luminous efficiency is relatively reduced. To date, the luminous efficiency of such types of white LEDs is on the order of 1/2 to 1/3 of the YAG series products, which still has drawbacks.

In order to overcome the above problems, the present invention provides an innovative vertical structure of the white LED. The problem of low luminous efficiency existing in the conventional vertical electrode white LED can be improved as well as the problem of the color shift shift caused in the conventional horizontal electrode white LED. The inventors of the present invention have studied to propose a new design in the field of white LED for a long time. According to the inventor's years of research experience and design using his experience knowledge, the present invention proposes and submits for registration which overcomes the above-mentioned problems.

In response to the above-described problems, an innovative vertical electrode structure of a white light emitting diode is provided to achieve the above and other objects that will become apparent in the following description. The present invention utilizes a combination of GaN LEDs and an optical wavelength conversion substrate. The optical wavelength conversion substrate absorbs blue light and emits yellow light of the GaN series LEDs. Yellow light is mixed with blue light of GaN series LEDs to produce white light. By using GaN series LEDs, white LEDs have better luminous efficiency. It is also possible to increase the thermal conductivity coefficient of the white LED. As a result, it increases the operating life of the component and makes it more suitable for high drive voltage applications. It can also increase electrostatic discharge (ESD) durability.

One of the objects of the present invention is to provide a vertical electrode structure of a white LED. White LEDs are formed using GaN series LEDs and an optical wavelength conversion substrate. In addition, it is a vertical electrode structure that reduces the unit area of the chip process and is further beneficial to the wire bonding and packaging process of the post fabrication process.

In order to achieve the above object and function, the present invention is to provide a vertical electrode structure of a white LED. First, sapphire is used as the substrate. Next, an epitaxially grown GaN series compound semiconductor is laminated as an LED structure. The metal reflective layer and conductive substrate are combined with the GaN series LED structure described above by thermal bonding techniques. Next, the sapphire substrate is removed using a laser lift-off technique. This method can produce GaN series LED structures of vertical electrode type. Next, a GaN series LED and a ZnTe or ZnSe light wavelength conversion substrate are combined to form a white LED of the present invention using a light-transmissive conductive adhesive layer. While the GaN series LEDs emit blue wavelengths, some of the blue light is absorbed by ZnTe or ZnSe to form yellow light. By mixing yellow light and blue light, white light can be formed.

The present invention seeks to overcome conventional white LED technology, such as the YAG phosphor used in horizontal electrode white LEDs. Since insulating sapphire is used as the substrate, its thermal conduction efficiency is low and heat dissipation is poor. As a result, while the higher drive current is applied for a long time, the YAG phosphor 16 is susceptible to heat damage. In addition, the conversion efficiency is lowered and the color difference is shifted. Horizontal electrodes increase the chip area required for manufacturing. In other words, the chip manufacturing capacity per unit area is reduced. In addition, wire bonding becomes more complex in the packaging manufacturing process. Therefore, the manufacturing cost is increased. In addition, even in vertical electrode technology, conventional white LEDs have some drawbacks. The luminous efficiency of the epitaxial layer of the ZnSe series is not as good as the GaN series, so the quality is still not ideal. As a result, the present invention provides a vertical electrode structure of a white LED with increased luminous efficiency of a GaN series LED. In addition, the vertical electrode structure can prevent the drawback of increased chip area of the horizontal electrode. In addition, white light may be generated by overcoming package and wire bonding problems.

Referring to Figure 3a, it is one of the preferred embodiments of the present invention showing a white LED structure. As shown in the figure, the vertical electrode white LED 1 of the first preferred embodiment firstly comprises a low temperature GaN buffer layer 11, an N-type AlInGaN ohmic contact layer 12, and an AlInGaN light emitting layer 13 on the sapphire substrate 10. And the P-type AlInGaN ohmic contact layer 14 is sequentially epitaxially grown. Next, the transparent conductive ohmic contact layer 15 and the metal reflective layer 16 are coated on the P-type AlInGaN ohmic contact layer 14 using either a deposition or sputter coding technique. The transparent conductive ohmic contact layer 15 and the metal reflective layer 16 are metal adhesion layers 17. As shown in FIG. 3B, the conductive substrate 100 is coated with the metal reflective layer 16 by a thermal bonding method by coating another conductive layer directly or by vapor deposition or sputtering. Next, the sapphire substrate 10 is removed using a laser lift-off or lapping technique to make the N-type AlInGaN ohmic contact layer 12 visible. Next, as shown in FIGS. 3C and 3D, on the N-type AlInGaN ohmic contact layer 12 of the GaN LED structure 4 of the vertical electrode type by deposition or sputtering technique, and on the N-type ZnSe or N-type ZnTe light. An N-type transmissive conductive adhesive layer 18 is formed on the wavelength conversion substrate 2. Next, as shown in FIG. 3E, the structure 4 and the structure 6 are bonded using a wafer bonding method. Next, the first electrode 20 and the second electrode 19 are formed. The N-type transmissive conductive adhesive layer 18 has good ohmic contact with the N-type AlInGaN ohmic contact layer 12 and the N-type ZnSe or N-type ZnTe optical wavelength conversion substrate, as well as better conductivity and light transmittance. When a suitable voltage is provided to the first electrode 20 and the second electrode 19, the AlInGaN light emitting layer 13 emits blue light between the P-N contact layers. Part of the blue light is absorbed by the N-type ZnSe or N-type ZnTe optical wavelength conversion substrate 2 to form yellow light. White light is formed by mixing blue light and yellow light.

The most commonly used structure in the preferred embodiment is a vertical electrode structure formed by the GaN LED structure 4, the conductive substrate 100, and the metal reflective layer 16. By using the N-type transmissive conductive adhesive layer 18, the optical wavelength conversion substrate 2 is adhered to the GaN LED structure 4. The metal reflective layer 16 cannot select reflection for the angle of incidence. Thus, the bandwidth of the reflection angle can be increased. In addition, the light efficiency of the light emitting layer 13 can be effectively reflected to increase the light emission efficiency. In addition, the present structure can increase thermal conductivity and ESD durability. As a result, it increases the operating life of the component and makes it more suitable for high drive voltage applications. In addition to the advantages described above, the vertical electrode structure can reduce the unit area of chip fabrication. It is also advantageous over the conventional wire bonding and packaging process of the latter process. Referring to Figure 4a, it is one of the preferred embodiments of the present invention showing a white LED structure. As shown in the figure, it is a second preferred embodiment of the present invention showing a white LED. First, the low-temperature GaN buffer layer 11, the N-type AlInGaN ohmic contact layer 12, the AlInGaN light emitting layer 13, and the P-type AlInGaN ohmic contact layer 14 are sequentially epitaxially grown on the sapphire substrate 10 to GaN. Form the LED structure. Next, the temporary substrate 110 is bonded to the P-type AlInGaN ohmic layer 14 using a thermal bonding method. As shown in FIG. 4B, the sapphire substrate 10 is then removed using laser lift-off or lapping techniques and the N-type AlInGaN ohmic contact layer 12 is shown. Next, on the N-type AlInGaN ohmic contact layer 12 forming the vertical electrode type GaN LED structure 4 by vapor deposition or sputtering technique and as shown in FIG. 3D, an N-type ZnSe or N-type ZnTe optical wavelength. The N-type transmissive conductive adhesive layer 18 is formed on the conversion substrate 2. Next, as shown in FIG. 4C, the structure 8 and the structure 6 are bonded using a wafer bonding method. Next, the temporary substrate 110 is removed to form a transparent conductive ohmic contact layer as a current diffusion layer on the P-type AlInGaN ohmic contact layer 12. In addition, the first electrode 20 and the second electrode 19 are manufactured. As shown in FIG. 4D, the N-type transmissive conductive adhesive layer 18 has good ohmic contact with the N-type AlInGaN ohmic contact layer 12 and the N-type ZnSe or N-type ZnTe optical wavelength converting substrate, as well as better conductivity and light transmission. Has When a suitable voltage is provided to the first electrode 20 and the second electrode 19, the AlInGaN light emitting layer 13 between the P-N contact layers emits blue light. Part of the blue light is absorbed by the N-type ZnSe or N-type ZnTe optical wavelength conversion substrate 2 to form yellow light. White light is formed by mixing blue light and yellow light. A preferred embodiment of the present invention uses a GaN LED structure of high luminous efficiency. In addition, the N-type transmissive conductive adhesive layer 18 is used to bond the optical wavelength converting substrate 2 to the GaN LED structure to form a vertical structure. This structure allows the white LED to have better luminous efficiency. In addition, the thermal conduction efficiency of the white LED can be increased. As a result, it increases the operating life of the component and makes it more suitable for high drive voltage applications. It can also increase ESD durability. In addition to the advantages described above, the vertical electrode structure can reduce the unit area of chip fabrication. It is also advantageous over conventional wire bonding and packaging processes.

In addition, referring to Figure 5a, another preferred embodiment of the present invention showing a white LED structure. As shown in the figure, a feature of another embodiment of the first preferred embodiment of the present invention is that the surface of the N-type AlInGaN ohmic contact layer 12 has a texturing structure. Therefore, the external light emission efficiency can be further improved.

Referring to Figure 5b, another preferred embodiment of the present invention showing a white LED structure. As shown in the figure, a feature of another embodiment other than the first embodiment of the present invention is that the surface of the optical wavelength conversion substrate 2 forms a texturing structure or a 2D photonic crystal structure (see FIG. 5C).

Figure 5d is another preferred embodiment of the present invention showing a white LED structure. As shown in the figure, the features of the embodiments other than the first embodiment of the present invention are that the contact area between the optical wavelength converting substrate 2 and the transparent conductive adhesive layer is between the optical wavelength converting substrate 2 and the second electrode 19. Is smaller than the surface. In addition, the contact area of the laminated structure of a transparent conductive adhesive layer and a GaN series semiconductor is the same as the contact area of a transparent conductive adhesive layer and an optical wavelength conversion substrate. As a result, the optical wavelength conversion substrate 2 is not parallel to the surface of the laminated structure of the GaN series semiconductor. The oblique angle is 50 to 70 degrees relative to the vertical direction.

Also, referring to FIG. 6A, FIG. 6A is one of preferred embodiments of the present invention showing a white LED structure. As shown in the figure, a feature of another embodiment other than the second embodiment of the present invention is that the surface of the ohmic contact layer 14 of the P-type GaN series semiconductor is a texturing structure.

Referring to Figure 6b, it is one of the preferred embodiments of the present invention showing a white LED structure. As shown in the figure, a feature of another embodiment other than the second embodiment of the present invention is that the N-type transmissive conductive adhesive layer 18 is a texturing structure.

Figure 6c is another preferred embodiment of the present invention showing a white LED structure. As shown in the figure, a feature of another embodiment other than the second embodiment of the present invention is that the contact area between the optical wavelength converting substrate 2 and the transparent conductive adhesive layer is between the optical wavelength converting substrate 2 and the second electrode 20. It is smaller than the contact area. In addition, the contact area of the laminated structure of a transparent conductive adhesive layer and a GaN series semiconductor is the same as the contact area of a transparent conductive adhesive layer and an optical wavelength conversion substrate. As a result, the optical wavelength conversion substrate 2 is not parallel to the surface of the laminated structure of the GaN series semiconductor. The oblique angle is 30 to 50 degrees relative to the vertical direction.

The present invention can improve the problem of low luminous efficiency existing in the conventional vertical electrode white LED as well as overcoming the chrominance shift problem caused in the conventional horizontal electrode white LED.

To date, embodiments of the present invention have been described with reference to specific embodiments. However, the present invention is not limited to these specific embodiments. In conclusion, the present invention is consistent with novelty and inventiveness and is applicable to industry. Thus, it complies with the essential components that can be registered. The present invention is deemed sufficient to be registered and hopes that the present application can be registered in practice.

Additional advantages and modifications will be possible by those skilled in the art. Thus, in a broader sense, the present invention is not limited to the representative embodiments and specific details shown and described herein. Accordingly, various modifications will be made without departing from the spirit or scope of the inventive concept as defined by the appended claims and their equivalents.

Figure 1 (a) is a view showing a conventional horizontal electrode structure of the GaN series LED.

Figure 1 (b) is a view showing a conventional horizontal electrode structure of a white LED.

2 shows a conventional vertical electrode design of a GaN series LED.

3A-3E show some of the preferred embodiments of the present invention showing a manufacturing flow diagram for a vertical electrode white LED.

4A-4D show some of the preferred embodiments of the present invention showing a manufacturing flow diagram for a vertical electrode white LED.

Figure 5a is a view showing another preferred embodiment of the present invention showing a white LED structure.

Figure 5b is a view showing another preferred embodiment of the present invention showing a white LED structure.

FIG. 5C illustrates another preferred embodiment of the present invention showing an optical wavelength conversion substrate having a 2D photonic crystal structure. FIG.

Figure 5d is a view showing another preferred embodiment of the present invention showing a white LED structure.

Figure 6a is a view showing one of the preferred embodiments of the present invention showing a white LED structure.

Figure 6b is a view showing one of the preferred embodiments of the present invention showing a white LED structure.

Figure 6c is a view showing another preferred embodiment of the present invention showing a white LED structure.

<Explanation of symbols for the main parts of the drawings>

1: vertical electrode white LED

11: low temperature GaN buffer layer

12: N-type AlInGaN ohmic contact layer

13: AlInGaN light emitting layer

14: P-type AlInGaN ohmic contact layer

15: transparent conductive ohmic contact layer

16: metal reflective layer

17 metal bonding layer

19: second electrode

20: first electrode

100: conductive substrate

Claims (18)

In the vertical structure of the white light emitting diode, A first electrode; A conductive substrate on the first electrode; A metal adhesive layer on the conductive substrate; A laminated structure of a GaN series semiconductor on the metal adhesive layer; A transparent conductive adhesive layer on the laminated structure of the GaN series semiconductor; An optical wavelength conversion substrate on the translucent conductive adhesive layer; And And a second electrode on the optical wavelength conversion substrate. The metal adhesion layer of claim 1, wherein the metal adhesive layer comprises a light transmissive ohmic contact layer and a metal reflecting layer, the metal reflecting layer is formed on the conductive substrate, and the light transmissive ohmic contact layer is formed on the metal reflecting layer. Vertical structure of white light emitting diode. The method of claim 1, wherein the transparent conductive adhesive layer is selected from indium tin oxide (ITO), indium molybdenum oxide (IMO), indium oxide, tin oxide, cadmium tin oxide, gallium oxide, indium zinc oxide, gallium zinc oxide or zinc oxide. A vertical structure of a white light emitting diode, characterized in that the N-type transparent conductive adhesive layer consisting of one. The vertical structure of a white light emitting diode according to claim 1, wherein the optical wavelength conversion substrate is selected from N-type ZnSe and N-type ZnTe. The vertical structure of a white light emitting diode according to claim 1, wherein the surface of the stacked structure of the GaN series semiconductor is a texturing structure. The vertical structure of a white light emitting diode according to claim 1, wherein the stacked structure of the GaN series semiconductor includes a P-type GaN series semiconductor ohmic contact layer, a light emitting layer, and an N-type GaN series semiconductor ohmic contact layer sequentially stacked. . The vertical structure of a white light emitting diode according to claim 1, wherein the surface of the ohmic contact layer of the N-type GaN series semiconductor has a texturing structure. The vertical structure of a white light emitting diode according to claim 1, wherein the surface of the optical wavelength conversion substrate is a texturing structure. The vertical structure of a white light emitting diode according to claim 8, wherein the texturing structure is a 2D photonic crystal structure. The vertical structure of a white light emitting diode according to claim 1, wherein the optical wavelength conversion substrate is not parallel to the surface of the laminated structure of the GaN series semiconductor, and has an oblique angle of 30 to 50 degrees relative to a vertical direction. In the vertical structure of the white light emitting diode, A first electrode; A transparent conductive ohmic contact layer under the first electrode; A laminated structure of a GaN series semiconductor under the translucent conductive ohmic contact layer; A transparent conductive adhesive layer under the laminated structure of the GaN series semiconductor; An optical wavelength conversion substrate under the transparent conductive adhesive layer; And And a second electrode under the optical wavelength conversion substrate. 12. The vertical structure of a white light emitting diode according to claim 11, wherein the GaN series semiconductor stacked structure is formed by sequentially stacking an N-type GaN series semiconductor ohmic contact layer, a light emitting layer, and a P-type GaN series semiconductor ohmic contact layer. The method of claim 11, wherein the transparent conductive adhesive layer is indium tin oxide (ITO), indium molybdenum oxide (IMO), indium oxide, tin oxide, cadmium tin oxide (CTO), gallium oxide, indium zinc oxide (IZO), gallium zinc A vertical structure of a white light emitting diode, characterized in that the N-type transmissive conductive adhesive layer consisting of one selected from oxide (GZO) or zinc oxide (ZnO). The vertical structure of a white light emitting diode according to claim 11, wherein the optical wavelength conversion substrate is selected from N-type ZnSe and N-type ZnTe. The vertical structure of a white light emitting diode according to claim 11, wherein the surface of the stacked structure of the GaN series semiconductor is a texturing structure. The vertical structure of a white light emitting diode according to claim 11, wherein the surface of the ohmic contact layer of the P-type GaN series semiconductor has a texturing structure. The vertical structure of a white light emitting diode according to claim 11, wherein the surface of the transparent conductive adhesive layer has a texturing structure. 12. The vertical structure of a white light emitting diode according to claim 11, wherein the optical wavelength conversion substrate is not parallel to the surface of the laminated structure of the GaN series semiconductor, and has an oblique angle of 30 to 50 degrees relative to a vertical direction.