CN115692562A - Epitaxial wafer and preparation method thereof, light-emitting device and display device - Google Patents

Abstract

The application relates to an epitaxial wafer and a preparation method thereof, a light-emitting device and a display device, wherein the epitaxial wafer comprises a substrate and an epitaxial lamination layer, the epitaxial lamination layer is arranged on the substrate, and the epitaxial lamination layer comprises a first epitaxial structure, a conductive adhesive layer and a second epitaxial structure which are sequentially laminated along the extending direction parallel to the substrate; the first epitaxial structure and the second epitaxial structure are fixedly bonded through a conductive adhesive layer; the first epitaxial structure comprises a first N-type semiconductor layer, a first active layer and a first P-type semiconductor layer; the second epitaxial structure includes a second N-type semiconductor layer, a second active layer, and a second P-type semiconductor layer. That is, the epitaxial stack includes two epitaxial structures, and then two active layers radiate light, so that the light density is significantly increased; in addition, the propagation direction of the polarized light in the TM mode is perpendicular to the front light-emitting surface, and light is easily extracted, so that the light extraction rate can be improved, the light-emitting efficiency is increased, and the light-emitting efficiency is obviously improved.

Description

Epitaxial wafer and preparation method thereof, light-emitting device and display device

Technical Field

The application relates to the field of display, in particular to an epitaxial wafer and a preparation method thereof, a light-emitting device and a display device.

Background

Light Emitting Diodes (LEDs) have the advantages of wide color gamut, high brightness, large viewing angle, low power consumption, long service life, and the like, and thus, LEDs are widely used in the display field. Such as the common stock exchange and financial information display, airport flight dynamic information display, port and station passenger guidance information display, stadium information display, road traffic information display, electric power scheduling, vehicle dynamic tracking and other scheduling command center information display, market shopping center and other service fields business propaganda information display, advertising media products and the like.

The luminance of the LED depends on the luminous efficiency, and the existing LED has low light extraction efficiency due to light absorption or polarization characteristic change, and thus has low luminous efficiency, which seriously affects the light output of the front of the LED, and thus causes unsatisfactory luminance of the LED.

Therefore, how to improve the light extraction efficiency and thus the light emitting efficiency is an urgent problem to be solved.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, the present application aims to provide an epitaxial wafer, a method for manufacturing the epitaxial wafer, a light emitting device and a display device, and aims to solve the problem that the light extraction efficiency is low, which results in low LED light emitting brightness.

A first aspect of the present application provides an epitaxial wafer, including: a substrate; the epitaxial lamination is arranged on the substrate and comprises a first epitaxial structure, a conductive adhesive layer and a second epitaxial structure which are sequentially laminated along the extending direction parallel to the substrate; the first epitaxial structure and the second epitaxial structure are fixedly bonded through the conductive adhesive layer; the first epitaxial structure comprises a first N-type semiconductor layer, a first active layer and a first P-type semiconductor layer which are sequentially stacked along the extending direction parallel to the substrate; the second epitaxial structure comprises a second N-type semiconductor layer, a second active layer and a second P-type semiconductor layer which are sequentially stacked along the extending direction parallel to the substrate.

In foretell epitaxial wafer, epitaxial lamination includes two epitaxial structures, compares in traditional LED light emitting module, and a more epitaxial structure, the light density that consequently can send is obviously stronger than the LED light emitting module that the tradition only set up an epitaxial structure, consequently, luminous efficacy obviously promotes. In addition, the first epitaxial structure, the second epitaxial structure, the internal laminated structure of the first epitaxial structure, and the internal laminated structure of the second epitaxial structure are all distributed in a direction parallel to the extending direction of the substrate, and any one of two surfaces of the epitaxial lamination layer, which are oppositely arranged along the growth direction of the epitaxial wafer, can be used as a front light-emitting surface. Therefore, even if the Al component is increased in order to increase the color depth of the ultraviolet light, so that the light-emitting mode is mainly changed from the TE mode to the TM mode, because the polarization propagation direction of the TM mode is perpendicular to the positive light-emitting surface, the light can be easily extracted, so that the light extraction rate can be improved, and the light-emitting efficiency can be increased.

In some embodiments, the first P-type semiconductor layer faces the second P-type semiconductor layer, and the first P-type semiconductor layer and the second P-type semiconductor layer are adhesively fixed by the conductive adhesive layer. Because the thickness of the P-type semiconductor layer is far less than that of the N-type semiconductor layer, the first P-type semiconductor layer and the second P-type semiconductor layer are bonded to each other, so that the first active layer and the second active layer are closer to each other, and then the light rays radiated by the first active layer and the light rays radiated by the second active layer are superposed with each other, so that the light rays are brighter and more concentrated.

In some embodiments, the first P-type semiconductor layer faces the second N-type semiconductor layer, and the first P-type semiconductor layer and the second N-type semiconductor layer are adhesively fixed by the conductive adhesive layer. Therefore, the thickness of the P-type semiconductor layer is generally much smaller than that of the N-type semiconductor layer. The first P-type semiconductor layer and the second N-type semiconductor layer are bonded to each other, so that the distance between the first active layer and the second active layer is short, and then the light radiated by the first active layer and the light radiated by the second active layer are overlapped with each other, so that the light is bright and concentrated.

In some embodiments, the material of the conductive adhesive layer includes a transparent conductive adhesive material. Adopt transparent conductive adhesive material, can do benefit to light and pass for the light of first active layer and second active layer well superposes, thereby increases light brightness, promotes the light extraction rate, increases light-emitting efficiency.

In some embodiments, the material of the conductive adhesive layer includes ACF or ACA. The ACA has lower curing temperature, the interconnection process is very simple, the process steps are few, and the production efficiency is improved and the cost is reduced. Wherein, ACF prepared by thermosetting resin such as epoxy resin has the advantages of high temperature stability, low thermal expansion and hygroscopicity, etc.

In some embodiments, a dimension of the conductive adhesive layer in the direction parallel to the extending direction of the substrate is greater than or equal to 0.5 micrometers and less than or equal to 3 micrometers. The thickness of the conductive adhesive layer is set to be 0.5-3 micrometers, so that the conductive adhesive layer can have good bonding force, the thickness of the epitaxial lamination layer can be enabled to be as small as possible, and the superposition of light rays radiated by the first active layer and the second active layer is facilitated.

In some embodiments, the conductive adhesive layer comprises a first conductive adhesive layer and a second conductive adhesive layer which are fixedly adhered; the first conductive adhesive layer is fixedly bonded with the first P-type semiconductor layer, and the second conductive adhesive layer is fixedly bonded with the second P-type semiconductor layer. Therefore, before the first epitaxial structure and the second epitaxial structure are bonded with each other, the two structures are the same, processing is convenient, and in batch processing, due to the fact that the structures of all the epitaxial structures are the same, misoperation is not prone to occurring.

In some embodiments, a dimension of the first epitaxial structure along a growth direction of the epitaxial wafer is greater than or equal to 0.5 microns and less than or equal to 10 microns; the size of the second epitaxial structure along the growth direction of the epitaxial wafer is greater than or equal to 0.5 micrometer and less than or equal to 10 micrometers. Therefore, the heights of the first epitaxial structure and the second epitaxial structure are lower, so that the heights of the first active layer and the second active layer are correspondingly lower, when light is transmitted in a TM mode, the time of transmission in the first active layer and the second active layer is shorter, and the light is absorbed less, so that the light extraction rate can be improved, and the light extraction efficiency is increased.

In some embodiments, the epitaxial stack further comprises a first current spreading layer and a second current spreading layer; the first current diffusion layer is stacked between the first P-type semiconductor layer and the conductive adhesive layer, and the second current diffusion layer is stacked between the second P-type semiconductor layer and the conductive adhesive layer. The first current diffusion layer and the second current diffusion layer can make the current diffusion effect higher.

A second application of the present application provides a light-emitting device comprising the epitaxial wafer, the P-side electrode layer, and the N-side electrode layer as described in any one of the first aspects of the present application; the epitaxial stack has a first surface and a second surface oppositely arranged along the growth direction of the epitaxial stack; the P-side electrode layer is arranged on the first surface and is laminated on at least part of the first P-type semiconductor layer, the conductive adhesive layer and at least part of the second P-type semiconductor layer; the N-side electrode layer is arranged on the second surface and is laminated on at least part of the first N-type semiconductor layer and at least part of the second N-type semiconductor layer. The epitaxial wafer is arranged in the light-emitting device, so that the light extraction efficiency is obviously improved, and the light extraction efficiency is improved. The P-side electrode layer and the N-side electrode layer are arranged on two different surfaces, so that current can be distributed on two sides, and the effective composite radiation area is increased.

In some embodiments, the size of the conductive adhesive layer along the direction parallel to the extending direction of the substrate is a; the dimension between the center of the first P type semiconductor layer parallel to the extending direction of the substrate and the center of the second P type semiconductor layer parallel to the extending direction of the substrate is b; the dimension c of the P-side electrode layer in the direction parallel to the extending direction of the substrate satisfies the following condition: c is greater than a and less than or equal to 0.5b. Therefore, the P-side electrode layer can be in good contact with the first P-type semiconductor layer and the second P-type semiconductor layer, shielding of light rays in a TM mode can be reduced, and therefore the light extraction rate is improved; in addition, the P-side electrode layer can realize more stable current input.

In some embodiments, the light emitting device further comprises an insulating reflective layer; the insulating reflecting layer is arranged between the second surface and the N-side electrode layer and covers the first active layer, the first P-type semiconductor layer, the conductive adhesive layer, the second P-type semiconductor layer and the second active layer. In this embodiment, the first N-type semiconductor layer and the second N-type semiconductor layer share one N-side electrode layer extending from the first N-type semiconductor layer to the second N-type semiconductor layer, and since the first P-type semiconductor layer and the second P-type semiconductor layer are located between the first N-type semiconductor layer and the second N-type semiconductor layer, an insulating reflective layer is provided in order to prevent the N-side electrode layer from contacting the first P-type semiconductor layer and/or the second P-type semiconductor layer when extending.

In this embodiment, the insulating reflective layer isolates the N-side electrode layer from the first active layer, the first P-type semiconductor layer, the conductive adhesive layer, the second P-type semiconductor layer, and the second active layer, so that electrical insulation can be achieved, and short circuit can be prevented. The insulating reflecting layer can also reflect the light rays radiated by the first active layer and the second active layer to the direction of the positive light-emitting surface, so that the light extraction rate is increased.

In other embodiments, the light emitting device includes two N-side electrode layers, one of the N-side electrode layers is stacked on at least a portion of the first N-type semiconductor layer, and the other of the N-side electrode layers is stacked on at least a portion of the second N-type semiconductor layer.

In this embodiment, two N-side electrode layers are provided, and the two N-side electrode layers are connected to the first N-type semiconductor layer and the second N-type semiconductor layer, that is, one N-side electrode layer is correspondingly connected to one N-type semiconductor layer, so that connection stability and alignment accuracy can be increased. And the whole extension lengths of the two N-side electrode layers are shorter, so that resources are saved.

When two N-side electrode layers are provided, an insulating reflective layer may also be provided, specifically, the insulating reflective layer is provided between the two N-side electrode layers.

A third aspect of the present application provides a display device comprising a driving circuit and the light emitting device of any one of the second aspects of the present application, wherein the light emitting device is electrically connected to the driving circuit. The display device is provided with the epitaxial wafer, so that the light extraction efficiency is obviously improved, and the light extraction efficiency is improved.

The fourth aspect of the present application provides a method for preparing an epitaxial wafer, which is specifically applicable to preparing the epitaxial wafer according to any one of the first aspects of the present application, and specifically includes the following steps: providing a first epitaxial structure and a second epitaxial structure; the first epitaxial structure comprises a first N-type semiconductor layer, a first active layer and a first P-type semiconductor layer which are sequentially stacked, and the second epitaxial structure comprises a second N-type semiconductor layer, a second active layer and a second P-type semiconductor layer which are sequentially stacked; bonding the first epitaxial structure and the second epitaxial structure through a conductive adhesive layer to form an epitaxial module; patterning the epitaxial module to separate the epitaxial module into a plurality of epitaxial stacks; transferring the epitaxial stack to a substrate; and the stacking direction of the first epitaxial structure, the conductive adhesive layer and the second epitaxial structure in the epitaxial stacking layer after transfer is parallel to the extending direction of the substrate.

The light density of the epitaxial wafer prepared by the method is obviously higher than that of the traditional LED light-emitting module with only one epitaxial structure, so that the light-emitting efficiency is obviously improved. In addition, the first epitaxial structure, the second epitaxial structure, the internal laminated structure of the first epitaxial structure, and the internal laminated structure of the second epitaxial structure are all distributed in a direction parallel to the extending direction of the substrate, and any one of two surfaces of the epitaxial lamination layer, which are oppositely arranged along the growth direction of the epitaxial wafer, can be used as a front light-emitting surface. Therefore, even if the Al component is increased in order to increase the color depth of the ultraviolet light, and thus the light-emitting mode is mainly changed from the TE mode to the TM mode, since the polarization direction of the TM mode is perpendicular to the front light-emitting surface, the light can be easily extracted, and thus the light extraction efficiency can be increased, and the light-emitting efficiency can be increased.

Drawings

Fig. 1 is a schematic structural diagram of an epitaxial wafer in the prior art.

Fig. 2 is a schematic structural diagram of an epitaxial wafer according to an embodiment of the present application.

Fig. 3 is a schematic view of a light-emitting mode structure of the epitaxial wafer shown in fig. 2.

Fig. 4 is a schematic structural diagram of an epitaxial wafer according to another embodiment of the present application.

Fig. 5 is a schematic structural diagram of an epitaxial wafer according to yet another embodiment of the present application.

Fig. 6 is a schematic structural diagram of a light emitting device according to an embodiment of the present application.

Fig. 7 is a schematic view of a current distribution of the light emitting device shown in fig. 6.

Fig. 8 is a schematic structural diagram of a light-emitting device according to another embodiment of the present application.

Fig. 9 is a schematic structural diagram of a light emitting device according to still another embodiment of the present application.

Fig. 10 is a schematic structural diagram of a light emitting device according to still another embodiment of the present application.

Fig. 11 is a schematic structural diagram of a light-emitting device according to still another embodiment of the present application.

Fig. 12 to 15 are schematic views illustrating a process of manufacturing the epitaxial wafer shown in fig. 2.

Fig. 16 to 25 are schematic views illustrating a manufacturing process of the light emitting device shown in fig. 9.

Description of reference numerals: the prior art is as follows: 1-P type semiconductor layer, 2-active layer, 3-N type semiconductor layer.

The application: 100-epitaxial lamination, 110-first epitaxial structure, 111-first N-type semiconductor layer, 112-first active layer, 113-first P-type semiconductor layer, 120-second epitaxial structure, 121-second N-type semiconductor layer, 122-second active layer, 123-second P-type semiconductor layer, 130-conductive adhesive layer, 131-first conductive adhesive layer, 132-second conductive adhesive layer, 200-P side electrode layer, 210-N side electrode layer, 300-insulating reflecting layer, 400-substrate, 500-first current diffusion layer, 510-second current diffusion layer, 600-first substrate, 610-second substrate, 700-temporary storage substrate.

Detailed Description

To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present application are given in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The terms "first" and "second", etc. in this application are for convenience of description only and should not be construed as limiting the present application.

The LED epitaxial wafer can emit red light, blue light, green light, ultraviolet light, and the like, the light emitting color of the epitaxial wafer mainly depends on the materials and doped elements used in the epitaxial process, generally, the commonly used semiconductor material of the infrared LED is InP (indium phosphide), the commonly used semiconductor material of the red LED is GaAs (gallium arsenide), alGaAs (aluminum gallium arsenide), gaAsP (gallium arsenic phosphide) and GaP (gallium phosphide), the commonly used semiconductor material of the yellow LED and the orange LED is AlGaInP (aluminum gallium indium phosphide), the commonly used semiconductor material of the green LED is InGaN (gallium indium nitride), the commonly used semiconductor material of the blue LED is InGaN (gallium indium nitride), and the commonly used semiconductor material of the ultraviolet LED is AlGaN (gallium aluminum nitride).

Among them, the red LED, the green LED, and the blue LED are widely used in traffic signal lamps, automobile signal lamps (brake lamps, head lamps), and the like. The infrared light LED is widely applied to the fields of communication and sensors, such as remote controllers of household appliances, security monitoring cameras, computer mice, sensors and the like.

And ultraviolet light-emitting diodes (UV LEDs) based on III-nitride wide-bandgap semiconductor materials have wide application prospects in the fields of sterilization, polymer curing, biochemical detection, non-line-of-sight communication, special illumination and the like. Compared with the traditional ultraviolet light source mercury lamp, the ultraviolet light emitting diode has the advantages of no mercury, environmental protection, small size, portability, low power consumption, low voltage and the like, and receives more and more attention in recent years.

Regardless of the color of the LED, manufacturers and users pay attention to the luminous efficiency, and the higher the luminous efficiency is, the less energy is consumed, the lower the cost is, and the wider the applicable range is; the lower the luminous efficiency, the more energy sources are consumed, the higher the cost is, and the applicable range is also reduced, so that the improvement of the luminous efficiency is an important focus in the industry and is an important current development trend.

Among them, the luminous efficiency of UV LED is particularly concerned, and AlGaN (gallium aluminum nitride) material is a core material for preparing UV LED. Al (aluminum) _x Ga _1-x The N material is a wide-bandgap direct band-gap semiconductor material, and the AlGaN energy gap can be continuously changed between 3.4eV and 6.2eV by adjusting the Al component in the ternary compound AlGaN, so that ultraviolet light with the wavelength ranging from 200nm to 400nm can be obtained. However, the light emitting efficiency of the currently prepared UV LED, especially the deep ultraviolet LED, is generally low, which limits the wide application of the UV LED.

The main reason for the low luminous efficiency of UV LEDs is their low light extraction efficiency. The factors that limit the light extraction efficiency of UV LEDs are mainly due to the strong absorption of ultraviolet light by P-type GaN, causing the light emitted from the front of the UV LED to be absorbed in large quantities. In addition, as the Al component increases and the wavelength decreases, the polarization characteristic of the uv light is changed, specifically, the light-emitting mode is changed from TE mode perpendicular to the growth plane of the active layer to TM (transverse magnetic wave) mode parallel to the growth plane of the active layer, the propagation direction of the polarized light in TE mode is perpendicular to the front surface of the LED, the light easily penetrates through the N-type semiconductor layer (about 3 um) or P-type semiconductor layer (about 0.1 um) with a small thickness and is easily extracted from the LED, while the propagation direction of the polarized light in TM mode is horizontal to the front surface of the LED, the light has a long path near the active layer (for a general large-sized LED, the light with a size of about 1000um × 1000um, the light with a horizontal propagation direction generally needs several hundreds um to reach the side surface of the LED), and is easily absorbed by the active layer, so that the light is not easily extracted from the LED.

Referring to fig. 1, fig. 1 is a schematic structural diagram of an epitaxial wafer in the prior art, which includes a P-type semiconductor layer 1, an active layer 2, and an N-type semiconductor layer 3 stacked in sequence from top to bottom. The positive light emitting surface is the upper surface of the P-type semiconductor layer, and at this time, the propagation direction of the polarized light in the TM mode is horizontal to the positive light emitting surface, and the light is easily absorbed by the active layer when traveling in a long path near the active layer, so that the light is not easily extracted from the LED.

In order to solve the problem that the light extraction rate of a UV LED is low, the embodiment of the application provides an epitaxial wafer. Of course, it can be understood by those skilled in the art that the epitaxial wafer provided in the embodiments of the present application can also be applied to LEDs with other colors to improve the light extraction efficiency of LEDs with other colors, such as red LEDs prepared based on AlGaAs (aluminum gallium arsenide), yellow LEDs and orange LEDs prepared based on AlGaInP (aluminum gallium indium phosphide), and so on.

Referring to fig. 2 and fig. 3, fig. 2 is a schematic structural diagram of an epitaxial wafer according to an embodiment of the present application, and fig. 3 is a schematic structural diagram of a light extraction mode of the epitaxial wafer shown in fig. 2. The epitaxial wafer provided by the embodiment of the application comprises: the epitaxial structure comprises a substrate 400 and an epitaxial lamination layer 100, wherein the epitaxial lamination layer 100 is arranged on the substrate 400, and the epitaxial lamination layer 100 comprises a first epitaxial structure 110, a conductive adhesive layer 130 and a second epitaxial structure 120 which are sequentially laminated along the extending direction parallel to the substrate 400; the first epitaxial structure 110 and the second epitaxial structure 120 are fixed by the conductive adhesive layer 130. The first epitaxial structure 110 includes a first N-type semiconductor layer 111, a first active layer 112, and a first P-type semiconductor layer 113 sequentially stacked in a direction parallel to an extending direction of the substrate 400; the second epitaxial structure 120 includes a second N-type semiconductor layer 121, a second active layer 122, and a second P-type semiconductor layer 123 sequentially stacked in a direction parallel to the extending direction of the substrate 400.

It is understood that the extending direction X of the substrate 400 is a direction from left to right as shown in fig. 2, or a direction from right to left as shown in fig. 2, and a Y direction perpendicular to the X direction is a growth direction of the epitaxial wafer. The substrate 400 mainly plays a role of bearing the epitaxial module epitaxial stack 100, and increases the structural stability of the epitaxial wafer.

That is, the epitaxial stack 100 includes two epitaxial structures, and compared with the conventional structure, there is one more epitaxial structure, so that the light density that can be emitted is significantly stronger than that of the conventional LED light-emitting module that is provided with only one epitaxial structure, and therefore, the light-emitting efficiency is significantly improved.

In addition, the first epitaxial structure 110, the second epitaxial structure 120, the internal laminated structure of the first epitaxial structure 110, and the internal laminated structure of the second epitaxial structure 120 are all distributed along a direction parallel to the extending direction of the substrate, and any one of two surfaces of the epitaxial stack 100, which are oppositely arranged along the growth direction of the epitaxial wafer, can be used as a positive light emitting surface, and the growth direction Y of the epitaxial wafer is perpendicular to the extending direction of the substrate, that is, the direction from bottom to top in fig. 3. Referring to fig. 3, fig. 3 is a schematic view illustrating a light-emitting mode structure of the epitaxial wafer shown in fig. 2, such that even if Al components are added to increase a color depth of the ultraviolet light, so that a light-emitting mode is mainly changed from a TE mode to a TM mode, since a propagation direction of the TM mode polarized light is perpendicular to a front light-emitting surface, light is easily extracted, and thus light extraction efficiency can be improved, thereby increasing light-emitting efficiency.

It can be understood that, when the LED light emitting module in the present embodiment is applied to a UV LED, the light radiated by the first active layer 112 and the second active layer 122 is ultraviolet light, and the wavelength of the ultraviolet light is between 320nm and 400 nm; alternatively, between 280nm and 320 nm; or, between 200nm and 280 nm.

When the wavelength of the ultraviolet light is between 320nm and 400nm, the radiated light is long wave ultraviolet light (UVA); when the wavelength of the radiated ultraviolet light is between 280nm-320nm, the radiated light is medium wave ultraviolet light (UVB); when the wavelength of the radiated ultraviolet light is between 200nm-280nm, the radiated light is short wave ultraviolet light (UVC).

Illustratively, the size of the first epitaxial structure 110 in the growth direction of the epitaxial wafer is greater than or equal to 0.5 microns and less than or equal to 10 microns; the dimension of the second epitaxial structure 120 in the growth direction of the epitaxial wafer is greater than or equal to 0.5 microns and less than or equal to 10 microns. Therefore, the heights of the first epitaxial structure 110 and the second epitaxial structure 120 are relatively low, and the heights of the first active layer 112 and the second active layer 122 are relatively low, so that when light propagates in the TM mode, the propagation time in the first active layer 112 and the second active layer 122 is relatively short, and the light is absorbed less, so that the light extraction rate can be improved, and the light extraction efficiency can be increased.

In some embodiments, the first P-type semiconductor layer 113 faces the second N-type semiconductor layer 121, and the first P-type semiconductor layer 113 and the second N-type semiconductor layer 121 are adhesively fixed by the conductive adhesive layer 130. Generally, the thickness of the P-type semiconductor layer is about 3 microns, and the thickness of the N-type semiconductor layer is about 0.1 micron, i.e., the thickness of the P-type semiconductor layer is much smaller than that of the N-type semiconductor layer. The first P-type semiconductor layer 113 and the second N-type semiconductor layer 121 are disposed to be adhered to each other such that the distance between the first active layer 112 and the second active layer 122 is relatively short, and then the light radiated from the first active layer 112 and the light radiated from the second active layer 122 are overlapped with each other such that the light is relatively bright and concentrated.

Referring to fig. 2 and 3, in other embodiments, the first P-type semiconductor layer 113 faces the second P-type semiconductor layer 123, and the first P-type semiconductor layer 113 and the second P-type semiconductor layer 123 are adhesively fixed by the conductive adhesive layer 130. Since the thickness of the P-type semiconductor layer in the extending direction of the substrate is about 3 micrometers, the thickness of the N-type semiconductor layer in the extending direction of the substrate is about 0.1 micrometer, that is, the thickness of the P-type semiconductor layer is much smaller than that of the N-type semiconductor layer, the first P-type semiconductor layer 113 and the second P-type semiconductor layer 123 are disposed to be adhered to each other, so that the first active layer 112 and the second active layer 122 are closer to each other, and the light emitted from the first active layer 112 and the light emitted from the second active layer 122 are overlapped with each other, so that the light is brighter and concentrated.

Illustratively, the material of the conductive adhesive layer 130 includes a transparent conductive adhesive material. The transparent conductive adhesive material is adopted, so that light can pass through the transparent conductive adhesive material, the light of the first active layer 112 and the light of the second active layer 122 are well overlapped, the light brightness is increased, the light extraction rate is improved, and the light extraction efficiency is increased. Specifically, the material of the conductive adhesive layer 130 includes an Anisotropic Conductive Film (ACF) or an Anisotropic Conductive Adhesive (ACA). Both ACA and ACF have conductive ball particles therein, and thus can conduct electricity. The ACA has lower curing temperature, the interconnection process is very simple, the process steps are few, and the production efficiency is improved and the cost is reduced. Wherein, ACF prepared by thermosetting resin such as epoxy resin has the advantages of high temperature stability, low thermal expansion and hygroscopicity, etc.

Illustratively, the size of the conductive adhesive layer 130 in the extending direction of the substrate is greater than or equal to 0.5 micrometers and less than or equal to 3 micrometers. When the thickness of the conductive adhesive layer 130 is less than 0.5 μm, the adhesive force of the conductive adhesive layer 130 may be weak; when the thickness of the conductive adhesive layer 130 is greater than 3 μm, the size of the entire epitaxial stack 100 is greatly affected, and the light superposition of the first active layer 112 and the second active layer 122 is affected. Thus, setting the thickness of the conductive adhesive layer 130 to be between 0.5 micrometers and 3 micrometers can ensure good adhesion of the conductive adhesive layer 130, minimize the thickness of the epitaxial stacked layer 100, and facilitate superposition of light rays radiated from the first active layer 112 and the second active layer 122.

Referring to fig. 4, fig. 4 is a schematic structural diagram of an epitaxial wafer according to another embodiment of the present application. In this embodiment, the first epitaxial structure 110 and the second epitaxial structure 120 are the same as the above-described embodiment except that the conductive adhesive layer 130 includes a first conductive adhesive layer 131 and a second conductive adhesive layer 132 that are adhesively fixed; the first conductive adhesive layer 131 is fixedly bonded to the first P-type semiconductor layer 113, and the second conductive adhesive layer 132 is fixedly bonded to the second P-type semiconductor layer 123. Therefore, before the first epitaxial structure 110 and the second epitaxial structure 120 are bonded with each other, a conductive adhesive layer is bonded with the first epitaxial structure and the second epitaxial structure, the structures of the first epitaxial structure and the second epitaxial structure are the same, processing is convenient, and misoperation is not prone to occurring during batch processing.

Referring to fig. 5, fig. 5 is a schematic structural diagram of an epitaxial wafer according to yet another embodiment of the present application. In this embodiment, the epitaxial stack 100 further includes a first current spreading layer 500 and a second current spreading layer 510; the first current diffusion layer 500 is stacked between the first P-type semiconductor layer 113 and the conductive adhesive layer 130, and the second current diffusion layer 510 is stacked between the second P-type semiconductor layer 123 and the conductive adhesive layer 130. It is understood that both the first current spreading layer 500 and the second current spreading layer 510 may be Indium Tin Oxides (ITO).

The first current diffusion layer 500 and the second current diffusion layer 510 may make the diffusion effect of the current higher.

Based on the epitaxial wafer provided by the above embodiments, some embodiments of the present application further provide a light emitting device, and the light emitting device may be prepared by using the epitaxial wafer provided by the above embodiments.

Specifically, referring to fig. 6, fig. 6 is a schematic structural diagram of a light emitting device according to an embodiment of the present application. The light emitting device includes an epitaxial wafer shown in fig. 2, and includes a P-side electrode layer 200 and an N-side electrode layer 210. Wherein the epitaxial stack has a first surface and a second surface oppositely arranged along the growth direction Y thereof, and the growth direction of the epitaxial wafer is perpendicular to the extending direction of the substrate 400. The P-side electrode layer 200 is disposed on the first surface and stacked on at least a portion of the first P-type semiconductor layer, the conductive adhesive layer 130, and at least a portion of the second P-type semiconductor layer; the N-side electrode layer 210 is disposed on the second surface, and is stacked on at least a portion of the first N-type semiconductor layer 111 and at least a portion of the second N-type semiconductor layer 121. N-side electrode layer 210 and P-side electrode layer 200 can facilitate connection with a driving circuit when the epitaxial wafer is finally used, so that the epitaxial wafer can smoothly emit light. Referring to fig. 7, fig. 7 is a schematic view showing current distribution of the light emitting device shown in fig. 6, wherein the P-side electrode layer 200 and the N-side electrode layer 210 are disposed on two different surfaces, so that current can be distributed on two sides, thereby increasing an effective recombination radiation area.

It can be understood that, since the distance between the first P-type semiconductor layer 113 and the second P-type semiconductor layer 123 is relatively short, the volume of the disposed P-side electrode layer 200 can be relatively small, and thus, the surface on which the P-side electrode layer 200 is disposed can be selected as a positive light emitting surface, that is, the first surface is a positive light emitting surface.

It is understood that in this embodiment, the substrate 400 may be specifically a circuit substrate, and then, in application, a plurality of epitaxial wafers arranged in an array may be disposed on the substrate 400. Therefore, the subsequent preparation of equipment such as a liquid crystal display and the like can be facilitated.

Exemplarily, referring to fig. 6, a dimension of the conductive adhesive layer 130 along a direction parallel to the extending direction of the substrate (i.e., X direction in the figure) is a; the dimension between the center of the first P-type semiconductor layer 113 parallel to the extending direction of the substrate and the center of the second P-type semiconductor layer 123 parallel to the extending direction of the substrate is b. The dimension c of the P-side electrode layer 200 in the direction parallel to the substrate extension direction satisfies the following condition: c is greater than a and less than or equal to 0.5b. Therefore, the P-side electrode layer 200 can be in good contact with the first P-type semiconductor layer 113 and the second P-type semiconductor layer 123, and shielding of light in a TM mode can be reduced, so that light extraction rate is improved. In general, the P-side electrode layer 200 is mostly made of metal, so the P-side electrode layer 200 can also play a role in reflecting light, thereby increasing the light extraction rate and improving the light extraction efficiency; in addition, P-side electrode layer 200 can also achieve a more stable current input.

Referring to fig. 8, fig. 8 is a schematic structural diagram of a light emitting device according to another embodiment of the present application. This embodiment provides a light emitting device including the epitaxial wafer shown in fig. 4, and including a P-side electrode layer 200 and an N-side electrode layer 210. The specific conditions of the P-side electrode layer and the N-side electrode layer are the same as those of the above embodiments, and are not described again.

Referring to fig. 9, fig. 9 is a schematic structural diagram of a light emitting device according to still another embodiment of the present application. This embodiment provides a light emitting device including the epitaxial wafer shown in fig. 5, and including a P-side electrode layer 200 and an N-side electrode layer 210. The specific conditions of the P-side electrode layer and the N-side electrode layer are the same as those of the above embodiments, and are not described again.

Referring to fig. 10, fig. 10 is a schematic structural diagram of a light emitting device according to still another embodiment of the present application. In this embodiment, the light emitting device includes an epitaxial wafer shown in fig. 2, and includes a P-side electrode layer 200, an N-side electrode layer 210, and an insulating reflective layer 300. The details of the P-side electrode layer 200 and the N-side electrode layer 210 are the same as those of the above embodiments, and are not repeated herein. Except that an insulating reflective layer 300 is disposed between the second surface and the N-side electrode layer 210, and the insulating reflective layer 300 covers the first active layer 112, the first P-type semiconductor layer 113, the conductive adhesive layer 130, the second P-type semiconductor layer 123, and the second active layer 122.

In this embodiment, the first N-type semiconductor layer 111 and the second N-type semiconductor layer 121 share one N-side electrode layer 210, the N-side electrode layer 210 extends from the first N-type semiconductor layer 111 to the second N-type semiconductor layer 121, and since the first P-type semiconductor layer 113 and the second P-type semiconductor layer 123 are positioned between the first N-type semiconductor layer 111 and the second N-type semiconductor layer 121, the insulating reflective layer 300 is provided in order to prevent the N-side electrode layer 210 from contacting the first P-type semiconductor layer 113 and/or the second P-type semiconductor layer 123 when it extends.

The insulating reflective layer 300 isolates the N-side electrode layer 210 from the first active layer 112, the first P-type semiconductor layer 113, the conductive adhesive layer 130, the second P-type semiconductor layer 123, and the second active layer 122, thereby achieving electrical insulation and preventing short circuit. The insulating reflective layer 300 may also reflect the light radiated from the first and second active layers 112 and 122 to the positive light emitting surface direction, thereby increasing the light extraction rate.

Wherein the substrate 400 is located on a surface of the N-side electrode layer 210 facing away from the second surface. The substrate 400 may be made of a conductive material or a non-conductive material, the substrate 400 is made of a high heat dissipation material, and the substrate 400 mainly plays a role of supporting the epitaxial stack 100. The substrate 400 may be a circuit substrate, etc., in particular, when manufacturing a light emitting device.

Referring to fig. 11, fig. 11 is a schematic structural diagram of a light emitting device according to still another embodiment of the present application. In this embodiment, the light emitting device includes the epitaxial wafer shown in fig. 4, and includes a P-side electrode layer 200, an N-side electrode layer 210, and an insulating reflective layer 300. The insulating reflective layer 300 and the P-side electrode layer 200 are the same as those in the above embodiments, and are not described again. The difference is that the light emitting device in this embodiment includes two N-side electrode layers 210, wherein one of the N-side electrode layers 210 is stacked on at least a portion of the first N-type semiconductor layer 111, and wherein the other N-side electrode layer 210 is stacked on at least a portion of the second N-type semiconductor layer 121.

In this embodiment, two N-side electrode layers 210 are provided, and the two N-side electrode layers 210 are respectively connected to the first N-type semiconductor layer 111 and the second N-type semiconductor layer 121, that is, one N-side electrode layer is correspondingly connected to one N-type semiconductor layer, so that connection stability and alignment accuracy can be increased. And the whole extension lengths of the two N-side electrode layers are shorter, so that resources are saved.

At this time, the two N-side electrode layers 210 have a space therebetween, and the insulating reflective layer 300 may be disposed between the two N-side electrode layers 210. Therefore, the space utilization rate can be improved, and the size of the light-emitting device can be reduced.

It can be understood by those skilled in the art that a buffer layer, a distributed bragg reflector layer, an electron blocking layer, an ohmic contact layer, and the like can be further provided in some embodiments, which are not described in detail in this application.

Referring to fig. 12 to 15, fig. 12 to 15 are schematic views illustrating a process of manufacturing the epitaxial wafer shown in fig. 2. The method for manufacturing the epitaxial wafer shown in fig. 2 specifically includes the following steps. The preparation method of the epitaxial wafer shown in fig. 4 and 5 may refer to the preparation method of the epitaxial wafer in fig. 2, and details are not repeated in this application.

Step S10: referring to fig. 12, a first epitaxial structure 110 and a second epitaxial structure 120 are provided; the first epitaxial structure 110 includes a first N-type semiconductor layer 111, a first active layer 112, and a first P-type semiconductor layer 113 that are sequentially stacked, and the second epitaxial structure 120 includes a second N-type semiconductor layer 121, a second active layer 122, and a second P-type semiconductor layer 123 that are sequentially stacked. The first epitaxial structure 110 and the second epitaxial structure 120 are identical and can be processed in batch.

Step S11: referring to fig. 13, the first epitaxial structure 110 and the second epitaxial structure 120 are bonded by a conductive adhesive layer 130 to form an epitaxial module. At this time, the first epitaxial structure 110 and the second epitaxial structure 120 are adhesively fixed as a whole.

Step S12: referring to fig. 14, the epitaxial module is patterned to separate the epitaxial module into a plurality of epitaxial stacks 100.

Step S13: referring to fig. 15, the epitaxial stack 100 is transferred to a substrate 400; wherein a stacking direction of the first epitaxial structure 110, the conductive adhesive layer 130 and the second epitaxial structure 120 in the transferred epitaxial stack 100 is parallel to an extending direction of the substrate 400.

Compared with the traditional structure, the epitaxial wafer prepared by the method has one more epitaxial structure, so that the luminous density of the emitted light is obviously higher than that of a module which is only provided with one epitaxial structure in the traditional structure, and the luminous efficiency is obviously improved.

In addition, the first epitaxial structure 110, the second epitaxial structure 120, the internal stacked structure of the first epitaxial structure 110, and the internal stacked structure of the second epitaxial structure 120 are all distributed along a direction parallel to the extending direction of the substrate, and any one of two surfaces of the epitaxial stack 100 facing each other along the growth direction of the epitaxial wafer may be used as a front light-emitting surface. Therefore, even if the Al component is increased in order to increase the color depth of the ultraviolet light, and thus the light-emitting mode is mainly changed from the TE mode to the TM mode, since the polarization direction of the TM mode is perpendicular to the front light-emitting surface, the light can be easily extracted, and thus the light extraction efficiency can be increased, and the light-emitting efficiency can be increased.

Referring to fig. 16 to 25, fig. 16 to 25 are schematic views illustrating a manufacturing process of the light emitting device shown in fig. 9, and specific steps are as follows. The light emitting device manufacturing process described in other embodiments refers to the light emitting device manufacturing process in fig. 9, and is not described in detail in this application.

Step S101: referring to fig. 16, a first epitaxial structure 110 provided with a first layer of conductive glue is provided, and a second epitaxial structure 120 provided with a second layer of conductive glue is provided. The first epitaxial structure 110 is grown on the first substrate 600, and the second epitaxial structure 120 is grown on the second substrate 610. A schematic view of the first epitaxial structure 110 is shown in fig. 8, and the second epitaxial structure is the same as the first epitaxial structure and is therefore not shown in the figure.

Specifically, the first epitaxial structure 110 includes a first N-type semiconductor layer 111, a first active layer 112, and a first current reflective layer, which are sequentially stacked, and the first conductive adhesive layer is bonded to the first current reflective layer; the second epitaxial structure 120 includes a second N-type semiconductor layer 121, a second active layer 122, and a second current reflective layer, which are sequentially stacked, and the second conductive adhesive layer is bonded to the second current reflective layer.

Step S102: referring to fig. 17, the first conductive adhesive layer and the second conductive adhesive layer are adhesively fixed, so that the first epitaxial structure 110 and the second epitaxial structure 120 are adhesively fixed as a whole.

Step S103: referring to fig. 18, the first substrate 600 of the first epitaxial structure 110 is peeled off. Specifically, laser ablation may be used.

Step S104: referring to fig. 19, a patterning process is performed on the whole of the first and second epitaxial structures 110 and 120 bonded thereto. At this point, the overall structure is separated into a plurality of epitaxial stacks 100.

Step S105: referring to fig. 20, portions of the epitaxial stack 100 are selectively stripped. Specifically, the second substrate 610 may be selectively irradiated with laser light to peel off the corresponding epitaxial stack 100.

Step S106: referring to fig. 21, the stripped epitaxial stack 100 is transferred to a temporary storage substrate 700.

Step S107: referring to fig. 22, an insulating reflective layer 300 is formed on a surface of the epitaxial stack 100 facing away from the temporary storage substrate 700, i.e., the second surface.

Step S108: referring to fig. 23, an N-side electrode layer 210 is prepared on the second surface of the epitaxial stack 100. The insulating reflective layer 300 is located between the second surface and the N-side electrode layer 210, and covers the first active layer 112, the first P-type semiconductor layer 113, the conductive adhesive layer 130, the second P-type semiconductor layer 123, and the second active layer 122.

Step S109: referring to fig. 24, the substrate 400 is prepared on the N-side electrode layer 210, and then the temporary storage substrate 700 is peeled off.

Step S110: referring to fig. 25, a P-side electrode layer 200 is prepared on a first surface of the epitaxial stack 100.

The light-emitting device prepared by the method comprises two epitaxial structures, and compared with the traditional LED light-emitting module, one epitaxial structure is added, so that the density of emitted light is obviously higher than that of the traditional LED light-emitting module with only one epitaxial structure, and the light-emitting efficiency is obviously improved. In addition, even if the Al component is added to increase the color depth of the ultraviolet light, thereby causing the light-emitting mode to be mainly changed from the TE mode to the TM mode, at this time, since the polarization propagation direction of the TM mode is perpendicular to the front light-emitting surface, the light is easily extracted, thereby increasing the light extraction efficiency and increasing the light-emitting efficiency.

It is understood that after step 106 and before step 107, step 1071 may be further included: the respective surfaces of the epitaxial stack 100 are roughened. Thereby, the light extraction efficiency can be improved.

It is also understood that after step S107 and before step S108, step 1081 may be further included: and arranging the ohmic contact layer by using a chemical vapor deposition method or a physical vapor deposition method.

The embodiment of the application also provides a display device which comprises the light-emitting device in any embodiment of the application. In the application, the display device may be a display device having a display effect and/or a touch effect, such as a mobile phone, a tablet computer, a notebook computer, and the like, which is not particularly limited.

It should be understood that the application is not limited to the above examples, and that modifications or changes may be made by those skilled in the art based on the above description, and all such modifications and changes are intended to fall within the scope of the appended claims.

Claims (14)

1. An epitaxial wafer, comprising:

a substrate;

the epitaxial lamination is arranged on the substrate and comprises a first epitaxial structure, a conductive adhesive layer and a second epitaxial structure which are sequentially laminated along the extending direction parallel to the substrate; the first epitaxial structure and the second epitaxial structure are fixedly bonded through the conductive adhesive layer;

the first epitaxial structure comprises a first N-type semiconductor layer, a first active layer and a first P-type semiconductor layer which are sequentially stacked along the extending direction parallel to the substrate; the second epitaxial structure comprises a second N-type semiconductor layer, a second active layer and a second P-type semiconductor layer which are sequentially stacked along the extending direction parallel to the substrate.

2. The epitaxial wafer of claim 1, wherein the first P-type semiconductor layer faces the second P-type semiconductor layer, and the first P-type semiconductor layer and the second P-type semiconductor layer are adhesively fixed by the conductive adhesive layer.

3. The epitaxial wafer of claim 1, wherein the first P-type semiconductor layer faces the second N-type semiconductor layer, and the first P-type semiconductor layer and the second N-type semiconductor layer are adhesively fixed by the conductive adhesive layer.

4. The epitaxial wafer of claim 1, wherein the material of the conductive adhesive layer comprises a transparent conductive adhesive material.

5. The epitaxial wafer of claim 1, wherein the conductive glue layer comprises a first conductive glue layer and a second conductive glue layer that are adhesively secured; the first conductive adhesive layer is fixedly bonded with the first epitaxial structure, and the second conductive adhesive layer is fixedly bonded with the second epitaxial structure.

6. The epitaxial wafer of any of claims 1 to 5, wherein the first epitaxial structure has a dimension in the growth direction of the epitaxial wafer greater than or equal to 0.5 microns and less than or equal to 10 microns; the size of the second epitaxial structure along the growth direction of the epitaxial wafer is greater than or equal to 0.5 micrometer and less than or equal to 10 micrometers.

7. The epitaxial wafer of any of claims 1 to 5, wherein the epitaxial stack further comprises a first current diffusion layer and a second current diffusion layer; the first current diffusion layer is stacked between the first P-type semiconductor layer and the conductive adhesive layer, and the second current diffusion layer is stacked between the second P-type semiconductor layer and the conductive adhesive layer.

8. A light emitting device, comprising: the epitaxial wafer, the P-side electrode layer, and the N-side electrode layer of any one of claims 1 to 7; the epitaxial stack has a first surface and a second surface oppositely arranged along the growth direction of the epitaxial stack;

the P-side electrode layer is arranged on the first surface and is laminated on at least part of the first P-type semiconductor layer, the conductive adhesive layer and at least part of the second P-type semiconductor layer; the N-side electrode layer is arranged on the second surface and is laminated on at least part of the first N-type semiconductor layer and at least part of the second N-type semiconductor layer.

9. The light-emitting device according to claim 8, wherein the light-emitting device comprises a plurality of the epitaxial wafers, and a plurality of the epitaxial wafers are distributed on the substrate in an array manner.

10. The light-emitting device according to claim 8, wherein the size of the conductive adhesive layer in a direction parallel to the extending direction of the substrate is a; the first P type semiconductor layer has a size b between the center parallel to the extending direction of the substrate and the center parallel to the extending direction of the substrate;

the dimension c of the P-side electrode layer in the growth direction of the epitaxial wafer meets the following condition: c is greater than a and less than or equal to 0.5b.

11. A light-emitting device according to any one of claims 8 to 10, further comprising an insulating reflective layer; the insulating reflecting layer is arranged on the second surface and covers the first active layer, the first P-type semiconductor layer, the conductive adhesive layer, the second P-type semiconductor layer and the second active layer.

12. The light-emitting device according to any one of claims 8 to 10, wherein the light-emitting device comprises two N-side electrode layers, one of the N-side electrode layers being stacked on at least a part of the first N-type semiconductor layer, and the other of the N-side electrode layers being stacked on at least a part of the second N-type semiconductor layer.

13. A display device, comprising:

a drive circuit; and

a light emitting device according to any one of claims 8 to 12; wherein the light emitting device is electrically connected to the driving circuit.

14. A method for preparing an epitaxial wafer is characterized by comprising the following steps:

providing a first epitaxial structure and a second epitaxial structure; the first epitaxial structure comprises a first N-type semiconductor layer, a first active layer and a first P-type semiconductor layer which are sequentially stacked, and the second epitaxial structure comprises a second N-type semiconductor layer, a second active layer and a second P-type semiconductor layer which are sequentially stacked;

bonding the first epitaxial structure and the second epitaxial structure through a conductive adhesive layer to form an epitaxial module;

patterning the epitaxial module to separate the epitaxial module into a plurality of epitaxial stacks;

transferring the epitaxial stack to a substrate; and the lamination direction of the first epitaxial structure, the conductive adhesive layer and the second epitaxial structure in the epitaxial lamination layer after transfer is parallel to the extension direction of the substrate.

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