Epitaxial layer structure and method of fabrication, light emitting chip and light emitting device

Abstract

The present application relates to a kind of epitaxial layer structure and manufacturing method, light emitting chip and light emitting device.Epitaxial layer structure includes N-type semiconductor layer, P-type semiconductor layer, active layer;N-type semiconductor layer includes N-type window layer, N-type window layer includes multiple first material layer and same number of second material layer, first material layer and second material layer are alternately arranged one by one;First material layer and second material layer are phosphide current spreading material with different refractive index, and the thickness of first material layer and second material layer is configured according to the wavelength of target light emitted by active layer to achieve the reflection of target light.In some implementation processes, more target light is emitted from P surface, and the light emitting efficiency of the light emitting chip formed finally is improved when light is emitted from P surface, so the overall brightness of the light emitting chip is also improved.

Description

Technical Field

[0001] This invention relates to the field of light-emitting chips, and more particularly to epitaxial layer structures and fabrication methods, light-emitting chips, and light-emitting devices. Background Technology

[0002] In recent years, displays composed of micron-sized MiniLEDs (Mini Light Emitting Diodes) and MicroLEDs (Micro Light Emitting Diodes) have been developed. Due to their small chip size and high integration, they have greater advantages over LCDs (Liquid Crystal Displays) and OLEDs (Organic Light Emitting Diodes) in terms of brightness, resolution, contrast, energy consumption, lifespan, response speed, and thermal stability.

[0003] However, in the epitaxial structure of conventional Mini LED, Micro LED and other light-emitting chips, the light emission efficiency is still not high, some light is wasted, and there is still room for improvement in brightness.

[0004] Therefore, improving the light emission efficiency of light-emitting chips is an urgent problem to be solved. Summary of the Invention

[0005] In view of the shortcomings of the above-mentioned related technologies, the purpose of this application is to provide an epitaxial layer structure and fabrication method, a light-emitting chip and a light-emitting device, in order to solve the problem of low light emission efficiency of the light-emitting chip.

[0006] An epitaxial layer structure, comprising: N-type semiconductor layer; P-type semiconductor layer; An active layer is disposed between the N-type semiconductor layer and the P-type semiconductor layer; The N-type semiconductor layer includes an N-type window layer, which includes multiple first material layers and an equal number of second material layers, with the first and second material layers alternately arranged. The first and second material layers are phosphide current spreading materials with different refractive indices, and the thickness of the first and second material layers is configured according to the wavelength of the target light emitted by the active layer to achieve reflection of the target light.

[0007] The aforementioned epitaxial layer structure, by designing the typically fixed-component N-type window layer as an alternating layer of two phosphide current-spreading materials with different refractive indices, enables the N-type window layer to reflect light. This means that while the N-type window layer better facilitates lateral current spread, it also reflects light. Consequently, more target light rays are emitted from the P-side, improving the light extraction efficiency of the final light-emitting chip at the P-side, and thus increasing the overall brightness of the chip.

[0008] Optionally, the N-type semiconductor layer further includes an ohmic contact layer, which is disposed on the side of the N-type window layer away from the active layer. The barrier of the first material layer is lower than that of the second material layer, and the layer of the N-type window layer closest to the ohmic contact layer is the first material layer.

[0009] The arrangement of the first material layer with a lower barrier closer to the ohmic contact layer creates a stepped barrier structure at the junction of the ohmic contact layer and the N-type window layer, which is more conducive to electron injection and allows the voltage required for the light-emitting chip to operate normally to be relatively reduced.

[0010] Optionally, the first material layer includes (Al) x Ga 1-x ) 0.5 In 0.5 P, 0≤x≤1; the second material layer includes (Al y Ga 1-y ) 0.5 In 0.5 P, 0≤y≤1, and x is not equal to y.

[0011] Alternatively, 0.15≤x≤0.45, 0.5≤y≤1; or, x=0, 0.5≤y≤1.

[0012] By controlling the composition content appropriately, the overall barrier difference of the N-type window layer is ensured, and a sufficient difference in refractive index is formed between the first and second material layers, which is beneficial to the reflection effect of the Bragg reflection structure.

[0013] Optionally, the thickness of each of the first material layers is equal, and the thickness of the first material layer is 41-46 nm; the thickness of each of the second material layers is equal, and the thickness of the second material layer is 47-54 nm.

[0014] In some implementation processes, the thickness of the first and second material layers mentioned above enables the N-type window layer to achieve a good reflection effect for red light. Based on the same inventive concept, this application also provides a method for fabricating an epitaxial layer structure, the method comprising: An N-type semiconductor layer is formed, wherein the N-type semiconductor layer includes an N-type window layer, the N-type window layer includes a plurality of first material layers and an equal number of second material layers, the first material layers and the second material layers are alternately arranged; the first material layers and the second material layers are phosphide current spreading materials with different refractive indices, and the thickness of the first material layers and the second material layers is configured according to the wavelength of the target light emitted by the active layer to achieve reflection of the target light; An active layer is formed on one side of the N-type semiconductor layer; A P-type semiconductor layer is formed on one side of the active layer.

[0015] The aforementioned epitaxial layer fabrication method, by alternately forming multiple cycles of first and second material layers as N-type window layers, improves the light extraction efficiency and overall brightness of the final light-emitting chip produced by the epitaxial layer structure, which is conducive to its fabrication. Furthermore, in some embodiments, it also reduces the operating voltage of the final light-emitting chip.

[0016] Based on the same inventive concept, this application also provides a light-emitting chip, comprising: An epitaxial layer structure, wherein the epitaxial layer structure is the epitaxial layer structure described above; The N-type electrode is electrically connected to the N-type semiconductor layer; The P-type electrode is electrically connected to the P-type semiconductor layer.

[0017] The aforementioned light-emitting chip, formed based on the epitaxial layer structure of the previous example, has high light extraction efficiency and higher overall brightness. Based on the same inventive concept, this application also provides a light-emitting device, comprising: Circuit board; The light-emitting chip is the aforementioned light-emitting chip, and the light-emitting chip is bonded to the die-bonding region of the circuit substrate.

[0018] Because the above-mentioned light-emitting device uses the above-mentioned light-emitting chip, the light-emitting chip has high light extraction efficiency and high overall brightness, resulting in better light-emitting efficiency and brightness of the light-emitting device. Attached Figure Description

[0019] Figure 1 A schematic diagram of the epitaxial layer structure provided in the embodiments of the present invention. Figure 1 ; Figure 2 This is a schematic diagram of the reflection spectrum of an N-type window layer provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the band structure provided in an embodiment of the present invention; Figure 4 A schematic diagram of the epitaxial layer structure provided in the embodiments of the present invention. Figure 2 ; Figure 5 This is a schematic diagram of the structure of the light-emitting chip provided in an embodiment of the present invention; Figure 6 A schematic diagram of the basic process of a method for fabricating an epitaxial layer structure provided in another optional embodiment of the present invention; Figure 7 A schematic flowchart illustrating a specific example of a method for fabricating an epitaxial layer structure, provided as another optional embodiment of the present invention; Figure 8 A schematic diagram of the fabrication process of an epitaxial layer structure, provided as another optional embodiment of the present invention; Explanation of reference numerals in the attached figures: 1 - N-type semiconductor layer; 11 - Ohmic contact layer; 12 - N-type window layer; 121 - First material layer; 122 - Second material layer; 13 - N-type confinement layer; 14 - N-type waveguide layer; 15 - N-type electrode; 31 - P-type waveguide layer; 32 - P-type confinement layer; 2 - Active layer; 3 - P-type semiconductor layer; 33 - Transition layer; 34 - Window layer; 35 - P-type electrode; 4 - Sapphire substrate layer; 5 - Growth substrate; 6 - Buffer layer; 7 - Etching stop layer; A - Band structure of N-type window layer in related technologies; B - Band structure of N-type window layer in the embodiments of the present invention; B1 - Lowest barrier region; B2 - Intermediate level barrier region; B3 - Highest barrier region. Detailed Implementation

[0020] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0021] Unless otherwise defined, 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 specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0022] In the epitaxial structure of light-emitting chips such as Mini LED and Micro LED, the light emission efficiency is still not high, and some light is wasted.

[0023] Therefore, this application aims to provide a solution that can solve the above-mentioned technical problems, the details of which will be described in subsequent embodiments.

[0024] Example: This embodiment provides an epitaxial layer structure; please refer to [link / reference]. Figure 1 As shown, the epitaxial layer structure sequentially includes: an N-type semiconductor layer 1, an active layer 2, and a P-type semiconductor layer 3.

[0025] The epitaxial layer structure in this embodiment can be fabricated on a growth substrate, i.e., formed on the growth substrate. The growth substrate can be any material capable of growing the epitaxial layer of the light-emitting chip, such as, but not limited to, Al2O3 (sapphire), SiC (silicon carbide), Si (silicon), GaAs (gallium arsenide), or (GaP) gallium phosphide, or other semiconductor materials, without limitation. Furthermore, in some embodiments, the substrate can be peeled off from the light-emitting chip during the fabrication of the epitaxial layer structure into the light-emitting chip.

[0026] The materials for the epitaxial layer structure can be selected from, but are not limited to, group III / V semiconductor materials such as Al (aluminum), Ga (gallium), In (indium), P (phosphorus), As (arsenic), or N (nitrogen). Common materials include, for example, GaN (gallium nitride) based materials, AlGaInP (aluminum gallium indium phosphorus) based materials, GaAs based materials, and so on.

[0027] The N-type semiconductor layer is doped with N-type dopant, and the P-type semiconductor layer is doped with P-type dopant. During light emission, the N-type semiconductor layer provides electrons, and the P-type semiconductor layer provides holes. Electrons and holes (collectively referred to as charge carriers) enter the active layer and recombine, thereby releasing light energy.

[0028] The active layer is located between the N-type semiconductor layer and the P-type semiconductor layer, and is the region where charge carriers combine and emit light.

[0029] In this embodiment, the active layer may include a multi-quantum well layer, which may include multiple quantum well layers and multiple barrier layers arranged alternately.

[0030] The N-type semiconductor layer in this embodiment includes an N-type window layer (or N-type extension layer, N-type current extension layer, etc.). In this embodiment and some related technologies, the N-type window layer is mainly used to enable better lateral current extension, that is, to make the current distribution more uniform throughout the device.

[0031] like Figure 1As shown, in this embodiment, the N-type window layer 12 is disposed on the side of the N-type semiconductor layer 1 away from the active layer 2. It includes multiple first material layers 121 and an equal number of second material layers 122, with the first material layers 121 and second material layers 122 alternately arranged. That is, a first material layer 121 and a second material layer 122 are sequentially arranged in pairs, and this is repeated multiple times. The first material layers 121 and second material layers 122 are phosphide current spreading materials with different refractive indices, and the thickness of the first material layers 121 and second material layers 122 is configured according to the wavelength of the target light emitted by the active layer 2 to achieve reflection of the target light. In practical applications, the N-type semiconductor layer may also include an ohmic contact layer. The electrode structure of the light-emitting chip may be disposed on the ohmic contact layer, but the current on the ohmic contact layer is mainly concentrated in the area near the electrode. The ohmic contact layer is disposed on the side of the N-type window layer away from the active layer, and the current is spread through the N-type window layer.

[0032] In this embodiment, a phosphide current-spreading material is used as the material for the N-type window layer, which enables excellent lateral current spread and improves the uniformity of current distribution. In related technologies, the window layer material is usually of a fixed composition. In this embodiment, by alternating first and second material layers with different refractive indices, the N-type window layer forms a Bragg reflection structure. That is, the N-type window layer in this embodiment not only better spreads the current laterally but also reflects light. The target light emitted from the active layer is reflected by the N-type window layer, resulting in more target light emanating from the P-side (or the side of the active layer pointing towards the P-type semiconductor layer), improving the light extraction efficiency of the final light-emitting chip when emitting light from the P-side. The wavelength of the target light in this embodiment, i.e., the light released after charge carriers recombine in the active layer, is typically determined by factors such as the specific materials and processes used in the epitaxial layer structure.

[0033] The thickness of the first and second material layers is equal to one-quarter of the reflection center wavelength of their reflection patterns divided by their respective refractive indices. It is understood that when the reflection center wavelength equals the wavelength of the target light, it indicates a good reflection effect on the target light, meaning a high reflectivity. Therefore, the thicknesses of the first and second material layers can be calculated based on the wavelength of the target light to ensure that the reflection center wavelength of the reflection pattern equals the wavelength of the target light. Of course, in practical applications, specific requirements for the reflectivity of the N-type window layer are not necessary. It is understood that as long as at least a portion of the target light is reflected, the light-emitting chip can achieve higher light extraction efficiency. Therefore, in practical applications, technicians can determine the thickness of the first and second material layers based on the desired reflection effect, as long as the N-type window layer can reflect the target light emitted by the active layer. This embodiment does not impose specific limitations on this. As a more specific example, the wavelength of the target light is approximately C. The thicknesses of the first and second material layers are determined based on this wavelength. The reflection spectra of the first and second material layers are as follows: Figure 2 As shown in the figure, the horizontal axis represents the wavelength of light, and the vertical axis represents the reflectivity of the Bragg reflection structure formed by the first and second material layers for the corresponding wavelength. It can be seen that as long as the wavelength of the target light is within a certain bandwidth range of the reflection spectrum (e.g., between c1 and c2), it can have a good reflection effect.

[0034] In some embodiments, the N-type semiconductor layer further includes an ohmic contact layer disposed on the side of the N-type window layer away from the active layer. The barrier of the first material layer is lower than that of the second material layer, and the first material layer is the layer closest to the ohmic contact layer in the N-type window layer. For example, please refer to [link to example description]. Figure 1 The structure, with the ohmic contact layer 11 on the side near the active layer 2, is sequentially... The first material layer 121 and the second material layer 122 are alternately and cyclically configured. Figure 3 The diagram illustrates the band structure of the N-type window layer. This includes the band structure A (dashed area in the diagram) of the N-type window layer in related technologies and the band structure B (solid area in the diagram) of the N-type window layer in this embodiment. In related technologies, the composition content of the N-type window layer is uniform throughout. Therefore, when electrons are injected from the previous layer into the N-type window layer, they directly encounter a high potential barrier, and the electron injection efficiency drops significantly at this point. This results in a higher voltage required for the light-emitting chip to operate normally. In this embodiment, the first and second material layers with different composition contents in the N-type window layer create different potential barriers in the band structure of the N-type window layer. By placing the first material layer, which has a lower potential barrier, closer to the ohmic contact layer, a stepped band structure is formed at the junction of the ohmic contact layer and the N-type window layer, as shown in the diagram. Figure 3In this band structure, the lowest barrier region B1 corresponds to the ohmic contact layer, the middle barrier region B2 corresponds to the first material layer, and the highest barrier region B3 corresponds to the second material layer. This stepped shape is more conducive to electron injection, which allows the voltage required for the light-emitting chip to work normally to be relatively reduced.

[0035] In some embodiments, the first material layer and the second material layer include (Al) x Ga 1-x ) 0.5 In 0.5 Material P, 0≤x≤1, the second material layer includes (Al) y Ga 1-y ) 0.5 In 0.5 P, 0 ≤ y ≤ 1, and x ≠ y. For example, both the first and second material layers contain the four elements Al, Ga, In, and P. The first and second material layers have different Al content, resulting in different refractive indices. To achieve the effect in the previous embodiment where the potential barrier of the first material layer is lower than that of the second material layer, the Al content of the first material layer can be controlled to be less than that of the second material layer, i.e., x < y. For AlGaInP materials, a higher Al content results in a relatively higher band gap, increasing the potential barrier between materials; conversely, a lower Al content results in a relatively smaller barrier. Therefore, when using AlGaInP materials, the potential barrier can be controlled by adjusting the Al content; simultaneously, changes in the Al content also cause changes in the refractive index.

[0036] AlGaInP materials with low Al content absorb light generated by radiative recombination in the active layer to a certain extent, especially showing significant absorption of red light in some implementations. Therefore, in some examples, 0.15≤x≤0.45, 0.5≤y≤1, meaning the first material layer is a low-Al Al content AlGaInP material and the second material layer is a high-Al Al content AlGaInP material. In these examples, the low-Al Al content AlGaInP material is not set to an excessively low value to reduce red light absorption and ensure red light extraction efficiency. In other examples, x=0, 0.5≤y≤1, meaning the first material layer contains no Al element and is GaInP material; GaInP also exhibits good light extraction efficiency when dealing with light wavelengths around 580nm. Furthermore, GaInP, AlGaInP, and AlInP (aluminum indium phosphide) are all excellent current spreading materials, and both the first and second material layers can maintain good current spreading effects.

[0037] This embodiment is mainly described using the example of the first and second material layers being materials containing the four elements Al, Ga, In, and P. However, it is understood that for other embodiments (such as AlGaInP materials and GaInP materials), the refractive index and / or potential barrier can also be controlled within a reasonable range by controlling the Al component content of the AlGaInP material, thereby achieving better results. Those skilled in the art can implement the technical solution of this invention for epitaxial layer structures with other material combinations accordingly.

[0038] As a more specific example, the first material layer includes (Al) x Ga 1-x 0.5In 0.5 P, where 0.15 ≤ x ≤ 0.45, the second material layer includes (Al) y Ga 1-y 0.5In 0.5 P, where 0.5 ≤ y ≤ 1. For example, x can be 0.2, 0.25, 0.27, 0.3, 0.35, 0.38, 0.4, 0.42, etc., and y can be 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.9, 0.95, etc. A higher Al content results in a higher bandgap, increasing the potential barrier difference between materials and reducing electron injection efficiency, leading to both decreased brightness and increased operating voltage. This example, through reasonable control of the component content, ensures a reasonable overall potential barrier difference for the N-type window layer and also allows for a sufficient difference in refractive index between the first and second material layers, thus facilitating the reflection effect of the formed Bragg reflection structure.

[0039] In some embodiments, the thickness of each first material layer is equal, and the thickness of the first material layer is 41-46 nm. Both material layers have equal thickness, with the second material layer having a thickness of 47-54 nm. In some specific examples, the emitted light is mainly... Regarding red light, in embodiments where both the first and second material layers are composed of materials containing the four elements Al, Ga, In, and P, especially when using the component content of the aforementioned example, the thickness of the first and second material layers allows the N-type window layer to achieve a good reflection effect for red light. Furthermore, when either the first or second material layer is GaInP, the aforementioned thickness setting also ensures that the N-type window layer achieves a good reflection effect for light with a wavelength of approximately 580 nm.

[0040] It is understandable that the greater the refractive index difference between the two layers in the Bragg reflector structure, the wider the reflection bandwidth, and the fewer logarithms (i.e., the number of layers) required to achieve a certain reflectivity. Therefore, in practical applications, in order to improve the reflection effect while controlling the thickness of the light-emitting chip, it is possible to choose a material layer with a greater difference in Al content between the first and second material layers, for example, 0.15≤x≤0.2, 0.8≤y≤1.

[0041] In some implementations, such as Figure 4 As shown, between the N-type window layer 12 and the active layer 2, there is also an N-type confinement layer 13, which comprises N-type doped Al0.5In0.5P. In some examples, the Al content in the second material layer 122 is greater than the Al content in the first material layer 121. Therefore, the composition of the second material layer 122 is closer to that of the N-type confinement layer 13, resulting in a better lattice match between the second material layer 122 and the N-type confinement layer 13. When the second material layer 122 is the layer in the N-type window layer 12 closest to the N-type confinement layer 13, the lattice quality will be relatively good.

[0042] As an example, the first and second material layers are alternated in a cycle of 25-35 cycles. Based on the aforementioned example of the first and second material layers, the 25-35 cycle arrangement typically enables a reflectivity of over 95% for the target light.

[0043] It is understood that in some embodiments, the epitaxial layer structure may also include other structures, such as one or more of the following: buffer layer, cutoff layer, window layer, waveguide layer, and P-type confinement layer. This embodiment does not limit this.

[0044] In this embodiment, the epitaxial layer structure is designed by alternating two materials with different component contents in an N-type window layer, which is typically of fixed composition. This allows the N-type window layer to reflect light, meaning it can better facilitate lateral current expansion while also reflecting light. Consequently, more target light rays are emitted from the P-side, improving the light extraction efficiency of the final light-emitting chip and thus increasing its overall brightness.

[0045] This embodiment also provides a light-emitting chip, which is fabricated based on the above-described epitaxial layer structure. Specifically, the light-emitting chip includes at least a portion of the epitaxial layer structure, particularly the N-type window layer. The chip also includes an N-type electrode electrically connected to the N-type semiconductor layer, and a P-type electrode electrically connected to the P-type semiconductor layer. For example, a stepped structure is etched into the epitaxial layer structure, extending from one side of the N-type semiconductor layer to the P-type semiconductor layer. The bottom of the stepped structure exposes the P-type semiconductor layer, and the P-type electrode of the light-emitting chip is electrically connected to the P-type semiconductor layer at the bottom of the stepped structure. In some embodiments, the epitaxial layer structure also includes an insulating layer. For example, the insulating layer insulates the P-type electrode from other layers in the P-type semiconductor layer within the stepped structure, allowing it to contact only the window layer. The insulating layer can be disposed on the surface of the epitaxial layer structure to form a protective layer.

[0046] As a further example, see Figure 5 The epitaxial layer structure of the light-emitting chip can be sequentially comprised of an ohmic contact layer 11, an N-type window layer 12, an N-type confinement layer 13, an N-type waveguide layer 14, an active layer 2, a P-type waveguide layer 31, a P-type confinement layer 32, a transition layer 33, and a window layer 34. The N-type electrode 15 of the light-emitting chip is disposed on the ohmic contact layer 11, and a stepped structure exposes the window layer 34. The P-type electrode 35 is connected to the window layer 34 through the stepped structure.

[0047] For example, such as Figure 5 The light-emitting chip in this embodiment may further include a sapphire substrate layer 4, in the epitaxial layer structure After formation, the epitaxial layer structure is bonded to the sapphire substrate layer 4. In this example, the sapphire substrate layer 4 is bonded to the window layer 34. On the top, the light-emitting chip emits light from the sapphire substrate layer 4.

[0048] The light-emitting chip in this embodiment is formed based on the epitaxial layer structure of the aforementioned example, resulting in higher light extraction efficiency and higher overall brightness. Furthermore, in some embodiments, its operating voltage is relatively low.

[0049] This embodiment also provides a light-emitting device, which includes a circuit board and a light-emitting chip, wherein the light-emitting chip is the aforementioned light-emitting chip. Because this light-emitting device uses the light-emitting chip described above, the light-emitting chip has high light extraction efficiency and high overall brightness, resulting in better luminous efficiency and brightness of the light-emitting device. The light-emitting device can be a display panel, such as a non-flexible display panel, or a flexible display panel. The display panel can include a chip array formed by multiple of the aforementioned light-emitting chips. The aforementioned light-emitting chips can be light-emitting chips of one color in the display panel, such as a red light-emitting chip formed by the aforementioned red epitaxial layer structure, or two or three colors of light-emitting chips can all use epitaxial layer structures with the aforementioned structure. It is understood that there may be corresponding differences in the semiconductor materials used in light-emitting chips of different colors, but the light extraction efficiency can be improved through the design of the N-type window layer. The display panel can be applied to various electronic devices for display or light emission, such as, but not limited to, various smart mobile terminals, displays, electronic advertising boards, etc.; the light-emitting device can also be an electronic device for lighting, such as lighting fixtures.

[0050] Another optional embodiment of the present invention: This embodiment provides a method for fabricating an epitaxial layer structure. This method can fabricate the epitaxial layer structure described in the above embodiment. Please refer to [link to documentation]. Figure 6 ,include: S101, Forming an N-type semiconductor layer; In practical applications, epitaxial layer structures can be formed on a growth substrate. In the following example, in order to improve lattice quality, a buffer layer can be set on the growth substrate before forming the layer structures of each semiconductor on the growth substrate.

[0051] The N-type semiconductor layer in this embodiment includes an N-type window layer, which includes multiple first material layers and an equal number of second material layers, with the first and second material layers alternately arranged. The first and second material layers are phosphide current spreading materials with different refractive indices, and the thicknesses of the first and second material layers are configured according to the wavelength of the target light emitted by the active layer to achieve reflection of the target light. In practical applications, the thickness is determined according to the actual reflection requirements, for example, the thickness is configured so that it can achieve a reflectivity of not less than 95% for the target light when set in 25-35 cycles.

[0052] That is, step S101 includes forming an N-type window layer, and specifically includes alternately forming a first material layer and a second material layer, and during the formation of the first material layer and the second material layer, the thickness of the first material layer and the second material layer is controlled according to the wavelength of reflection required.

[0053] S102. An active layer is formed on one side of the N-type semiconductor layer; It is understandable that the N-type semiconductor layer is grown on the growth substrate or a buffer layer on the growth substrate, and the active layer is formed on the side of the N-type semiconductor layer away from the growth substrate.

[0054] S103. A P-type semiconductor layer is formed on one side of the active layer; The structures in the epitaxial layer structure described above are formed sequentially. For structures not specifically described in this embodiment or the preceding embodiments, their growth process and specific arrangement can adopt existing processes or arrangements, and this embodiment does not impose any limitations. It is understood that, as mentioned in the preceding embodiments, in some implementations, the epitaxial layer structure may also include other layer structures. Depending on the arrangement position of these structures, steps to form other layer structures may be included before or after the corresponding steps of the preceding steps S101, S102, S103, S104, and S105.

[0055] This embodiment also provides a specific example illustrating the steps of the epitaxial layer structure fabrication method of this embodiment. For further explanation, see Figure 7 The method for fabricating the epitaxial layer structure in this example includes: S201, Provides a growth substrate; like Figure 8 In (a) of this example, the growth substrate 5 is GaAs. The epitaxial layer of the light-emitting chip in this example is mainly formed using MOCVD (Metal-organic Chemical Vapor Deposition) technology. When growing the epitaxial layer of the light-emitting chip using MOCVD technology, the growth substrate 5 can be purged with H2 (hydrogen gas) or cleaned by other methods. At the same time, the temperature inside the MOCVD reaction chamber is controlled at 650-750℃ to remove oxygen elements from the reaction chamber and ensure the cleanliness of the elements inside the reaction chamber.

[0056] S202, Grow a buffer layer on the growth substrate; See Figure 8 In (b) of this example, the main material of the buffer layer 6 is also GaAs. The buffer layer 6 can be N-type doped, such as by doping with Si elements, to achieve lattice matching with the substrate.

[0057] S203. A corrosion-stopping layer is grown on the buffer layer; See Figure 8 In (c) of this example, the main material of the corrosion stop layer 7 is N-type doped GaInP (gallium indium phosphide), and its composition content can be Ga0.5In0.5P.

[0058] S204. An ohmic contact layer is grown on the corrosion stop layer; See Figure 8 In example (d), the main material of the ohmic contact layer 11 is N-type doped GaAs. In practice, the growth substrate 5, buffer layer 6, and etching stop layer 7 provided or formed in steps S201, S202, and S203 may also be removed during the subsequent fabrication of the light-emitting chip, thus completely exposing the ohmic contact layer 11, on which the N-type electrode 15 of the light-emitting chip is disposed. The structure of the formed light-emitting chip can be referred to in the aforementioned embodiment.

[0059] S205. An N-type window layer is grown on the ohmic contact layer; See Figure 8 In (e), the main material of the N-type window layer 12 in this example is AlGaInP, which is also N-type doped. Its specific composition can be found in the aforementioned embodiments. The process of growing the N-type window layer 12 can specifically include the following steps: S2051, Grow a first material layer on the current surface; The current surface is the surface furthest from the substrate at this point in the epitaxial layer structure's growth. When the N-type window layer 12 is initially grown, the first material layer 121 forms on the surface of the ohmic contact layer 11. After at least one cycle of the first material layer 121 and the second material layer 122 have been grown, the first material layer 121 forms on the surface of the second material layer 122 from the previous cycle. As a more specific example, under conditions of a temperature of 690-740°C, a chamber pressure of 50-80 mbar, and a V / III ratio (the ratio of the molar flow rates of the introduced Group V and Group III sources) of 150-250, using phosphine as a Group V source, silane as an n-type dopant source, hydrogen as a carrier gas, and introducing a certain proportion of Group III sources of trimethylgallium, trimethylaluminum, and trimethylindium, while controlling the deposition time, a layer with a thickness of 41-46 nm (Al) is grown. x Ga 1-x 0.5In 0.5 P serves as the first material layer 121.

[0060] S2052, Grow a second material layer on the current surface; The growth method of the second material layer 122 is basically the same as that of the first material layer 121. The main difference is that the ratio of trimethylgallium and trimethylaluminum in the group III source is changed, so that the deposited material becomes a high-Al content (Al) material. y Ga 1-y ) 0.5 In 0.5 The P-layer, with a deposition thickness of 47-54 nm, consists of Al0. y Ga 1-y ) 0.5 In0.5 P serves as the second material layer 122. Each execution of step S2052 is equivalent to completing one growth cycle.

[0061] The above steps S2051 and S2052 are continuously repeated until the growth of the first material layer 121 and the second material layer 122 for the predetermined cycle is completed. For example, the number of first material layers 121 and second material layers 122 can be 25-35 pairs, and the more pairs of first material layers 121 and second material layers 122, the higher the reflectivity.

[0062] S206. Grow an N-type confinement layer on the N-type window layer; See Figure 8 In (f) of this example, the main material of the N-type confinement layer 13 is N-type doped AlInP, specifically it can be... Al 0.5 In 0.5 P.

[0063] S207. Growing an N-type waveguide layer on an N-type confinement layer; See Figure 8 In (g), to prevent doped impurities from entering the active layer, the N-type semiconductor layer closest to the active layer is the N-type waveguide layer 14. In this example, the main material of the N-type waveguide layer 14 is undoped AlGaInP.

[0064] S208. An active layer is grown on an N-type waveguide layer; See Figure 8 In (h), the active layer 2 in this example may include multiple quantum well layers and multiple quantum barrier layers, in which the quantum well layers and quantum barrier layers grow alternately.

[0065] S209. Grow a P-type waveguide layer on the active layer; See Figure 8 In (i), to prevent doped impurities from entering the active layer, the layer closest to the active layer in the P-type semiconductor layer is the P-type waveguide layer 31. In this example, the main material of the P-type waveguide layer 31 is undoped AlGaInP.

[0066] See Figure 8In step (j), after step S209, a P-type confinement layer 32, a transition layer 33, and a window layer 34 can be grown sequentially. These structures can all be grown using methods found in the prior art, and their materials can also be materials used in the prior art. For example, the main material of the P-type confinement layer 32 can be P-type doped AlInP, similar to the N-type confinement layer 13, both used to confine carriers in the active layer 2 to improve luminous efficiency; the main material of the transition layer 33 is AlGaInP, and by controlling the ratio of Al and Ga components in the transition layer 33, its lattice is positioned between the P-type confinement layer 32 and the window layer 34 to achieve better crystal quality; the main material of the window layer 34 can be P-type doped GaP, and the window layer 34 can also help with current expansion, and in this example, it is also the light-emitting window.

[0067] The epitaxial layer fabrication method of this embodiment alternately forms multiple cycles of first and second material layers as N-type window layers, which improves the light extraction efficiency and overall brightness of the final light-emitting chip due to the favorable epitaxial layer structure. Furthermore, in some embodiments, it also reduces the operating voltage of the final light-emitting chip.

[0068] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An epitaxial layer structure, characterized in that, include: N-type semiconductor layer; P-type semiconductor layer; An active layer is disposed between the N-type semiconductor layer and the P-type semiconductor layer; The N-type semiconductor layer includes an N-type window layer, which includes multiple first material layers and an equal number of second material layers, with the first material layers and second material layers alternately arranged. The first material layers and second material layers are phosphide current spreading materials with different refractive indices, and the thicknesses of the first material layers and second material layers are configured according to the wavelength of the target light emitted by the active layer to achieve reflection of the target light, forming a Bragg reflection structure. The N-type semiconductor layer further includes an ohmic contact layer, which is disposed on the side of the N-type window layer away from the active layer. The barrier of the first material layer is lower than that of the second material layer. The first material layer is the layer in the N-type window layer closest to the ohmic contact layer. The barrier structure of the first material layer at the N-type window layer forms a stepped shape. The thickness of the first material layer and the second material layer is equal to one-quarter of the reflection center wavelength of their reflection patterns divided by their respective refractive indices.

2. The epitaxial layer structure as described in claim 1, characterized in that, The first material layer includes (Al) x Ga 1-x ) 0.5 In 0.5 P, 0≤x≤1; the second material layer includes (Al) y Ga 1-y ) 0.5 In 0.5 P, 0≤y≤1, and x is not equal to y.

3. The epitaxial layer structure as described in claim 2, characterized in that, 0.15≤x≤0.45, 0.5≤y≤1; or, x=0, 0.5≤y≤1.

4. The epitaxial layer structure as described in claim 3, characterized in that, The thickness of each of the first material layers is equal, and the thickness of the first material layer is 41-46 nm. The thickness of each of the second material layers is equal, and the thickness of the second material layer is 47-54 nm.

5. The epitaxial layer structure as described in claim 3, characterized in that, The N-type window layer and the active layer further include an N-type confinement layer; The N-type confinement layer comprises N-type doped Al. 0.5 In 0.5 P.

6. The epitaxial layer structure as described in claim 3, characterized in that, The first material layer and the second material layer alternate in one cycle, with a total of 25-35 cycles.

7. A method for fabricating an epitaxial layer structure, applied to realize the epitaxial layer structure as described in any one of claims 1-6, characterized in that, The method for fabricating the epitaxial layer structure includes: An N-type semiconductor layer is formed, wherein the N-type semiconductor layer includes an N-type window layer, the N-type window layer includes a plurality of first material layers and an equal number of second material layers, the first material layers and the second material layers are alternately arranged; the first material layers and the second material layers are phosphide current spreading materials with different refractive indices, and the thickness of the first material layers and the second material layers is configured according to the wavelength of the target light emitted by the active layer to achieve reflection of the target light; An active layer is formed on one side of the N-type semiconductor layer; A P-type semiconductor layer is formed on one side of the active layer.

8. A light-emitting chip, characterized in that, include: An epitaxial layer structure, wherein the epitaxial layer structure is the epitaxial layer structure according to any one of claims 1-6; The N-type electrode is electrically connected to the N-type semiconductor layer; The P-type electrode is electrically connected to the P-type semiconductor layer.

9. A light-emitting device, characterized in that, include: Circuit board; The light-emitting chip is the light-emitting chip according to claim 8, and the light-emitting chip is bonded to the die-bonding region of the circuit substrate.

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