Epitaxial wafer, manufacturing method thereof and light-emitting chip

Abstract

The invention relates to an epitaxial wafer, a manufacturing method thereof and a light-emitting chip. The epitaxial wafer comprises a substrate; the epitaxial layer is arranged on the substrate and comprises an N-type semiconductor layer, an active layer and a P-type semiconductor layer which are stacked in sequence, and the P-type semiconductor layer comprises a P-type waveguide layer; the content of an Al component in the P-type waveguide layer decreases progressively from the direction away from the active layer, the content of a Ga component in the P-type waveguide layer increases progressively from the direction away from the active layer, and the forbidden bandwidth of one side, close to the active layer, of the P-type waveguide layer is larger than that of the active layer. The P-type waveguide layer can block fast moving electrons, the electrons are not prone to overflowing from the side, close to the P-type waveguide layer, of the active area, recombination of the electrons outside the active area is reduced, the recombination probability of the electrons and holes in the active area is increased, and the light-emitting efficiency of the light-emitting chip is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular, to an epitaxial wafer, a manufacturing method thereof, and a light-emitting chip. Background Art

[0002] An LED (Light Emitting Diode) is an electronic component that directly converts electrical energy into light energy. Compared with traditional ones, it has the advantages of high efficiency, energy saving, environmental protection, and long life, and plays an important role in energy conservation, emission reduction, and green development. It has now been widely used in displays and lighting. In an LED chip, the number of carriers in the active region and the probability of recombination of electron-hole pairs affect the internal quantum efficiency of the LED chip.

[0003] Currently, although the effective mass of electrons is smaller than that of holes, the mobility of electrons is larger than that of holes, which causes some electrons not to be confined in the active layer, and recombination luminescence occurs outside the active layer, generating light sources in other wavelength bands, reducing the number of carriers in the active region, and reducing the recombination probability of electrons and holes in the active region, thus affecting the light-emitting efficiency of the LED chip.

[0004] Therefore, how to reduce the recombination of electrons outside the active region is an urgent problem to be solved. Summary of the Invention

[0005] In view of the deficiencies of the above-mentioned related technologies, the purpose of the present application is to provide an epitaxial wafer, a manufacturing method thereof, and a light-emitting chip, aiming to solve the problem of recombination luminescence of electrons outside the active layer.

[0006] An epitaxial wafer, comprising:

[0007] A substrate;

[0008] An epitaxial layer disposed on the substrate, the epitaxial layer comprising an N-type semiconductor layer, an active layer, and a P-type semiconductor layer stacked in sequence, and the P-type semiconductor layer includes a P-type waveguide layer;

[0009] The Al component content in the P-type waveguide layer decreases in the direction away from the active layer, the Ga component content in the P-type waveguide layer increases in the direction away from the active layer, and the band gap width of the side of the P-type waveguide layer close to the active layer is greater than the band gap width of the active layer.

[0010] In the above-mentioned epitaxial wafer, the Al component content of the P-type waveguide layer decreases in the direction away from the active layer, such that the Al component content on the side of the P-type waveguide layer close to the active layer is relatively high, the bandgap width on the side of the P-type waveguide layer close to the active layer is larger, and the bandgap width on the side of the P-type waveguide layer close to the active layer is greater than the bandgap width of the active layer, which can form a barrier to fast-moving electrons, making it difficult for electrons to overflow from the side of the active region close to the P-type waveguide layer, reducing the recombination of electrons outside the active region, increasing the recombination probability of electrons and holes in the active region, and improving the light-emitting efficiency of the light-emitting chip. Moreover, the decreasing of the Al component content in the direction away from the active layer makes the Al component content on the side of the P-type waveguide layer far from the active layer relatively small, reducing the overall content of the Al component, decreasing the probability of reaction between Al and oxygen atoms, and improving the electrical performance of the light-emitting chip.

[0011] Based on the same inventive concept, the present application also provides a light-emitting chip, comprising:

[0012] a first electrode, a second electrode; and

[0013] the epitaxial wafer as described above, wherein the first electrode is electrically connected to the N-type semiconductor layer, and the second electrode is electrically connected to the P-type semiconductor layer.

[0014] The above-mentioned light-emitting chip comprises an epitaxial wafer, in which the Al component content of the P-type waveguide layer decreases in the direction away from the active layer, such that the Al component content on the side of the P-type waveguide layer close to the active layer is relatively high, the bandgap width on the side of the P-type waveguide layer close to the active layer is larger, and the bandgap width on the side of the P-type waveguide layer close to the active layer is greater than the bandgap width of the active layer, which can form a barrier to fast-moving electrons, making it difficult for electrons to overflow from the side of the active region close to the P-type waveguide layer, reducing the recombination of electrons outside the active region, increasing the recombination probability of electrons and holes in the active region, and improving the light-emitting efficiency of the light-emitting chip. Moreover, the decreasing of the Al component content in the direction away from the active layer makes the Al component content on the side of the P-type waveguide layer far from the active layer relatively small, reducing the overall content of the Al component, decreasing the probability of reaction between Al and oxygen atoms, and improving the electrical performance of the light-emitting chip.

[0015] Based on the same inventive concept, the present application also provides a manufacturing method of the above-mentioned epitaxial wafer, comprising:

[0016] forming an epitaxial layer on the substrate;

[0017] The forming of the epitaxial layer includes: sequentially growing the N-type semiconductor layer, the active layer, and the P-type semiconductor layer, and the P-type semiconductor layer includes the P-type waveguide layer.

[0018] In the method for manufacturing the above epitaxial wafer, the grown P-type semiconductor layer includes a P-type waveguide layer. The Al composition content of the P-type waveguide layer decreases in the direction away from the active layer, such that the Al composition content on the side of the P-type waveguide layer close to the active layer is relatively large, and the bandgap width on the side of the P-type waveguide layer close to the active layer is larger. Moreover, the bandgap width on the side of the P-type waveguide layer close to the active layer is greater than the bandgap width of the active layer, which can form a barrier to fast-moving electrons, preventing electrons from easily spilling out from the side of the active region close to the P-type waveguide layer, reducing the recombination of electrons outside the active region, increasing the recombination probability of electrons and holes in the active region, and improving the light-emitting efficiency of the light-emitting chip. In addition, the decreasing Al composition content in the direction away from the active layer results in a relatively small Al composition content on the side of the P-type waveguide layer far from the active layer, reducing the overall content of the Al composition, decreasing the probability of reaction between Al and oxygen atoms, and improving the electrical performance of the light-emitting chip. Description of the Drawings

[0019] Figure 1 FIG. is a schematic structural diagram of an epitaxial wafer provided by an embodiment of the present application;

[0020] Figure 2 FIG. is a schematic structural diagram of an epitaxial wafer including a reflective layer provided by an embodiment of the present application;

[0021] Figure 3 FIG. is a schematic diagram of the Al composition gradient provided by an embodiment of the present application;

[0022] Figure 4 FIG. is a schematic energy band structure diagram of an epitaxial wafer provided by an embodiment of the present application;

[0023] Description of the Reference Numerals:

[0024] 1 - Substrate; 2 - N-type semiconductor layer; 201 - N-type confinement layer; 202 - N-type waveguide layer; 3 - Active layer; 4 - P-type semiconductor layer; 401 - P-type waveguide layer; 402 - P-type confinement layer; 5 - Buffer layer; 6 - Reflective layer; 7 - Transition layer; 8 - Current spreading layer. Detailed Embodiments

[0025] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0027] In an LED chip, the number of carriers in the active region and the probability of electron-hole pair recombination affect the internal quantum efficiency of the LED chip. Although the effective mass of electrons is smaller than that of holes, the mobility of electrons is larger than that of holes, causing some electrons not to be confined in the active layer and recombining and emitting light outside the active layer, generating light sources in other wavelength bands, reducing the number of carriers in the active region, decreasing the recombination probability of electrons and holes in the active region, and affecting the luminous efficiency of the LED chip.

[0028] Based on this, the present application hopes to provide a solution that can solve the above technical problems, and its detailed content will be elaborated in the subsequent embodiments.

[0029] This embodiment provides an epitaxial wafer, as Figures 1 - 4 shown, including a substrate 1 and an epitaxial layer provided on the substrate 1. The epitaxial layer includes an N-type semiconductor layer 2, an active layer 3, and a P-type semiconductor layer 4 stacked in sequence. It can be understood that the material of the substrate 1 in this embodiment can be selected according to the light source color requirements of the light-emitting chip. For example, when the light-emitting chip needs to emit red light, the substrate 1 can be a GaAs substrate 1. In this embodiment, an N-type semiconductor layer 2 may be between the substrate 1 and the active layer 3. In some application scenarios, a P-type semiconductor layer 4 may also be between the substrate 1 and the active layer 3. The N-type semiconductor layer 2 in this embodiment may include an N-type confinement layer 201 and an N-type waveguide layer 202. The P-type semiconductor layer 4 may include a P-type waveguide layer 401 and a P-type confinement layer 402, but is not limited thereto. The N-type semiconductor layer 2 and the P-type semiconductor layer 4 may also be provided with other layer structures according to needs. The active layer 3 in this embodiment may include a quantum well layer, a quantum barrier layer, and may also include other structures.

[0030] The P-type semiconductor layer 4 in this embodiment includes a P-type waveguide layer 401. The Al component content in the P-type waveguide layer 401 decreases in the direction away from the active layer 3, and the Ga component content in the P-type waveguide layer 401 increases in the direction away from the active layer 3. The bandgap width of the side of the P-type waveguide layer 401 close to the active layer 3 is greater than the bandgap width of the active layer 3. It can be understood that the P-type waveguide layer 401 in this embodiment is a P-type doped layer, which can provide holes. The Al component content and Ga component content in the P-type waveguide layer 401, that is, the proportion of the Al component and Ga component in the P-type waveguide layer 401. In this embodiment, the bandgap width of the side of the P-type waveguide layer 401 close to the active layer 3 is greater than the bandgap width of the active layer 3, that is, the bandgap width of the side of the P-type waveguide layer 401 close to the active layer 3 is greater than the bandgap width of the quantum barrier layer in the active layer 3. In this embodiment, the thickness of the P-type waveguide layer 401 can be set according to needs, for example, it can be 0.07 μm to 0.1 μm.

[0031] In this embodiment, the Al component content in the P-type waveguide layer 401 decreases in the direction away from the active layer 3. This can make the Al component content on the side of the P-type waveguide layer 401 close to the active layer 3 large and the Al component content on the side away from the active layer 3 small. A relatively large Al component content means a relatively large bandgap width of the P-type waveguide layer 401. That is, the side of the P-type waveguide layer 401 close to the active layer 3 has a higher barrier strength. The high barrier blocks the fast-moving electrons, making it difficult for electrons to overflow from the side of the active region close to the P-type waveguide layer 401, and reducing the recombination of electrons outside the active region. On the other hand, the small Al component content on the side away from the active layer 3 makes the overall content of the Al component in the P-type waveguide layer 401 relatively low, reducing the probability of the reaction between Al and oxygen atoms and improving the electrical performance of the light-emitting chip.

[0032] In some embodiments, the material of the P-type waveguide layer 401 may include (Al X Ga 1-X ) Y In 1-Y P, where 0 < X ≤ 1 and 0 < Y < 1. The In component content in this embodiment can remain unchanged, which is more conducive to controlling the Al component content and Ga component content during the growth process. In some application scenarios, the In component content can also be gradually changed, which can be specifically set according to needs. In some embodiments, X can be greater than or equal to 0.6 and less than or equal to 1, 0.6 ≤ X ≤ 1. As Figure 4 shown, this can make the bandgap width of the P-type waveguide layer 401 greater than that of the active layer 3, that is, the bandgap width of the side of the P-type waveguide layer 401 away from the active layer 3 is also greater than that of the active layer 3. Thus, the overall potential energy of the P-type waveguide layer 401 can be increased, making the light emitted from the active layer 3 more likely to pass through the P-type waveguide layer 401, reducing the probability of light being absorbed by the P-type waveguide layer 401, and improving the light-emitting efficiency of the light-emitting chip. In some embodiments, the bandgap width of the side of the P-type waveguide layer 401 away from the active layer 3 can also be equal to that of the active layer 3; in some application scenarios, X can also be less than 0.6, as long as the blocking effect of the P-type waveguide layer 401 on electrons can be achieved. In this embodiment, the sum of the Al component content and the Ga component content can be close to or equal to the In component content. For example, Y in this embodiment can be greater than or equal to 0.45 and less than or equal to 0.55. When the sum of the Al component content and the Ga component content is equal to the In component content, then Y is equal to 0.5. At this time, the material of the P-type waveguide layer 401 includes (Al X Ga 1-X ) 0.5 In 0.5 P. If 0.6 ≤ X ≤ 1, then in one example, the P-type waveguide layer 401 can gradually change from Al 0.5 In 0.5 P to (Al 0.6Ga 0.4 ) 0.5 In 0.5 P.

[0033] In some embodiments, as Figure 3 shown, the Al component content in the P-type waveguide layer 401 decreases linearly in the direction away from the active layer 3. The linear decrease can reduce the manufacturing difficulty of the P-type waveguide layer 401 and also achieve the blocking effect of the P-type waveguide layer 401 on electrons, reducing the overall content of the Al component. In some application scenarios, the Al component content in the P-type waveguide layer 401 can also decrease non-linearly in the direction away from the active layer 3. For example, the rate of decrease of the Al component content can gradually increase or gradually decrease.

[0034] In this embodiment, when the substrate 1 is a gallium arsenide substrate 1, to solve the problem of light absorption of the gallium arsenide substrate 1, a reflective layer 6 can also be provided on the substrate 1. The reflective layer 6 can have a distributed Bragg reflector composite layer structure, that is, a first reflectivity layer and a second reflectivity layer are alternately provided. The reflectivity of the first reflectivity layer is less than that of the second reflectivity layer. Thus, the light vertically incident on the substrate 1 can be reflected using the Bragg reflection principle, improving the light output characteristics. In one example, the first reflectivity layer can be made of AlAs and the second reflectivity layer can be made of AlGaAs. However, it is not limited thereto. The epitaxial wafer can also include other layer structures. For example, in one example, as Figure 2 shown, the epitaxial wafer can include a GaAs buffer layer 5, an AlGaAs / AlAs DBR reflective layer 6, an N-type confinement layer 201, an N-type waveguide layer 202, an active layer 3, a P-type waveguide layer 401, a P-type confinement layer 402, a transition layer 7, and a P-GaP current spreading layer 8 grown sequentially on the GaAs substrate 1.

[0035] In the above epitaxial wafer, the Al component content in the P-type waveguide layer 401 decreases in the direction away from the active layer 3, such that the Al component content on the side of the P-type waveguide layer 401 close to the active layer 3 is relatively large. The bandgap width on the side of the P-type waveguide layer 401 close to the active layer 3 is larger, and the bandgap width on the side of the P-type waveguide layer 401 close to the active layer 3 is greater than the bandgap width of the active layer 3, which can form a barrier to fast-moving electrons. It is not easy for electrons to overflow from the side of the active region close to the P-type waveguide layer 401, reducing the recombination of electrons outside the active region and increasing the recombination probability of electrons and holes in the active region, improving the luminous efficiency of the light-emitting chip. Moreover, the decrease of the Al component content in the direction away from the active layer 3 makes the Al component content on the side of the P-type waveguide layer 401 far from the active layer 3 relatively small, reducing the overall content of the Al component, reducing the probability of reaction between Al and oxygen atoms, and improving the electrical performance of the light-emitting chip.

[0036] Another alternative embodiment of the present application:

[0037] This embodiment provides a light-emitting chip, including a first electrode, a second electrode; and the epitaxial wafer as described above. The first electrode is electrically connected to the N-type semiconductor layer 2, and the second electrode is electrically connected to the P-type semiconductor layer 4.

[0038] This embodiment does not specifically limit the materials and shapes of the positive electrode and the negative electrode. For example, the materials of the electrodes may include but are not limited to at least one of Cr, Ni, Al, Ti, Au, Pt, W, Pb, Rh, Sn, Cu, Ag.

[0039] The light-emitting chip in this embodiment includes but is not limited to at least one of a high-brightness LED light-emitting chip, a Mini LED (Mini Light Emitting Diode, submillimeter light-emitting diode), a Micro LED (Micro Light Emitting Diode, micron-scale light-emitting diode), and a nano-scale light-emitting diode. The light-emitting chip in this embodiment can be a flip-chip LED chip or a vertical LED chip. And the light-emitting chip in this embodiment can be a red-light LED chip that emits red light. Of course, it can also be set as an LED chip that emits light of other colors according to requirements, which will not be elaborated here one by one.

[0040] The above light-emitting chip includes an epitaxial wafer. The Al component content of the P-type waveguide layer 401 in the epitaxial wafer decreases in the direction away from the active layer 3, so that the Al component content on the side of the P-type waveguide layer 401 close to the active layer 3 is relatively large, the bandgap width on the side of the P-type waveguide layer 401 close to the active layer 3 is larger, and the bandgap width on the side of the P-type waveguide layer 401 close to the active layer 3 is greater than the bandgap width of the active layer 3, which can block the fast-moving electrons, and it is not easy for the electrons to overflow from the side of the active region close to the P-type waveguide layer 401, reducing the recombination of electrons outside the active region, increasing the recombination probability of electrons and holes in the active region, and improving the light-emitting efficiency of the light-emitting chip. And the decrease in the Al component content in the direction away from the active layer 3 makes the Al component content on the side of the P-type waveguide layer 401 far from the active layer 3 relatively small, reducing the total content of the Al component, reducing the probability of the reaction between Al and oxygen atoms, and improving the electrical performance of the light-emitting chip.

[0041] Another optional embodiment of the present application:

[0042] This embodiment provides a method for manufacturing an epitaxial wafer, including the following steps:

[0043] An epitaxial layer is provided on the substrate 1.

[0044] Among them, the epitaxial layer is set to include: an N-type semiconductor layer 2, an active layer 3, and a P-type semiconductor layer 4 are grown in sequence. The P-type waveguide layer 401 in this embodiment is the same as the P-type waveguide layer 401 in the above embodiment, and will not be elaborated here. In some embodiments, before setting the epitaxial layer, the substrate 1 can be purged with H2 first, and at the same time, the reaction chamber temperature is set to 650-750 °C. High-temperature treatment can better remove the contained water vapor.

[0045] In some embodiments, the material of the P-type waveguide layer 401 includes (Al X Ga 1-X ) Y In 1-Y P, where 0.6 ≤ X ≤ 1 and 0.45 ≤ Y ≤ 0.55. Growing the P-type waveguide layer 401 includes:

[0046] Controlling the input amount of the aluminum source to gradually decrease, the input amount of the gallium source to gradually increase, and the input amount of the indium source to remain unchanged. Keeping the input amount of the indium source unchanged is more conducive to controlling the content of the Al component and the content of the Ga component during the growth process.

[0047] In the above method for fabricating the epitaxial wafer, the grown P-type semiconductor layer 4 includes a P-type waveguide layer 401. The Al component content of the P-type waveguide layer 401 decreases in the direction away from the active layer 3, so that the Al component content on the side of the P-type waveguide layer 401 close to the active layer 3 is relatively large, and the bandgap width on the side of the P-type waveguide layer 401 close to the active layer 3 is larger. Moreover, the bandgap width on the side of the P-type waveguide layer 401 close to the active layer 3 is greater than the bandgap width of the active layer 3, which can block the fast-moving electrons, and it is not easy for the electrons to overflow from the side of the active region close to the P-type waveguide layer 401, reducing the recombination of electrons outside the active region, increasing the recombination probability of electrons and holes in the active region, and improving the luminous efficiency of the light-emitting chip. And the Al component content decreases in the direction away from the active layer 3, so that the Al component content on the side of the P-type waveguide layer 401 far from the active layer 3 is relatively small, reducing the total content of the Al component, reducing the probability of the reaction between Al and oxygen atoms, and improving the electrical performance of the light-emitting chip.

[0048] It should be understood that the application of the present application is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present application.

Claims

1. An epitaxial wafer, characterized in that, Comprising: A substrate; An epitaxial layer disposed on the substrate, the epitaxial layer comprising an N-type semiconductor layer, an active layer, and a P-type semiconductor layer stacked in sequence, and the P-type semiconductor layer comprising a P-type waveguide layer; The Al component content in the P-type waveguide layer decreases in the direction away from the active layer, the Ga component content in the P-type waveguide layer increases in the direction away from the active layer, and the bandgap width of the side of the P-type waveguide layer close to the active layer is greater than the bandgap width of the active layer.

2. The epitaxial wafer according to claim 1, characterized in that, The material of the P-type waveguide layer includes (Al X Ga 1-X ) Y In 1- Y P, where 0 < X ≤ 1 and 0 < Y < 1.

3. The epitaxial wafer according to claim 2, characterized in that, The In component content remains unchanged.

4. The epitaxial wafer according to claim 2, characterized in that, The X is greater than or equal to 0.6 and less than or equal to 1.

5. The epitaxial wafer according to claim 2, characterized in that, The Y is greater than or equal to 0.45 and less than or equal to 0.

55.

6. The epitaxial wafer according to any one of claims 1-5, characterized in that, The Al component content in the P-type waveguide layer decreases linearly in the direction away from the active layer.

7. The epitaxial wafer according to any one of claims 1-5, characterized in that, The thickness of the P-type waveguide layer is 0.07 μm to 0.1 μm.

8. A light-emitting chip, characterized in that, Comprising: A first electrode and a second electrode; And The epitaxial wafer according to any one of claims 1-7, wherein the first electrode is electrically connected to the N-type semiconductor layer, and the second electrode is electrically connected to the P-type semiconductor layer.

9. A method for manufacturing an epitaxial wafer according to any one of claims 1-7, characterized in that, Comprising: An epitaxial layer is provided on the substrate; The providing of the epitaxial layer includes: growing the N-type semiconductor layer, the active layer, and the P-type semiconductor layer in sequence, and the P-type semiconductor layer includes the P-type waveguide layer.

10. The method for manufacturing an epitaxial wafer according to claim 9, characterized in that, The material of the P-type waveguide layer includes (Al X Ga 1-X ) Y In 1-Y P, where 0.6 ≤ X ≤ 1 and 0.45 ≤ Y ≤ 0.

55. Growing the P-type waveguide layer includes: Controlling the gradually decreasing of the input amount of the aluminum source, the gradually increasing of the input amount of the gallium source, and the input amount of the indium source remains unchanged.

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