Epitaxial structure and chip
By using alternating layers of gradient Al(x)Ga(1-x)As and Ga(y)As(1-y) layers in the epitaxial structure and a thin film design, the mismatch stress and thermal stress problems of VCSEL modules were solved, improving their reliability and optical performance.
Patent Information
- Application Number
- CN202423106616.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-16
- Publication Date
- 2025-12-05
- Estimated Expiration
- 2034-12-16
AI Technical Summary
Existing VCSEL modules suffer from severe mismatch stress and thermal stress problems due to the different lattice constants and thermal expansion coefficients of their multilayer structures, which affects their reliability and performance.
By alternating layers of gradient Al(x)Ga(1-x)As and Ga(y)As(1-y) layers in the epitaxial structure, and combined with thin film layer design, the material composition ratio and stress thickness are adjusted to release mismatch stress and thermal stress, and to match the lattice constant and thermal expansion coefficient of each layer.
It effectively adjusts mismatch stress and thermal stress, improves the performance of epitaxial structures, and enhances the reliability and optical properties of VCSELs.
Smart Images
Figure CN223638789U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor technology, specifically to an epitaxial structure and a chip. Background Technology
[0002] For high-speed VCSEL (Vertical-Cavity Surface-Emitting Laser) components used in data center servers, high-temperature and high-current reliability verification is required. However, because VCSELs use multiple pairs of BDRs (Distributed Bragg Reflectors) to achieve a reflectivity of over 99%, the lattice constants and thermal expansion coefficients between layers differ, resulting in severe mismatch stress and thermal stress. This is a critical problem that urgently needs to be overcome for high-speed communication VCSELs. Utility Model Content
[0003] The purpose of this application is to provide an epitaxial structure and chip that can effectively adjust mismatch stress and thermal stress, thereby improving the performance of the epitaxial structure.
[0004] One aspect of this application provides an epitaxial structure, including a substrate, an N-type distributed Bragg reflector, a multiple quantum well layer, a P-type distributed Bragg reflector, and a contact layer stacked from bottom to top, wherein the contact layer includes Al layers stacked from bottom to top. (x) Ga (1-x) As layer and Ga (y) As (1-y) Layer, or Al (x) Ga (1-x) As layer and GaAs layer.
[0005] Optionally, the Al (x) Ga (1-x) In the As layer, x ranges from 10% to 90%, and the Ga... (y) As (1-y) The range of y in the layer is between 10% and 90%.
[0006] Optionally, the Al (x) Ga (1-x) The As layer has multiple layers, and the Al layers are described in multiple layers. (x) Ga (1-x) Al layers with the same x value (x) Ga (1-x) As layers are arranged in alternating layers.
[0007] Optionally, the multilayer Al (x) Ga (1-x)The As layers are arranged from bottom to top in descending order of x value.
[0008] Optionally, the Al (x) Ga (1-x) The lattice constant of AlGaAs in the As layer is between 5A° and 6A°. (y) As (1-y) The lattice constant of GaAs in the layer is between 5A° and 6A°.
[0009] Optionally, a thin film layer is further arranged on the contact layer, and the thin film layer comprises a silicon nitride thin film layer.
[0010] Optionally, the thin film layer has multiple layers, and the thicknesses of the multiple layers are different.
[0011] Optionally, the thin film layer has three layers, and the lattice constants of the two layers from bottom to top are between 100A° and 150A° and between 1500A° and 1800A° respectively.
[0012] In another aspect of the embodiment of the present application, a chip is provided, comprising the epitaxial structure described above.
[0013] The epitaxial structure and the chip provided by the embodiment of the present application can gradually change the values of x and y, which are the concentrations of Al and Ga respectively, to adjust the material composition ratio of the contact layer, correct the stress thickness of the contact layer, and then release the mismatch stress and thermal stress generated due to the difference between the lattice constants and the thermal expansion coefficients of the layers, adjust the deformation of the upper layer of the VCSEL caused by expansion, and match the tensile and compressive stress. The stress between the contact layer and the thin film layer is matched, the chip is protected from the influence of thermal expansion, the optical phase is corrected, and the characteristics are improved. BRIEF DESCRIPTION OF DRAWINGS
[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. Other related drawings can also be obtained by those skilled in the art without creative labor.
[0015] Figure 1 is one of the epitaxial structure schematic diagrams provided by the embodiment;
[0016] Figure 2 is a contact layer structure schematic diagram of the epitaxial structure provided by the embodiment;
[0017] Figure 3is a schematic diagram of an epitaxial structure provided by the embodiment two;
[0018] Figure 4 is a schematic diagram of a thin film layer structure of the epitaxial structure provided by the embodiment.
[0019] Icon: 10-Substrate; 11-N-type Distributed Bragg Reflector; 12-Multiple Quantum Well Layer; 13-P-type Distributed Bragg Reflector; 14-Contact Layer; 141-P-AlGaAs Layer; 142-P-AlGaAs Layer; 143-P-AlGaAs Layer; 144-P-AlGaAs Layer; 145-P-AlGaAs Layer; 146-GaAs Layer; 15-Thin Film Layer; 151-First Thin Film Layer; 152-Second Thin Film Layer; 153-Third Thin Film Layer. 0.7 Ga 0.3 As Layer; 142-P-Al 0.3 Ga 0.7 As Layer; 143-P-Al 0.1 Ga 0.9 As Layer; 144-P-Al 0.3 Ga 0.7 As Layer; 145-P-Al 0.1 Ga 0.9 As Layer; 146-GaAs Layer; 15-Thin Film Layer; 151-First Thin Film Layer; 152-Second Thin Film Layer; 153-Third Thin Film Layer. DETAILED DESCRIPTION
[0020] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application.
[0021] In the description of the present application, it should be noted that the directions or position relationships indicated by the terms “inner”, “outer” and the like are based on the directions or position relationships shown in the drawings, or the directions or position relationships in which the products of the present application are usually placed, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements must have a particular direction, be constructed and operated in a particular direction, and therefore cannot be understood as limiting the present application. In addition, the terms “first”, “second” and the like are only used for differentiation in description, and cannot be understood as indicating or implying relative importance.
[0022] It should also be noted that, unless otherwise explicitly specified and limited, the terms “set”, “connected” should be understood broadly, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be directly connected, or indirectly connected through an intermediate medium, or can be connected inside two elements. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.
[0023] Please refer to Figure 1 and Figure 2As shown, this application embodiment provides an epitaxial structure, including: a substrate 10, an N-type distributed Bragg reflector 11, a multiple quantum well layer 12, a P-type distributed Bragg reflector 13, and a contact layer 14 stacked from bottom to top. The contact layer 14 includes Al-type distributed Bragg reflectors stacked from bottom to top. (x) Ga (1-x) As layer and Ga (y) As (1-y) Layer, or Al (x) Ga (1-x) As layer and GaAs layer 146.
[0024] Among them, contact layer 14, such as Figure 2 As shown, it includes Al (x) Ga (1-x) As layer and Ga (y) As (1-y) The layers are: x represents the concentration of Al, and y represents the concentration of Ga. The values of x and y can be gradually changed to adjust the material composition ratio of the contact layer 14, thereby releasing the mismatch stress and thermal stress caused by the difference in lattice constant and thermal expansion coefficient between the layers, and thus improving the overall performance of the epitaxial structure.
[0025] Furthermore, a distributed Bragg reflector in an epitaxial structure is an optical element typically composed of multiple layers of dielectric thin films, each with a different refractive index. It reflects light of a specific wavelength through interference. The principle is based on the interference effect of multiple dielectric films; when light passes through these films, the layers with different refractive indices reflect and transmit the light. By precisely designing the thickness and refractive index of the films, specific reflection characteristics can be achieved. Distributed Bragg reflectors are usually composed of alternating stacks of high- and low-refractive-index materials, forming a periodic structure that reflects light of a specific wavelength.
[0026] For example, the epitaxial structure of this application includes a P-type distributed Bragg reflector 13 and an N-type distributed Bragg reflector 11, wherein the P-type distributed Bragg reflector 13 includes 20 to 25 layers of reflectors (dielectric thin films) and the N-type distributed Bragg reflector 11 includes 30 to 35 layers of reflectors, for different applications.
[0027] Furthermore, A l (x) Ga (1-x) In the As layer, x ranges from 10% to 90%, and in the Ga layer... (y) As (1-y) The range of y in the layer is between 10% and 90%.
[0028] Figure 2 In the example, depending on the value of x, A l (x) Ga (1-x)The As layer can have multiple layers, for example, each consisting of PA layers stacked from bottom to top. 0.7 Ga 0.3 As layer 141, PA l 0.3 Ga 0.7 As layer 142, PA l 0.1 Ga 0.9 As layer 143, PA l 0.3 Ga 0.7 As layer 144 and PA l 0.1 Ga 0.9 As layer 145.
[0029] Among them, PA l 0.3 Ga 0.7 As layer and PA l 0.1 Ga 0.9 The As layer has two layers and they are set alternately. That is to say, when As... (x) Ga (1-x) When there are multiple As layers, multiple Al layers (x) Ga (1-x) Al in layer A with the same x value (x) Ga (1-x) As layers are arranged in alternating layers.
[0030] And the above-mentioned multi-layer Al (x) Ga (1-x) In the As layer, the overall arrangement is stacked from bottom to top according to the x value from largest to smallest.
[0031] In some embodiments, such as Figure 2 As shown, the top layer is GaAs layer 146. In some other embodiments, the top layer may also be Ga... (y) As (1-y) Layer, Ga (y) As (1-y) There can also be multiple layers, according to the above A l (x) Ga (1-x) The settings for the AS layer can be followed as instructed.
[0032] A l (x) Ga (1-x) The lattice constant of the basic AlGaAs in the As layer is between 5 Å and 6 Å, and Ga... (y) As (1-y) The lattice constant of the basic GaAs in the layer is between 5 Å and 6 Å. Figure 2 In the examples, the lattice constant of GaAs is between 5 Å and 10 Å.
[0033] For example, the lattice constant of Al GaAs can be 5.6611 A°, and the lattice constant of GaAs can be 5.653 A°. Thus, the lattice constant of the Ga(y)As(1-y) layer and the GaAs layer 146 can be obtained as follows. Figure 2 The lattice constant of the Ga(y)As(1-y) layer and the GaAs layer 146 when x of each layer is different.
[0034] The present application can correct the stress thickness of the contact layer 14 by using the gradually changing concentration value of x of Al, and adjust the deformation of the upper layer of the VCSEL due to expansion in cooperation with the central wavelength, so that the tensile and compressive stresses are matched.
[0035] On this basis, as shown in Figure 3 The contact layer 14 is further provided with a thin film layer 15, and in some embodiments, the thin film layer 15 includes a silicon nitride thin film layer 15. By providing the thin film layer 15, a tensile and compressive stress matching structure is formed together with the contact layer 14.
[0036] Specifically, the thin film layer 15 has multiple layers, and the thicknesses of the multiple thin film layers 15 are different. The deposition speed and the gas ratio during deposition of the multiple thin film layers 15 are different, so that the deposition thicknesses of the thin film layers 15 are different.
[0037] For example, as shown in Figure 4 The thin film layer 15 has three layers, which are a first thin film layer 151, a second thin film layer 152, and a third thin film layer 153. The lattice constants of the first thin film layer 151 and the second thin film layer 152 from bottom to top are between 100 A° and 150 A° and between 1500 A° and 1800 A°, respectively, and the lattice constant of the third thin film layer 153 on the top is adjusted according to the required power to form a reflection layer and an anti-reflection layer.
[0038] In summary, the present application uses the method of changing the concentration distribution to form Al(x)Ga(1-x)As layers and Ga(y)As(1-y) layers for the upper contact layer 14, especially near the surface of the uppermost layer 0.5um-0.6um, to form a structure similar to a barrier (potential barrier layer). By alternating the layers with Al(x)Ga(1-x)As concentration x varying by 10%-90%, the x is adjusted by a small amount, and then the gradually changing Al(x)Ga(1-x)As layer is inserted as a barrier, and x is taken as 10% at the end, which is matched to the GaAs layer 146, and then matched with the ultra-thin thin film layer 15, and three to five layers of thin film layers 15 are deposited to achieve the effect of stress absorption.
[0039] The epitaxial structure of the present application adjusts the deformation of the upper layer of the VCSEL due to expansion, so that the tensile and compressive stresses are matched, and the stress between the thin film layer 15 is matched. When protecting the chip from the influence of thermal expansion, the optical phase is also corrected, so that the characteristics are improved.
[0040] It should be noted that the deposition thickness of the thin film layer 15 and the stress of the three-layer thin film layer 15 also need to be matched, so different temperatures and pressures need to be controlled. The epitaxial gradual barrier needs to be specially designed and simulated to achieve high reflectivity and control power, so that the optical light is more saturated and the efficiency is improved.
[0041] On the other hand, the present application also discloses a chip comprising the epitaxial structure of any one of the above.
[0042] The chip contains the same structure and advantages as the epitaxial structure in the foregoing embodiments. The structure and advantages of the epitaxial structure have been described in detail in the foregoing embodiments, and will not be repeated here.
[0043] The above is only an embodiment of the present application and is not used to limit the protection scope of the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.
Claims
1. An epitaxial structure, characterized by, The contact layer further comprises a thin film layer, and the thin film layer comprises a silicon nitride thin film layer. a substrate, an N-type distributed Bragg reflector, a multiple quantum well layer, a P-type distributed Bragg reflector, a contact layer, the contact layer including, stacked from bottom to top, Al (x) Ga (1-x) As layer and a Ga (y) As (1-y) layer, or an Al (x) Ga (1-x) As layer and a GaAs layer.
2. The epitaxial structure of claim 1, wherein The Al (x) Ga (1-x) x ranges between 10% and 90% in the Ga (y) As (1-y) y ranges between 10% and 90% in the As 3. The epitaxial structure of claim 2, wherein, The Al (x) Ga (1-x) The As layer has multiple layers, and the Al layers are described in multiple layers. (x) Ga (1-x) The Al layers with the same x value (x) Ga (1-x) As layers are arranged in alternating layers.
4. The epitaxial structure of claim 3, wherein, The multilayered Al (x) Ga (1-x) The layers of As are stacked from bottom to top in descending order of the value of x.
5. The epitaxial structure of claim 1, wherein The Al (x) Ga (1-x) The lattice constant of AlGaAs in the As layer is between 5 A° and 6 A°, the Ga (y) As (1-y) The lattice constant of GaAs in the As layer is between 5 A° and 6 A°.
6. Epitaxial structure according to any one of claims 1 to 5, characterized in that The thin film layer has multiple layers, and the multiple layers have different thicknesses.
7. The epitaxial structure of claim 6, wherein The thin film layer has three layers, and the two layers from the bottom have lattice constants of 100A°-150A° and 1500A°-1800A°, respectively.
8. The epitaxial structure of claim 7, wherein, The epitaxial structure according to any one of claims 1-8.
9. A chip, characterized by