Quantum cascade light-emitting structure and its preparation method

Abstract

The present invention provides a quantum cascade light-emitting structure and a preparation method thereof. The quantum cascade light-emitting structure comprises: an active layer; the active layer comprises a first active layer group to an Mth active layer group stacked along a first direction; any mth active layer group presents a superlattice structure and comprises a plurality of mth active layer units stacked along the first direction; any mth active layer unit comprises an mth barrier layer and an mth potential well layer alternately stacked along the first direction; the equivalent material of any mth barrier layer is In x Al 1‑x As, the equivalent material of any mth potential well layer is In y Ga 1‑y As; M is an integer greater than or equal to 1, and m is an integer greater than or equal to 1 and less than or equal to M; wherein the x of at least two barrier layers in each active layer unit in at least one active layer group is different; and / or the y of at least two potential well layers in each active layer unit in at least one active layer group is different.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a quantum cascade light-emitting structure and a preparation method thereof. Background Art

[0002] Quantum cascade lasers (QCLs) are a new type of semiconductor laser and a significant achievement in semiconductor band engineering. Their operating wavelengths extend from the mid-wave infrared (MWIR) to the terahertz (THz) band. Quantum cascade lasers based on the InGaAs / InAlAs / InP material system exhibit unique advantages in the MWIR and LWIR bands. Due to their small size, light weight, and low power consumption, QCL-based directional infrared countermeasure systems are suitable for more complex applications, particularly as airborne equipment to protect aircraft and other aircraft. Beyond security applications, QCLs have demonstrated potential importance in areas such as gas detection and free-space optical communications. MWIR and LWIR QCLs operate in the 4μm-12μm wavelength range, making them suitable not only for detecting a variety of trace gases but also as highly anticipated light sources for free-space optical communications. Multi-wavelength QCLs are a crucial development direction for both trace gas detection and free-space optical communications. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is how to obtain a larger wavelength adjustment range and reduce the difficulty of the process, thereby providing a quantum cascade light-emitting structure and a preparation method thereof.

[0004] The present application provides a quantum cascade light-emitting structure, which is a quantum cascade laser, comprising: an active layer; wherein the active layer comprises a first active layer group to an Mth active layer group stacked along a first direction, and any mth active layer group presents a superlattice structure and comprises a plurality of mth active layer units stacked along the first direction, and any mth active layer unit comprises an mth barrier layer and an mth potential well layer alternately stacked along the first direction; and the equivalent material of any mth barrier layer is In x Al 1-x As, the equivalent material of any mth potential well layer is In y Ga 1-y As; M is an integer greater than or equal to 1, m is an integer greater than or equal to 1 and less than or equal to M; wherein any mth potential well layer includes a first type mth sub-potential well layer and a second type mth sub-potential well layer alternately stacked along a first direction, the second type mth sub-potential well layer is located between adjacent first type mth sub-potential well layers, and the material of the first type mth sub-potential well layer is In y1 Ga 1-y1As, the material of the second type mth sub-potential well layer is InAs; any mth barrier layer includes a first type mth sub-barrier layer and a second type mth sub-barrier layer alternately stacked along the first direction, and the second type mth sub-barrier layer is located between adjacent first type mth sub-barrier layers; the material of the first type mth sub-barrier layer is InAs x1 Al 1-x1 As, the material of the mth sub-barrier layer of the second type is AlAs; wherein, the x of at least two barrier layers in each active layer unit in at least one active layer group is different; and / or, the y of at least two potential well layers in each active layer unit in at least one active layer group is different.

[0005] Optionally, for different m1th active layer groups and m2th active layer groups, x in at least one m1th barrier layer in the m1th active layer group and each m2th barrier layer in the m2th active layer group is different, and y in at least one m1th potential well layer in the m1th active layer group and each m2th potential well layer in the m2th active layer group is different; M is an integer greater than or equal to 2, m1 is an integer greater than or equal to 1 and less than or equal to M, m2 is an integer greater than or equal to 1 and less than or equal to M, and m1 is not equal to m2.

[0006] Optionally, for different m1th active layer groups and m2th active layer groups, the thicknesses of at least one m1th barrier layer in the m1th active layer group and each m2th barrier layer in the m2th active layer group along the first direction are different, and the thicknesses of at least one m1th potential well layer in the m1th active layer group and each m2th potential well layer in the m2th active layer group along the first direction are different; M is an integer greater than or equal to 2, m1 is an integer greater than or equal to 1 and less than or equal to M, m2 is an integer greater than or equal to 1 and less than or equal to M, and m1 is not equal to m2.

[0007] Optionally, 0.53≤y<1, 0<x≤0.52.

[0008] Optionally, the thickness of any m-th barrier layer is 0.1 nm to 100 nm; the thickness of any m-th potential well layer is 0.1 nm to 100 nm.

[0009] Optionally, the thickness of each first-type m-th sub-potential well layer is greater than 0.5 monoatomic layer, and the thickness of each second-type m-th sub-potential well layer is greater than 0.5 monoatomic layer.

[0010] Optionally, the thickness of each first-type m-th sub-barrier layer is greater than 0.5 monoatomic layer, and the thickness of each second-type m-th sub-barrier layer is greater than 0.5 monoatomic layer.

[0011] The present application also provides a method for preparing a quantum cascade light-emitting structure, wherein the quantum cascade light-emitting structure is a quantum cascade laser, comprising: forming an active layer; wherein forming the active layer comprises: forming a first active layer group to an Mth active layer group stacked along a first direction, wherein any mth active layer group presents a superlattice structure and comprises a plurality of mth active layer units stacked along the first direction, wherein any mth active layer unit comprises an mth barrier layer and an mth potential well layer alternately stacked along the first direction; and wherein the equivalent material of any mth barrier layer is In x Al 1-x As, the equivalent material of any mth potential well layer is In y Ga 1-y As; M is an integer greater than or equal to 1, m is an integer greater than or equal to 1 and less than or equal to M; wherein forming any mth potential well layer comprises: forming a first type mth sub-potential well layer and a second type mth sub-potential well layer alternately stacked along a first direction, the second type mth sub-potential well layer is located between adjacent first type mth sub-potential well layers, and the material of the first type mth sub-potential well layer is In y1 Ga 1-y1 As, the material of the second type m-th sub-barrier layer is InAs; wherein, forming any m-th barrier layer includes: forming a first type m-th sub-barrier layer and a second type m-th sub-barrier layer alternately stacked along a first direction, the second type m-th sub-barrier layer is located between adjacent first type m-th sub-barrier layers; the material of the first type m-th sub-barrier layer is InAs x1 Al 1-x1 As, the material of the mth sub-barrier layer of the second type is AlAs; wherein, the x of at least two barrier layers in each active layer unit in at least one active layer group is different; and / or, the y of at least two potential well layers in each active layer unit in at least one active layer group is different.

[0012] Optionally, forming a first type m-th potential well layer and a second type m-th potential well layer alternately stacked along a first direction, including: obtaining a design thickness of the m-th potential well layer of p single atomic layers; obtaining a total design thickness of the first basic epitaxial layer of p*y single atomic layers, and obtaining a total design thickness of the second basic epitaxial layer of p*(1-y) single atomic layers; the material of the first basic epitaxial layer is InAs, and the material of the second basic epitaxial layer is GaAs; obtaining a design growth rate of the first basic epitaxial layer of r1 single atomic layers / s, and obtaining a design growth rate of the second basic epitaxial layer of r2 single atomic layers / s; obtaining a total design thickness of the first basic epitaxial layer according to the design growth rate of the first basic epitaxial layer and the total design thickness of the first basic epitaxial layer Growth time t1=(p*y / r1)s; according to the designed growth rate of the second basic epitaxial layer and the total designed thickness of the second basic epitaxial layer, the total designed growth time t2=(p*(1-y) / r2)s of the second basic epitaxial layer is obtained, wherein t1 is greater than t2; the second basic epitaxial layer is divided into the first second sub-basic epitaxial layer to the n1-th second sub-basic epitaxial layer; n1 is an integer greater than or equal to 2; in the process of continuously growing the first basic epitaxial layer within the growth time t3, the first second sub-basic epitaxial layer to the n1-th second sub-basic epitaxial layer are intermittently grown within the growth time t3, t3=t1, and the growth time of each second sub-basic epitaxial layer is t2 / n1; the interval time t2 for growing adjacent second sub-basic epitaxial layers is t s =(t3-t2) / (n1-1); within t2 / n1, the second basic epitaxial layer and the first basic epitaxial layer react to form the mth sub-potential well layer of the first type; at the interval time t s The first basic epitaxial layer forms the mth sub-well layer of the second type.

[0013] Optional. The value of p ranges from 1 to 400.

[0014] Optional, t s *r1 is greater than 0.5 monoatomic layer; (r1+r2)*t2 / n1 is greater than 0.5 monoatomic layer; n1 .

[0015] Optionally, forming an m-th sub-barrier layer of a first type and an m-th sub-barrier layer of a second type alternately stacked along a first direction, including: obtaining a design thickness of the m-th barrier layer of q single atomic layers; obtaining a total design thickness of the third basic epitaxial layer of q*x single atomic layers, and obtaining a total design thickness of the fourth basic epitaxial layer of q*(1-x) single atomic layers; the material of the third basic epitaxial layer is InAs, and the material of the fourth basic epitaxial layer is AlAs; obtaining a design growth rate of the third basic epitaxial layer of r3 single atomic layers / s, and obtaining a design growth rate of the fourth basic epitaxial layer of r4 single atomic layers / s; obtaining a total design thickness of the third basic epitaxial layer according to the design growth rate of the third basic epitaxial layer and the total design thickness of the third basic epitaxial layer. The growth time is calculated as t4=(q*x / r3)s; the total design growth time of the fourth basic epitaxial layer is obtained as t5=(q*(1-x) / r4)s according to the design growth rate of the fourth basic epitaxial layer and the total design thickness of the fourth basic epitaxial layer, wherein t5 is greater than t4; the third basic epitaxial layer is divided into the first third sub-basic epitaxial layer to the n2th third sub-basic epitaxial layer; n2 is an integer greater than or equal to 2; in the process of continuously growing the fourth basic epitaxial layer within the growth time t6, the first third sub-basic epitaxial layer to the n2th third sub-basic epitaxial layer are grown at intervals within the growth time t6, t6=t5, and the growth time of each third sub-basic epitaxial layer is t4 / n2; the interval time for growing adjacent third sub-basic epitaxial layers is t s ’ =(t6-t4) / (n2-1); within t4 / n2, the third basic epitaxial layer and the fourth basic epitaxial layer react to form the mth sub-barrier layer of the first type; at the interval time t s ’ The fourth base epitaxial layer forms an m-th sub-barrier layer of the second type.

[0016] Optional. The value range of q is 1~400.

[0017] Optional, t s ’ *r4 is greater than 0.5 monoatomic layer; (r3+r4)*t4 / n2 is greater than 0.5 monoatomic layer; n2 2r4*(t5-t4)+1.

[0018] Optionally, y of the a-th m-th potential well layer in each m-th active layer unit in the m-th active layer group is different from y in the b-th m-th potential well layer, a is an integer greater than or equal to 1, b is an integer greater than or equal to 1, and a is not equal to b; in the process of forming the a-th m-th potential well layer, the As source furnace, the first In source furnace and the first Ga source furnace in the reaction chamber are used; in the process of forming the b-th m-th potential well layer, the As source furnace, the first In source furnace and the first Ga source furnace in the reaction chamber are used.

[0019] Optionally, x in the a-th m-th barrier layer in any m-th active layer unit in the m-th active layer group is different from x in the b-th m-th barrier layer, a is an integer greater than or equal to 1, b is an integer greater than or equal to 1, and a is not equal to b; in the process of forming the a-th m-th barrier layer, the As source furnace, the second In source furnace and the first Al source furnace in the reaction chamber are used; in the process of forming the b-th m-th barrier layer, the As source furnace, the second In source furnace and the first Al source furnace in the reaction chamber are used.

[0020] The technical solution of the present invention has the following beneficial effects:

[0021] The quantum cascade light-emitting structure provided by the technical solution of the present invention has at least two barrier layers in each active layer unit of at least one active layer group having different x values; and / or at least two potential well layers in each active layer unit of at least one active layer group having different y values. By designing the values of x and y to adjust the lasing wavelength of any mth active layer group, the lasing wavelength of any mth active layer group can be selected within a larger wavelength range. This expands the optional range of the lasing wavelength of any mth active layer group. Moreover, any mth potential well layer includes a first type mth sub-potential well layer and a second type mth sub-potential well layer alternately stacked along a first direction, and the first type mth sub-potential well layer and the second type mth sub-potential well layer alternately stacked are equivalent to the mth potential well layer. Any mth barrier layer includes a first type mth sub-barrier layer and a second type mth sub-barrier layer alternately stacked along the first direction, and the first type mth sub-barrier layer and the second type mth sub-barrier layer alternately stacked are equivalent to the mth barrier layer. This reduces the difficulty of the preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is a structural diagram of a quantum cascade light-emitting structure according to an embodiment of the present application;

[0024] Figure 2 A timing diagram of forming the mth sub-potential well layer of the first type and the mth sub-potential well layer of the second type in one embodiment of the present application;

[0025] Figure 3 In one embodiment of the present application, an m-th sub-barrier layer of a first type and an m-th sub-barrier layer of a second type are formed. DETAILED DESCRIPTION

[0026] The research found that in the related technologies, the active region of high-performance medium-wave infrared and long-wave infrared quantum cascade lasers adopts strain compensation design, using multi-cycle In y Ga 1-y As / In x Al 1-x As multi-quantum well structure is used as the active region structure of quantum cascade laser. Each period contains dozens of layers of In with different thicknesses. y Ga 1-y As / In x Al 1-x As alternating layers, the tensile stress and compressive stress between adjacent layers are partially offset, while the In single cycle y Ga 1-y As / In x Al 1-x The total strain of the As superlattice structure is generally less than 200 arcsec. y Ga 1-y In component y of As, In x Al 1-x The In composition x of As and the thickness of each layer within a single period can determine the active region structure of a quantum cascade laser with a specific wavelength. Although adjusting the thickness of each layer within a single period can adjust the designed lasing wavelength of the quantum cascade laser within a certain range, it is difficult to achieve a change in the designed lasing wavelength over a larger wavelength range.

[0027] On this basis, the present application provides a quantum cascade light-emitting structure and a preparation method thereof, which can obtain a larger wavelength adjustment range.

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] An embodiment of the present invention provides a quantum cascade light emitting structure, referring to Figure 1 , including: an active layer 130 .

[0032] refer to Figure 1 The quantum cascade light emitting structure further includes: a first confinement layer 110; a first waveguide layer 120 located on one side of the first confinement layer 110 along the first direction; wherein the active layer 130 is located on a side of the first waveguide layer 120 that is away from the first confinement layer 110 along the first direction. The quantum cascade light emitting structure further includes: a second waveguide layer 140 located on a side of the active layer 130 that is away from the first waveguide layer 120 along the first direction; and a second confinement layer 150 located on a side of the second waveguide layer 140 that is away from the active layer 130 along the first direction.

[0033] The quantum cascade light emitting structure may further include: a substrate layer 100 located on a side of the first confinement layer 110 away from the first waveguide layer 120 .

[0034] The active layer includes a first active layer group to an Mth active layer group stacked along a first direction, and any mth active layer group presents a superlattice structure and includes a plurality of mth active layer units stacked along the first direction, and any mth active layer unit includes an mth barrier layer and an mth potential well layer alternately stacked along the first direction; and the equivalent material of any mth barrier layer is In x Al 1-x As, the equivalent material of any mth potential well layer is In y Ga 1-y As; M is an integer greater than or equal to 1, and m is an integer greater than or equal to 1 and less than or equal to M; wherein the x of at least two barrier layers in each active layer unit in at least one active layer group is different; and / or the y of at least two potential well layers in each active layer unit in at least one active layer group is different.

[0035] Wherein, any m-th potential well layer includes a first type m-th sub-potential well layer and a second type m-th sub-potential well layer alternately stacked along a first direction, the second type m-th sub-potential well layer is located between adjacent first type m-th sub-potential well layers, and the material of the first type m-th sub-potential well layer is In y1 Ga 1-y1As, the material of the second type mth sub-potential well layer is InAs; any mth barrier layer includes a first type mth sub-barrier layer and a second type mth sub-barrier layer alternately stacked along the first direction, and the second type mth sub-barrier layer is located between adjacent first type mth sub-barrier layers; the material of the first type mth sub-barrier layer is InAs x1 Al 1-x1 As, the material of the second type m-th sub-barrier layer is AlAs.

[0036] In this embodiment, the x of at least two barrier layers in each active layer unit in at least one active layer group is different; and / or, the y of at least two potential well layers in each active layer unit in at least one active layer group is different. By designing the values of x and y to adjust the lasing wavelength of any mth active layer group, the lasing wavelength of any mth active layer group can be selected within a larger wavelength range. The optional range of the lasing wavelength of any mth active layer group is expanded. The flexibility of the design of the quantum cascade light-emitting structure is expanded. The mth potential well layer is equivalent to the alternating stacking of the first type mth sub-potential well layer and the mth sub-potential well layer of the second type, and the mth barrier layer is equivalent to the alternating stacking of the first type mth sub-barrier layer and the second type mth sub-barrier layer. This reduces the difficulty of the preparation process.

[0037] In this embodiment, any m-th active layer group has a superlattice structure and includes a plurality of m-th active layer units stacked along a first direction. In any m-th active layer group, a plurality of m-th active layer units are repeatedly arranged along the first direction, so that any m-th active layer group has a superlattice structure. In any m-th active layer unit, the m-th active layer unit includes a plurality of m-th barrier layers and a plurality of m-th potential well layers, with the m-th barrier layers and the m-th potential well layers alternately stacked along the first direction.

[0038] In one embodiment, in any m-th active layer unit, multiple m-th barrier layers have the same thickness, and multiple m-th potential well layers have the same thickness. By designing at least two m-th barrier layers with different x values and / or at least two m-th potential well layers with different y values in any m-th active layer unit, any m-th active layer group emits light of a certain wavelength. Specifically, it can be that in any m-th active layer unit, all m-th barrier layers have different x values and / or all m-th potential well layers have different y values. It can also be that in any m-th active layer unit, some number of m-th barrier layers have different x values. It can also be that in any m-th active layer unit, some number of m-th potential well layers have different y values.

[0039] In one embodiment, in any m-th active layer unit, at least two m-th barrier layers have different thicknesses, and at least two m-th potential well layers have different thicknesses. By designing at least two m-th barrier layers with different x values and / or at least two m-th potential well layers with different y values, at least two m-th barrier layers with different thicknesses, and at least two m-th potential well layers with different thicknesses in any m-th active layer unit, any m-th active layer group emits light of a certain wavelength. By designing the thickness and composition of any m-th active layer group, the selectable range of lasing wavelengths for any m-th active layer group is further expanded. Specifically, in any m-th active layer unit, some number of m-th barrier layers have different thicknesses, and some number of m-th potential well layers have different thicknesses. Alternatively, in any m-th active layer unit, some number of m-th barrier layers have different thicknesses, and all m-th potential well layers have different thicknesses. Specifically, in any m-th active layer unit, all m-th barrier layers have different x values and / or all m-th potential well layers have different y values. Alternatively, in any m-th active layer unit, some number of m-th barrier layers have different x values. Alternatively, in any m-th active layer unit, some number of m-th potential well layers have different y values.

[0040] In one embodiment, the active layer includes a first active layer group to an Mth active layer group stacked along a first direction. When M is greater than or equal to 2, different active layer groups emit different wavelengths. Accordingly, the quantum cascade light emitting structure is a multi-wavelength quantum cascade light emitting structure.

[0041] In one embodiment, for different m1-th active layer groups and m2-th active layer groups, x is different in at least one m1-th barrier layer in the m1-th active layer group and each m2-th barrier layer in the m2-th active layer group, and y is different in at least one m1-th potential well layer in the m1-th active layer group and each m2-th potential well layer in the m2-th active layer group; M is an integer greater than or equal to 2, m1 is an integer greater than or equal to 1 and less than or equal to M, and m2 is an integer greater than or equal to 1 and less than or equal to M. m1 is not equal to m2. Alternatively, for different m1-th active layer groups and m2-th active layer groups, x is different in some of the m1-th barrier layers in the m1-th active layer group and each m2-th barrier layer in the m2-th active layer group, or x is different in all of the m1-th barrier layers in the m1-th active layer group and each m2-th barrier layer in the m2-th active layer group. It may be that, for different m1th active layer groups and m2th active layer groups, y in a portion of the m1th potential well layers in the m1th active layer group and each m2th potential well layer in the m2th active layer group is different, or y in all the m1th potential well layers in the m1th active layer group and each m2th potential well layer in the m2th active layer group is different.

[0042] In one embodiment, for different m1-th active layer groups and m2-th active layer groups, at least one m1-th barrier layer in the m1-th active layer group and each m2-th barrier layer in the m2-th active layer group have different thicknesses along the first direction, and at least one m1-th potential well layer in the m1-th active layer group and each m2-th potential well layer in the m2-th active layer group have different thicknesses along the first direction; M is an integer greater than or equal to 2, m1 is an integer greater than or equal to 1 and less than or equal to M, m2 is an integer greater than or equal to 1 and less than or equal to M, and m1 is not equal to m2. Alternatively, for different m1-th active layer groups and m2-th active layer groups, some of the m1-th barrier layers in the m1-th active layer group and each m2-th barrier layer in the m2-th active layer group have different thicknesses along the first direction, or all of the m1-th barrier layers in the m1-th active layer group and each m2-th barrier layer in the m2-th active layer group have different thicknesses along the first direction. It may be that, for different m1th active layer groups and m2th active layer groups, the thicknesses of some m1th potential well layers in the m1th active layer group and the m2th potential well layers in the m2th active layer group along the first direction are different, or, the thicknesses of all m1th potential well layers in the m1th active layer group and the m2th potential well layers in the m2th active layer group along the first direction are different.

[0043] In one embodiment, 0<y<1, 0<x<1.

[0044] In one embodiment, 0.53≤y<1, 0<x≤0.52. In other embodiments, the values of y and x can also be other values.

[0045] In one embodiment, the thickness of any mth barrier layer is 0.1nm~100nm, for example, 0.1nm, 0.5nm, 1nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm. Preferably, the thickness of any mth barrier layer is 0.1nm~10nm; the thickness of any mth potential well layer is 0.1nm~100nm, for example, 0.1nm, 0.5nm, 1nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm. Preferably, the thickness of any mth potential well layer is 0.1nm~10nm.

[0046] In one embodiment, any m-th potential well layer includes a first type m-th sub-potential well layer and a second type m-th sub-potential well layer alternately stacked along a first direction, the second type m-th sub-potential well layer is located between adjacent first type m-th sub-potential well layers, the first type m-th sub-potential well layer is a three-element layer, and the second type m-th sub-potential well layer is a two-element layer; the material of the first type m-th sub-potential well layer is In y1Ga 1-y1 As, the material of the second type m-th sub-potential well layer is InAs.

[0047] In one embodiment, the thickness of each first-type m-th sub-potential well layer is greater than 0.5 monoatomic layers. It should be noted that the monoatomic layer herein refers to a layer of atoms in the first-type m-th sub-potential well layer in the first direction. The thickness of each second-type m-th sub-potential well layer is greater than 0.5 monoatomic layers. It should be noted that the monoatomic layer herein refers to a layer of atoms in the second-type m-th sub-potential well layer in the first direction.

[0048] The material of the first type m-th potential well layer is In y1 Ga 1-y1 As, the material of the m-th sub-potential well layer of the second type is InAs. The total thickness of the multi-layer first-type m-th sub-potential well layer in any m-th potential well layer is L1 monoatomic layers, where the monoatomic layer refers to a layer of atoms of the m-th sub-potential well layer of the first type in the first direction. The total thickness of the multi-layer second-type m-th sub-potential well layer in any m-th potential well layer is L2 monoatomic layers, where the monoatomic layer refers to a layer of atoms of the m-th sub-potential well layer of the second type in the first direction. The equivalent material of the m-th potential well layer is InAs. y Ga 1-y As, the thickness of the mth potential well layer is L monoatomic layers, where a monoatomic layer refers to a layer of atoms in the first direction of the equivalent material of the mth potential well layer. Then y1*L1+L2=y*L; (1–y1)*L1=(1-y)*L.

[0049] In one embodiment, any m-th barrier layer includes a first type m-th sub-barrier layer and a second type m-th sub-barrier layer alternately stacked along a first direction, and the second type m-th sub-barrier layer is located between adjacent first type m-th sub-barrier layers; the first type m-th sub-barrier layer is a three-element layer, and the second type m-th sub-barrier layer is a two-element layer; the material of the first type m-th sub-barrier layer is In x1 Al 1-x1 As, the material of the second type m-th sub-barrier layer is AlAs.

[0050] In one embodiment, the thickness of each first-type m-th sub-barrier layer is greater than 0.5 monoatomic layers. It should be noted that the monoatomic layer herein refers to a layer of atoms in the first-type m-th sub-barrier layer in the first direction. The thickness of each second-type m-th sub-barrier layer is greater than 0.5 monoatomic layers. It should be noted that the monoatomic layer herein refers to a layer of atoms in the second-type m-th sub-barrier layer in the first direction.

[0051] The material of the m-th sub-barrier layer of the first type is In x1 Al1-x1 As, the material of the m-th sub-barrier layer of the second type is AlAs. The total thickness of the multi-layer m-th sub-barrier layer of the first type in any m-th barrier layer is K1 monoatomic layers, where the monoatomic layer refers to a layer of atoms of the m-th sub-barrier layer of the first type in the first direction. The total thickness of the multi-layer m-th sub-barrier layer of the second type in any m-th barrier layer is K2 monoatomic layers, where the monoatomic layer refers to a layer of atoms of the m-th sub-barrier layer of the second type in the first direction. The equivalent material of the m-th barrier layer is In x Al 1-x As, the thickness of the mth barrier layer is K monoatomic layers, where a monoatomic layer refers to a layer of atoms in the first direction of the equivalent material of the mth barrier layer. Therefore, (1-x1)*K1+K2=(1-x)*K; x1*K1=x*K.

[0052] On the other hand, the present application also provides a method for preparing a quantum cascade light-emitting structure, comprising: forming an active layer; wherein forming the active layer comprises: forming a first active layer group to an Mth active layer group stacked along a first direction, wherein any mth active layer group presents a superlattice structure and comprises a plurality of mth active layer units stacked along the first direction, wherein any mth active layer unit comprises an mth barrier layer and an mth potential well layer alternately stacked along the first direction; and wherein the equivalent material of any mth barrier layer is In x Al 1- x As, the equivalent material of any mth potential well layer is In y Ga 1-y As; M is an integer greater than or equal to 1, m is an integer greater than or equal to 1 and less than or equal to M;

[0053] Wherein, forming any mth potential well layer includes: forming a first type mth sub-potential well layer and a second type mth sub-potential well layer alternately stacked along a first direction, the second type mth sub-potential well layer is located between adjacent first type mth sub-potential well layers, and the material of the first type mth sub-potential well layer is In y1 Ga 1-y1 As, the material of the second type m-th potential well layer is InAs;

[0054] The formation of any m-th barrier layer includes: forming a first type m-th sub-barrier layer and a second type m-th sub-barrier layer alternately stacked along a first direction, wherein the second type m-th sub-barrier layer is located between adjacent first type m-th sub-barrier layers; the material of the first type m-th sub-barrier layer is In x1 Al 1-x1 As, the material of the m-th sub-barrier layer of the second type is AlAs;

[0055] The x values of at least two barrier layers in each active layer unit in at least one active layer group are different; and / or the y values of at least two potential well layers in each active layer unit in at least one active layer group are different.

[0056] In this embodiment, the method for fabricating a quantum cascade light-emitting structure further includes: forming a first confinement layer on one side of the substrate layer along a first direction; forming a first waveguide layer on a side of the first confinement layer facing away from the substrate layer; wherein forming the active layer includes: forming the active layer on a side of the first waveguide layer facing away from the first confinement layer. The method for fabricating a quantum cascade light-emitting structure further includes: forming a second waveguide layer on a side of the active layer facing away from the first waveguide layer; and forming a second confinement layer on a side of the second waveguide layer facing away from the active layer.

[0057] In this embodiment, any m-th active layer group has a superlattice structure and includes a plurality of m-th active layer units stacked along a first direction. In any m-th active layer group, a plurality of m-th active layer units are repeatedly arranged along the first direction, so that any m-th active layer group has a superlattice structure. In any m-th active layer unit, the m-th active layer unit includes a plurality of m-th barrier layers and a plurality of m-th potential well layers, with the m-th barrier layers and the m-th potential well layers alternately stacked along the first direction.

[0058] In one embodiment, in any m-th active layer unit, the thicknesses of the multiple m-th barrier layers are the same, and the thicknesses of the multiple m-th potential well layers are the same.

[0059] In one embodiment, in any m-th active layer unit, at least two m-th barrier layers have different thicknesses, and at least two m-th potential well layers have different thicknesses.

[0060] In one embodiment, the active layer includes a first active layer group to an Mth active layer group stacked along a first direction. When M is greater than or equal to 2, different active layer groups emit different wavelengths. Accordingly, the quantum cascade light emitting structure is a multi-wavelength quantum cascade light emitting structure.

[0061] In one embodiment, for different m1-th active layer groups and m2-th active layer groups, x in at least one m1-th barrier layer in the m1-th active layer group and each m2-th barrier layer in the m2-th active layer group is different, and y in at least one m1-th potential well layer in the m1-th active layer group and each m2-th potential well layer in the m2-th active layer group is different; M is greater than or equal to 2, m1 is an integer greater than or equal to 1 and less than or equal to M, and m2 is an integer greater than or equal to 1 and less than or equal to M. m1 is not equal to m2.

[0062] In one embodiment, for different m1-th active layer groups and m2-th active layer groups, the thicknesses of at least one m1-th barrier layer in the m1-th active layer group and each m2-th barrier layer in the m2-th active layer group along the first direction are different, and the thicknesses of at least one m1-th potential well layer in the m1-th active layer group and each m2-th potential well layer in the m2-th active layer group along the first direction are different; M is greater than or equal to 2, m1 is an integer greater than or equal to 1 and less than or equal to M, m2 is an integer greater than or equal to 1 and less than or equal to M, and m1 is not equal to m2.

[0063] In one embodiment, forming any m-th potential well layer includes: forming a first type m-th sub-potential well layer and a second type m-th sub-potential well layer alternately stacked along a first direction, wherein the second type m-th sub-potential well layer is located between adjacent first type m-th sub-potential well layers, the first type m-th sub-potential well layer is a three-element layer, and the second type m-th sub-potential well layer is a two-element layer; the material of the first type m-th sub-potential well layer is In y1 Ga 1-y1 As, the material of the second type m-th sub-potential well layer is InAs.

[0064] In one embodiment, an m-th sub-potential well layer of a first type and an m-th sub-potential well layer of a second type alternately stacked along a first direction are formed, including: obtaining a design thickness of the m-th potential well layer of p single atomic layers, where a single atomic layer refers to a layer of atoms of the equivalent material of the m-th potential well layer in the first direction; obtaining a total design thickness of the first basic epitaxial layer of p*y single atomic layers, where a single atomic layer refers to a layer of atoms of the first basic epitaxial layer in the first direction; obtaining a total design thickness of the second basic epitaxial layer of p*(1-y) single atomic layers, where a single atomic layer refers to a layer of atoms of the second basic epitaxial layer in the first direction; the material of the first basic epitaxial layer is InAs, and the material of the second basic epitaxial layer is GaAs; obtaining a design growth rate of the first basic epitaxial layer of r1 single atomic layers / s, where a single atomic layer refers to a layer of atoms of the first basic epitaxial layer in the first direction; obtaining a design growth rate of the second basic epitaxial layer of r2 single atomic layers / s, where the single atomic layer refers to a layer of atoms in the second basic epitaxial layer in the first direction; according to the designed growth rate of the first basic epitaxial layer and the total designed thickness of the first basic epitaxial layer, the total designed growth time of the first basic epitaxial layer is obtained as t1=(p*y / r1)s; according to the designed growth rate of the second basic epitaxial layer and the total designed thickness of the second basic epitaxial layer, the total designed growth time of the second basic epitaxial layer is obtained as t2=(p*(1-y) / r2)s, wherein t1 is greater than t2; the second basic epitaxial layer is divided into the first second sub-basic epitaxial layer to the n1th second sub-basic epitaxial layer; n1 is an integer greater than or equal to 2; in the process of continuously growing the first basic epitaxial layer within the growth time t3, the first second sub-basic epitaxial layer to the n1th second sub-basic epitaxial layer are intermittently grown within the growth time t3, t3=t1, and the growth time of each second sub-basic epitaxial layer is t2 / n1; the interval time for growing adjacent second sub-basic epitaxial layers is t s =(t3-t2) / (n1-1); within t2 / n1, the second basic epitaxial layer and the first basic epitaxial layer react to form the mth sub-potential well layer of the first type; at the interval time t s The first basic epitaxial layer forms the mth sub-well layer of the second type.

[0065] The start time of the growth of the first second sub-basic epitaxial layer is the same as the start time of the growth of the first basic epitaxial layer, and the end time of the growth of the n1th second sub-basic epitaxial layer is the same as the end time of the growth of the first basic epitaxial layer. This avoids excessive lattice mismatch at the interface between the mth sub-potential well layer and the mth barrier layer of the first type, reducing the possibility of local relaxation.

[0066] In one embodiment, the value range of p is 1-400, such as 1, 10, 20, 30, 50, 80, 100, 200, 300 or 400. Preferably, the value range of p is 1-30.

[0067] In one embodiment, t s *r1 is greater than 0.5 monoatomic layers, where the monoatomic layer refers to a layer of atoms in the mth sub-potential well layer of the second type in the first direction; (r1+r2)*t2 / n1 is greater than 0.5 monoatomic layers, where the monoatomic layer refers to a layer of atoms in the mth sub-potential well layer of the first type in the first direction; n1 .

[0068] n1=(t3-t2) / t s +1.

[0069] Wherein, y1=r1 / (r1+r2). The thickness of each mth potential sub-well layer of the first type is (r1+r2)*t2 / n1. The thickness of each mth potential sub-well layer of the second type is t s *r1.

[0070] In this embodiment, the x values of at least two potential barrier layers in each active layer unit in at least one active layer group are different; and / or the y values of at least two potential well layers in each active layer unit in at least one active layer group are different. Any mth potential well layer comprises: a first type mth sub-potential well layer and a second type mth sub-potential well layer alternately stacked along a first direction, the second type mth sub-potential well layer being located between adjacent first type mth sub-potential well layers, the first type mth sub-potential well layer being a three-element layer, and the second type mth sub-potential well layer being a two-element layer; the material of the first type mth sub-potential well layer is In y1 Ga 1-y1 As, the material of the m-th sub-potential well layer of the second type is InAs. Accordingly, during the continuous growth of the first basic epitaxial layer within the growth time t3, the first second sub-basic epitaxial layer to the n1-th second sub-basic epitaxial layer are grown at intervals within the growth time t3, thereby forming the m-th sub-potential well layer of the first type and the m-th sub-potential well layer of the second type.

[0071] The y values of at least two potential well layers in each active layer unit in at least one active layer group are different. For example, the y values of the a-th m-th potential well layer and the b-th m-th potential well layer in each m-th active layer unit in the m-th active layer group are different. Here, a is an integer greater than or equal to 1, b is an integer greater than or equal to 1, and a is not equal to b. In forming the a-th m-th potential well layer, an As source furnace, a first In source furnace, and a first Ga source furnace are used in a reaction chamber. In atoms emitted by the first In source furnace react with As atoms emitted by the As source furnace to form a first basic epitaxial layer. Ga atoms emitted by the first Ga source furnace react with As atoms emitted by the As source furnace to form a second sub-basic epitaxial layer. The thickness of the first type m-th sub-potential well layer is controlled by the growth time of the second sub-basic epitaxial layer. The thickness of the second type m-th sub-potential well layer is controlled by setting the interval time between adjacent second sub-basic epitaxial layers. Thus, multiple layers of the first type m-th sub-potential well layers and multiple layers of the second sub-basic epitaxial layers are equivalent to the a-th m-th potential well layer. During the formation of the bth mth potential well layer, an As source furnace, a first In source furnace, and a first Ga source furnace are used in a reaction chamber. In atoms emitted by the first In source furnace react with As atoms emitted by the As source furnace to form a first basic epitaxial layer. Ga atoms emitted by the first Ga source furnace react with As atoms emitted by the As source furnace to form a second sub-basic epitaxial layer. The thickness of the first type mth sub-potential well layer is controlled by the growth time of the second sub-basic epitaxial layer, and the thickness of the second type mth sub-potential well layer is controlled by setting the interval time between adjacent second sub-basic epitaxial layers. In this way, multiple layers of the first type mth sub-potential well layer and multiple layers of the second sub-basic epitaxial layer are equivalent to the bth mth potential well layer. The ath mth potential well layer and the bth mth potential well layer have different In compositions, but the ath mth potential well layer and the bth mth potential well layer can share the As source furnace, the first In source furnace, and the first Ga source furnace, reducing the requirement for the number of source furnaces. When the number of source furnaces is limited, the wavelength range of the multi-wavelength quantum cascade light-emitting structure that can be grown is increased.

[0072] In this embodiment, during the formation of the mth potential well layer, the temperature of the As source furnace remains constant, the temperature of the first In source furnace remains constant, the temperature of the first Ga source furnace remains constant, and the power of the As source furnace remains constant, the power of the first In source furnace remains constant, and the power of the first Ga source furnace remains constant to ensure a stable growth process. The equipment used to form the mth potential well layer is a molecular beam epitaxy equipment, and the process used to form the mth potential well layer is a molecular beam epitaxy process.

[0073] In the related art, the growth y Ga 1-yThe As source furnace, Ga source furnace and In source furnace that As adopts, in the same time, the As source furnace emits As atom, the Ga source furnace emits Ga atom, and the In source furnace emits In atom. If the value of y changes, it is necessary to change the temperature of the Ga source furnace and / or the In source furnace so that the beam current of the Ga source furnace emitting Ga atoms and the beam current of the In source furnace emitting In atoms are changed. However, the temperature of the Ga source furnace and / or the In source furnace is changed. One way is: adopt different Ga source furnaces, and different Ga source furnaces have different temperatures. Adopt different In source furnaces, and different In source furnaces have different temperatures. However, the number of sources furnaces used is increased like this. Another way is: regulate the temperature of same Ga source furnace, regulate the temperature of same In source furnace. However, regulating the temperature requires certain time, is difficult to guarantee the stability of growth process.

[0074] In one embodiment, forming any m-th barrier layer includes: forming a first type m-th sub-barrier layer and a second type m-th sub-barrier layer alternately stacked along a first direction, wherein the second type m-th sub-barrier layer is located between adjacent first type m-th sub-barrier layers; the first type m-th sub-barrier layer is a three-element layer, and the second type m-th sub-barrier layer is a two-element layer; the material of the first type m-th sub-barrier layer is In x1 Al 1-x1 As, the material of the second type m-th sub-barrier layer is AlAs.

[0075] In one embodiment, an m-th sub-barrier layer of a first type and an m-th sub-barrier layer of a second type alternately stacked along a first direction are formed, including: obtaining a design thickness of the m-th barrier layer of q single atomic layers, where the single atomic layer refers to a layer of atoms of the equivalent material of the m-th barrier layer in the first direction; obtaining a total design thickness of the third basic epitaxial layer of q*x single atomic layers, where the single atomic layer refers to a layer of atoms of the third basic epitaxial layer in the first direction; obtaining a total design thickness of the fourth basic epitaxial layer of q*(1-x) single atomic layers, where the single atomic layer refers to a layer of atoms of the fourth basic epitaxial layer in the first direction; the material of the third basic epitaxial layer is InAs, and the material of the fourth basic epitaxial layer is AlAs; obtaining a design growth rate of the third basic epitaxial layer of r3 single atomic layers / s, where the single atomic layer refers to a layer of atoms of the third basic epitaxial layer in the first direction; obtaining a design growth rate of the fourth basic epitaxial layer of r4 single atomic layers / s, where the single atomic layer refers to a layer of atoms in the first direction of the fourth basic epitaxial layer; according to the designed growth rate of the third basic epitaxial layer and the total designed thickness of the third basic epitaxial layer, the total designed growth time t4=(q*x / r3)s of the third basic epitaxial layer is obtained; according to the designed growth rate of the fourth basic epitaxial layer and the total designed thickness of the fourth basic epitaxial layer, the total designed growth time t5=(q*(1-x) / r4)s of the fourth basic epitaxial layer is obtained, wherein t5 is greater than t4; the third basic epitaxial layer is divided into the first third sub-basic epitaxial layer to the n2th third sub-basic epitaxial layer; n2 is an integer greater than or equal to 2; in the process of continuously growing the fourth basic epitaxial layer within the growth time t6, the first third sub-basic epitaxial layer to the n2th third sub-basic epitaxial layer are intermittently grown within the growth time t6, t6=t5, and the growth time of each third sub-basic epitaxial layer is t4 / n2; the interval time t for growing adjacent third sub-basic epitaxial layers is t s ’ =(t6-t4) / (n2-1); within t4 / n2, the third basic epitaxial layer and the fourth basic epitaxial layer react to form the mth sub-barrier layer of the first type; at the interval time t s ’ The fourth base epitaxial layer forms an m-th sub-barrier layer of the second type.

[0076] The start time of the first third sub-epitaxial layer growth is the same as the start time of the fourth basic epitaxial layer growth, and the end time of the n2th third sub-epitaxial layer growth is the same as the end time of the fourth basic epitaxial layer growth. This avoids excessive lattice mismatch at the interface between the first type mth sub-barrier layer and the mth potential well layer, reducing the possibility of local relaxation. The presence of the second type mth sub-barrier layer helps to raise the barrier of the mth barrier layer, suppressing the thermal escape of electrons.

[0077] In one embodiment, the value range of q is 1-400, such as 1, 10, 20, 30, 50, 80, 100, 200, 300 or 400. Preferably, the value range of q is 1-30.

[0078] In one embodiment, t s ’ *r4 is greater than 0.5 monoatomic layers, where the monoatomic layer refers to a layer of atoms in the mth sub-barrier layer of the second type in the first direction; (r3+r4)*t4 / n2 is greater than 0.5 monoatomic layers, where the monoatomic layer refers to a layer of atoms in the mth sub-barrier layer of the first type in the first direction; n2 2r4*(t5-t4)+1.

[0079] n2=(t6-t4) / t s ’ +1.

[0080] Wherein, x1=r3 / (r3+r4). The thickness of each mth sub-barrier layer of the first type is (r3+r4)*t4 / n2. The thickness of each mth sub-barrier layer of the second type is t s ’ *r4.

[0081] In this embodiment, the x values of at least two potential well layers in each active layer unit of at least one active layer group are different; and / or the y values of at least two potential well layers in each active layer unit of at least one active layer group are different. Any m-th potential barrier layer includes: a first type m-th sub-barrier layer and a second type m-th sub-barrier layer alternately stacked along a first direction, the second type m-th sub-barrier layer is located between adjacent first type m-th sub-barrier layers, and the material of the first type m-th sub-barrier layer is In x1 Al 1-x1 As, the material of the m-th sub-barrier layer of the second type is AlAs. Accordingly, during the continuous growth of the fourth basic epitaxial layer within the growth time t6, the first to n2-th third sub-basic epitaxial layers are alternately grown within the growth time t6, thereby forming the m-th sub-barrier layer of the first type and the m-th sub-barrier layer of the second type.

[0082] The x values of at least two barrier layers in any active layer unit in at least one active layer group are different. For example, the x value of the a-th m-th barrier layer in any m-th active layer unit in the m-th active layer group is different from the x value of the b-th m-th barrier layer. Here, a is an integer greater than or equal to 1, b is an integer greater than or equal to 1, and a is not equal to b. During the formation of the a-th m-th barrier layer, an As source furnace, a second In source furnace, and a first Al source furnace are used in a reaction chamber. In atoms emitted from the second In source furnace react with As atoms emitted from the As source furnace to form a third sub-basic epitaxial layer, and Al atoms emitted from the first Al source furnace react with As atoms emitted from the As source furnace to form a fourth basic epitaxial layer. The thickness of the first type m-th sub-barrier layer is controlled by the growth time of the third sub-basic epitaxial layer, and the thickness of the second type m-th sub-barrier layer is controlled by setting the interval time between adjacent third sub-basic epitaxial layers. In this way, multiple first type m-th sub-barrier layers and multiple m-th sub-barrier layers are equivalent to the a-th m-th barrier layer. During the formation of the bth mth barrier layer, an As source furnace, a second In source furnace, and a first Al source furnace are used in a reaction chamber. In atoms emitted from the second In source furnace react with As atoms emitted from the As source furnace to form a third sub-basic epitaxial layer, and Al atoms emitted from the first Al source furnace react with As atoms emitted from the As source furnace to form a fourth sub-basic epitaxial layer. The thickness of the first type mth sub-barrier layer is controlled by the growth time of the third sub-basic epitaxial layer, and the thickness of the second type mth sub-barrier layer is controlled by setting the interval between adjacent third sub-basic epitaxial layers. In this way, multiple layers of the first type mth sub-barrier layer and multiple layers of the mth sub-barrier layer are equivalent to the bth mth barrier layer. The ath mth barrier layer and the bth mth barrier layer have different In compositions, but the ath mth barrier layer and the bth mth barrier layer can share the As source furnace, the second In source furnace, and the first Al source furnace, reducing the requirement for the number of source furnaces. When the number of source furnaces is limited, the wavelength range of the multi-wavelength quantum cascade light-emitting structure that can be grown is increased.

[0083] In this embodiment, during the formation of the mth barrier layer, the temperature of the As source furnace remains constant, the temperature of the second In source furnace remains constant, and the temperature of the first Al source furnace remains constant. The power of the As source furnace remains constant, the power of the second In source furnace remains constant, and the power of the first Al source furnace remains constant to ensure a stable growth process. The mth barrier layer is formed using molecular beam epitaxy equipment and a molecular beam epitaxy process.

[0084] Any m-th barrier layer and any m-th potential well layer can share the same As source furnace during the growth process, thereby reducing the requirement on the number of source furnaces.

[0085] In one embodiment, the first In source furnace and the second In source furnace may be the same In source furnace, or the first In source furnace and the second In source furnace may be different In source furnaces.

[0086] In the related art, the growth x Al 1-x The As source furnace, Al source furnace and In source furnace used by As, in the same time, the As source furnace emits As atoms, the Al source furnace emits Al atoms, and the In source furnace emits In atoms. If the value of x changes, it is necessary to change the temperature of the Al source furnace and / or the In source furnace so that the beam current of the Al source furnace emitting Al atoms and the beam current of the In source furnace emitting In atoms are changed. However, to change the temperature of the Al source furnace and / or the In source furnace, one way is: adopt different Al source furnaces, different Al source furnaces have different temperatures, adopt different In source furnaces, different In source furnaces have different temperatures. However, this increases the number of source furnaces used. Another way is: adjust the temperature of the same Al source furnace, adjust the temperature of the same In source furnace, however, adjusting the temperature requires a certain amount of time, which is difficult to ensure the stability of the growth process.

[0087] In this embodiment, the preparation method of the quantum cascade light-emitting structure has low verification requirements and can cope with the growth of different quantum cascade light-emitting structures through simple verification, thereby reducing verification costs and improving verification efficiency, and has great industrial application value.

[0088] The method for fabricating a quantum cascade light-emitting structure only requires pre-verification of the growth rates of the first basic epitaxial layer, the second substrate epitaxial layer, the third basic epitaxial layer, and the fourth basic epitaxial layer. This allows the growth of the first to Mth active layer groups capable of emitting different wavelengths, eliminating the need for separate verification of the first to Mth active layer groups emitting different wavelengths. This improves actual epitaxial production efficiency and reduces costs. Furthermore, the method for fabricating a quantum cascade light-emitting structure of the present invention has a wide range of applications.

[0089] The first basic epitaxial layer and the third basic epitaxial layer are both made of InAs, and the designed growth rate of the first basic epitaxial layer is the same as the designed growth rate of the third basic epitaxial layer. Alternatively, the designed growth rate of the first basic epitaxial layer and the designed growth rate of the third basic epitaxial layer are different.

[0090] In a specific embodiment, as an example, an mth active layer unit includes an mth barrier layer and an mth potential well layer alternately stacked along a first direction, and the equivalent material of the mth barrier layer is In 0.36 Al 0.64 As, the equivalent material of the mth potential well layer is In 0.57 Ga 0.3As, the designed thickness of the mth potential well layer is p monoatomic layers, which is 29 angstroms, about 9.83 monoatomic layers, and the designed thickness of the mth barrier layer is q monoatomic layers, which is 29 angstroms, about 10.10 monoatomic layers.

[0091] When the equivalent material of the mth potential well layer is In 0.57 Ga 0.3 As, the total design thickness of the first basic epitaxial layer is p*y monoatomic layers = 5.6 monoatomic layers, the total design thickness of the second basic epitaxial layer is p*(1-y) monoatomic layers = 4.23 monoatomic layers, the design growth rate of the first basic epitaxial layer is 0.5 monoatomic layers / s, the design growth rate of the second basic epitaxial layer is 0.5 monoatomic layers / s, the total design growth time of the first basic epitaxial layer is t1 = (p*y / r1)s = 11.21s, and the total design growth time of the second basic epitaxial layer is t2 = (p*(1-y) / r2)s = 8.45s. t1 is greater than t2. Let n1 = 3, and divide the second basic epitaxial layer into a first second sub-basic epitaxial layer, a second second sub-basic epitaxial layer, and a third second sub-basic epitaxial layer. t s =(t3-t2) / (n1-1)=1.38s, at the interval time t s A second type m-th potential well layer is formed, and the thickness of each second type m-th potential well layer is t s *r1=0.69 monoatomic layers, t s *r1 is greater than 0.5 monoatomic layers. Within t2 / n1, the second sub-basic epitaxial layer reacts with the first basic epitaxial layer to form the m-th sub-potential well layer of the first type. t2 / n1 = 2.82 s. The thickness of each m-th sub-potential well layer of the first type is (r1 + r2) * t2 / n1 = 2.82 monoatomic layers. (r1 + r2) * t2 / n1 is greater than 0.5 monoatomic layers.

[0092] When the equivalent material of the mth barrier layer is In 0.36 Al 0.64 As, the total design thickness of the third basic epitaxial layer is q*x monoatomic layers = 3.64 monoatomic layers, the total design thickness of the fourth basic epitaxial layer is q*(1-x) monoatomic layers = 6.46 monoatomic layers, the design growth rate of the third basic epitaxial layer is 0.5 monoatomic layers / s, the design growth rate of the fourth basic epitaxial layer is 0.5 monoatomic layers / s, the total design growth time of the third basic epitaxial layer is t4 = (q*x / r3)s = 7.27s, and the total design growth time of the fourth basic epitaxial layer is t5 = (q*(1-x) / r4)s = 12.93s. t5 is greater than t4. Let n2 = 4, and divide the third basic epitaxial layer into a first third sub-basic epitaxial layer, a second third sub-basic epitaxial layer, a third third sub-basic epitaxial layer, and a fourth third sub-basic epitaxial layer. t s’ =(t6-t4) / (n2-1)=1.41s, at the interval time t s ’ The mth sub-barrier layer of the second type is formed, and the thickness of each mth sub-barrier layer of the second type is t s ’ *r4=0.94 monoatomic layers, t s ’ *r4 is greater than 0.5 monoatomic layers. Within t4 / n2, the third sub-basic epitaxial layer and the fourth basic epitaxial layer react to form the m-th sub-barrier layer of the first type, t4 / n2 = 1.82 s, and the thickness of each m-th sub-barrier layer of the first type is (r3 + r4) * t4 / n2 = 1.82 monoatomic layers. (r3 + r4) * t4 / n2 is greater than 0.5 monoatomic layers.

[0093] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A quantum cascade light emitting structure, wherein the quantum cascade light emitting structure is a quantum cascade laser, characterized in that: include: active layer; The active layer includes a first active layer group to an Mth active layer group stacked along a first direction, and any mth active layer group presents a superlattice structure and includes a plurality of mth active layer units stacked along the first direction, and any mth active layer unit includes an mth barrier layer and an mth potential well layer alternately stacked along the first direction; the equivalent material of any mth barrier layer is In x Al 1-x As, the equivalent material of any mth potential well layer is In y Ga 1-y As; M is an integer greater than or equal to 1, m is an integer greater than or equal to 1 and less than or equal to M; Wherein, any m-th potential well layer includes a first type m-th sub-potential well layer and a second type m-th sub-potential well layer alternately stacked along a first direction, the second type m-th sub-potential well layer is located between adjacent first type m-th sub-potential well layers, and the material of the first type m-th sub-potential well layer is In y1 Ga 1-y1 As, the material of the second type mth sub-potential well layer is InAs; any mth barrier layer includes a first type mth sub-barrier layer and a second type mth sub-barrier layer alternately stacked along the first direction, and the second type mth sub-barrier layer is located between adjacent first type mth sub-barrier layers; the material of the first type mth sub-barrier layer is InAs x1 Al 1-x1 As, the material of the m-th sub-barrier layer of the second type is AlAs; The x values of at least two barrier layers in each active layer unit in at least one active layer group are different; and / or the y values of at least two potential well layers in each active layer unit in at least one active layer group are different.

2. The quantum cascade light emitting structure according to claim 1, characterized in that: For different m1-th active layer groups and m2-th active layer groups, x in at least one m1-th barrier layer in the m1-th active layer group and each m2-th barrier layer in the m2-th active layer group is different, y in at least one m1-th potential well layer in the m1-th active layer group and each m2-th potential well layer in the m2-th active layer group is different; M is an integer greater than or equal to 2, m1 is an integer greater than or equal to 1 and less than or equal to M, m2 is an integer greater than or equal to 1 and less than or equal to M, and m1 is not equal to m2.

3. The quantum cascade light emitting structure according to claim 1, characterized in that: For different m1-th active layer groups and m2-th active layer groups, the thicknesses of at least one m1-th barrier layer in the m1-th active layer group and each m2-th barrier layer in the m2-th active layer group along the first direction are different, and the thicknesses of at least one m1-th potential well layer in the m1-th active layer group and each m2-th potential well layer in the m2-th active layer group along the first direction are different; M is an integer greater than or equal to 2, m1 is an integer greater than or equal to 1 and less than or equal to M, m2 is an integer greater than or equal to 1 and less than or equal to M, and m1 is not equal to m2.

4. The quantum cascade light emitting structure according to claim 1, characterized in that: 0.53≤y<1,0<x≤0.52。 5. The quantum cascade light emitting structure according to claim 1, characterized in that: The thickness of any m-th barrier layer is 0.1 nm to 100 nm; the thickness of any m-th potential well layer is 0.1 nm to 100 nm.

6. The quantum cascade light emitting structure according to claim 1, characterized in that: The thickness of the mth sub-potential well layer of the first type in each layer is greater than 0.5 monoatomic layer, and the thickness of the mth sub-potential well layer of the second type in each layer is greater than 0.5 monoatomic layer.

7. The quantum cascade light emitting structure according to claim 1, characterized in that: The thickness of each first-type m-th sub-barrier layer is greater than 0.5 monoatomic layer, and the thickness of each second-type m-th sub-barrier layer is greater than 0.5 monoatomic layer.

8. A method for preparing a quantum cascade light-emitting structure, wherein the quantum cascade light-emitting structure is a quantum cascade laser, characterized in that: include: forming an active layer; The forming of the active layer includes: forming a first active layer group to an Mth active layer group stacked along a first direction, wherein any mth active layer group has a superlattice structure and includes a plurality of mth active layer units stacked along the first direction, and any mth active layer unit includes an mth barrier layer and an mth potential well layer alternately stacked along the first direction; and the equivalent material of any mth barrier layer is In x Al 1-x As, the equivalent material of any mth potential well layer is In y Ga 1-y As; M is an integer greater than or equal to 1, m is an integer greater than or equal to 1 and less than or equal to M; Wherein, forming any mth potential well layer includes: forming a first type mth sub-potential well layer and a second type mth sub-potential well layer alternately stacked along a first direction, the second type mth sub-potential well layer is located between adjacent first type mth sub-potential well layers, and the material of the first type mth sub-potential well layer is In y1 Ga 1-y1 As, the material of the second type m-th potential well layer is InAs; The formation of any m-th barrier layer includes: forming a first type m-th sub-barrier layer and a second type m-th sub-barrier layer alternately stacked along a first direction, wherein the second type m-th sub-barrier layer is located between adjacent first type m-th sub-barrier layers; the material of the first type m-th sub-barrier layer is In x1 Al 1-x1 As, the material of the m-th sub-barrier layer of the second type is AlAs; The x values of at least two barrier layers in each active layer unit in at least one active layer group are different; and / or the y values of at least two potential well layers in each active layer unit in at least one active layer group are different.

9. The method for preparing a quantum cascade light-emitting structure according to claim 8, wherein: Forming a first type mth sub-potential well layer and a second type mth sub-potential well layer alternately stacked along a first direction, comprising: Obtaining a designed thickness of the mth potential well layer as p monoatomic layers; The total design thickness of the first basic epitaxial layer is obtained to be p*y monoatomic layers, and the total design thickness of the second basic epitaxial layer is obtained to be p*(1-y) monoatomic layers; the material of the first basic epitaxial layer is InAs, and the material of the second basic epitaxial layer is GaAs; Obtaining a designed growth rate of the first basic epitaxial layer as r1 monoatomic layers / s, and obtaining a designed growth rate of the second basic epitaxial layer as r2 monoatomic layers / s; Obtain the total designed growth time t1=(p*y / r1)s of the first basic epitaxial layer according to the designed growth rate of the first basic epitaxial layer and the total designed thickness of the first basic epitaxial layer; Obtaining a total designed growth time t2 = (p*(1-y) / r2)s for the second basic epitaxial layer according to a designed growth rate of the second basic epitaxial layer and a total designed thickness of the second basic epitaxial layer, wherein t1 is greater than t2; The second basic epitaxial layer is divided into a first second sub-basic epitaxial layer to an n1th second sub-basic epitaxial layer; n1 is an integer greater than or equal to 2; During the process of continuously growing the first basic epitaxial layer within the growth time t3, the first second sub-basic epitaxial layer to the n1th second sub-basic epitaxial layer are grown at intervals within the growth time t3, t3=t1, and the growth time of each second sub-basic epitaxial layer is t2 / n1; the interval time for growing adjacent second sub-basic epitaxial layers is t s =(t3-t2) / (n1-1); within t2 / n1, the second basic epitaxial layer and the first basic epitaxial layer react to form the mth sub-potential well layer of the first type; at the interval time t s The first basic epitaxial layer forms the mth sub-well layer of the second type.

10. The method for preparing a quantum cascade light emitting structure according to claim 9, wherein: The value range of p is 1~400.

11. The method for preparing a quantum cascade light emitting structure according to claim 9, wherein: t s *r1 is greater than 0.5 monoatomic layer; (r1+r2)*t2 / n1 is greater than 0.5 monoatomic layer; n1 .

12. The method for preparing a quantum cascade light-emitting structure according to claim 8, wherein: Forming first-type m-th sub-barrier layers and second-type m-th sub-barrier layers alternately stacked along a first direction, comprising: The designed thickness of the mth barrier layer is obtained as q monoatomic layers; The total design thickness of the third basic epitaxial layer is q*x monoatomic layers, and the total design thickness of the fourth basic epitaxial layer is q*(1-x) monoatomic layers; the material of the third basic epitaxial layer is InAs, and the material of the fourth basic epitaxial layer is AlAs; The designed growth rate of the third basic epitaxial layer is obtained as r3 monoatomic layers / s, and the designed growth rate of the fourth basic epitaxial layer is obtained as r4 monoatomic layers / s; According to the design growth rate of the third basic epitaxial layer and the total design thickness of the third basic epitaxial layer, the total design growth time t4 = (q * x / r3) s is obtained; Obtaining a total designed growth time t5=(q*(1-x) / r4)s for the fourth basic epitaxial layer according to a designed growth rate of the fourth basic epitaxial layer and a total designed thickness of the fourth basic epitaxial layer, wherein t5 is greater than t4; The third basic epitaxial layer is divided into a first third sub-basic epitaxial layer to an n2th third sub-basic epitaxial layer; n2 is an integer greater than or equal to 2; During the continuous growth of the fourth basic epitaxial layer within the growth time t6, the first third sub-basic epitaxial layer to the n2th third sub-basic epitaxial layer are grown at intervals within the growth time t6, t6=t5, and the growth time of each third sub-basic epitaxial layer is t4 / n2; the interval time for growing adjacent third sub-basic epitaxial layers is t s ’ =(t6-t4) / (n2-1); within t4 / n2, the third basic epitaxial layer and the fourth basic epitaxial layer react to form the mth sub-barrier layer of the first type; at the interval time t s ’ The fourth base epitaxial layer forms an m-th sub-barrier layer of the second type.

13. The method for preparing a quantum cascade light emitting structure according to claim 12, wherein: The value range of q is 1~400.

14. The method for preparing a quantum cascade light emitting structure according to claim 12, wherein: t s ’ *r4 is greater than 0.5 monoatomic layer; (r3+r4)*t4 / n2 is greater than 0.5 monoatomic layer; n2 2r4*(t5-t4)+1.

15. The method for preparing a quantum cascade light emitting structure according to claim 8, wherein: In each m-th active layer unit in the m-th active layer group, y of the a-th m-th potential well layer is different from y in the b-th m-th potential well layer, a is an integer greater than or equal to 1, b is an integer greater than or equal to 1, and a is not equal to b; in the process of forming the a-th m-th potential well layer, an As source furnace, a first In source furnace, and a first Ga source furnace in the reaction chamber are used; During the process of forming the bth mth potential well layer, an As source furnace, a first In source furnace, and a first Ga source furnace in the reaction chamber are used.

16. The method for preparing a quantum cascade light emitting structure according to claim 8, characterized in that: x of the a-th m-th barrier layer in any m-th active layer unit in the m-th active layer group is different from x in the b-th m-th barrier layer, a is an integer greater than or equal to 1, b is an integer greater than or equal to 1, and a is not equal to b; in the process of forming the a-th m-th barrier layer, an As source furnace, a second In source furnace, and a first Al source furnace in the reaction chamber are used; During the process of forming the bth and mth barrier layers, an As source furnace, a second In source furnace, and a first Al source furnace in the reaction chamber are used.

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