Short-wave quantum cascade laser structure and preparation method thereof

Abstract

The present disclosure provides a short-wavelength quantum cascade laser structure and a method for fabricating the same. The short-wavelength quantum cascade laser structure comprises an N-type indium phosphide substrate, on which is sequentially grown an N-type indium phosphide buffer layer, an N-type indium phosphide lower waveguide, a quantum cascade gain region structure, an N-type indium phosphide upper waveguide, an N-type indium phosphide graded doping layer, and an N-type indium phosphide upper contact high-doped layer. The quantum cascade gain region structure comprises an alternating structure of multi-periodic strain-compensated quantum wells and quantum barriers, which is lattice mismatched with the N-type InP substrate. The quantum wells are made of indium gallium arsenide, and the quantum barriers are epitaxially grown in sequence of indium aluminum arsenide, aluminum arsenide, and indium aluminum arsenide. This laser structure reduces the difficulty of epitaxially growing a short-wavelength quantum cascade laser, improves the tolerance of material growth, increases injection efficiency, reduces the probability of carrier thermal escape, and increases the operating temperature of the device.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor material technology, and in particular to a short-wave quantum cascade laser structure and a preparation method thereof. Background Art

[0002] The use of InP-based quantum cascade lasers (QCLs) for mid-infrared gas sensing, infrared countermeasures, and free-space communications is a current research hotspot. The mid-infrared band (3-20 μm) contains a large number of absorption peaks for gas molecules, which can be further divided into short-wave infrared (3-4 μm), medium-wave infrared (4-8 μm), and long-wave infrared (8-20 μm) based on wavelength. For applications such as infrared countermeasures and free-space communications, lasers with high power, high efficiency, and high beam quality are required. Long-wave infrared quantum cascade lasers are difficult to increase in power due to their low photon energy and strong free-carrier absorption. Mid-wave infrared quantum cascade lasers have an atmospheric transmittance of no more than 60% due to absorption by molecules such as water vapor. In contrast, the atmospheric transmittance of short-wave infrared, such as those near 4 μm, is even higher than 90%. Therefore, the use of short-wave quantum cascade lasers is theoretically more advantageous in applications such as infrared countermeasures.

[0003] Currently, there are many reports of medium-wave infrared and long-wave infrared quantum cascade lasers with electro-optical conversion efficiencies exceeding 10%. However, for short-wave infrared, such as 4μm wavelength quantum cascade lasers, the electro-optical conversion efficiency does not exceed 6%. An important factor limiting the performance of short-wave quantum cascade lasers is carrier leakage, that is, the parasitic energy levels and continuous states where electrons escape to the upper energy level. An effective method is to use InGaAs and InAlAs quantum well barrier pairs with large strain (above 1.5%) to increase the depth of the quantum well. Although theoretically, the use of materials with greater strain can further improve the performance of short-wave quantum cascade lasers, this large strain material design has the following two problems.

[0004] First, the growth of large strain materials is very difficult. Currently, the use of strain-compensated InGaAs and InAlAs multi-period superlattice structures to achieve high-performance quantum cascade lasers is an important technical approach. The thinnest epitaxial layer of a quantum cascade laser is less than 1nm, and the total number of layers is thousands of layers. The current scientific research field mainly uses the molecular beam epitaxy method, and its growth temperature is usually around 500°C. Another material epitaxy method widely used in the industry, namely metal organic chemical vapor deposition (MOCVD), has a growth temperature usually greater than 600 degrees Celsius. In heterostructures, due to the different thermal expansion coefficients of different materials, as the growth temperature increases, the thermal mismatch between the active area and the substrate becomes more serious, and the epitaxial layer is prone to dislocations and even relaxation, which greatly increases the difficulty of MOCVD material growth. Therefore, in the process of epitaxial growth, not only the optimization of hardware conditions including substrate, reaction chamber design, reactant materials, etc. is required, but also long-term iterative optimization of growth conditions is required;

[0005] Second, when the Al content in highly strained InAlAs exceeds 70%, the indirect energy valley becomes the primary limiting factor in the material's performance. Unlike medium- and long-wave quantum cascade lasers, short-wave quantum cascade lasers operate at higher photon energies. As the Al content increases, the X and L energy valleys shift downward, bringing upper-level electrons very close to the indirect energy valleys. This increases the probability of electrons scattering into the indirect energy valleys through intervalley scattering, leading to carrier leakage. Summary of the Invention

[0006] In view of the above problems, the present invention provides a short-wave quantum cascade laser structure to solve the above-mentioned technical problems.

[0007] One aspect of the present disclosure provides a short-wavelength quantum cascade laser structure, comprising: an N-type indium phosphide substrate, on which are sequentially grown an N-type indium phosphide buffer layer, an N-type indium phosphide lower waveguide, a quantum cascade gain region structure, an N-type indium phosphide upper waveguide, an N-type indium phosphide graded doping layer, and an N-type indium phosphide upper contact high-doped layer; wherein the quantum cascade gain region structure is an alternating structure of multi-periodic strain-compensated quantum wells and quantum barriers, and is lattice-mismatched with the N-type indium phosphide substrate; the quantum wells are made of indium gallium arsenide, and the quantum barriers are epitaxially grown in sequence of indium aluminum arsenide, aluminum arsenide, and indium aluminum arsenic materials.

[0008] Optionally, in the indium gallium arsenide material of the quantum well, the gallium component ranges from 0 to 0.47; in the indium aluminum arsenide material of the quantum barrier, the aluminum component ranges from 0.48 to 1.

[0009] Optionally, the material of the quantum well is In 0.7 Ga 0.3 As, the indium aluminum arsenide material of the quantum barrier is In 0.36 Al0.64 As.

[0010] Optionally, the strain of the quantum cascade gain region is 1%.

[0011] Optionally, the quantum cascade gain region includes 30 to 50 periods, each period includes 16 to 20 layers of the quantum wells and quantum barriers, and the total number of layers ranges from 500 to 1000 layers.

[0012] Optionally, the thickness of a single layer of the quantum barrier is 0.5 to 4 nm, and the thickness of a single layer of the quantum well is 1 to 6 nm.

[0013] Another aspect of the present disclosure provides a preparation method, which is applied to the short-wave quantum cascade laser structure as described in any one of the first aspects, comprising: performing high-temperature deoxidation on an N-type indium phosphide substrate in a PH3 environment; growing an N-type indium phosphide buffer layer on the N-type indium phosphide substrate, with a doping concentration of 2E17; epitaxially growing an N-type indium phosphide lower waveguide on the N-type indium phosphide buffer layer, with a doping concentration of 2E16; epitaxially growing a plurality of periods of alternating quantum wells and quantum barriers on the N-type indium phosphide lower waveguide to form a quantum cascade gain region with an average doping concentration of is 2E16; an N-type indium phosphide upper waveguide is epitaxially grown on the quantum cascade gain region, with a doping concentration of 2E16; an N-type indium phosphide graded doping layer is epitaxially grown on the N-type indium phosphide upper waveguide, with a doping concentration gradually changing from 2E16 to 4E17; an InP high-doped contact layer is epitaxially grown on the N-type indium phosphide graded doping layer, with a doping concentration of 4E18; wherein, when growing the quantum barriers of the quantum cascade gain region, in the process of growing the indium aluminum arsenic material layer, the indium source is turned off for a preset time and then turned on again to produce an aluminum arsenide material layer in the indium aluminum arsenic material layer.

[0014] Optionally, the Group III source materials for preparing the short-wave quantum cascade laser include trimethylgallium, trimethylindium, and trimethylaluminum, the Group V source materials include arsine and phosphine, and the doping source material includes silane.

[0015] Optionally, the growth temperature of each layer of the short-wave quantum cascade laser structure is 600°C to 660°C; the molar flow rate ratio of the Group V source to the Group III source is 30 to 185; the growth rate is controlled between 0.2nm / s and 0.6nm / s; and the pause time after each layer is completed is 0 to 4s.

[0016] At least one of the above technical solutions adopted in the embodiments of the present disclosure can achieve the following beneficial effects:

[0017] (1) The design provided by the present invention reduces the difficulty of epitaxial growth of short-wave quantum cascade lasers and can improve the fault tolerance of material growth. Since the critical thickness of the epitaxial film is exponentially related to the strain of the material, the greater the mismatch of the material, the more stringent the requirements for the material growth conditions. Compared with the short-wave quantum cascade lasers of large strain (more than 1.5%) material systems, the present invention uses In2O3 with lower strain. 0.7 Ga 0.3 As、In 0.36 Al 0.64 As (approximately 1% strain) material system, the material growth window is wider, and the material defect density and interface roughness are reduced;

[0018] (2) The present invention can improve the internal quantum efficiency of short-wave quantum cascade lasers. A major factor limiting the performance of quantum cascade lasers is their low internal quantum efficiency. From the perspective of energy bands, parasitic upper energy levels are inevitably present in the active region. Electrons injected into the region in the previous cycle have a certain probability of transitioning to the parasitic energy level, causing carrier leakage. The introduction of AlAs intercalation can increase the energy gap ΔE between the parasitic energy level and the upper energy level by about 30 meV, thereby reducing the probability of carriers escaping to the parasitic energy level and improving the injection efficiency.

[0019] (3) The present invention is beneficial for improving the temperature characteristics of quantum cascade lasers. As the operating temperature of the laser increases, the probability of carriers in its active region thermally escaping across the conduction band steps to the continuous state increases, and the slope efficiency and threshold current density of the laser degrade accordingly, until it becomes inoperable. The introduction of the AlAs layer increases the height of the continuous state in the injection region, thereby reducing the probability of carrier thermal escape and increasing the operating temperature of the device, which is more promising in extreme operating environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] For a more complete understanding of the present disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0021] Figure 1 A schematic diagram of a short-wave quantum cascade laser structure provided by an embodiment of the present disclosure is shown schematically;

[0022] Figure 2 The diagram schematically shows a conduction band structure diagram within one cycle of a common short-wave quantum cascade laser under an external electric field of 100 kV / cm provided by an embodiment of the present disclosure;

[0023] Figure 3 Schematically shows a conduction band structure diagram within one cycle of a short-wave quantum cascade laser with an AlAs layer inserted under an external electric field of 100 kV / cm provided by an embodiment of the present disclosure;

[0024] Figure 4A high-resolution X-ray diffraction (XRD) characterization diagram of a short-wave quantum cascade laser structure epitaxial material provided by an embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0025] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0026] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of the features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0027] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0028] Figure 1 A schematic diagram of a short-wave quantum cascade laser structure provided by an embodiment of the present disclosure is schematically shown.

[0029] like Figure 1 As shown, an embodiment of the present disclosure provides a short-wave quantum cascade laser structure, including: an N-type indium phosphide (InP) substrate, on which an N-type InP buffer layer, an N-type InP lower waveguide, a quantum cascade gain region structure, an N-type InP upper waveguide, an N-type InP gradient doping layer and an N-type InP upper contact high doping layer are sequentially grown.

[0030] The quantum cascade gain region structure is an alternating structure of multi-periodic strain-compensated quantum wells and quantum barriers, which is lattice mismatched with the N-type InP substrate. The material of the quantum well is InGaAs (In x Ga y As z ), the quantum barrier is indium aluminum arsenide (In x Al y As z ), aluminum arsenide (AlAs) and indium aluminum arsenide materials are grown epitaxially in sequence.

[0031] Optionally, in the indium gallium arsenide material of the quantum well, the gallium component ranges from 0 to 0.47; in the indium aluminum arsenide material of the quantum barrier, the aluminum component ranges from 0.48 to 1.

[0032] Preferably, the material of the quantum well is In 0.7 Ga 0.3 As, the indium aluminum arsenide material of the quantum barrier is In 0.36 Al 0.64 As, 1% strain.

[0033] In this embodiment, the gain region structure as a whole adopts low strain In 0.7 Ga 0.3 As、In 0.36 Al 0.64 As (1% strain), and when growing the InAlAs barrier, the In source is turned off for a period of time and then turned on again to form an InAlAs-AlAs-InAlAs structure. This can reduce the overall stress distribution of the material, aiming to improve the success rate and fault tolerance of the short-wave quantum cascade structure growth while improving the device performance of the quantum cascade laser.

[0034] Optionally, the quantum cascade gain region includes 30 to 50 periods, each period includes 16 to 20 layers of the quantum wells and quantum barriers, the total number of layers ranges from 500 to 1000 layers, the thickness of a single layer of the quantum barrier is 0.5 to 4 nm, and the thickness of a single layer of the quantum well is 1 to 6 nm.

[0035] Figure 2 The diagram schematically shows the conduction band structure of a common short-wave quantum cascade laser within one cycle under an external electric field of 100 kV / cm provided by an embodiment of the present disclosure.

[0036] like Figure 2 Figure 2 shows a partial conduction band diagram of a conventional strain-compensated QCL structure with a design wavelength of approximately 4μm under an applied electric field of 100kV / cm. Each period in the quantum cascade gain region can be functionally divided into a light-emitting region and an extraction region (injection region). Electrons in the upper energy level E3 of the light-emitting region transition to the lower energy level E2 through radiation, emitting a photon. The lower-energy-level electrons then relax to the E1 energy level through longitudinal optical phonon scattering and are transported to the injection region of the next period through the microband formed in the extraction region, forming periodic cascade optical amplification. The E4 energy level, located above the E3 energy level, is the primary source of carrier leakage. On the one hand, electrons from the previous period have a certain probability of being injected into the E4 energy level, resulting in a reduction in injection efficiency. On the other hand, electrons in the E3 energy level have a certain probability of being thermally excited to the E4 energy level, resulting in a reduction in internal quantum efficiency.

[0037] Figure 3The conduction band structure diagram within one cycle of a short-wave quantum cascade laser with an inserted AlAs layer under an external electric field of 100 kV / cm provided by an embodiment of the present disclosure is schematically shown.

[0038] In this embodiment, the location and thickness of the AlAs intercalation layer need to be designed. This embodiment controls the thickness of the AlAs layer to two atomic monolayers and inserts the AlAs layer only in the injection region. This improves the material interface quality and reduces interface roughness scattering in the light-emitting region, thereby lowering the threshold current density.

[0039] contrast Figure 2 、 Figure 3 The introduction of the AlAs layer has little effect on the positions of the upper energy level E3, the lower energy level E2 and the extracted energy level E1, but it can significantly increase the interval between the parasitic energy levels E4 and E3 from 24meV to 55meV. The upper and lower energy level lifetimes in the AlAs (without AlAs) short-wave quantum cascade structure are calculated to be 4.1 (3.6) ps and 0.23 (0.4) ps, respectively, and the transition matrix element is 0.98 (0.47) nm, which theoretically greatly improves the internal quantum efficiency.

[0040] Another aspect of the present disclosure provides a preparation method for use in Figure 1 The short-wave quantum cascade laser structure shown includes operations S1 to S7.

[0041] S1, in a PH3 environment, the N-type indium phosphide substrate is subjected to high-temperature deoxidation.

[0042] S2, growing an N-type indium phosphide buffer layer on an N-type indium phosphide substrate, with a doping concentration of 2E17.

[0043] S3, epitaxially growing an N-type indium phosphide lower waveguide on the N-type indium phosphide buffer layer, with a doping concentration of 2E16.

[0044] S4, epitaxially grows multiple periods of alternating quantum wells and quantum barriers on the N-type indium phosphide lower waveguide to form a quantum cascade gain region with an average doping concentration of 2E16.

[0045] When growing the quantum barriers of the quantum cascade gain region, during the process of growing the indium aluminum arsenide material layer, the indium source is turned off for a preset time and then turned on again to produce an aluminum arsenide material layer in the indium aluminum arsenide material layer.

[0046] S5, epitaxially growing an N-type indium phosphide upper waveguide on the quantum cascade gain region with a doping concentration of 2E16.

[0047] S6, epitaxially growing an N-type indium phosphide graded doping layer on the N-type indium phosphide upper waveguide, with the doping concentration gradually changing from 2E16 to 4E17.

[0048] S7, epitaxially growing an InP high-doped contact layer on the N-type indium phosphide graded doping layer, with a doping concentration of 4E18.

[0049] Among them, the III-group source materials for preparing short-wave quantum cascade lasers include trimethylgallium (TMGa), trimethylindium (TMIn), and trimethylaluminum (TMAl); the V-group source materials include arsine (AsH3) and phosphine (PH3); and the doping source material includes silane (SiH4, diluted to 200 ppm in H2).

[0050] Optionally, the growth temperature of each layer of the short-wave quantum cascade laser structure is 600°C to 660°C; the molar flow rate ratio of the Group V source to the Group III source is 30 to 185; the growth rate is controlled between 0.2nm / s and 0.6nm / s; and the pause time after each layer is completed is 0 to 4s.

[0051] The following is a specific embodiment of preparing a short-wave quantum cascade laser structure. The epitaxial growth process from bottom to top includes:

[0052] The first step is to use metal organic chemical vapor deposition technology to deoxidize the InP substrate at high temperature in a PH3 environment;

[0053] In the second step, a Si-doped InP buffer layer was grown on an N-type InP substrate using metal organic chemical vapor deposition technology. The thickness of the layer was 400 nm and the doping concentration was 2E17.

[0054] In the third step, a 3μm thick InP lower waveguide layer with a doping concentration of 2E16 is epitaxially grown on the buffer layer using metal organic chemical vapor deposition technology;

[0055] In the fourth step, a quantum cascade gain region with a total thickness of 1.7 μm and a total of 40 periods was epitaxially grown on the InP lower waveguide layer using metal organic chemical vapor deposition technology, with an average doping concentration of 2E16.

[0056] In the fifth step, a 3μm thick InP upper waveguide layer with a doping concentration of 2E16 is epitaxially grown on the gain region using metal organic chemical vapor deposition technology;

[0057] In the sixth step, a 600nm thick InP graded doping layer is epitaxially grown on the InP upper waveguide layer using metal organic chemical vapor deposition technology, with the doping concentration gradually changing from 2E16 to 4E17.

[0058] In the seventh step, a 400nm thick InP high-doped contact layer with a doping concentration of 4E18 is epitaxially grown on the InP graded doping layer using metal organic chemical vapor deposition technology.

[0059] The specific conditions of the metal organic chemical vapor deposition method used include:

[0060] The equipment used was Aixtron CCS 3x2” MOCVD equipment;

[0061] On InP N-type highly doped substrate (2×10 18 cm -3 ) to grow 1% strained AlAs-QCLs using trimethylgallium (TMGa), trimethylindium (TMIn), and trimethylaluminum (TMAl) as Group III sources, arsine (AsH3) and phosphine (PH3) as Group V sources, and silane (SiH4) as a dopant source (diluted to 200 ppm in H2). Typical growth parameters are within the following ranges: all materials are grown in a low-pressure environment of 100 mbar, using H2 as the carrier gas, and other impurities are filtered through a palladium tube and purifier. The total flow rate is set at approximately 8000 sccm; the growth temperature range is 600°C to 660°C; the molar flow ratio of Group V to Group III is 30 to 185; the growth rate is controlled between 0.2 nm / s and 0.6 nm / s; and the dwell time for each layer is 0 to 4 s.

[0062] It's important to note that the QCL active region consists of 500-1000 layers of InGaAs wells and InAlAs barrier layers, with thicknesses ranging from 0.5-6nm. Due to the high MOCVD growth temperature and difficulty controlling the interface, strain compensation in the material must be as precise as possible, meaning the thickness and alloy composition must be precisely controlled to the highest possible level. The material grown according to this design exhibits exceptional quality. Furthermore, the insertion of the AlAs layer increases the spacing between the upper energy level and the parasitic energy level of the upper energy level, thereby improving injection efficiency and ultimately boosting the device's electro-optical conversion efficiency.

[0063] Figure 4 A high-resolution X-ray diffraction (XRD) characterization diagram of a short-wave quantum cascade laser structure epitaxial material provided by an embodiment of the present disclosure is schematically shown.

[0064] like Figure 4 As shown in the figure, the characterization parameters used were: Omega-2Theta scanning, a 3° scanning range, a 0.001° step size, and a single step time of 0.4 seconds. Multiple distinct and steep satellite peaks can be observed in the figure, with a half-width at half maximum of only 15 to 20 arc seconds. Multiple satellite diffraction peaks are an important criterion for evaluating high-quality heterojunctions. This demonstrates that despite the presence of thousands of strain-mismatched layers of InGaAs and InAlAs, the material still possesses a smooth interface and good in-plane uniformity in layer thickness and composition.

[0065] It should be noted that the implementation case shown above is not limited to 4μm wavelength. By inserting an AlAs layer based on the use of 1% strain compensation, the wavelength can be further extended to shorter wavelengths. This greatly reduces the difficulty of material growth and is conducive to obtaining high-quality epitaxial materials. At the same time, in theory, performance comparable to that of a single-component large-strain QCL can be achieved.

[0066] The short-wave quantum cascade laser structure provided by the embodiment of the present disclosure reduces the difficulty of epitaxial growth of short-wave quantum cascade lasers and can improve the fault tolerance of material growth. Since the critical thickness of the epitaxial film is exponentially related to the strain of the material, the greater the mismatch of the material, the more stringent the conditions for material growth. Compared with the short-wave quantum cascade laser of the large strain (above 1.5%) material system, the embodiment of the present disclosure adopts the lower strain In 0.7 Ga 0.3 As、In 0.36 Al 0.64 As (approximately 1% strain) material system, the material growth window is wider, and the material defect density and interface roughness are reduced.

[0067] The short-wave quantum cascade laser structure provided by the disclosed embodiments can improve the internal quantum efficiency of short-wave quantum cascade lasers. A major factor limiting the performance of quantum cascade lasers is their low internal quantum efficiency. From the perspective of energy bands, parasitic upper energy levels are unavoidable in the active region. Electrons injected into the region in the previous cycle have a certain probability of transitioning to the parasitic energy level, causing carrier leakage. Introducing an AlAs intercalation layer can increase the energy gap ΔE between the parasitic energy level and the upper energy level by approximately 30 meV, thereby reducing the probability of carriers escaping to the parasitic energy level and improving injection efficiency.

[0068] The short-wavelength quantum cascade laser structure provided by the disclosed embodiments is beneficial for improving the temperature characteristics of quantum cascade lasers. As the operating temperature of the laser increases, the probability of carriers within its active region thermally escaping across the conduction band steps to the continuous state increases, causing the laser's slope efficiency and threshold current density to degrade, ultimately rendering it inoperable. The introduction of the AlAs layer increases the height of the continuous state in the injection region, thereby reducing the probability of carrier thermal escape and increasing the device's operating temperature, making it more promising in extreme operating environments.

[0069] Those skilled in the art will appreciate that the features described in the various embodiments and / or claims of this disclosure may be combined and / or coupled in various ways, even if such combinations and / or couplings are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure may be combined and / or coupled in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or couplings are intended to fall within the scope of this disclosure.

[0070] Although the present disclosure has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made to the present disclosure without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Therefore, the scope of the present disclosure should not be limited to the above-described embodiments, but should be determined not only by the appended claims but also by the equivalents of the appended claims.

Claims

1. A short-wave quantum cascade laser structure, characterized in that: include: An N-type indium phosphide substrate, on which an N-type indium phosphide buffer layer, an N-type indium phosphide lower waveguide, a quantum cascade gain region structure, an N-type indium phosphide upper waveguide, an N-type indium phosphide graded doping layer, and an N-type indium phosphide upper contact high-doping layer are sequentially grown; The quantum cascade gain region structure is an alternating structure of multi-periodic strain-compensated quantum wells and quantum barriers, which is lattice mismatched with the N-type indium phosphide substrate; The material of the quantum well is indium gallium arsenide, and the quantum barrier is epitaxially grown in sequence using indium aluminum arsenide, aluminum arsenide, and indium aluminum arsenide materials. The material of the quantum well is In 0.7 Ga 0.3 As, the indium aluminum arsenide material of the quantum barrier is In 0.36 Al 0.64 As; The strain of the quantum cascade gain region is 1%; The thickness of the aluminum arsenide in the quantum barrier is two atomic monolayers, and the aluminum arsenide layer is inserted only in the injection region; The thickness of a single layer of the quantum barrier is 0.5-4 nm, and the thickness of a single layer of the quantum well is 1-6 nm.

2. The short-wave quantum cascade laser structure according to claim 1, characterized in that: The quantum cascade gain region includes 30 to 50 periods, each period includes 16 to 20 layers of the quantum wells and quantum barriers, and the total number of layers ranges from 500 to 1000 layers.

3. A preparation method, applied to the short-wave quantum cascade laser structure according to any one of claims 1 to 2, characterized in that: include: In a PH3 environment, the N-type indium phosphide substrate is subjected to high-temperature deoxidation; Growing an N-type indium phosphide buffer layer on the N-type indium phosphide substrate, with a doping concentration of 2E17; Epitaxially growing an N-type indium phosphide lower waveguide on the N-type indium phosphide buffer layer, with a doping concentration of 2E16; Epitaxially growing a plurality of periods of alternating quantum wells and quantum barriers on the N-type indium phosphide lower waveguide to form a quantum cascade gain region with an average doping concentration of 2E16; Epitaxially growing an N-type indium phosphide upper waveguide on the quantum cascade gain region, with a doping concentration of 2E16; Epitaxially growing an N-type indium phosphide graded doping layer on the N-type indium phosphide upper waveguide, with the doping concentration gradually changing from 2E16 to 4E17; Epitaxially growing an InP high-doped contact layer on the N-type indium phosphide graded doping layer, with a doping concentration of 4E18; When growing the quantum barriers of the quantum cascade gain region, during the process of growing the indium aluminum arsenide material layer, the indium source is turned off for a preset time and then turned on again to produce an aluminum arsenide material layer in the indium aluminum arsenide material layer.

4. The preparation method according to claim 3, characterized in that The III-group source materials for preparing the short-wave quantum cascade laser include trimethyl gallium, trimethyl indium, and trimethyl aluminum; the V-group source materials include arsine and phosphine; and the doping source material includes silane.

5. The preparation method according to claim 4, characterized in that The growth temperature of each layer in the short-wave quantum cascade laser structure is 600°C to 660°C; the molar flow rate ratio of the Group V source to the Group III source is 30 to 185; the growth rate is controlled between 0.2 nm / s and 0.6 nm / s; and the pause time after each layer is completed is 0 to 4 seconds.

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