Superlattice infrared detector and method of manufacture
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LASER RES INST OF SHANDONG ACAD OF SCI
- Filing Date
- 2026-03-18
- Publication Date
- 2026-06-16
Smart Images
Figure CN122227685A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of gas detection technology, and in particular to a superlattice infrared detector and its fabrication method. Background Technology
[0002] Infrared detection technology has wide applications in environmental monitoring, industrial security, and medical diagnosis, among which gas detection in the mid-infrared band (3-5μm) is particularly important. InAs / GaSb superlattice materials have become an ideal choice for detectors in this band due to their tunable band structure, high absorption coefficient, and excellent low-temperature performance.
[0003] However, traditional InAs / GaSb superlattice infrared detectors suffer from significant technical bottlenecks. A lattice mismatch exists between the GaSb substrate and the InAs / GaSb superlattice functional layer, and this difference in lattice constant leads to a large number of dislocation defects at the interface. Current technologies typically employ a single GaSb buffer layer to mitigate this problem, but its strain relief effect is limited, resulting in a still high dislocation density at the interface between the substrate and the buffer layer. This not only significantly increases the device's dark current and reduces its responsivity but also affects the detector's low-temperature operational stability.
[0004] More seriously, high dislocation density can also lead to a decrease in the accuracy of detection wavelength modulation. In applications such as trace gas detection, even a tiny deviation in the detection wavelength (even 0.1 nm) can cause a significant decrease in detection sensitivity. Summary of the Invention
[0005] This application provides a superlattice infrared detector and its fabrication method to solve the problems of high dislocation density, large dark current, and poor low-temperature stability of existing detectors using a single buffer layer.
[0006] In a first aspect, this application provides a superlattice infrared detector, comprising: Substrate; A gradient composition buffer layer grown on the surface of a substrate; Superlattice functional layer grown on the surface of gradient composition buffer layer; Electrode contact layer grown on the surface of the superlattice functional layer; The gradient composition buffer layer includes a first component, the proportion of which gradually increases from zero to a preset proportion along the growth direction of the gradient composition buffer layer; the preset proportion of which is not higher than 20%; the first component is a component not included in the substrate and is a component included in the superlattice functional layer.
[0007] The aforementioned superlattice infrared detector, by setting a gradient composition buffer layer on the substrate with the composition percentage gradually increasing from zero to a preset value along the growth direction, can achieve a gradual transition of the lattice constant, thereby effectively releasing the lattice mismatch stress between the substrate and the functional layer and significantly reducing the interface dislocation density. The superlattice infrared detector using the embodiments of this application can significantly reduce dark current, improve responsivity, and enhance the detector's operational stability and wavelength modulation accuracy in low-temperature environments, fundamentally improving detection performance.
[0008] In one possible implementation of the first aspect, the substrate is a GaSb material; The gradient component buffer layer is made of GaInSb material; the first component is In.
[0009] The aforementioned superlattice infrared detector, by gradually introducing In composition on the GaSb substrate, forms a lattice constant gradient change that matches the superlattice functional layer, which can specifically alleviate the lattice mismatch problem between GaSb and InAs / GaSb superlattices, and improve strain release efficiency and the consistency of overall device performance.
[0010] In one possible implementation of the first aspect, the superlattice functional layer includes a P-type superlattice layer, an intrinsic superlattice absorption layer, and an N-type superlattice layer stacked sequentially from bottom to top.
[0011] The aforementioned superlattice infrared detector, by further refining the superlattice functional layer into a structure of P-type superlattice layer, intrinsic superlattice absorption layer and N-type superlattice layer, can form a complete PN junction photodiode structure based on the crystal quality optimized by the gradient buffer layer. This helps to achieve efficient carrier separation and collection, enhances the detection efficiency of photogenerated signals, and maintains a low dark current, making it suitable for high-performance mid-infrared detection applications.
[0012] In one possible implementation of the first aspect, the p-type superlattice layer comprises a superlattice structure consisting of a first material and a GaSb material arranged in a periodic pattern; the first material is p-type doped InAs(Be). The intrinsic superlattice absorption layer consists of a superlattice structure composed of InAs and GaSb materials arranged in a periodic manner. The N-type superlattice layer comprises a superlattice structure consisting of a second material and GaSb material arranged in a periodic pattern; the second material is N-type doped InAs(Si).
[0013] The aforementioned superlattice infrared detector, through precise doping and material combination, not only ensures the low-defect crystal quality advantage brought by the gradient buffer layer, but also optimizes the superlattice band structure and carrier transport characteristics, thereby improving the detectivity, response speed and wavelength selectivity, which is especially beneficial for the precise wavelength matching of trace gas detection.
[0014] In one possible implementation of the first aspect, the thickness of the gradient component buffer layer is 1.5~2μm.
[0015] The aforementioned superlattice infrared detector, by limiting the thickness of the gradient composition buffer layer, can ensure sufficient strain release while avoiding the accumulation of crystal defects or increased process costs caused by excessive thickness. It balances device performance and fabrication feasibility based on optimized lattice matching, ensuring that the detector has low dark current, high responsivity and good process controllability.
[0016] In one possible implementation of the first aspect, the periodic thickness of the intrinsic superlattice absorption layer is 500-1000 nm, and the thickness of the superlattice periodic unit is 30-80 Å.
[0017] The aforementioned superlattice infrared detector, by limiting the periodic thickness of the intrinsic superlattice absorption layer and the thickness of the periodic unit, can further improve the light absorption efficiency and wavelength accuracy under the crystal quality conditions optimized by the gradient buffer layer, thereby achieving higher quantum efficiency and detection sensitivity, and is especially suitable for application scenarios with extremely high requirements for detection wavelength accuracy.
[0018] In one possible implementation of the first aspect, the thickness of the P-type superlattice layer is 300-500 nm, and the thickness of the superlattice periodic unit is 30-60 Å; the thickness of the N-type superlattice layer is 300-500 nm, and the thickness of the superlattice periodic unit is 30-60 Å.
[0019] The aforementioned superlattice infrared detector, by limiting the thickness of the P-type and N-type superlattice layers and the thickness of the periodic cells, can maintain low dark current and high responsivity while ensuring a balance between carrier injection and collection, optimizing the device's electrical performance, achieving stable PN junction characteristics on the basis of high-quality crystals, and improving the reliability and detection consistency of the device during long-term operation.
[0020] Secondly, embodiments of this application provide a method for fabricating a superlattice infrared detector, used to fabricate the superlattice infrared detector of the first aspect, comprising: The pretreated substrate is placed in the growth chamber; the pretreatment includes surface cleaning and deoxidation. A superlattice infrared detector is obtained by sequentially growing a gradient composition buffer layer, a superlattice functional layer, and an electrode contact layer on the substrate surface. The gradient composition buffer layer includes a first component, the proportion of which gradually increases from zero to a preset proportion along the growth direction of the gradient composition buffer layer. The first component is a component not included in the substrate and is included in the superlattice functional layer.
[0021] The aforementioned method for fabricating a superlattice infrared detector involves pre-treating a substrate and sequentially growing a gradient composition buffer layer, a superlattice functional layer, and an electrode contact layer on it. The gradient composition buffer layer uses a first composition that gradually increases from zero to a predetermined percentage, enabling a continuous transition of the lattice constant during fabrication and reducing dislocation defects. This technique ensures high-quality device structure and stable performance at the process level, while also demonstrating repeatability and feasibility for industrial production.
[0022] In one possible implementation of the second aspect, the substrate is GaSb material; the gradient composition buffer layer is GaInSb material; and the first composition is In composition. A gradient composition buffer layer grown on the substrate surface includes: As the In composition increases, a gradient composition buffer layer is grown on the substrate surface under the conditions of linearly increasing In source furnace temperature in the range of 970~990℃, linearly decreasing Ga source furnace temperature in the range of 1020~1030℃, and constant Sb source furnace temperature.
[0023] The above-mentioned method for fabricating superlattice infrared detectors achieves atomic-level gradient composition distribution by precisely controlling the source furnace temperature and growth conditions, thereby maximizing strain release effect, reducing defects, and improving the controllability of crystal quality and device performance.
[0024] In one possible implementation of the second aspect, a gradient composition buffer layer is grown on the substrate surface, comprising: During the growth of the gradient composition buffer layer on the substrate surface, RHEED oscillation calibration is used to ensure atomic-level flatness.
[0025] The above-mentioned method for fabricating superlattice infrared detectors avoids introducing additional defects due to interface fluctuations by real-time monitoring of the smoothness and composition uniformity of thin film growth, thereby further improving the consistency of detector performance and yield in the fabrication process.
[0026] It is understood that other beneficial effects that the technical solution of the second aspect provided above can achieve can be referred to the beneficial effects of the first aspect and any of its optional implementation methods, and will not be repeated here.
[0027] As can be seen from the above technical solution, the superlattice infrared detector and its fabrication method provided in this application, by setting a buffer layer with a gradual composition gradient between the substrate and the superlattice functional layer, can more fully release the substrate strain, effectively eliminate the influence of the substrate on the superlattice functional layer, and improve the detector's detection sensitivity and operational stability. Simultaneously, it achieves the synergy of gradual lattice strain release and infrared anti-reflection protection, effectively reducing interface dislocation density and surface reflectivity, making it suitable for high-sensitivity detection of trace gases such as CH4. Attached Figure Description
[0028] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0029] Figure 1 A schematic diagram of the hierarchical structure of the superlattice infrared detector provided in the embodiments of this application; Figure 2 This is a schematic diagram of the hierarchical structure of the superlattice functional layer in the superlattice infrared detector provided in the embodiments of this application; Figure 3 A flowchart illustrating the fabrication method of the superlattice detector provided in this application embodiment.
[0030] Wherein, 1-substrate; 2-gradient composition buffer layer; 3-superlattice functional layer; 4-electrode contact layer; 31-P-type superlattice layer; 32-Intrinsic superlattice absorption layer; 33-N-type superlattice layer. Detailed Implementation
[0031] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of this application.
[0032] In the description of this application, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.
[0033] Furthermore, in this application, directional terms such as "upper" and "lower" are defined relative to the orientation of the components shown in the accompanying drawings. It should be understood that these directional terms are relative concepts, used for relative description and clarification, and can change accordingly depending on the orientation of the components in the accompanying drawings.
[0034] To facilitate understanding of the plan, the following explanations are provided for relevant terms: Superlattice infrared detectors are high-performance infrared photoelectric detection devices based on artificial quantum structures. Their core structure consists of periodic multilayer stacks formed by alternating growth of two or more semiconductor materials with atomic-level precision. Through band structure engineering, they achieve precise detection of specific infrared bands. Taking InAs / GaSb superlattices as an example, their unique type-II band alignment characteristics allow electrons and holes to be spatially separated, effectively reducing Auger recombination noise. They also possess advantages such as tunable band structure, high quantum efficiency, and high operating temperature.
[0035] Lattice mismatch refers to the stress accumulation phenomenon caused by the difference in lattice constants between the substrate and the epitaxial layer during heteroepitaxial growth. When the lattice constants of the two semiconductor materials are inconsistent (such as lattice mismatch between a GaSb substrate and an InAs / GaSb superlattice), dislocation defects and stress fields will be generated at the interface, severely affecting device performance. This mismatch leads to an increase in interface dislocation density, increases dark current, and reduces carrier lifetime, which is a key factor restricting the improvement of infrared detector performance.
[0036] Because existing InAs / GaSb superlattice infrared detectors typically involve directly growing a superlattice functional layer on a GaSb substrate or placing a single-component GaSb buffer layer between the substrate and the functional layer, these approaches cannot completely solve the lattice mismatch problem caused by differences in lattice constants, resulting in lower performance of existing superlattice infrared detectors. Furthermore, in existing solutions, the trade-off between dark current and detection wavelength accuracy is difficult to balance, failing to simultaneously meet the requirements for high sensitivity and high accuracy, thus limiting the application of these detectors in trace gas detection scenarios.
[0037] To address the aforementioned issues, this application provides an InAs / GaSb superlattice technology solution assisted by a gradient strain buffer layer. In this solution, the In composition of the gradient GaInSb buffer layer gradually increases along the thickness direction, which can gradually release the lattice strain, reduce the interface dislocation density, and achieve more accurate detection wavelength detector growth.
[0038] See Figure 1 This is a schematic diagram of the hierarchical structure of the superlattice infrared detector provided in the embodiments of this application.
[0039] Depend on Figure 1 As shown, the superlattice infrared detector provided in this application embodiment may include a substrate 1, a gradient composition buffer layer 2, a superlattice functional layer 3, and an electrode contact layer 4 stacked from bottom to top. The gradient composition buffer layer 2 includes a first component, the proportion of which gradually increases from zero to a preset proportion along the growth direction of the gradient composition buffer layer 2; the first component is a component not included in the substrate 1 and is included in the superlattice functional layer 3.
[0040] In some embodiments, the gradient component buffer layer 2, the superlattice functional layer 3, and the electrode contact layer 4 can be grown sequentially from bottom to top on the substrate 1 using molecular beam epitaxy to form a complete superlattice infrared detector.
[0041] In some embodiments, substrate 1 can be GaSb material; as the basic support layer of the entire detector structure, GaSb substrate can be selected as (100) crystal orientation semi-insulating GaSb material, wherein (100) crystal orientation has the best epitaxial growth characteristics, which can ensure the high-quality growth of subsequent epitaxial layers; the semi-insulating characteristics can effectively suppress the negative impact of the substrate on device performance and reduce the generation of leakage current.
[0042] In some embodiments, when the substrate 1 is GaSb material and the superlattice functional layer 3 is an InAs / GaSb superlattice functional layer, there is a lattice mismatch between the GaSb substrate and the InAs / GaSb superlattice functional layer. To solve this problem, in this embodiment, a gradient composition buffer layer 2 is first grown on the substrate 1, and then the superlattice functional layer 3 is grown on the surface of the gradient composition buffer layer 2. The lattice strain can be gradually released based on the gradient composition buffer layer 2, avoiding problems such as large dark current caused by lattice mismatch.
[0043] In some embodiments, the gradient composition buffer layer 2 can be GaInSb material; the first component is In component, that is, along the growth direction (thickness direction) of the gradient composition buffer layer 2, the content (component ratio) of In component gradually changes from 0 to a preset value (e.g., any value within a range not exceeding 20%). This gradual design achieves a smooth transition of the lattice constant and effectively alleviates the lattice mismatch between the substrate and the functional layer.
[0044] In the strain release mechanism of the gradient component buffer layer 2, the component gradient reduces the gradient of lattice constant change, thus avoiding sudden strain release; secondly, the dislocations generated during the gradient process can be redistributed and annihilated within the buffer layer, reducing propagation to the functional layer; finally, an appropriate gradient rate can ensure the sufficiency and uniformity of strain release.
[0045] In some embodiments, the thickness of the gradient component buffer layer 2 can be 1.5~2μm, which can ensure a small gradient rate and a high strain release effect within a limited preparation time and cost.
[0046] As can be seen from the above technical solutions, the superlattice infrared detector provided in this application embodiment can more fully release the strain of the substrate by setting a buffer layer with a gradient composition gradient between the substrate and the superlattice functional layer, completely eliminate the influence of the substrate on the superlattice functional layer, and improve the detection sensitivity and working stability of the detector.
[0047] See Figure 2 This is a schematic diagram of the hierarchical structure of the superlattice functional layer in the superlattice infrared detector provided in the embodiments of this application.
[0048] In some embodiments, such as Figure 2 As shown, the superlattice functional layer 3 may include a P-type superlattice layer 31, an intrinsic superlattice absorption layer 32, and an N-type superlattice layer 33 stacked sequentially from bottom to top.
[0049] Specifically, the P-type superlattice layer 31 may include a superlattice structure composed of a first material and a GaSb material arranged in a periodic manner; the first material is P-type doped InAs(Be).
[0050] In this embodiment, the p-type InAs(Be) / GaSb superlattice layer is located at the bottom of the superlattice functional layer 3 and is directly grown on the upper surface of the gradient composition buffer layer 2. This layer can use Be as the p-type dopant, with the doping concentration controlled at 5 × 10⁻⁶. 17 ~1×10 18 cm -3 The choice of Be dopant is based on its high solid solubility and low diffusion coefficient, which ensures precise control and stability of doping. The thickness of the superlattice periodic unit is designed to be 30-60 Å, with the InAs layer thickness being 15-25 Å and the GaSb layer thickness being 15-35 Å. This periodic structure can achieve type-II band alignment, which is beneficial for carrier separation and transport.
[0051] In some embodiments, the total thickness of the p-type superlattice layer 31 can be 300-500 nm. This thickness range ensures sufficient hole injection efficiency while avoiding an increase in series resistance due to excessive thickness. During material growth, the As / Sb beam current ratio and growth temperature need to be precisely controlled to ensure interface quality and cycle consistency.
[0052] In some embodiments, the intrinsic superlattice absorber layer 32 may include a superlattice structure composed of InAs and GaSb materials arranged in a periodic manner.
[0053] In this embodiment, the intrinsic superlattice absorption layer 32 is a key functional region of the detector, responsible for the absorption of infrared photons and the generation of charge carriers. The design of this layer fully considers optimized absorption in the mid-infrared band, allowing its periodic thickness to be controlled within 500-1000 nm and the thickness of the superlattice periodic units to be 30-80 Å. By adjusting the thickness ratio of the InAs and GaSb layers, the cutoff wavelength of the detector can be precisely controlled, enabling it to cover the 3-5 μm mid-infrared band.
[0054] Specifically, the design of the superlattice period of the intrinsic superlattice absorber layer 32 is based on quantum mechanical principles, achieving optimal optical performance through band engineering. The thicknesses of the InAs and GaSb layers in each periodic unit are precisely calculated to ensure good wavefunction overlap and high optical matrix elements. In some embodiments, when the InAs layer thickness is 20-40 Å and the GaSb layer thickness is 25-45 Å, the detector can have a high absorption coefficient in the target wavelength band.
[0055] In some embodiments, the N-type superlattice layer 33 may include a superlattice structure composed of a second material and a GaSb material arranged in a periodic manner; the second material is N-type doped InAs(Si).
[0056] In this embodiment, the N-type InAs(Si) / GaSb superlattice layer is located on top of the superlattice functional layer 3. Si is used as the N-type dopant, and the doping concentration can be comparable to that of the P-type layer, for example, 5 × 10⁻⁶. 17 ~1×10 18 cm -3 The choice of Si dopant is based on its excellent electrical properties and stability. The superlattice periodic design of this layer is consistent with that of the p-type layer, ensuring bandgap matching throughout the functional region.
[0057] In some embodiments, the thickness of the superlattice periodic unit of the N-type superlattice layer is preferably 30-60 Å, which is beneficial for the separation and transport of charge carriers.
[0058] In some embodiments, the total thickness of the N-type superlattice layer 33 can be 300-500 nm, ensuring a balance between electron injection efficiency and hole injection efficiency. During growth, special attention needs to be paid to interface quality control to avoid increased interface roughness due to temperature changes or beam fluctuations.
[0059] In some embodiments, the electrode contact layer 4 may be made of highly doped GaSb(Si) material with a doping concentration greater than 5 × 10⁻⁶. 18 cm -3 The thickness is 200-300 nm. This design is based on the formation mechanism of ohmic contacts; high doping concentration can effectively reduce contact resistance and improve the response speed of the device. At the same time, appropriate thickness can ensure mechanical stability and process compatibility.
[0060] In this embodiment, the selection of electrode materials takes into account band matching and process feasibility. GaSb exhibits good band continuity with the N-type superlattice layer, enabling the formation of high-quality ohmic contacts. In subsequent processes, contact characteristics can be further optimized through treatments such as annealing.
[0061] See Figure 3This application also provides a method for fabricating the superlattice detector provided in any of the foregoing embodiments, by... Figure 3 As shown, the methods may include: S100: Place the pretreated substrate into the growth chamber; the pretreatment includes surface cleaning and deoxidation.
[0062] Specifically, before placing the substrate into the growth chamber, two basic operations can be performed on the substrate: surface cleaning and deoxidation, to ensure high epitaxial quality in subsequent operations.
[0063] Taking the InAs / GaSb superlattice infrared gas detector provided in this embodiment as an example, the surface cleaning process may include: The GaSb substrate undergoes surface cleaning, specifically ultrasonic cleaning (e.g., alternating ultrasonic cleaning with acetone and ethanol to remove organic contaminants; followed by rinsing with deionized water to remove residual ions). After cleaning, it is dried with high-purity N2 and then placed into the MBE (Molecular Beam Epitaxy) sample chamber. The entire surface cleaning process should be carried out in an ultra-clean environment to avoid secondary contamination.
[0064] After surface cleaning, deoxidation can be performed. For example, the GaSb substrate can be transferred to the growth chamber after the sample injection chamber is evacuated, and deoxidation can be performed on the substrate at a temperature of 520~540℃ for 15 minutes. Under these process conditions, the oxidation removal can be ensured to be thorough, while avoiding the decomposition of the substrate surface due to excessive temperature.
[0065] S200: A superlattice infrared detector is obtained by sequentially growing a gradient composition buffer layer, a superlattice functional layer and an electrode contact layer on the substrate surface; the gradient composition buffer layer includes a first component, the proportion of the first component gradually increases from zero to a preset proportion along the growth direction of the gradient composition buffer layer; the first component is a component not included in the substrate and is a component included in the superlattice functional layer.
[0066] In some embodiments, when a gradient composition buffer layer, a superlattice functional layer and an electrode contact layer are sequentially grown on the substrate surface, the following specific operation steps can be used to achieve this. It should be understood that the materials and process parameters listed in the implementation methods described in the embodiments of this application are only examples. In actual applications, the materials and process parameters involved can be reasonably replaced based on different needs, and no limitation is imposed here.
[0067] During the growth of the gradient composition buffer layer, the In source baffle, Ga source baffle, and Sb source baffle can be opened. Based on the growth of the gradient composition GaInSb buffer layer on the GaSb substrate surface, the In source furnace temperature increases linearly with increasing In composition, while the Ga source furnace temperature decreases linearly. Specifically, the Ga source furnace temperature range can be 1020~1030℃; the In source furnace temperature range can be 970~990℃; and the Sb source furnace temperature remains constant. In some embodiments, precise composition gradients can be achieved through a computer-controlled temperature program based on the correlation between source furnace temperature and beam current intensity.
[0068] In some embodiments, the growth process of the gradient component buffer layer can be based on RHEED (Reflection High Energy Electron Diffraction) oscillation calibration to ensure atomic-level flatness.
[0069] Since a complete oscillation cycle corresponds to the growth of a monolayer (ML) of the surface atomic layer, the growth rate can be accurately calculated by measuring the period of the oscillation curve. Using RHEED oscillation ensures a stable growth rate. For example, by monitoring the RHEED oscillation period, the stability of the In and Ga source beams can be determined, preventing abrupt compositional changes. If the oscillation period drifts, it indicates a change in the source furnace temperature or beam current, allowing for timely adjustments. Furthermore, during gradient growth, an increase in In composition means a gradual change in the surface lattice constant. Correspondingly, the spacing and intensity of the RHEED diffraction pattern change with the lattice. By observing the pattern evolution in real time, it can be confirmed that the In composition increases according to a preset curve, rather than a step change. In some embodiments, by integrating the area under the RHEED oscillation curve, the thickness of the grown film can be accurately calculated, ensuring that the buffer layer thickness falls within the range of 1.5~2 μm and is synchronized with the gradient change in In composition.
[0070] In some embodiments, during the growth of the superlattice functional layer, a P-type InAs / GaSb superlattice layer, an intrinsic InAs / GaSb superlattice layer, and an N-type InAs / GaSb superlattice layer can be sequentially grown on the surface of the gradient composition buffer layer. The specific process can be as follows: P-type InAs / GaSb superlattice layer growth steps: Open the Be source baffle and the As source baffle, and grow a P-type InAs / GaSb superlattice layer on the surface of the gradient composition GaInSb buffer layer. As source furnace temperature: 1050℃, Be source furnace temperature: 870℃, doping concentration: 5×10⁻⁶ 17 ~1×10 18 cm -3 about.
[0071] Intrinsic InAs / GaSb superlattice layer growth steps: Turn off the Be source baffle and grow an intrinsic InAs / GaSb superlattice layer on the P-type InAs / GaSb superlattice layer.
[0072] N-type InAs / GaSb superlattice layer growth steps: Open the Si source baffle and grow an N-type InAs / GaSb superlattice layer on the intrinsic InAs / GaSb superlattice layer. Si source furnace temperature: 1220~1230℃; substrate temperature: 430℃; doping concentration: 5×10⁻⁶. 17 ~1×10 18 cm -3 about.
[0073] Next, the highly doped N-type GaSb electrode contact layer growth step can be performed: The In source baffle and As source baffle are turned off, and a highly doped N-type GaSb electrode contact layer with a thickness of 250 nm is grown on the N-type InAs / GaSb superlattice layer. The substrate temperature is raised to 460℃, the Si source furnace temperature is 1250~1260℃, and the doping concentration is >5×10⁻⁶. 18 cm -3 .
[0074] Finally, the Ga source baffle and Si source baffle can be turned off, leaving only Sb protection, and the temperature can be lowered to 300°C. Then, the Sb source can be turned off, the growth chamber can be cooled to room temperature, and the prepared superlattice detector (epitaxy wafer) can be taken out.
[0075] It should be understood that, in order to enable the superlattice detector in the embodiments of this application to adapt to gas detection of other different wavelengths, superlattice functional layers can also be grown using superlattice structures of other period thicknesses. The embodiments of this application do not impose specific limitations.
[0076] As can be seen from the above embodiments, the InAs / GaSb superlattice infrared gas detector prepared by the above method with a gradient strain buffer layer as an auxiliary achieves the synergy of gradual release of lattice strain and infrared light anti-reflection protection, effectively reducing the interface dislocation density and surface reflectivity, improving the detector's detection sensitivity and working stability, and is suitable for high-sensitivity detection of trace gases such as CH4, thereby improving the detector's applicability and detection stability.
[0077] The technical effects of the methods and apparatus provided in this application can be found in the descriptions of any of the foregoing system embodiments, and will not be repeated here.
[0078] The above specific embodiments further illustrate the purpose, technical solution and beneficial effects of this application. It should be understood that the above are only specific embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solution of this application should be included within the scope of protection of this application.
Claims
1. A superlattice infrared detector, characterized in that, include: Substrate (1); A gradient composition buffer layer (2) is grown on the upper surface of the substrate (1); A superlattice functional layer (3) is grown on the surface of the gradient component buffer layer (2); Electrode contact layer (4) grown on the upper surface of the superlattice functional layer (3); The gradient component buffer layer (2) includes a first component, the proportion of which gradually increases from zero to a preset proportion along the growth direction of the gradient component buffer layer (2); the first component is a component not included in the substrate (1) and is a component included in the superlattice functional layer (3).
2. The superlattice infrared detector according to claim 1, characterized in that, The substrate (1) is made of GaSb material; The gradient component buffer layer (2) is made of GaInSb material; the first component is an In component.
3. A superlattice infrared detector according to claim 2, characterized in that, The superlattice functional layer (3) includes a P-type superlattice layer (31), an intrinsic superlattice absorption layer (32), and an N-type superlattice layer (33) stacked sequentially from bottom to top.
4. A superlattice infrared detector according to claim 3, characterized in that, The P-type superlattice layer (31) comprises a superlattice structure composed of a first material and a GaSb material arranged in a periodic manner; the first material is P-type doped InAs(Be). The intrinsic superlattice absorption layer (32) comprises a superlattice structure composed of InAs and GaSb materials arranged in a periodic manner; The N-type superlattice layer (33) includes a superlattice structure composed of a second material and a GaSb material arranged in a periodic manner; the second material is N-type doped InAs(Si).
5. A superlattice infrared detector according to any one of claims 1 to 4, characterized in that, The thickness of the gradient component buffer layer (2) is 1.5~2μm.
6. A superlattice infrared detector according to claim 4, characterized in that, The intrinsic superlattice absorption layer (32) has a periodic thickness of 500~1000nm and a superlattice periodic unit thickness of 30-80Å.
7. A superlattice infrared detector according to claim 4, characterized in that, The thickness of the P-type superlattice layer (31) is 300-500 nm, and the thickness of the superlattice periodic unit is 30-60 Å; the thickness of the N-type superlattice layer (33) is 300-500 nm, and the thickness of the superlattice periodic unit is 30-60 Å.
8. A method for fabricating a superlattice infrared detector, used to fabricate the superlattice infrared detector of claim 1, characterized in that, include: The pretreated substrate is placed in the growth chamber; The pretreatment includes surface cleaning and deoxidation. The superlattice infrared detector is obtained by sequentially growing a gradient composition buffer layer, a superlattice functional layer, and an electrode contact layer on the substrate surface; the gradient composition buffer layer includes a first component, and the proportion of the first component gradually increases from zero to a preset proportion along the growth direction of the gradient composition buffer layer. The proportion of the preset component is no higher than 20%; The first component is a component not contained in the substrate and is a component contained in the superlattice functional layer.
9. The method for fabricating a superlattice infrared detector according to claim 8, characterized in that, The substrate is made of GaSb material; the gradient composition buffer layer is made of GaInSb material; The first component is an In component; A gradient composition buffer layer is grown on the substrate surface, comprising: As the In composition increases, the gradient composition buffer layer is grown on the substrate surface under the conditions of linearly increasing In source furnace temperature in the range of 970~990℃, linearly decreasing Ga source furnace temperature in the range of 1020~1030℃, and constant Sb source furnace temperature.
10. The method for fabricating a superlattice infrared detector according to claim 9, characterized in that, Growing the gradient composition buffer layer on the substrate surface includes: During the growth of the gradient component buffer layer on the substrate surface, RHEED oscillation calibration is performed to ensure atomic-level flatness.