A plasmon resonance enhanced microstructure for infrared photodetectors and its preparation method

Abstract

The present application provides a plasmon resonance enhanced microstructure and preparation method for an infrared photodetector, which belongs to the technical field of medium-wave infrared photodetectors, including: when using a medium-wave infrared photodetector, incident light is irradiated downward from above the top resonance layer, and the array-arranged microstructure composed of the bottom resonance layer, the dielectric block and the top resonance layer can excite a plasmon mode. Through the joint action of the top resonance layer and the bottom resonance layer, a surface plasmon resonance effect is induced near the surface of the photosensitive layer. The dielectric block is embedded in the bottom resonance layer to localize the incident light to a shallower depth in the photosensitive surface, thereby enhancing the local electric field intensity, reducing the reflection phenomenon of the photosensitive surface, and improving the detector's light absorption rate, thereby improving the quantum efficiency of the medium-wave infrared photodetector.

Description

Technical Field

[0001] The present application belongs to the technical field of medium-wave infrared photoelectric detectors, and specifically relates to a plasma resonance enhanced microstructure of an infrared photoelectric detector and a preparation method thereof. Background Art

[0002] Medium-wave infrared (MWIR) photodetectors are widely used in both industrial and civilian applications. However, the quantum efficiency of MWIR photodetectors is affected by the high reflectivity of the photosensitive surface and the low infrared light absorption efficiency of the material. Artificial microstructures for MWIR photodetectors have been developed, but these structures generally suffer from low light localization efficiency and significant energy losses, resulting in limited enhancement of the quantum efficiency of MWIR photodetectors. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0004] To this end, a first aspect of the present invention provides a plasmon resonance enhanced microstructure for an infrared photodetector.

[0005] A second aspect of the present invention provides a method for preparing a plasmon resonance enhanced microstructure of an infrared photodetector.

[0006] In view of this, according to a first aspect of an embodiment of the present application, a plasmon resonance enhancement microstructure for an infrared photodetector is proposed, comprising:

[0007] A bottom resonance layer, the bottom resonance layer is arranged on the photosensitive surface of the infrared photodetector;

[0008] a dielectric block group, the dielectric block group including a plurality of dielectric blocks, wherein first ends of the dielectric blocks are embedded in the bottom resonance layer, and the dielectric blocks are arranged on the bottom resonance layer in the form of a periodic array;

[0009] The top resonance layer is provided on the end surface of the second end of the dielectric block.

[0010] In a feasible embodiment, the plasmon resonance enhancement microstructure of the infrared photodetector further includes:

[0011] a positioning hole group, the positioning hole group including a plurality of positioning holes, the positioning holes penetrating the bottom resonance layer along the thickness direction of the bottom resonance layer, the positioning holes being arranged on the bottom resonance layer in the form of a periodic array, and the first end of the dielectric block being embedded in the positioning holes;

[0012] The dielectric blocks correspond to the positioning holes one by one.

[0013] In a feasible embodiment, the dimensions of the cross sections of the dielectric block are the same, the dimensions of the cross sections of the positioning holes are the same, and the dimensions of the cross sections of the dielectric block are the same as the dimensions of the cross sections of the positioning holes.

[0014] The top resonance layer covers the dielectric block, and the sizes of the cross sections of the top resonance layer are the same. The size of the cross section of the top resonance layer is the same as that of the cross section of the dielectric block.

[0015] In a feasible embodiment, the period of the array of positioning holes is 5 / 6 of the peak detection wavelength of the infrared photodetector;

[0016] The maximum width of the cross section of the positioning hole is 1 / 3 to 1 / 2 of the peak detection wavelength of the infrared photodetector.

[0017] In a feasible embodiment, the bottom resonance layer is a metal film;

[0018] The thickness of the bottom resonance layer is 20nm~40nm.

[0019] In one feasible embodiment, the material of the dielectric block is a semiconductor or a semiconductor oxide;

[0020] The height of the dielectric block is 300nm~400nm.

[0021] In a feasible embodiment, the material of the dielectric block is the same as that of the photosensitive surface, and the relative deviation of the dielectric constant of the dielectric block material and the dielectric constant of the photosensitive surface material is no more than 15%.

[0022] In one feasible embodiment, the top resonance layer is a metal film;

[0023] The thickness of the top resonance layer is the same as that of the bottom resonance layer.

[0024] According to a second aspect of an embodiment of the present application, a method for preparing a plasmon resonance enhanced microstructure of an infrared photodetector is provided. The method is used to prepare a plasmon resonance enhanced microstructure of an infrared photodetector according to any of the above technical solutions. The method comprises:

[0025] depositing a bottom resonant layer on the photosensitive surface of the infrared photodetector;

[0026] A hole pattern arranged in a periodic array is produced on the bottom resonance layer, and the bottom resonance layer is etched according to the hole pattern;

[0027] depositing a dielectric block and a top resonant layer to obtain a sample;

[0028] The sample is immersed in an organic solvent to strip the photoresist and remove the structure whose vertical projection on the bottom resonance layer is outside the hole pattern.

[0029] In a feasible implementation, the bottom resonance layer is subjected to inductively coupled plasma dry etching to obtain a bottom resonance layer having positioning holes arranged in a periodic array.

[0030] Compared with the prior art, the plasmon resonance enhanced microstructure and preparation method of an infrared photodetector of the present application have the following beneficial effects:

[0031] The plasma resonance enhancement microstructure of the infrared photodetector provided in the embodiment of the present application includes a bottom resonance layer, a dielectric block group and a top resonance layer. When using the medium-wave infrared photodetector, the incident light is irradiated downward from above the top resonance layer. The bottom resonance layer, the dielectric block and the top resonance layer constitute an array-arranged microstructure that can excite the plasmon mode. Through the joint action of the top resonance layer and the bottom resonance layer, a surface plasmon resonance effect is induced near the surface of the photosensitive layer. The dielectric block is embedded in the bottom resonance layer to localize the incident light to a shallower depth in the photosensitive surface, enhance the local electric field intensity, reduce the reflection phenomenon of the photosensitive surface, and improve the detector's absorption rate of light, thereby improving the quantum efficiency of the medium-wave infrared photodetector; the top resonance layer and the bottom resonance layer form a vertical resonant cavity through the dielectric block in the middle. The incident light is reflected multiple times between the top resonance layer and the bottom resonance layer to form a standing wave mode, further compressing the light field to the shallow area of the photosensitive surface, enhancing energy localization through resonant feedback, reducing the reflection loss of light on the surface of the photosensitive surface, and improving the photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0033] Figure 1 A first schematic three-dimensional structural diagram of a plasmon resonance enhancement microstructure of an infrared photodetector according to an embodiment of the present application;

[0034] Figure 2 A first schematic cross-sectional view of a plasmon resonance enhanced microstructure of an infrared photodetector according to an embodiment of the present application;

[0035] Figure 3 A first schematic top view of a plasmon resonance enhanced microstructure of an infrared photodetector according to an embodiment of the present application;

[0036] Figure 4A second schematic structural diagram of a plasmon resonance enhanced microstructure of an infrared photodetector according to an embodiment of the present application;

[0037] Figure 5 A third schematic structural diagram of a plasmon resonance enhanced microstructure of an infrared photodetector according to an embodiment of the present application;

[0038] Figure 6 A schematic flowchart of the steps of a method for preparing a plasmon resonance enhanced microstructure of an infrared photodetector according to an embodiment of the present application;

[0039] Figure 7 is the two-dimensional photocurrent density map of the medium-wave infrared photodetector;

[0040] Figure 8 Two-dimensional photocurrent density map of the mid-wave infrared photodetector after integrating the microstructure;

[0041] Figure 9 The zero-bias detectivity curves at room temperature before and after integrating the microstructure on the wave infrared photodetector;

[0042] in, Figures 1 to 5 The corresponding relationship between the reference numerals and component names is as follows:

[0043] 1. Bottom resonance layer; 2. Dielectric block; 3. Top resonance layer; 4. Photosensitive surface; 5. Positioning hole. DETAILED DESCRIPTION

[0044] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0045] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0046] In this application, unless otherwise specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0047] The preferred embodiments of the present application are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0048] like Figures 1 to 3 As shown, according to the first aspect of the embodiment of the present application, a plasma resonance enhanced microstructure of an infrared photodetector is proposed, including: a bottom resonance layer 1, a dielectric block group and a top resonance layer 3; the bottom resonance layer 1 is arranged above the photosensitive surface 4 of the infrared photodetector; the dielectric block group includes a plurality of dielectric blocks 2, the first end of the dielectric block 2 is embedded in the bottom resonance layer 1, and the dielectric blocks 2 are arranged on the bottom resonance layer 1 in the form of a periodic array; the top resonance layer 3 is arranged above the end face of the second end of the dielectric block 2.

[0049] The plasma resonance enhancement microstructure of the infrared photodetector provided in the embodiment of the present application includes a bottom resonance layer 1, a dielectric block group and a top resonance layer 3. When the medium-wave infrared photodetector is used, the incident light is irradiated downward from above the top resonance layer 3. The microstructure arranged in an array consisting of the bottom resonance layer 1, the dielectric block 2 and the top resonance layer 3 can excite the plasmon mode. Through the joint action of the top resonance layer 3 and the bottom resonance layer 1, a surface plasmon resonance effect is induced near the surface of the photosensitive layer. The dielectric block 2 is embedded in the bottom resonance layer 1 to localize the incident light at the bottom resonance layer 1. In the shallower depth of the photosensitive surface 4, the local electric field intensity is enhanced, the reflection phenomenon of the photosensitive surface 4 is reduced, the detector's absorption rate of light is improved, and the quantum efficiency of the medium-wave infrared photodetector is improved; the top resonance layer 3 and the bottom resonance layer 1 form a vertical resonance cavity through the intermediate dielectric block 2, and the incident light is reflected multiple times between the top resonance layer 3 and the bottom resonance layer 1 to form a standing wave mode, further compressing the light field to the shallow area of the photosensitive surface 4, enhancing energy localization through resonant feedback, reducing the reflection loss of light on the surface of the photosensitive surface 4, and improving the photoelectric conversion efficiency.

[0050] It should be noted that a periodic array refers to a regular structure formed by repeated arrangement of multiple structural units in a two-dimensional or three-dimensional space according to a fixed period (interval).

[0051] As a preferred solution, the infrared photoelectric detector is a medium-wave infrared photoelectric detector.

[0052] like Figure 2 As shown, in a feasible embodiment, the plasma resonance enhanced microstructure of the infrared photodetector also includes: a positioning hole group, the positioning hole group includes a plurality of positioning holes 5, the positioning holes 5 penetrate the bottom resonance layer 1 along the thickness direction of the bottom resonance layer 1, the positioning holes 5 are arranged in the form of a periodic array on the bottom resonance layer 1, and the first end of the dielectric block 2 is embedded in the positioning hole 5; wherein, the dielectric block 2 corresponds to the positioning hole 5 one by one.

[0053] In this technical solution, the dielectric block 2 is embedded in the corresponding positioning hole 5 to ensure the accuracy of the period of the dielectric block 2 array, thereby improving the position accuracy in the horizontal direction of the top resonance layer, avoiding large differences between the actual microstructure period and the designed microstructure period, preventing the surface plasmon resonance mode from changing, and avoiding the resonance shift caused by the structural deviation between the bottom resonance layer 1 and the corresponding top resonance layer 3, thereby improving the stability of the plasmon resonance, and thereby improving the compression effect on the light field, localizing the light field in the shallow area of the photosensitive surface 4, and ensuring the microstructure's enhancement effect on the detector quantum efficiency.

[0054] like Figure 2 As shown, in a feasible embodiment, the sizes of the various cross sections of the dielectric block 2 are the same, the sizes of the various cross sections of the positioning holes 5 are the same, and the size of the cross section of the dielectric block 2 is the same as the size of the cross section of the positioning holes 5; the top resonance layer 3 covers the dielectric block 2, the sizes of the various cross sections of the top resonance layer 3 are the same, and the size of the cross section of the top resonance layer 3 is the same as the size of the cross section of the dielectric block 2.

[0055] In this technical solution, the dielectric block 2 maintains the same cross-sectional dimensions as the positioning holes 5, so that the propagation phase of the light field in the positioning holes 5 arranged in a periodic array is consistent. By eliminating the scattering loss caused by size mutation, the surface plasmon wave vector is matched with the dielectric waveguide mode, thereby enhancing the effect of the localized effect of the light field; the top resonance layer 3 maintains the same cross-sectional dimensions as the dielectric block 2, forming a closed resonant cavity, so that the incident light is reflected multiple times in the vertical direction, and the light field is compressed to the shallow layer of the photosensitive surface 4 through the standing wave effect, thereby improving the light absorption efficiency.

[0056] In this technical solution, the cross-sectional dimensions of the positioning holes 5 and the dielectric block 2 are identical. They serve as alignment references during the photolithography process, precisely controlling the cross-sectional dimensions of the dielectric block 2 and preventing increased errors after stacking the top resonant layer 3, thereby preventing a shift in the plasma resonance peak. Maintaining the cross-sectional dimensions of the dielectric block 2 and the top resonant layer 3 during the stripping process reduces organic solvent erosion of the microstructure sidewalls, ensuring smoothness and cleanliness of the microstructure sidewalls and, consequently, periodic accuracy of the microstructure.

[0057] Furthermore, the dielectric block 2 is a columnar body. In some examples, such as Figure 1 、 Figure 4 and Figure 5 The cross section of the dielectric block 2 can be square, circular or rectangular, that is, the dielectric block 2 can be a cuboid or a cylinder.

[0058] In a feasible embodiment, the period of the array of positioning holes 5 is 5 / 6 of the peak detection wavelength of the medium-wave infrared photoelectric detector; the maximum width of the cross section of the positioning holes 5 is 1 / 3 to 1 / 2 of the peak detection wavelength of the medium-wave infrared photoelectric detector.

[0059] In this technical solution, the period of the array of positioning holes 5 is set to 5 / 6 of the peak detection wavelength to ensure that the arrangement of the positioning holes 5 meets the surface wave phase matching condition and forms a standing wave resonance; at the same time, the positioning holes 5 structure arranged in a periodic array form a photonic crystal band gap, which suppresses the propagation of non-target wavelengths and avoids the positioning holes 5 period parameter being too large, causing the band gap to shift to the long-wave region, thereby preventing the reduction of the local efficiency of the medium-wave infrared. By setting the maximum width of the cross section of the positioning hole 5 to 1 / 3 to 1 / 2 of the peak detection wavelength of the medium-wave infrared photodetector, it is ensured that the resonance mode covers the medium-wave infrared band. The size of the positioning hole 5 is close to the subwavelength scale. Through Mie resonance and diffraction effects, the incident light is scattered to the shallow area below the photosensitive surface 4, thereby increasing the optical path and reducing reflection loss. At the same time, the ratio of the size of the positioning hole 5 to the wavelength determines the frequency range of the resonance mode. By making the maximum width of the cross section of the positioning hole 5 1 / 3 to 1 / 2 of the peak detection wavelength of the medium-wave infrared photodetector, the difficulty in exciting high-order modes caused by too small a size and the multi-mode coupling noise caused by too large a size are avoided, thereby facilitating the improvement of the photoelectric conversion efficiency and effect.

[0060] In a feasible implementation manner, the bottom resonance layer 1 is a metal film; the thickness of the bottom resonance layer 1 is 20 nm to 40 nm.

[0061] In this technical solution, the coupling of incident light and free electrons in the metal film excites surface plasmon resonance, localizing the light field within the subwavelength scale of the shallow layer of the photosensitive surface 4, significantly enhancing the local electric field intensity; the thickness of the bottom resonance layer 1 is set to 20nm~40nm to match the thickness of the bottom resonance layer 1 with the penetration depth of the surface plasmon, avoiding the discontinuity and unevenness of the bottom resonance layer 1 due to being too thin, resulting in increased losses; at the same time, avoiding the bottom resonance layer 1 being too thick to cause light absorption saturation and reduce the resonance quality factor; the metal film also undertakes the heat conduction function, and the metal film of this size has a moderate thickness, which can reduce the heat capacity while maintaining low radiation thermal conductivity, thereby avoiding a surge in dark current at high temperatures.

[0062] In some examples, the metal in the metal film of the bottom resonance layer 1 can be gold (Au), silver (Ag), or aluminum (Al).

[0063] In a feasible implementation manner, the material of the dielectric block 2 is semiconductor or semiconductor oxide; the height of the dielectric block 2 is 300 nm to 400 nm.

[0064] In this technical solution, the height of the dielectric block 2 is designed to be 300nm~400nm, so that the height of the dielectric block 2 matches the penetration depth of the surface plasmon resonance, so that the light field is mainly localized on the surface of the photosensitive surface 4. By optimizing the thickness of the dielectric block 2, the interaction between the light field and the material is maximized.

[0065] In some examples, the semiconductor material may be silicon (Si), germanium (Ge), or indium arsenide (InAs); and the semiconductor oxide material may be titanium oxide, zinc oxide, tungsten oxide, tin oxide, indium oxide, or tantalum pentoxide.

[0066] In a feasible embodiment, the material of the dielectric block 2 is the same as that of the photosensitive surface 4 , and the relative deviation of the dielectric constant of the material of the dielectric block 2 and the dielectric constant of the material of the photosensitive surface 4 is no more than 15%.

[0067] In this technical solution, the relative deviation of the dielectric constant of the material of the dielectric block 2 and the dielectric constant of the material of the photosensitive surface 4 is set within 15%, so that the Fresnel reflection coefficient of the incident light at the interface between the photosensitive surface 4 and the dielectric block 2 is reduced to below 0.5%; at the same time, the wave vector matching condition of the surface plasmon is easier to meet, and the offset of the surface plasmon resonance wavelength can be precisely controlled to ensure effective coverage of the 3μm~5μm medium-wave infrared band and optimize the light field coupling efficiency; the dielectric block 2 and the photosensitive surface 4 are made of the same material, which can achieve stress matching between the dielectric block 2 and the photosensitive surface 4, avoid cracking of the metal film, and extend the service life of the microstructure.

[0068] In a feasible implementation, the top resonance layer 3 is a metal film; the thickness of the top resonance layer 3 is the same as that of the bottom resonance layer 1 .

[0069] In this technical solution, the top resonance layer 3 and the bottom resonance layer 1 have the same thickness, so that the resonance frequencies of the top resonance layer 3 and the bottom resonance layer 1 match, the resonance efficiency is optimized, the natural frequencies of the top resonance layer 3 and the bottom resonance layer 1 converge, mechanical fatigue caused by the superposition of multi-frequency resonances is avoided, the local amplitude is reduced, and the service life of the microstructure is extended; at the same time, the top resonance layer 3 and the bottom resonance layer 1 have the same thickness, which can also reduce interface reflection and enhance the light field coupling efficiency.

[0070] In some examples, the metal in the top resonance layer 3 metal film can be gold (Au), silver (Ag), or aluminum (Al).

[0071] like Figure 6 As shown, according to the second aspect of the present application, a method for preparing a plasmon resonance enhanced microstructure of an infrared photodetector is proposed, which is used to prepare the plasmon resonance enhanced microstructure of an infrared photodetector as described in any of the above technical solutions, comprising:

[0072] Step 100: depositing a bottom resonance layer 1 on the photosensitive surface 4 of the medium-wave infrared photodetector;

[0073] Step 200: forming a hole pattern arranged in a periodic array on the bottom resonance layer 1, and etching the bottom resonance layer 1 according to the hole pattern;

[0074] Step 300: depositing a dielectric block 2 and a top resonance layer 3 to obtain a sample;

[0075] Step 400: Immerse the sample in an organic solvent, strip the photoresist, and remove the structure on the bottom resonance layer 1 whose vertical projection is outside the hole pattern.

[0076] The preparation method of the plasma resonance enhanced microstructure of the infrared photodetector provided by the embodiment of the present application is to achieve micron-level positioning of the dielectric block 2 by engraving a hole pattern arranged in the form of a periodic array on the bottom resonance layer 1, and to etch the bottom resonance layer 1 according to the hole pattern, thereby improving the accuracy of the microstructure after the dielectric block 2 and the top resonance layer 3 are deposited; the photoresist is stripped in an organic solvent, and the redundant structure on the dielectric block 2 and the bottom resonance layer 1 is removed to avoid tearing of the microstructure, and the microstructure is stripped without damage, thereby further ensuring the accuracy of the microstructure after preparation; when using the medium-wave infrared photodetector, the incident light is irradiated downward from above the top resonance layer 3, and the periodically arranged microstructure composed of the bottom resonance layer 1, the dielectric block 2 and the top resonance layer 3 can excite the The plasmon mode, through the joint action of the top resonance layer 3 and the bottom resonance layer 1, induces a surface plasmon resonance effect near the surface of the photosensitive layer. The dielectric block 2 is embedded in the bottom resonance layer 1 to localize the incident light within a shallow depth in the photosensitive surface 4, enhance the local electric field intensity, reduce the reflection phenomenon of the photosensitive surface 4, and improve the detector's absorption rate of light, thereby improving the quantum efficiency of the medium-wave infrared photodetector; the top resonance layer 3 and the bottom resonance layer 1 form a vertical resonant cavity through the dielectric block 2 in the middle. The incident light is reflected multiple times between the top resonance layer 3 and the bottom resonance layer 1 to form a standing wave mode, further compressing the light field to the shallow area of the photosensitive surface 4, enhancing energy localization through resonant feedback, reducing the reflection loss of light on the surface of the photosensitive surface 4, and improving the photoelectric conversion efficiency.

[0077] Furthermore, the bottom resonance layer 1 is deposited in a high vacuum environment at a deposition rate of 2nm / min to 5nm / min; the dielectric block 2 is deposited in a high vacuum environment at a deposition rate of 20nm / min to 100nm / min; and the top resonance layer 3 is deposited in a high vacuum environment at a deposition rate of 2nm / min to 5nm / min. This reduces residual gas molecules such as oxygen and water vapor and prevents chemical reactions between the materials of each layer and the gas during the deposition process, thereby ensuring the chemical purity of the entire microstructure. By depositing the bottom resonance layer 1 and the top resonance layer 3 at a lower deposition rate, the atomic-level precision of the bottom resonance layer 1 and the top resonance layer 3 is ensured, and the stress accumulation within the bottom resonance layer 1 and the top resonance layer 3 is reduced, avoiding lattice distortion or interface defects. This also facilitates precise control of the coating thickness, thereby improving the overall preparation accuracy of the microstructure.

[0078] In some examples, the material of dielectric block 2 may be single crystal, polycrystalline, or amorphous material.

[0079] In some examples, the bottom resonance layer 1 can be deposited on the photosensitive surface 4 by a thermal evaporation process, an electron beam evaporation process, or a magnetron sputtering process.

[0080] In some examples, a mask lithography process, a laser direct writing process, or an electron beam lithography process may be used to form a periodically arrayed hole pattern on the bottom resonance layer 1 .

[0081] In some examples, the dielectric block 2 and the top resonant layer 3 can be deposited on the photosensitive surface 4 using a thermal evaporation process, an electron beam evaporation process, or a magnetron sputtering process.

[0082] In some examples, the organic solvent may be acetone or nitrogen-methylpyrrolidone.

[0083] In a feasible embodiment, the bottom resonance layer 1 is subjected to inductively coupled plasma dry etching to obtain the bottom resonance layer 1 having positioning holes 5 arranged in a periodic array.

[0084] In this technical solution, inductively coupled plasma dry etching independently regulates the ion concentration (RF coil power) and bombardment energy (bias power). The ion concentration and energy can be independently controlled, which helps to improve the etching accuracy and efficiency. The verticality of the side wall of the positioning hole 5 reaches 88°±1°, reducing the verticality error of the side wall of the positioning hole 5. At the same time, it can reduce the size deviation of the positioning hole 5 and improve the accuracy of the period of the positioning hole 5, meeting the consistency requirements of the periodic holes and the resonance matching requirements of the positioning holes 5; inductively coupled plasma dry etching is performed at low temperature, which can avoid thermal stress distortion of the bottom resonance layer 1 caused by high temperature, prevent cracking of the edges of the periodic holes, and ensure that the side wall of the positioning hole 5 is smooth, so as to achieve precise control of the period of the positioning hole 5 array.

[0085] The method for preparing the plasma resonance enhanced microstructure of the infrared photodetector provided in the embodiment of the present application is applied to the plasma resonance enhanced microstructure of the infrared photodetector such as any of the above-mentioned technical solutions. Therefore, the method for preparing the plasma resonance enhanced microstructure of the infrared photodetector has all the beneficial effects of the plasma resonance enhanced microstructure of the infrared photodetector of the above-mentioned technical solutions, which will not be elaborated here.

[0086] Example 1:

[0087] This embodiment provides an artificial microstructure for enhancing the light utilization efficiency of a medium-wave infrared photodetector, such as Figure 1 As shown, it includes a bottom resonance layer 1, a dielectric block 2 and a top resonance layer 3. The thickness of the bottom resonance layer 1 is 20nm, and the material is Au. There is a positioning hole 5 structure arranged in the form of a periodic array on the bottom resonance layer 1. The positioning hole 5 is square in shape, the side length of the square is 1.25μm, and the period of the array of square positioning holes 5 is 2.75μm. The height of the dielectric block 2 is 300nm, and the material is Si. The thickness of the top resonance layer 3 is 20nm, and the material is Au. When in use, the incident light is irradiated downward from the top of the top resonance layer 3, and through the joint action of the top resonance layer 3 and the bottom resonance layer 1, it is localized in the shallower area below the bottom resonance layer 1, and is finally absorbed by the infrared photodetector and converted into a current signal output.

[0088] When preparing the microstructure, first, Au is deposited on the photosensitive surface 4 of the medium-wave infrared photodetector at a deposition rate of 2 nm / min using a thermal evaporation process to form a bottom resonance layer 1 of a metal thin film structure; then, a mask plate photolithography process is used to engrave a square hole pattern arranged in the form of a periodic array on the bottom resonance layer 1; then, the bottom resonance layer 1 is dry-etched using an inductively coupled plasma etching process to obtain a bottom resonance layer 1 having square positioning holes 5 arranged in the form of a periodic array; then, a Si dielectric block is deposited on the bottom resonance layer 1 at a deposition rate of 20 nm / min and an Au thin film is deposited at a deposition rate of 2 nm / min using a thermal evaporation process to form a dielectric block 2 and a top resonance layer 3 to obtain a sample; finally, the sample is soaked in acetone, and the excess photoresist, Si dielectric and Au thin film on the surface of the sample are peeled off and removed to complete the preparation of a microstructure with a square cross-section.

[0089] Example 2:

[0090] This embodiment provides an artificial microstructure for enhancing the light utilization efficiency of a medium-wave infrared photodetector, such as Figure 4As shown, it includes a bottom resonance layer 1, a dielectric block 2 and a top resonance layer 3. The thickness of the bottom resonance layer 1 is 30nm, and the material is Ag. There is a positioning hole 5 structure arranged in the form of a periodic array on the bottom resonance layer 1. The shape of the positioning hole 5 is circular, the diameter of the circle is 1.5μm, and the period of the array of circular positioning holes 5 is 2.5μm. The height of the dielectric block 2 is 350nm, and the material is Ge. The thickness of the top resonance layer 3 is 30nm, and the material is Ag. When in use, the incident light is irradiated downward from the top of the top resonance layer 3, and through the joint action of the top resonance layer 3 and the bottom resonance layer 1, it is localized in the shallower area below the bottom resonance layer 1, and is finally absorbed by the infrared photodetector and converted into a current signal output.

[0091] When preparing the microstructure, first, Ag is deposited on the photosensitive surface 4 of the medium-wave infrared photodetector at a deposition rate of 3 nm / min using an electron beam evaporation process to form a bottom resonance layer 1 of a metal thin film structure; then, a circular hole pattern arranged in the form of a periodic array is engraved on the bottom resonance layer 1 using a laser direct writing process; then, the bottom resonance layer 1 is dry-etched using an inductively coupled plasma etching process to obtain a bottom resonance layer 1 having circular positioning holes 5 arranged in the form of a periodic array; then, a Ge dielectric block is deposited on the bottom resonance layer 1 at a deposition rate of 50 nm / min and an Ag thin film is deposited at a deposition rate of 3 nm / min using an electron beam evaporation process to form a dielectric block 2 and a top resonance layer 3 to obtain a sample; finally, the sample is soaked in acetone, and the excess photoresist, Ge dielectric and Ag thin film on the surface of the sample are stripped off and removed to complete the preparation of a microstructure with a square cross-section.

[0092] Example 3:

[0093] This embodiment provides an artificial microstructure for enhancing the light utilization efficiency of a medium-wave infrared photodetector, such as Figure 5 As shown, it includes a bottom resonance layer 1, a dielectric block 2 and a top resonance layer 3. The bottom resonance layer 1 has a thickness of 40 nm and is made of Al. The bottom resonance layer 1 has a positioning hole 5 structure arranged in the form of a periodic array. The positioning hole 5 is in the shape of a rectangle with a length of 1.5 μm and a width of 1.25 μm. The period of the array of rectangular positioning holes 5 is 2.75 μm. The height of the dielectric block 2 is 400 nm and is made of InAs. The thickness of the top resonance layer 3 is 40 nm and is made of Al. When in use, the incident light is irradiated downward from the top of the top resonance layer 3, and through the joint action of the top resonance layer 3 and the bottom resonance layer 1, it is localized in the shallower area below the bottom resonance layer 1, and is finally absorbed by the infrared photodetector and converted into a current signal output.

[0094] When preparing the microstructure, first, Al is deposited on the photosensitive surface 4 of the medium-wave infrared photodetector at a deposition rate of 5 nm / min using a magnetron sputtering process to form a bottom resonance layer 1 of a metal thin film structure; then, a mask plate photolithography process is used to engrave a rectangular hole pattern arranged in the form of a periodic array on the bottom resonance layer 1; then, the bottom resonance layer 1 is dry-etched using an inductively coupled plasma etching process to obtain a bottom resonance layer 1 having rectangular positioning holes 5 arranged in the form of a periodic array; then, an InAs dielectric block is deposited on the bottom resonance layer 1 at a deposition rate of 100 nm / min and an Al thin film is deposited at a deposition rate of 5 nm / min using a thermal evaporation process to form a dielectric block 2 and a top resonance layer 3 to obtain a sample; finally, the sample is soaked in acetone, and the excess photoresist, InAs dielectric and Au thin film on the surface of the sample are stripped off and removed to complete the preparation of the microstructure with a rectangular cross-section.

[0095] The microstructure prepared in Example 2 is integrated on a medium-wave infrared photodetector, as shown in FIG. Figure 4 shown.

[0096] Figure 7 The photogenerated carrier generation rate inside the device is shown when the microstructure is not integrated on the mid-wave infrared photodetector. Figure 8 The photogenerated carrier generation rate inside the device after the microstructure in Example 2 is integrated on the medium-wave infrared photodetector is shown; by comparison Figure 7 and Figure 8 The photogenerated carrier generation rates inside the two devices can be analyzed. Compared with the device without integrated microstructure, the photogenerated carrier generation rate in the absorption layer of the device with integrated microstructure is significantly improved, and the position with the highest increase is located in the shallow range directly below the microstructure; it can be proved that the microstructure excites localized surface plasmon resonance on the device surface of the medium-wave infrared photodetector, thereby improving the utilization rate of the medium-wave infrared photodetector for incident light. Figure 9 The black curve in the figure shows the variation of the photocurrent response of the mid-wave infrared photodetector device with wavelength. Figure 9 The red curve in the middle shows the variation of the device photocurrent with wavelength after the integrated microstructure. Figure 9 It can be seen that integrating microstructures on medium-wave infrared photodetectors has a significant effect on improving the photocurrent of the device and improving the photoresponsivity of the device.

[0097] It is understandable that in the same infrared photodetector, the photogenerated carrier generation rate is strictly proportional to the photocurrent, so Figure 7 and Figure 8 The photogenerated carrier generation rate of the device shown can intuitively determine the photocurrent density in the device.

[0098] It is easy for those skilled in the art to understand that the above embodiments can be freely combined and superimposed without conflict.

[0099] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application. The above are merely preferred embodiments of the present application. It should be noted that those skilled in the art may make various improvements and variations without departing from the technical principles of the present application, and such improvements and variations shall also be considered within the scope of protection of the present application.

Claims

1. A plasmon resonance enhanced microstructure for an infrared photodetector, characterized in that: The plasmon resonance enhancement microstructure of the infrared photodetector includes: A bottom resonance layer, wherein the bottom resonance layer is arranged on a photosensitive surface of the infrared photodetector; a dielectric block group, the dielectric block group comprising a plurality of dielectric blocks, wherein first ends of the dielectric blocks are embedded in the bottom resonance layer, and the dielectric blocks are arranged on the bottom resonance layer in the form of a periodic array; a top resonance layer, the top resonance layer being disposed on an end surface of the second end of the dielectric block; a positioning hole group, the positioning hole group including a plurality of positioning holes, the positioning holes penetrating the bottom resonance layer along a thickness direction of the bottom resonance layer, the positioning holes being arranged on the bottom resonance layer in a periodic array, the first end of the dielectric block being embedded in the positioning holes; Wherein, the dielectric blocks correspond to the positioning holes one by one.

2. The plasmon resonance enhanced microstructure of an infrared photodetector according to claim 1, characterized in that: The dimensions of the cross sections of the dielectric blocks are the same, the dimensions of the cross sections of the positioning holes are the same, and the dimensions of the cross sections of the dielectric blocks are the same as the dimensions of the cross sections of the positioning holes; The top resonance layer covers the dielectric block. The sizes of the cross sections of the top resonance layer are the same. The size of the cross section of the top resonance layer is the same as that of the cross section of the dielectric block.

3. The plasmon resonance enhanced microstructure of an infrared photodetector according to claim 1, characterized in that: The period of the array of positioning holes is 5 / 6 of the peak detection wavelength of the infrared photodetector; The maximum width of the cross section of the positioning hole is 1 / 3 to 1 / 2 of the peak detection wavelength of the infrared photoelectric detector.

4. The plasmon resonance enhanced microstructure of an infrared photodetector according to claim 1, wherein: The bottom resonance layer is a metal film; The thickness of the bottom resonance layer is 20 nm to 40 nm.

5. The plasmon resonance enhanced microstructure of an infrared photodetector according to claim 1, characterized in that: The material of the dielectric block is semiconductor or semiconductor oxide; The height of the dielectric block is 300nm-400nm.

6. The plasmon resonance enhanced microstructure of an infrared photodetector according to claim 5, characterized in that: The material of the dielectric block is the same as that of the photosensitive surface, and the relative deviation of the dielectric constant of the material of the dielectric block and the dielectric constant of the material of the photosensitive surface is no more than 15%.

7. The plasmon resonance enhanced microstructure of an infrared photodetector according to claim 4, characterized in that: The top resonance layer is a metal film; The thickness of the top resonance layer is the same as the thickness of the bottom resonance layer.

8. A method for preparing a plasmon resonance enhanced microstructure of an infrared photodetector, characterized in that: A method for preparing a plasmon resonance enhanced microstructure of an infrared photodetector according to any one of claims 1 to 7, the preparation method comprising: depositing a bottom resonant layer on the photosensitive surface of the infrared photodetector; Producing a hole pattern arranged in a periodic array on the bottom resonance layer, and etching the bottom resonance layer according to the hole pattern; depositing a dielectric block and a top resonant layer to obtain a sample; The sample is immersed in an organic solvent, the photoresist is stripped off, and the structure whose vertical projection on the bottom resonance layer is located outside the hole pattern is removed.

9. The method for preparing a plasmon resonance enhanced microstructure of an infrared photodetector according to claim 8, characterized in that: The bottom resonance layer is subjected to inductively coupled plasma dry etching to obtain the bottom resonance layer having positioning holes arranged in a periodic array.

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