All-silicon microporous structure for enhancing wide-spectrum absorption in photon residence mode and preparation method of all-silicon microporous structure

Abstract

The invention belongs to the technical field of very long wave infrared detection, and particularly relates to an all-silicon microporous structure for enhancing wide-spectrum absorption in a photon residence mode and a preparation method of the all-silicon microporous structure. The all-silicon micropore structure sequentially comprises a high-purity silicon substrate, a heavily-doped silicon plasma layer, a lightly-doped silicon active absorption layer and an intrinsic pure silicon barrier layer from bottom to top, and further comprises a periodic micropore array structure with a parabola-shaped side wall, and the structure is embedded into the lightly-doped silicon active absorption layer. According to the micropore array structure with the parabola-shaped side wall, coupling of wide-spectrum photons is achieved, and a high-order diffraction mode deviating from the vertical direction is excited; and meanwhile, a heavily doped silicon plasma layer compatible with an all-silicon process is introduced, so that a photon residence mode is successfully realized. Under the combined action of the design, the photon capture efficiency of the thin active absorption layer in a very long wave wide spectrum range is maximized, and the performance of photoelectric devices such as an infrared detector and a solar cell can be remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of very long wave infrared detection, and specifically relates to an all-silicon microporous structure with photon residence mode enhanced broadband absorption and a preparation method thereof. Background Art

[0002] The long-wave and very-long-wave ranges contain rich material and chemical information, and therefore are of great significance in the fields of astronomical observation and environmental monitoring. The common silicon, germanium, and gallium-arsenic semiconductor materials have intrinsic band gaps of 1.12eV, 0.66eV, and 1.42eV, respectively. Among these materials, germanium has the longest response wavelength, which ends at 1.85μm, and cannot detect spectral information with longer wavelengths. In order to achieve sub-bandgap absorption, it is necessary to introduce impurity energy levels into semiconductor materials. However, when the transition from intrinsic inter-band transition to impurity band transition is transformed, the peak absorption coefficient decays by more than 1 order of magnitude. This problem greatly limits the further expansion of the absorption wavelength and hinders the further exploration of the application potential of long-wave and very-long-wave detection in multiple fields.

[0003] The traditional method to solve the absorption problem of extrinsic silicon materials based on impurity transitions is to increase the material thickness. However, for extrinsic detectors in the very long wavelength range, this approach will not only increase the device size and the dark current associated with it, but also reduce the device response speed.

[0004] Effective strategies to enhance absorption in thin absorption layers include the introduction of artificial microstructures such as surface plasmons, guided mode resonance, and light trapping. By introducing a photon capture structure, it is possible to avoid adding additional dark current and confine photons to the active region, thereby improving the quantum efficiency in a specific wavelength range. At present, metal photon capture resonance structures and dielectric guided mode resonance structures are mainly used in the long-wave and very long-wave ranges. Although they can achieve photon localization at specific peaks and enhance the absorption effect, they cannot be applied to the design of highly sensitive broadband detectors. By designing regular and periodically arranged artificial micro-nano structures, the absorption of long-wave and wide spectral bands can be enhanced. However, this type of structure requires the introduction of a thin metal layer on the surface of the light trapping structure to stimulate the skin effect and achieve photon confinement. However, the introduction of metal not only increases the photon loss in the long-wave and very long-wave ranges, but is also not suitable for the manufacture of large-scale uniform array devices. In addition, traditional periodic regular structures make it difficult for photons to effectively reside, limiting their application in related fields.

[0005] Therefore, it is necessary to develop new structures that can break through the existing absorption limitations in order to achieve high-sensitivity, wide-spectrum absorption of long and very long waves and improve photon retention efficiency. Summary of the invention

[0006] To overcome the deficiencies of the above-mentioned prior art, the present invention designs an all-dielectric microporous array structure with parabolic sidewalls, achieving enhanced photon absorption in a wide spectral range without introducing noble metals and being compatible with the actual silicon device industry. Such an all-dielectric process structure is expected to be widely applied to the design of highly sensitive wide-spectrum detectors for various material systems.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] In the first aspect of the present invention, there is provided an all-silicon microporous structure for enhancing wide-spectrum absorption in a photon residence mode. The all-silicon microporous structure includes, from bottom to top, a high-purity silicon substrate, a heavily doped silicon plasma layer, a lightly doped silicon active absorption layer, and an intrinsic pure silicon blocking layer. It also includes an all-dielectric microstructure, which is a periodic microporous array with parabolic sidewalls. The all-dielectric microstructure is embedded in the lightly doped silicon active absorption layer of the material. The doping element of the heavily doped silicon plasma layer is boron, and the doping element of the lightly doped silicon active absorption layer is gallium.

[0009] The present invention constructs a surface-patterned microstructure, introduces a periodic microporous array with a parabolic shape whose structural period is comparable to the incident wavelength, excites and guides high-order diffraction modes, and combines with a heavily doped semiconductor plasma layer to retain the photon residence mode in the absorption layer, thereby enabling the lightly doped silicon active absorption layer to achieve high absorption efficiency of photons in a very long wavelength wide spectral range.

[0010] Preferably, the pore diameter range of the all-dielectric microstructure is: D1 = 7.6 - 7.8 μm, D2 = 8.2 - 8.4 μm, the period P is 10 - 18 μm, and the number of pores exceeds 100.

[0011] Preferably, the all-silicon microporous structure has a maximum photon capture efficiency in the very long wavelength range of 14 - 20 μm.

[0012] Preferably, the resistivity of the high-purity silicon substrate > 10000 Ω·cm, and the thickness is 400 - 500 μm.

[0013] Preferably, the doping concentration of boron in the heavily doped silicon plasma layer ≥ 1×10 20 cm -3 .

[0014] Preferably, the doping concentration of gallium in the lightly doped silicon active absorption layer is between 1×10 15 cm -3 ~1×10 18 cm -3 , and the thickness of the absorption layer is 4 - 7 μm.

[0015] Preferably, the thickness of the intrinsic pure silicon blocking layer is 2 - 5 μm, and the resistivity > 5000 Ω·cm.

[0016] The second aspect of the present invention provides a method for preparing the all - silicon microporous structure with enhanced broadband absorption in the photon residence mode described in the first aspect, including the following steps:

[0017] S1. Prepare a heavily doped silicon plasma layer on a high - purity silicon substrate by high - dose and high - energy ion implantation;

[0018] S2. Place the sample into a molecular beam epitaxy device and grow a lightly doped silicon active absorption layer and an intrinsic pure silicon blocking layer by molecular beam epitaxy;

[0019] S3. Complete the surface patterning of the regional microstructure through photolithography, ultraviolet exposure, and development, and then complete the preparation of the all - dielectric microstructure through an optimized deep reactive ion beam etching process.

[0020] Preferably, the optimized deep reactive ion beam etching process is specifically as follows: set the power of the etching equipment to 700 - 900 W, the substrate bias voltage to 50 - 70 W, the SF6 gas flow rate to 90 - 120 sccm, the C4F8 gas flow rate to 90 - 120 sccm, and the O2 flow rate to 7 - 15 sccm; the etching process is 14 - 18 cycles of alternating protection and etching, and after etching, heat to remove the photoresist.

[0021] Preferably, in S1, the injection conditions include an injection angle deflected 6 - 8° from the vertical direction, an energy of 70 - 90 keV, and a dose of 1 - 5×10 15 cm -2 , and the prepared thickness is above 0.2 μm.

[0022] The third aspect of the present invention provides the application of the all - silicon microporous structure with enhanced broadband absorption in the photon residence mode described in the first aspect in optoelectronic devices, and the optoelectronic devices include infrared detectors and solar cells.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] The present invention discloses an all-silicon microporous structure for enhancing broadband absorption in a photon residence mode. The all-silicon microporous structure sequentially includes a high-purity silicon substrate, a heavily doped silicon plasma layer, a lightly doped silicon active absorption layer, and an intrinsic pure silicon blocking layer from bottom to top. It also includes a periodic microporous array structure with parabolic sidewalls, and this structure is embedded in the lightly doped silicon active absorption layer. The preparation method is as follows: First, the preparation of the surface heavily doped silicon plasma layer material is completed by high-dose and high-energy ion implantation; then the sample is placed in a molecular beam epitaxy device for the epitaxy of the lightly doped silicon active absorption layer and the blocking layer; and then the preparation of the regularly arranged microporous structure with parabolic sidewalls on the surface is completed through photolithographic patterning and customized deep reactive ion etching micro-nano processes. The designed microporous array structure with parabolic sidewalls in the present invention realizes the coupling of photons in a wide spectral range and excites high-order diffraction modes deviating from the vertical direction; at the same time, a heavily doped silicon plasma layer compatible with the all-silicon process is introduced to successfully achieve the photon residence mode. Under the combined action of the above-mentioned designs, the photon capture efficiency of the thin active absorption layer in the very long wavelength broadband range is maximized.

[0025] It can be seen that the all-silicon microporous structure of the present invention, relying on the microporous array structure with parabolic sidewalls, excites and guides high-order diffraction modes, and is combined with a heavily doped semiconductor plasma layer to make photons reside in the absorption layer, greatly improving the photon absorption efficiency of the lightly doped silicon active absorption layer in the very long wavelength broadband. The all-silicon system has low cost and good compatibility, simplifying the preparation process. The application of this structure can significantly improve the performance of optoelectronic devices such as infrared detectors and solar cells, providing a solution for the miniaturization and high performance of optoelectronic devices, and promoting the technological innovation of the optoelectronic industry. Brief Description of the Drawings

[0026] Figure 1 is a schematic diagram of the all-silicon microporous structure in the photon residence mode and a partial schematic diagram of the sidewall of the all-dielectric microporous array;

[0027] Figure 2 is the top view and sidewall view of the all-dielectric microporous array structure under a scanning electron microscope;

[0028] Figure 3 is the Poynting vector distribution of the all-silicon microporous structure in the photon residence mode, showing the horizontal vector distribution and the existence of the photon residence mode;

[0029] Figure 4 is the comparison of the absorption rates of the all-silicon microporous structure in the photon residence mode, the periodic straight-hole all-silicon micro-structure, and the planar all-silicon structure;

[0030] Figure 5Absorption rate distributions of all-silicon structures with photon residence modes of different structural parameters; among them, (a) shows the changes and distributions of the absorption rate when changing the physical quantity depth H, with the fixed periodic physical quantity P = 12 μm, the physical quantity D1 / D2 = 0.95 (D2 = 8.2 μm), and the physical quantity depths H being 3 μm, 5 μm, and 8 μm respectively; (b) shows the changes and distributions of the absorption rate when changing the physical quantity period P, with the physical quantity depth H being 5 μm, the physical quantity D1 / D2 = 0.95 (D2 = 8.2 μm), and the periods P being 10 μm, 12 μm, and 14 μm respectively; (c) shows the changes and distributions of the absorption rate when changing the physical quantity D1 / D2, with the physical quantity depth H being 5 μm, the period P being 12 μm, and the physical quantity D1 / D2 (D2 = 8.2 μm) being 0.7, 0.8, 0.9, and 0.95 respectively. Detailed implementation manners

[0031] The following further describes the detailed implementation manners of the present invention. It should be noted here that the descriptions of these implementation manners are used to help understand the present invention, but do not constitute a limitation to the present invention. In addition, the technical features involved in the various implementation manners of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] The experimental methods in the following examples are all conventional methods unless otherwise specified, and the test materials used in the following examples are all available through conventional commercial channels unless otherwise specified.

[0033] Example: An all-silicon microporous structure for enhancing broadband absorption in photon residence mode and a preparation method

[0034] As Figure 1 shown, the all-silicon microporous structure sequentially includes a high-purity silicon substrate 1, a heavily doped silicon plasma layer 2, a lightly doped silicon active absorption layer 3, an intrinsic pure silicon barrier layer 4, and the all-dielectric microstructure 5 from bottom to top. The all-dielectric microstructure 5 is a periodic microporous array with a parabolic sidewall shape;

[0035] The resistivity of the high-purity silicon substrate 1 > 10000 Ω·cm, and the thickness is 450 μm; the doping element of the heavily doped silicon plasma layer 2 is boron, and the doping concentration = 1×10 20 cm -3 ; the doping element of the lightly doped silicon active absorption layer 3 is gallium, and the doping concentration is 3×10 17 cm -3, with a thickness of 5 μm; the thickness of the intrinsic pure silicon blocking layer 4 is 3 μm, and the resistivity > 5000 Ω·cm; the all-dielectric microstructure 5 is embedded in the lightly doped silicon active absorption layer 3 of the material, and the diameter range of the pores is: D1 = 7.6 - 7.8 μm, D2 = 8.2 - 8.4 μm (in this embodiment, D1 = 7.8 μm and D2 = 8.2 μm are taken as examples), the period P is 10 - 18 μm (in this embodiment, P = 12 μm is taken as an example), the number of pores exceeds 100 (in this embodiment, 27666 is taken as an example), and the basic periodic boundary condition settings are maintained.

[0036] The preparation method of the above-mentioned all-silicon microporous structure includes the following steps:

[0037] (1) A heavily doped silicon plasma layer 2 is formed on a substrate 1 of intrinsic silicon (resistivity > 10000 Ω·cm) with a thickness of about 450 μm by ion implantation of boron element. The implantation conditions include an angular deflection of 7° from the vertical direction, an energy of 80 keV, and a dose of 1.5×10 15 cm -2 . A heavily doped silicon plasma layer 2 with a thickness of 0.25 μm and a doping concentration of 1×10 20 cm -3 is prepared (note: the original thickness of the substrate 1 is 450 μm, and a 0.25-μm-thick plasma layer 2 is formed on its upper surface, so the actual thickness of the substrate 1 is about 450 μm).

[0038] (2) Further, a 5-μm-thick lightly doped silicon active absorption layer 3 and a 3-μm-thick intrinsic pure silicon blocking layer 4 structure are formed by molecular beam epitaxy. During the growth of this material, the ultra-high vacuum degree of the molecular beam epitaxy chamber is 10 -6 torr, and the temperature of the substrate is 580 °C.

[0039] (3) The silicon wafer is cleaned, that is, it is ultrasonically cleaned in a ultrasonic cleaner with perchloroethylene, acetone, isopropyl alcohol, and deionized water for more than 10 minutes respectively, then dried with a nitrogen gun and baked on a hot plate. The temperature of the hot plate is 150 °C and the time is 15 minutes. After drying, AZ1518 photoresist is spin-coated on the silicon wafer, the spinning speed is 1000 revolutions per second, the acceleration is 500 revolutions per second, and the spinning time is 45 seconds, achieving a 3-μm-thick spin-coating of AZ1518 photoresist;

[0040] (4) The silicon wafer is pre-baked on a hot plate at a temperature of 100 °C for 60 seconds. Then the silicon wafer is placed in an ultraviolet exposure device (model MA / BA6 double-sided alignment lithography machine) for exposure, and the exposure dose is 319 mj / cm 2, the hard contact mode is adopted. After exposure, the silicon wafer is developed and patterned with AZ300 developing liquid, and the developing time is 90 seconds. Then it is dried with a nitrogen gun and post-baked at a temperature of 100 °C for 1 minute.

[0041] (5) The patterned silicon wafer is placed into a deep silicon etching equipment (Samco, Japan, model RIE-400iPB). In order to fabricate a fully dielectric microporous array structure with a parabolic sidewall shape, the power of the etching equipment is set to 800 W, the substrate bias voltage is 60 W, the SF6 gas flow rate is 100 sccm, the C4F8 gas flow rate is 100 sccm, and the O2 flow rate is 10 sccm. The etching process consists of 16 cycles of alternating protection and etching, and the etching depth is 5 μm. Then, acetone solution is used for heating to remove the photoresist for 10 minutes at a heating temperature of 60 °C. Finally, a microporous array with a parabolic sidewall shape, namely the fully dielectric microstructure 5, is fabricated. Among them, the diameter range of the holes is: D1 = 7.6 - 7.8 μm, D2 = 8.2 - 8.4 μm (such as D1 = 7.8 μm, D2 = 8.2 μm), the period P is 10 - 18 μm (such as P = 12 μm), and the number of holes exceeds 100 (such as 27,666 holes).

[0042] Figure 2 Top view and sidewall view of the all-silicon microstructure with a photon trapping mode with a structural period P of 12 μm, D1 = 7.8 μm, D2 = 8.2 μm, and depth H of 5 μm for the fully dielectric microstructure 5 under a scanning electron microscope; showing the structure of the fully dielectric microporous array with a parabolic sidewall shape.

[0043] Figure 3 (11) Poynting vector distribution of the all-silicon microstructure with a photon trapping mode (structural period P = 12 μm, D1 = 7.8 μm, D2 = 8.2 μm, depth H = 5 μm) prepared in Example 1 under finite element simulation and analysis; showing the interaction process between the incident light and the microstructure, and successfully exciting the photon trapping mode. With the help of this mode, the photon energy can be efficiently coupled to the active absorption layer, converting the longitudinal mode of the photon into a horizontally confined mode, and greatly enhancing the interaction strength between light and the weakly absorbing medium.

[0044] Figure 4Absorption rate distributions of the all-silicon microporous structure with a photon residence mode prepared in Example 1 (structural period P = 12 μm, D1 = 7.8 μm, D2 = 8.2 μm, depth H = 5 μm), the periodic straight-hole all-silicon microstructure, and the planar all-silicon structure. It can be seen that the absorption rate of the all-silicon microporous structure with a photon residence mode is significantly higher than that of the planar reference structure within the wavelength range of 14 - 20 μm, and is also higher than that of the periodic straight-hole all-silicon microstructure. Among them, the periodic straight-hole all-silicon microstructure and the planar all-silicon structure are control structures. The all-dielectric microstructure 5 of the periodic straight-hole all-silicon microstructure is a straight-hole type microporous array, and the planar all-silicon structure is a traditional all-silicon structure without the all-dielectric microstructure 5.

[0045] In addition, on the basis of the above research in this embodiment, the influence of the all-silicon microporous structure with a photon residence mode with different structural parameters on the absorption rate was also explored, and the results are as Figure 5 shown. Among them, Figure 5 (a) shows the change and distribution of the absorption rate when changing the physical quantity depth H, with the periodic physical quantity P = 12 μm and the physical quantity D1 / D2 = 0.95 (D2 = 8.2 μm), and the physical quantity depth H is 3 μm, 5 μm, and 8 μm respectively; the results show that when the structural parameter depth H = 5 μm, the absorption rate reaches the maximum within the wavelength range of 14 - 20 μm. Figure 5 (b) shows the change and distribution of the absorption rate when changing the physical quantity period P, with the physical quantity depth H = 5 μm and the physical quantity D1 / D2 = 0.95 (D2 = 8.2 μm), and the period P is 10 μm, 12 μm, and 14 μm respectively; the results show that when the period P = 12 μm, the absorption rate reaches 30% and above within the wavelength range of 14 - 20 μm. Figure 5 (c) shows the change and distribution of the absorption rate when changing the physical quantity D1 / D2, with the physical quantity depth H = 5 μm, the period P = 12 μm, and the physical quantity D1 / D2 (D2 = 8.2 μm) being 0.7, 0.8, 0.9, and 0.95 respectively; the results show that the physical quantity D1 / D2 has an obvious influence on the distribution of the absorption rate. Combining the above results, the optimal absorption efficiency can be achieved when the period P = 12 μm, the depth H = 5 μm, and D1 / D2 is close to 0.95. Therefore, through the optimization and design of the structural parameters, the present invention obtains the adapted parameter values. These results provide key design principles and systematic methods for constructing an all-silicon microporous structure with a photon residence mode to enhance broadband absorption, and are expected to contribute to the technological breakthrough and practical application in this field.

[0046] In summary, the present invention introduces a periodic microporous array with a parabolic shape whose structural period is comparable to the incident wavelength to excite the horizontal transmission mode, and combines a bottom heavily doped plasma layer to achieve the residence and strong localization effects of the horizontal photon mode, maximizing the photon capture efficiency of the thin-film active absorption layer in a very long wavelength broad spectrum range. The application of this structure can significantly improve the performance of optoelectronic devices such as infrared detectors and solar cells, and has broad application prospects.

[0047] The above has described the embodiments of the present invention in detail, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions, and variations made to these embodiments still fall within the protection scope of the present invention.

Claims

1. A fully silicon microporous structure with enhanced broadband absorption in a photon residence mode, characterized in that, The all-silicon microporous structure includes, from bottom to top, a high-purity silicon substrate (1), a heavily doped silicon plasma layer (2), a lightly doped silicon active absorption layer (3), and an intrinsic pure silicon blocking layer (4). It also includes a all-dielectric microstructure (5). The all-dielectric microstructure (5) is a periodic microporous array (5) with a parabolic sidewall shape. The all-dielectric microstructure (5) is embedded in the lightly doped silicon active absorption layer (3) of the material. The doping element of the heavily doped silicon plasma layer (2) is boron, and the doping element of the lightly doped silicon active absorption layer (3) is gallium.

2. The all-silicon microporous structure for enhancing broadband absorption with a photon residence mode according to claim 1, characterized in that, The pore diameter range of the all-dielectric microstructure (5) is: D1 = 7.6 - 7.8 μm, D2 = 8.2 - 8.4 μm, the period P is 10 - 18 μm, and the number of pores exceeds 100.

3. The all-silicon microporous structure for enhancing broadband absorption with a photon residence mode according to claim 1, characterized in that, The all-silicon microporous structure has a maximized photon capture efficiency in the very long wavelength range of 14 - 20 μm.

4. The all-silicon microporous structure for enhancing broadband absorption by photon residence mode according to claim 1, characterized in that, The resistivity of the high-purity silicon substrate (1) > 10000 Ω·cm, and the thickness is 400 - 500 μm.

5. The all-silicon microporous structure with enhanced broadband absorption in the photon residence mode according to claim 1, characterized in that The doping concentration of boron in the heavily doped silicon plasma layer (2) ≥ 1×10 20 cm -3 .

6. The all-silicon microporous structure for enhancing broadband absorption with a photon residence mode according to claim 1, characterized in that, The doping concentration of gallium in the lightly doped silicon active absorption layer (3) is 1×10 15 cm -3 ~1×10 18 cm -3 , and the thickness of the absorption layer is 4 - 7 μm.

7. The all-silicon microporous structure with enhanced broadband absorption in a photon residence mode according to claim 1, wherein The thickness of the intrinsic pure silicon blocking layer (4) is 2 - 5 μm, and the resistivity > 5000 Ω·cm.

8. The preparation method of the all-silicon microporous structure with enhanced broadband absorption in the photon residence mode according to any one of claims 1-7, characterized in that, It includes the following steps: S1. Prepare the heavily doped silicon plasma layer (2) on the high-purity silicon substrate (1) by high-dose and high-energy ion implantation. S2. Place the sample into a molecular beam epitaxy device and grow the lightly doped silicon active absorption layer (3) and the intrinsic pure silicon blocking layer (4) by molecular beam epitaxy. S3. Complete the surface patterning of the regional microstructure through photolithography, ultraviolet exposure, and development, and then prepare the all-dielectric microstructure (5) through an optimized deep reactive ion beam etching process.

9. The preparation method of the all-silicon microporous structure with enhanced broadband absorption by photon residence mode according to claim 8, characterized in that, The optimized deep reactive ion beam etching process is specifically as follows: Set the power of the etching equipment to 700 - 900 W, the substrate bias voltage to 50 - 70 W, the SF6 gas flow rate to 90 - 120 sccm, the C4F8 gas flow rate to 90 - 120 sccm, and the O2 flow rate to 7 - 15 sccm. The etching process is 14 - 18 cycles of alternating protection and etching, and then heat to remove the photoresist after etching.

10. Use of the all-silicon microporous structure with enhanced broadband absorption in the photon residence mode according to any one of claims 1-7 in optoelectronic devices, characterized in that, The optoelectronic device includes an infrared detector and a solar cell.

Images