A full-silicon microcellular structure with photon residence mode enhanced broadband absorption and a preparation method thereof

Abstract

The present application belongs to the field of very long wave infrared detection technology, and particularly relates to a full-silicon micro-pore structure with photon standing mode enhanced wide spectrum absorption and a preparation method. The full-silicon micro-pore structure from bottom to top is high-purity silicon substrate, heavily doped silicon plasma layer, lightly doped silicon active absorption layer and intrinsic pure silicon barrier layer, further comprising a periodic micro-pore array structure with parabolic sidewall, and the structure is embedded into the lightly doped silicon active absorption layer. The micro-pore array structure with parabolic sidewall designed in the present application realizes the coupling of wide spectrum photons and excites high-order diffraction modes deviated from the vertical direction; meanwhile, the heavily doped silicon plasma layer compatible with the full-silicon process is introduced, and the photon standing mode is successfully realized. Under the joint action of the above designs, the photon capture efficiency of the thin active absorption layer in the very long wave wide spectrum range is maximized, and the performance of photoelectric devices such as infrared detectors and solar cells can be significantly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of very long wave infrared detection, and particularly relates to a full-silicon micro-porous structure with photon residence mode enhanced wide-spectrum absorption and a preparation method thereof. BACKGROUND

[0002] The long wave and very long wave range contains rich material and chemical information, and thus is of great significance in the fields of astronomical observation, environmental monitoring and the like. Common silicon, germanium and gallium arsenide semiconductor materials have intrinsic band gaps of 1.12 eV, 0.66 eV and 1.42 eV respectively. Among these materials, the germanium material has the longest response wavelength, which is cut off at 1.85 μm, and cannot detect spectral information with a longer wavelength. In order to realize sub-bandgap absorption, impurity energy levels need to be introduced into the semiconductor material. However, when the intrinsic band transition is changed into the impurity band transition, 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 excavation of the application potential of the long wave and very long wave detection in multiple fields.

[0003] In order to solve the absorption problem of the non-intrinsic silicon material based on impurity transition, the traditional method is to increase the material thickness. However, for the non-intrinsic detector in the very long wave range, this method not only increases the volume of the device and the dark current related thereto, but also reduces the response speed of the device.

[0004] The effective strategies for enhancing absorption in a thin absorption layer include introducing surface plasmons, guided mode resonance, light trapping and the like artificial microstructures. By introducing a photon trapping structure, the additional dark current can be avoided, and the photons can be constrained in the active region, thereby improving the quantum efficiency in a specific waveband range. At present, the long wave and very long wave range mainly applies metal photon trapping resonance structures and dielectric guided mode resonance structures, although they can realize the localization of photons at a specific peak position and enhance the absorption effect, but cannot be applied to the design of high-sensitivity wideband detectors. By designing regular and periodic artificial micro-nano structures, the absorption in the long wave wideband can be enhanced. However, a metal thin layer needs to be introduced on the surface of the light trapping structure to excite the skin effect and realize photon confinement. However, the introduction of metal not only increases the photon loss in the long wave and very long wave range, but also is not suitable for the manufacture of large-scale uniform array devices. In addition, the traditional periodic regular structure cannot effectively trap photons, which limits its application in related fields.

[0005] Therefore, it is necessary to develop a new structure which can break through the existing absorption limitation, so as to realize high-sensitivity and wideband absorption in the long wave and very long wave range, and improve the photon residence efficiency. SUMMARY

[0006] In order to overcome the above-mentioned deficiencies of the prior art, the present application designs a full dielectric micro-hole array structure with parabolic sidewall, realizes wide-band photon absorption enhancement without introducing noble metal, and is compatible with actual silicon device industry, so that the full dielectric process structure is expected to be widely applied to high-sensitivity wide-band detector design of various material systems.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0008] The present application provides a full silicon micro-hole structure for enhancing wide-band absorption of photon standing mode, which comprises, 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 barrier layer, further comprises a full dielectric microstructure, the full dielectric microstructure is a periodic micro-hole array with parabolic sidewall, and the full 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 application introduces a periodic micro-hole array with parabolic sidewall by constructing a surface patterned microstructure, excites and guides high-order diffraction modes, and combines a heavily doped semiconductor plasma layer to make photon standing modes stay in the absorption layer, so that the lightly doped silicon active absorption layer realizes high absorption efficiency of photons in a very long wave wide-band range.

[0010] Preferably, the hole diameter of the full dielectric microstructure ranges from D1=7.6 to 7.8 μm and D2=8.2 to 8.4 μm, the period P is 10 to 18 μm, and the number of holes is more than 100.

[0011] Preferably, the full silicon micro-hole structure has maximum photon capture efficiency in a very long wave range of 14 to 20 μm.

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

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

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

[0015] Preferably, the intrinsic pure silicon barrier layer has a thickness of 2-5 microns and a resistivity of >5000 ohm*cm.

[0016] The second aspect of the application provides a preparation method of the full-silicon micro-porous structure with photon standing mode enhanced wide-spectrum absorption according to the first aspect, comprising the following steps:

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

[0018] S2, placing the sample into a molecular beam epitaxy device to complete the growth of a lightly doped silicon active absorption layer and an intrinsic pure silicon barrier layer by molecular beam epitaxy;

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

[0020] Preferably, the optimized deep reactive ion beam etching process is as follows: the power of the etching device is set to 700-900 W, the substrate bias is 50-70 W, the SF6 gas flow is 90-120 sccm, the C4F8 gas flow is 90-120 sccm, and the O2 flow is 7-15 sccm; the etching process is 14-18 cycles of alternating protection and etching, and after etching, heating and adhesive removal can be performed.

[0021] Preferably, in S1, the implantation conditions include an angle of 6-8° deviated from the vertical direction, an energy of 70-90 keV, and a dose of 1-5*10 15 cm -2 , and the prepared layer has a thickness of 0.2 microns or more.

[0022] The third aspect of the application provides an application of the full-silicon micro-porous structure with photon standing mode enhanced wide-spectrum absorption according to the first aspect in an optoelectronic device, and the optoelectronic device includes an infrared detector and a solar cell.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] The application discloses a full-silicon micro-pore structure for photon standing mode enhanced wide-spectrum absorption, which comprises, 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 barrier layer, and further comprises a periodic micro-pore array structure with parabolic sidewalls, and the structure is embedded into the lightly doped silicon active absorption layer.

[0025] It can be seen that, by virtue of the micro-pore array structure with parabolic sidewalls, the full-silicon micro-pore structure of the application excites and guides high-order diffraction modes, and the heavily doped semiconductor plasma layer is introduced to make the photon stay in the absorption layer, so that the photon absorption efficiency of the lightly doped silicon active absorption layer in a very long wave wide spectrum is greatly improved. The full-silicon system has low cost and good compatibility, and the preparation process is simplified. The application of the structure can significantly improve the performance of photoelectric devices such as infrared detectors and solar cells, provides a scheme for miniaturization and high performance of photoelectric devices, and promotes the technological innovation of the optoelectronic industry. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 FIG. 1 is a schematic diagram of a photon standing mode full-silicon micro-pore structure and a partial schematic diagram of a full-dielectric micro-pore array sidewall;

[0027] Figure 2 FIG. 3 is a top view and a sidewall view of a full-dielectric micro-pore array structure under a scanning electron microscope;

[0028] Figure 3 FIG. 5 is a Poynting vector distribution of the photon standing mode full-silicon micro-pore structure, which shows the horizontal vector distribution and the existence of the photon standing mode;

[0029] Figure 4 FIG. 7 is an absorption rate comparison of the photon standing mode full-silicon micro-pore structure, a periodic straight-hole full-silicon microstructure and a planar full-silicon structure;

[0030] Figure 5The absorptivity distribution of an all-silicon structure with different photon dwell modes is shown. (a) shows the change and distribution of absorptivity when the physical quantity depth H is changed, with a fixed period physical quantity P = 12 μm, physical quantity D1 / D2 = 0.95 (D2 = 8.2 μm), and physical quantity depth H of 3 μm, 5 μm, and 8 μm, respectively; (b) shows the change and distribution of absorptivity when the physical quantity period P is changed, with a physical quantity depth H of 5 μm, physical quantity D1 / D2 = 0.95 (D2 = 8.2 μm), and physical quantity period P of 10 μm, 12 μm, and 14 μm, respectively; (c) shows the change and distribution of absorptivity when the physical quantity D1 / D2 is changed, with a physical quantity depth H of 5 μm, period P of 12 μm, and physical quantity D1 / D2 (D2 = 8.2 μm) of 0.7, 0.8, 0.9, and 0.95, respectively. Detailed Implementation

[0031] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0033] Example: An all-silicon microporous structure for enhanced broadband absorption by photon dwelling mode and its preparation method

[0034] like Figure 1 As shown, 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, an intrinsically pure silicon barrier layer 4, and the all-dielectric microstructure 5, wherein the all-dielectric microstructure 5 is a periodic array of micropores with parabolic sidewalls.

[0035] The high-purity silicon substrate 1 has a resistivity > 10000 Ω·cm and a thickness of 450 μm; the heavily doped silicon plasma layer 2 is doped with boron, with a doping concentration of 1 × 10⁻⁶. 20 cm -3 The lightly doped silicon active absorber layer 3 is doped with gallium, and the doping concentration is 3 × 10⁻⁶. 17 cm -3The thickness is 5 μm; the thickness of the intrinsically pure silicon barrier layer 4 is 3 μm, and the resistivity is >5000 Ω·cm; the all-dielectric microstructure 5 is embedded in the lightly doped silicon active absorber layer 3 of the material, and the diameter of the pores ranges from D1 to 7.6 to 7.8 μm, D2 to 8.2 to 8.4 μm (in this embodiment, D1 = 7.8 μm and D2 = 8.2 μm are used as examples), the period P is 10 to 18 μm (in this embodiment, P = 12 μm is used as an example), the number of pores exceeds 100 (in this embodiment, 27666 are used as an example), and the basic periodic boundary condition setting is maintained.

[0036] The above-mentioned method for preparing all-silicon microporous structures includes the following steps:

[0037] (1) A heavily doped silicon plasma layer 2 was formed on an intrinsic silicon substrate 1 with a thickness of approximately 450 μm (resistivity > 10000 Ω·cm) by ion implantation of boron. The implantation conditions included an implantation angle deflection of 7° perpendicular to the direction of rotation, an energy of 80 keV, and a dose of 1.5 × 10⁻⁶. 15 cm -2 A thickness of 0.25 μm and a doping concentration of 1 × 10⁻⁶ were obtained. 20 cm -3 The heavily doped silicon plasma layer 2 (Note: The original thickness of substrate 1 was 450 μm, and a 0.25 μm thick plasma layer 2 was formed on its upper surface, so the actual thickness of substrate 1 is about 450 μm).

[0038] (2) Further, a 5 μm thick lightly doped silicon active absorber layer 3 and a 3 μm thick intrinsically pure silicon barrier layer 4 are formed by molecular beam epitaxy. During the growth of this material, the ultra-high vacuum degree of the molecular beam epitaxy cavity is 10. -6 torr, the substrate temperature is 580℃.

[0039] (3) The silicon wafer was cleaned by ultrasonic cleaning with tetrachloroethylene, acetone, isopropanol and deionized water for more than 10 minutes each, followed by drying with a nitrogen gun and baking with a hot plate at 150°C for 15 minutes. After drying, AZ1518 photoresist was spin-coated onto the silicon wafer at a spin speed of 1000 rpm and an acceleration of 500 rpm for 45 seconds, achieving a 3μm thick AZ1518 photoresist spin coating.

[0040] (4) Preheat the silicon wafer on a hot plate at 100°C for 60 seconds. Then, expose the silicon wafer in an ultraviolet lithography machine (model MA / BA6 double-sided alignment lithography machine) at an exposure dose of 319 mJ / cm². 2After exposure, the silicon wafer is developed using AZ300 developer for 90 seconds. Then, the silicon wafer is blown dry using a nitrogen gun and is subjected to post-exposure baking at 100°C for 1 minute.

[0041] (5) The patterned silicon wafer is placed in a deep silicon etching device (RIE-400iPB, samco, Japan) to prepare a full dielectric micro-hole array structure with parabolic sidewalls. The power of the etching device is set to 800 W, the substrate bias is 60 W, the SF6 gas flow is 100 sccm, the C4F8 gas flow is 100 sccm, and the O2 flow is 10 sccm. The etching process is 16 cycles of alternating protection and etching, and the etching depth is 5 μm. Then, the silicon wafer is subjected to acetone solution heating and degumming for 10 minutes at a heating temperature of 60°C. Finally, a micro-hole array with parabolic sidewalls, i.e., a full dielectric microstructure 5, is obtained. The diameter of the holes ranges from D1 = 7.6-7.8 μm to D2 = 8.2-8.4 μm (e.g., D1 = 7.8 μm and D2 = 8.2 μm), the period P is 10-18 μm (e.g., P = 12 μm), and the number of holes is more than 100 (e.g., 27666 holes).

[0042] Figure 2 FIG. 5 is a top view and a sidewall view of a photonic standing wave mode full silicon microstructure with a structure period P of 12 μm, D1 = 7.8 μm, D2 = 8.2 μm, and a depth H of 5 μm, according to an embodiment of the present application. The structure of the full dielectric micro-hole array with parabolic sidewalls is shown.

[0043] Figure 3 FIG. 6 is a Poynting vector distribution of a photonic standing wave mode full silicon microstructure (structure period P = 12 μm, D1 = 7.8 μm, D2 = 8.2 μm, and depth H = 5 μm) prepared in Example 1 under finite element simulation analysis. The interaction process between incident light and the microstructure is shown, and the photonic standing wave mode is successfully excited. With this mode, the photonic energy can be efficiently coupled to the active absorption layer, the photonic longitudinal mode is converted into a horizontal constraint mode, and the interaction strength between light and a weak absorption medium is greatly enhanced.

[0044] Figure 4The absorption rate distribution of the photonic standing mode full-silicon micro-hole structure (structure period P = 12 μm, D1 = 7.8 μm, D2 = 8.2 μm, depth H = 5 μm) prepared in Example 1, the periodic straight-hole full-silicon microstructure, and the planar full-silicon structure. It can be seen that the absorption rate of the photonic standing mode full-silicon micro-hole structure is obviously higher than that of the planar reference structure and the periodic straight-hole full-silicon microstructure in the wavelength range of 14-20 microns. Among them, the periodic straight-hole full-silicon microstructure and the planar full-silicon structure are control structures, the full-dielectric microstructure 5 of the periodic straight-hole full-silicon microstructure is a straight-hole type micro-hole array, and the planar full-silicon structure is a traditional full-silicon structure without the full-dielectric microstructure 5.

[0045] In addition, on the basis of the above research of the present embodiment, the influence of the photonic standing mode full-silicon micro-hole structure with different structure parameters on the absorption rate is also explored, and the results are shown in Figure 5 Figure 5 (a) is the change and distribution of absorption rate when the physical quantity depth H is changed, the period 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 structure parameter depth H = 5 μm, the absorption rate reaches the maximum in the wavelength range of 14-20 μm. Figure 5 (b) is the change and distribution of absorption rate when the period physical quantity P is changed, the physical quantity depth H is 5 μm, 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 in the wavelength range of 14-20 μm. Figure 5 (c) is the change and distribution of absorption rate when the physical quantity D1 / D2 is changed, the physical quantity depth H is 5 μm, the period P is 12 μm, and the physical quantity D1 / D2 (D2 = 8.2 μm) is 0.7, 0.8, 0.9 and 0.95 respectively; the results show that the physical quantity D1 / D2 has a significant influence on the distribution of absorption rate. In summary, when the period P = 12 μm, the depth H = 5 μm, and D1 / D2 is close to 0.95, the optimal absorption efficiency can be achieved. Therefore, by optimizing and designing the structure parameters, the present application obtains the adaptive parameter values. These achievements provide key design principles and systematic methods for constructing photonic standing mode full-silicon micro-hole structures to enhance wide-spectrum absorption, and are expected to help technical breakthroughs and practical applications in this field.

[0046] ​As can be seen from the above, the application excites horizontal transmission mode by introducing a periodic micro-hole array with parabolic shape and a structure period corresponding to the incident wavelength, and realizes the residence and strong local effect of horizontal photon mode by combining with a bottom heavily doped plasma layer, so that the photon capture efficiency of a thin layer active absorption layer in a very long wave spectrum range is maximized. The application of the structure can significantly improve the performance of photoelectric devices such as infrared detectors and solar cells, and has a broad application prospect.

[0047] The embodiments of the application are described in detail above, but the application is not limited to the described embodiments. For those skilled in the art, various changes, modifications, replacements and variations of the embodiments can be made without departing from the principles and spirits of the application, and still fall within the protection scope of the application.

Claims

1. An all-silicon photonic stopband mode enhanced broadband absorption microcavity, characterized in that, The full-silicon micro-porous structure comprises 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 barrier layer (4), and further comprises a full-dielectric micro-structure (5), which is a periodic micro-porous array with parabolic sidewalls and is formed by deep reactive ion beam etching, and is embedded in the lightly-doped silicon active absorption layer (3) with the intrinsic pure silicon barrier layer (4) as the starting point; 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; the full-dielectric micro-structure (5) is formed by deep reactive ion beam etching of the intrinsic pure silicon barrier layer (4) and the lightly-doped silicon active absorption layer (3).

2. A photonic stopband mode enhanced broad spectrum absorbing all-silicon photonic crystal structure according to claim 1, wherein, The pore diameter of the full-dielectric micro-structure (5) ranges from D1=7.6-7.8 μm to D2=8.2-8.4 μm, the period P is 10-18 μm, and the number of pores is more than 100; D1 is the pore diameter of the narrow end of the parabolic sidewall micro-pore in the full-dielectric micro-structure (5), D2 is the pore diameter of the wide end of the parabolic sidewall micro-pore in the full-dielectric micro-structure (5), and the period P is the distance between the centers of two adjacent micro-pores in the periodic micro-pore array of the full-dielectric micro-structure (5).

3. A photonic stopband mode enhanced broad spectrum absorbing all-silicon photonic crystal structure according to claim 1, wherein, The full-silicon micro-porous structure has maximized photon capture efficiency in the very long wave range of 14-20 μm.

4. A photonic stopband mode enhanced broad spectrum absorbing all-silicon photonic crystal structure according to claim 1, wherein, The high-purity silicon substrate (1) has a resistivity of >10000 Ω·cm and a thickness of 400-500 μm.

5. A photonic stopband mode enhanced broad spectrum absorbing all-silicon photonic crystal structure according to claim 1, wherein, The boron doping concentration in the heavily doped silicon plasma layer (2) is ≥ 1 x 10 20 cm -3 .

6. A photonic stopband mode enhanced broad spectrum absorbing all-silicon photonic crystal structure according to claim 1, wherein, The doping concentration of gallium in the lightly doped silicon active absorption layer (3) is 1 x 10 15 cm -3 ~ 1 x 10 18 cm -3 , and the thickness of the absorption layer is 4 ~ 7 μm.

7. A photonic stopband mode enhanced broad spectrum absorbing all-silicon photonic crystal structure according to claim 1, wherein, The intrinsic pure silicon barrier layer (4) has a thickness of 2-5 μm and a resistivity of >5000 Ω·cm.

8. The method of producing a photonic band gap enhanced wide spectrum absorbing all-silicon micro-porous structure according to any one of claims 1 to 7, characterized in that, The method comprises the following steps: S1, preparation of the heavily-doped silicon plasma layer (2) on the high-purity silicon substrate (1) by high-dose and high-energy ion implantation; S2, growth of the lightly-doped silicon active absorption layer (3) and the intrinsic pure silicon barrier layer (4) by molecular beam epitaxy in a molecular beam epitaxy device; S3, surface patterning of the region micro-structure by photolithography, ultraviolet exposure, and development, and preparation of the full-dielectric micro-structure (5) by an optimized deep reactive ion beam etching process; the optimized deep reactive ion beam etching process is as follows: the power of the etching device is set to 700-900 W, the substrate bias is 50-70 W, the SF6 gas flow rate is 90-120 sccm, the C4F8 gas flow rate is 90-120 sccm, and the O2 flow rate is 7-15 sccm; the etching process is 14-18 cycles of alternating protection and etching, and after etching, heating is performed for adhesive removal.

9. Use of the all-silicon photonic stopband-enhanced microcavity structure according to any one of claims 1 to 7 in an optoelectronic device, characterized in that, The optoelectronic device comprises an infrared detector and a solar cell.

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