Light capture and radiation cooling superstructure and infrared sensor

Abstract

The invention provides a light capture and radiation cooling superstructure and an infrared sensor, and aims to solve the problem that weak infrared light detection always has challenges due to the fact that the sensitivity of a detector is reduced due to existence of various noises in infrared detection. Aiming at various noises of an infrared detector, the invention provides a bionic solution which comprises a light capture and radiation cooling superstructure and an infrared sensor. According to the light capture and radiation cooling super-structure bionic butterfly wing, a metal-medium-metal (MIM) structure is composed of a gold layer with holes with sub-near infrared wavelength (800-2500nm) in the surface, a medium layer and a bottom titanium metal reflecting layer, strong plasmon resonance can be formed on the incident surface, light reflection and transmission are reduced, light absorption is achieved to the maximum extent, and the light capture and radiation cooling super-structure bionic butterfly wing has the advantages of being high in light capture and radiation cooling performance and good in radiation cooling performance. Meanwhile, far infrared light of an atmospheric transmission window (8-13 microns) can be emitted, radiation cooling of the sensor is achieved, and thermal noise of the device is reduced to the maximum extent.

Description

Technical Field

[0001] The present invention belongs to the field of infrared light detectors, and particularly relates to a light trapping and radiative cooling superstructure and an infrared sensor. Background Art

[0002] Infrared detectors, as important tools for sensing invisible light, have been widely studied due to their diverse applications (such as military reconnaissance, industrial inspection, medical diagnosis, medicine, environmental monitoring, and security monitoring).

[0003] Currently, the main commercial light detectors mainly rely on narrow bandgap semiconductor materials (such as HgCdTe, InSb, PbS, etc.) or thermosensitive materials (such as vanadium oxide). However, due to the high preparation cost, strong low-temperature dependence, material toxicity, and process limitations of these materials, their further applications in the field of light detection are severely restricted. With the development of two-dimensional materials and quantum dot materials, they gradually show their unique potential in this field (such as room-temperature working ability, flexibility, small volume, low-cost solution method preparation, spectral tunability, and dual-band detection, high gain and stability). However, they still face the influence of thermal noise, shot noise, and low-frequency noise, resulting in an increase in the dark current of the detector and a decrease in the signal-to-noise ratio and sensitivity, and also restricting their applications in weak signal detection (such as single-photon imaging and deep space exploration). Summary of the Invention

[0004] Aiming at the above technical problems, the present invention provides a light trapping and radiative cooling superstructure and an infrared sensor. By designing the structure of the infrared sensor, it can effectively optimize the problems brought by various noises.

[0005] To achieve the above object, the technical solution of the present invention is as follows: On the one hand, the present invention provides a light trapping and radiative cooling superstructure, which sequentially includes a MIM structure composed of a gold layer, an insulating dielectric layer, and a titanium metal reflective layer from top to bottom, and the gold layer has a plurality of holes.

[0006] In one preferred embodiment, the holes on the gold layer are rectangular, circular, or irregular in shape.

[0007] In one preferred embodiment, the shape of the holes on the gold layer is preferably rectangular, and the side length of the rectangle is 1 - 1.5 μm, and the edge spacing between adjacent rectangular holes is 100 - 200 nm.

[0008] In one preferred embodiment, the thickness of the gold layer is 50 - 150 nm.

[0009] In one preferred embodiment, the thickness of the titanium metal reflective layer is 100 - 150 nm.

[0010] In one preferred embodiment, the insulating dielectric layer is a photovoltaic structure layer.

[0011] In one preferred embodiment, the photovoltaic structure layer includes at least one of a PN structure, a PIN structure, or a PP-IN-N structure.

[0012] The second invention of the present invention provides an infrared sensor, which includes the light-trapping and radiative cooling superstructure and the FET of any one of the above embodiments. The light-trapping and radiative cooling superstructure is located above the FET. The FET includes an insulating substrate, a channel, a source metal electrode, a drain metal electrode, and a hafnium dioxide high-k layer. The channel is arranged on the insulating substrate. The source metal electrode is connected to the starting end of the channel. The drain metal electrode is connected to the terminating end of the channel. The hafnium dioxide high-k layer is isolated between the light-trapping and radiative cooling superstructure and the FET. The capacitance generated by the photovoltaic structure layer couples the charges inside the capacitance to the conductive channel of the FET through electrostatic induction to collect photocurrent.

[0013] In one preferred embodiment, the photovoltaic structure layer in the light-trapping and radiative cooling superstructure is a PP - IN - N structure composed of a nickel oxide layer, a lead sulfide quantum dot layer, and a zinc oxide layer from top to bottom.

[0014] In one preferred embodiment, the thickness of the nickel oxide layer is 20 - 60 nm, the thickness of the lead sulfide quantum dot layer is 600 - 700 nm, and the thickness of the zinc oxide layer is 40 - 100 nm.

[0015] In one preferred embodiment, the channel is made of carbon nanotubes.

[0016] In one preferred embodiment, the source metal electrode and the drain metal electrode are gold electrodes.

[0017] Due to the adoption of the above technical solutions, the present invention has the following advantages and positive effects compared with the prior art: (1) According to the structure of butterfly wings and the principle of surface plasmon resonance, gold is selected as the material for the bionic structure due to its high surface electron density state and stability. A number of holes are opened on the gold layer, and the holes can be circular holes, rectangular holes or irregular holes. Titanium metal is selected as the radiation layer because its lower work function can adjust the threshold voltage of the FET. The gold layer with holes, the titanium metal reflection layer and the dielectric layer form a metal-dielectric-metal (MIM) structure, which can form strong surface plasmon resonance on the incident surface, reduce light reflection and transmission, maximize light absorption, and at the same time can emit far-infrared light in the atmospheric transmission window (8-13μm) to achieve radiative cooling. When applied to an infrared sensor, it can reduce the sensor temperature and maximize the reduction of device thermal noise.

[0018] (2) The present invention proposes an integrated structure of light trapping and radiative cooling, considering the problem of device cooling while enhancing light absorption, and applying it to an infrared sensor. A bionic solution is proposed for the problem of various noises in a weak infrared background. Compared with the traditional solution to various noise interference problems in a weak infrared background, various liquid nitrogen cooling devices or various complex circuits and algorithms are required for processing. Starting from the structure of the device itself, the present invention considers the causes of various noises and obtains more performance gains through lower-cost structure optimization.

[0019] (3) Compared with traditional optoelectronic FETs, using an externally applied gate voltage to turn on the channel increases power consumption. At the same time, photo-generated carriers are directly generated in the conductive channel to form a loop, and it is impossible to avoid current-related noises. The present invention proposes a field effect transistor structure with self-photovoltaic and capacitive gate. Through the internal electric field of the photovoltaic structure layer, photo-generated carriers are accumulated on the hole absorption and titanium metal layers to form a capacitor, and the charges are coupled to the conductive channel through electrostatic induction, thereby turning on the conductive channel of the field effect transistor and completing the collection of photo-generated carriers. Since the conductive channel is turned on by capacitive coupling of photo-generated carriers, it avoids the formation of a loop of photo-generated carriers directly in the channel and avoids current-related noises, such as flicker noise and shot noise. At the same time, without using an externally applied gate voltage to turn on the channel, the dynamic power consumption of the device is further reduced. Brief Description of the Drawings

[0020] Figure 1 It is a schematic diagram of the overall device structure of the infrared sensor of the present invention; Figure 2 It is a schematic diagram of the FDTD calculation structure; Figure 3Figures (a)-(c) are the electric field distribution diagrams of the integrated FET-type infrared sensor with a light-trapping radiative cooling superstructure and a self-photovoltaic / capacitance gate at the absorption peaks in the near-infrared and atmospheric transmission windows; (d)-(f) are the electric field distribution diagrams of the integrated FET-type infrared sensor with a self-photovoltaic / capacitance gate without a light-trapping and radiative cooling structure at the absorption peaks in the near-infrared and atmospheric transmission windows; Figure 4 are the absorption spectra of infrared sensors with and without a light-trapping and radiative cooling superstructure in different bands. The red curve is the absorption spectrum of the infrared sensor with a light-trapping and radiative cooling superstructure in the near-infrared and atmospheric transmission windows, and the blue curve is the absorption spectrum of the infrared sensor without a light-trapping and radiative cooling structure; Figure 5 is the schematic diagram of the equivalent circuit of the sensor device, C j is PP - IN - N is the junction capacitance of the self-photovoltaic structure, and Rs is PP - IN - N is the load equivalent impedance of the self-photovoltaic part, and Rj is PP - IN - N is the equivalent junction resistance of the self-photovoltaic part, C GS is the equivalent capacitance between the capacitance gate and the source of the capacitance gate FET, C GD is the equivalent capacitance between the capacitance gate and the drain in the capacitance gate FET structure, C D s is the equivalent capacitance between the source and the drain of the capacitance gate FET, Ro is the equivalent channel resistance of the capacitance gate FET, R L is the equivalent load resistance of the capacitance gate FET, g m V GS is the equivalent transconductance between the capacitance gate and the source of the capacitance gate FET. Detailed implementation

[0021] In infrared detection, due to the existence of various noises, the sensitivity of the detector decreases, making the detection of weak infrared light always challenging. In response to the various noises of infrared detectors, the present invention provides a bionic solution, including an integrated superstructure of light trapping and radiative cooling and an infrared sensor. Among them, the light trapping and radiative cooling superstructure imitates the butterfly wing, and is composed of a gold layer with holes having sub-near-infrared wavelength (800 - 2500nm) dimensions on the surface, an intermediate dielectric layer, and a bottom titanium metal reflective layer to form a metal-dielectric-metal (MIM) structure, which can form strong surface plasmon polariton resonances on the incident surface, reduce light reflection and transmission, maximize light absorption, and at the same time be able to emit far-infrared light in the atmospheric transmission window (8 - 13μm) to achieve radiative cooling of the sensor and maximize the reduction of device thermal noise. The infrared sensor includes an integrated superstructure of light trapping and radiative cooling and a FET (field effect transistor). The photovoltaic structure in the integrated superstructure of light trapping and radiative cooling and the FET structure form a self-photovoltaic / capacitance-gate integrated FET-type infrared sensor. The capacitance formed by the photo-generated carriers accumulating on hafnium dioxide (high-k layer) under the action of an electric field is used to couple the charges into the channel, thereby opening the conductive channel of the field effect transistor to complete the collection of photo-generated carriers. Since the conductive channel is opened by capacitive coupling of photo-generated carriers without forming a loop, current-related noises such as flicker noise and shot noise can be maximally reduced.

[0022] The following further details the light trapping and radiative cooling superstructure and infrared sensor proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer.

[0023] Embodiment 1: Design of the light trapping and radiative cooling superstructure: According to the structure of the butterfly wing and the principle of surface plasmon polariton resonance, gold is selected as the material of the bionic structure because of its high surface electron density state and stability. According to the influence of different structures on the absorption rate, the structural parameters of the gold structure, thickness, hole spacing, hole size and shape ( Figure 2 ) are adjusted. Titanium metal is selected as the reflective layer because its low work function can adjust the threshold voltage of the FET. Therefore, the light trapping and radiative cooling superstructure includes, from top to bottom, a MIM structure composed of a gold layer, a dielectric layer, and a titanium metal reflective layer, and there are multiple holes on the gold layer. The holes on the gold layer can be rectangular, circular or irregular in shape. Preferably, having the maximum absorption rate, the thickness of the gold layer is 50 - 150nm, the holes on the gold layer are rectangular, and the side length of the rectangle is 1 - 1.5μm, and the edge spacing between adjacent rectangular holes is 100 - 200nm. Further optimization, as Figure 2 shown, the thickness of the gold layer is 50nm, the rectangular holes are square holes, the side length is 1.2μm, and the edge spacing between adjacent square holes is 100nm.

[0024] In a preferred embodiment, the thickness of the titanium metal reflective layer is 100 - 150 nm. Further optimized, the thickness of the titanium metal reflective layer is 120 nm.

[0025] In a preferred embodiment, the insulating dielectric layer is a photovoltaic structure layer.

[0026] The photovoltaic structure layer at least includes one of PN structure, PIN structure or PP - IN - N structure.

[0027] According to the theory of the MIM structure, it is necessary to optimize the parameters of the dielectric layer material. Among them, the thickness and refractive index are important parameters. Preferably, the photovoltaic structure layer selects PP - IN - N structure, which has a PP formed by a nickel oxide layer with a thickness of 20 - 60 nm, a lead sulfide quantum dot layer of 600 - 700 nm, and a zinc oxide layer of 40 - 100 nm - IN - N structure.

[0028] After the optimized parameter design, the infrared sensor with the light trapping and radiative cooling superstructure of this embodiment is compared with the infrared sensor without the light trapping and radiative cooling superstructure (blank control) in the near-infrared absorption at 1 - 3 μm and the absorption spectrum at 8 - 13 μm. As Figure 4 shown, the absorption intensity of the infrared sensor with the light trapping and radiative cooling superstructure has a significant increase both at the wavelength of 1 - 3 μm and at the wavelength of 8 - 13 μm.

[0029] Observe the electric field distribution diagrams at the absorption peaks in the near-infrared and atmospheric transmission windows of the infrared sensor with the light trapping and radiative cooling superstructure of this embodiment and the infrared sensor without the light trapping and radiative cooling superstructure (blank control). The results are as Figure 3 shown, Figure 3 in which (a)-(c) is the xy interface electric field of the infrared sensor with the light trapping and radiative cooling superstructure, which has a significant increase compared with the xy interface electric field of the blank control device ( Figure 3 in which (d)-(f)), especially at the resonance peaks of 1.22 μm, 2.22 μm and 9.21 μm.

[0030] Example 2: Design of the self-photovoltaic / capacitance-gate integrated FET-type infrared sensor structure: Based on the in-depth study of the working principle of the device, a mechanism based on the capacitive coupling of the photo-generated electric field is designed to couple charges into the channel, and a self-photovoltaic structure and capacitance-gate integrated FET-type sensor is proposed. As Figure 1-2As shown, the infrared sensor includes the light trapping and radiative cooling superstructure and the FET of any of the above embodiments. The light trapping and radiative cooling superstructure is located on the upper layer of the FET. The FET includes an insulating substrate, a carbon nanotube channel, a source metal electrode, a drain metal electrode, and a hafnium dioxide high-k layer. The carbon nanotube channels are arranged on the insulating substrate. The source metal electrode is connected to the starting end of the carbon nanotube channel, and the drain metal electrode is connected to the terminating end of the carbon nanotube channel. The hafnium dioxide high-k layer is isolated between the light trapping and radiative cooling superstructure and the FET. The capacitance generated by the photovoltaic structure layer couples the charges inside the capacitance to the conductive channel of the FET through electrostatic induction to collect the photocurrent. Both the source metal electrode and the drain metal electrode are gold electrodes, and the insulating substrate is silicon dioxide with a thickness of 100 nm and silicon with a thickness of 500 μm.

[0031] Among them, photovoltaic structures, such as: PN junction type photovoltaic structures, PIN type photovoltaic structures, and PP - IN - N-type structures. PP - IN - The N-type structure exhibits a larger photo-generated voltage due to the energy band alignment engineering. The photovoltaic structure is composed of a nickel oxide layer, a lead sulfide quantum dot layer, and a zinc oxide layer from top to bottom in the PP - IN - N structure, as Figure 1-2 shown, the PP-IN-N structure is specifically a P-type hole collection layer nickel oxide layer, P - type lead sulfide quantum dots, I-type lead sulfide quantum dots, N - type lead sulfide quantum dots, and an N-type electron collection layer zinc oxide from top to bottom. The thickness of the nickel oxide layer is 20 - 60 nm, the thickness of the lead sulfide quantum dot layer is 600 - 700 nm, and the thickness of the zinc oxide layer is 40 - 100 nm. By absorbing light and generating a photo-voltage in the PP - IN - N photovoltaic structure and performing photo-voltage amplification and charge transport in the carbon nanotube FET, the photovoltaic structure and the carbon nanotube FET are isolated by hafnium dioxide. Among them, PP - IN - The photo-response generated by the N photovoltaic structure can be coupled to the carbon nanotube channel through capacitive gating for further amplification. The optical gain is mainly determined by the transconductance of the photo-voltage converted carbon nanotubes. Since PP - IN - the N photovoltaic structure and the carbon nanotube channel are separated by hafnium dioxide and are in an open-circuit configuration, no current-related noise, including shot noise and flicker noise, will be generated.

[0032] Such as Figure 5 shown, in the equivalent circuit of the entire sensor, PP - IN -Between the N photovoltaic structure and the capacitive gate FET, C GD Capacitive isolation is adopted, and a loop cannot be formed. Only through capacitive coupling can the photo-generated charges be coupled into the capacitive gate FET to form a current between the source and the drain.

[0033] In summary, an infrared sensor of the present invention can effectively reduce various noises and improve the sensitivity of the infrared sensor through the optimization and design of the structure.

[0034] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, provided that these changes fall within the scope of the claims of the present invention and its equivalent technologies, they still fall within the protection scope of the present invention.

Claims

1. A light-trapping and radiative cooling superstructure, characterized in that, It successively includes a MIM structure composed of a gold layer, a dielectric layer, and a titanium metal reflective layer from top to bottom, and there are a plurality of holes on the gold layer.

2. The light-trapping and radiative cooling superstructure according to claim 1, wherein The holes on the gold layer are rectangular, circular or irregular in shape.

3. The light trapping and radiative cooling superstructure according to claim 2, wherein The holes on the gold layer are rectangular, and the side length of the rectangle is 1 - 1.5 μm, and the edge distance between adjacent rectangular holes is 100 - 200 nm.

4. The light trapping and radiative cooling superstructure according to claim 1, wherein The thickness of the gold layer is 50 - 150 nm.

5. The light-trapping and radiative cooling superstructure according to claim 1, wherein The thickness of the titanium metal reflective layer is 100 - 150 nm.

6. The light trapping and radiative cooling superstructure according to claim 1, wherein The dielectric layer is a photovoltaic structure layer.

7. The optical trapping and radiative cooling superstructure according to claim 6, wherein The photovoltaic structure layer at least includes one of a PN structure, a PIN structure, or a P - - IN - N structure.

8. An infrared sensor, characterized in that, It includes the light trapping and radiative cooling superstructure and the FET according to any one of claims 1 - 7. The light trapping and radiative cooling superstructure is located on the upper layer of the FET. The FET includes an insulating substrate, a channel, a source metal electrode, a drain metal electrode, and a hafnium dioxide high-k layer. The channel is arranged on the insulating substrate. The source metal electrode is connected to the starting end of the carbon nanotube channel, the drain metal electrode is connected to the terminating end of the carbon nanotube channel, and the hafnium dioxide high-k layer is isolated between the light trapping and radiative cooling superstructure and the FET.

9. The infrared sensor according to claim 8, wherein, The photovoltaic structure layer in the light trapping and radiative cooling superstructure is a PP-IN-N structure composed of a nickel oxide layer, a lead sulfide quantum dot layer, and a zinc oxide layer from top to bottom.

10. The infrared sensor according to claim 9, characterized in that, The thickness of the nickel oxide layer is 20 - 60 nm, the thickness of the lead sulfide quantum dot layer is 600 - 700 nm, and the thickness of the zinc oxide layer is 40 - 100 nm.

11. The infrared sensor according to claim 8, characterized in that, The channel is made of carbon nanotubes.

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