Heterojunction-based ferroelectric capacitor type photodetector device and preparation and application thereof

Abstract

A kind of ferroelectric capacitor type photoelectric detection device based on heterojunction, including bottom electrode, GeSn layer, SiGeSn layer, ferroelectric dielectric layer and top electrode arranged in sequence;GeSn layer and SiGeSn layer form SiGeSn / GeSn heterojunction, i.e.semiconductor layer;Photoelectric detection information is characterized by depletion layer capacitance state: wherein, without light signal, no polarization flip current, depletion layer capacitance is low capacitance state;With light signal, polarization flip current is generated, and depletion layer capacitance is in high capacitance state;Depletion layer capacitance is the capacitance generated by the depletion layer at the contact interface of the semiconductor layer formed by SiGeSn / GeSn heterostructure and ferroelectric dielectric layer, the present application realizes mid-infrared wide spectrum detection function, simultaneously, the heterostructure formed by semiconductor greatly improves the detection sensitivity of photoelectric detection device, and has low power consumption and high integration degree characteristics.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of microelectronic devices, and relates to a photoelectric detection device, in particular to a ferroelectric capacitor type photoelectric detection device based on a heterojunction and preparation and application thereof. BACKGROUND

[0002] At present, the mainstream photoelectric detection device is a resistance type detector, and its principle is that when the photon energy of incident light exceeds the band gap width of a semiconductor material, the energy of incident photons is absorbed by the semiconductor material, the valence band electrons are transitioned, and an electron-hole pair is formed, thereby changing the resistance value of the semiconductor. Different resistance values of the semiconductor can produce different reading currents under an applied bias, and light detection is realized. However, the leakage current of this resistance type photoelectric detection device inevitably leads to additional static power consumption, which seriously reduces its energy efficiency. Moreover, current commercial high-speed low-noise photoelectric detection devices are mainly composed of some traditional III-V or II-VI semiconductor materials, and occupy a dominant position in the market. For example, photoelectric detection devices for the visible-near infrared waveband (0.78-1.0 μm) are mainly composed of semiconductor materials such as silicon (Si), germanium (Ge), indium gallium arsenide (InGaAs), etc. However, the band gap of these semiconductor materials is limited, so the absorption edge of the photoelectric detection device made of these semiconductor materials cannot cover the mid-infrared waveband. Due to the limitation of the material itself, improving the structure of the semiconductor material of the detector has become a breakthrough point for the further development of infrared technology. In addition, the quantum well structure commonly used in the photoelectric detection device is a sandwiched superlattice, and its detection mechanism is completely different from that of the traditional detector. It relies on the quantum mechanical interaction between photons and electrons in a quantum well structure to complete the detection. However, due to the limitations of the structure and the material itself, not all light signals incident on the photoelectric detection device can be absorbed by the semiconductor material to generate photo-generated carriers, and not all photo-generated electrons and photo-generated holes generated inside the semiconductor can be collected by the electrode to finally generate photocurrent. Therefore, when the light signal incident on the photoelectric detection device is relatively weak, the photoelectric detection device often cannot respond, thereby greatly reducing the sensitivity of the photoelectric detection device. Therefore, the above limitations of the existing mid-infrared photoelectric detection device limit the development of mid-infrared detection technology. SUMMARY

[0003] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a ferroelectric capacitor type photoelectric detection device based on a heterojunction and preparation and application thereof, so as to realize the function of mid-infrared wide spectrum detection, greatly improve the detection sensitivity of the photoelectric detection device by using a heterojunction composed of a semiconductor, and have the characteristics of low power consumption and high integration.

[0004] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0005] A ferroelectric capacitor type photoelectric detection device based on a heterojunction, comprising, from bottom to top, a bottom electrode, a semiconductor layer, a ferroelectric dielectric layer and a top electrode; the top electrode is made of a transparent conductive material; the semiconductor layer is composed of a GeSn layer and a SiGeSn layer arranged in sequence;

[0006] The GeSn layer and the SiGeSn layer are both made of P-type material, the GeSn layer is located below the SiGeSn layer and forms a SiGeSn / GeSn heterojunction with the SiGeSn layer, and the top electrode applies a positive voltage; or, the GeSn layer and the SiGeSn layer are both made of N-type material, the GeSn layer is located above the SiGeSn layer and forms a GeSn / SiGeSn heterojunction with the SiGeSn layer, and the top electrode applies a negative voltage.

[0007] The photoelectric detection information is characterized by the state of the depletion layer capacitor: in the case of no light signal, there is no polarization reversal current, and the depletion layer capacitor is in a low capacitance state; in the case of light signal, a polarization reversal current is generated, and the depletion layer capacitor is in a high capacitance state; the depletion layer capacitor is the capacitor generated by the depletion layer at the contact interface between the semiconductor layer and the ferroelectric dielectric layer.

[0008] In one embodiment, the light signal is a mid-infrared waveband light signal or contains a mid-infrared waveband light signal.

[0009] In one embodiment, the material of the bottom electrode is any one of tungsten, titanium, copper, aluminum, platinum, iridium, ruthenium, tungsten nitride, titanium nitride, tantalum nitride, iridium oxide, ruthenium oxide, tungsten carbide, titanium carbide, tungsten silicide, titanium silicide and tantalum silicide; the material of the ferroelectric dielectric layer is any one of HYO, HZO, HSO, HAO, BFO, PZT, BST and ZnSnO3.

[0010] In one embodiment, the transparent conductive material is ITO or PEDOT.

[0011] In one embodiment, the thickness of the GeSn layer and the SiGeSn layer is in the range of 200-250 nm, and the thickness of the ferroelectric dielectric layer is in the range of 50-70 nm.

[0012] In one embodiment, in the absence of light, a depletion region is formed at the interface of the SiGeSn / GeSn heterojunction, and when both the GeSn layer and the SiGeSn layer are P-type materials, a built-in electric field is formed from the P-type SiGeSn to the P-type GeSn; when both the GeSn layer and the SiGeSn layer are N-type materials, a built-in electric field is formed from the N-type GeSn to the N-type SiGeSn; the built-in electric field is configured to separate photo-generated carriers in a directional manner under illumination conditions, so as to increase the concentration of minority carriers in the semiconductor layer, and further increase the response strength of the polarization charge in the ferroelectric layer.

[0013] In one embodiment, when both the GeSn layer and the SiGeSn layer are P-type materials, the doping element of GeSn and SiGeSn is boron, and the doping concentration is 10 18 cm -3 ; when both the GeSn layer and the SiGeSn layer are N-type materials, the doping element is phosphorus, and the doping concentration is 10 18 cm -3 .

[0014] The application also provides a preparation method of the ferroelectric capacitor type photodetector based on a heterojunction, comprising the following specific steps:

[0015] 1) using an atomic layer deposition process, when both the GeSn layer and the SiGeSn layer are P-type materials, depositing a SiGeSn layer above the GeSn layer to form a semiconductor layer; when both the GeSn layer and the SiGeSn layer are N-type materials, depositing a GeSn layer above the SiGeSn layer to form a semiconductor layer;

[0016] 2) using a magnetron sputtering or atomic layer deposition process, depositing a layer of ferroelectric material above the semiconductor layer to form a ferroelectric layer;

[0017] 3) using a sputtering process, growing a layer of transparent conductive material above the ferroelectric layer to form a top electrode;

[0018] 4) using a sputtering process, growing an electrode material below the semiconductor layer to form a bottom electrode.

[0019] In one embodiment, the sputtering process of steps 3) and 4) is to first vacuumize the reaction chamber until the vacuum pressure in the reaction chamber reaches 0.02 Torr, and then perform sputtering to form the top electrode and the bottom electrode under the conditions of a sputtering power of 300-400 W and an argon pressure of 5 mTorr.

[0020] The ferroelectric capacitor type photodetector based on a heterojunction can be used in night vision imaging equipment.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] In the first aspect, the electrode polarization state of the ferroelectric dielectric layer is regulated by photoelectricity, and then the depletion layer capacitance state of the semiconductor layer is edited, the detection information of the photoelectric detection device is represented by the depletion layer capacitance state of the semiconductor layer, so that the detector has the function of sensing optical signals.

[0023] In the second aspect, the heterostructure is composed of semiconductor materials with small band gaps, which can realize a larger spectral detection range, and effectively separate photo-generated carriers by the traction of the built-in electric field formed inside, so that the minority carrier concentration in the semiconductor near the ferroelectric dielectric layer rises sharply, and the response strength of the polarization charge in the ferroelectric dielectric layer increases. Therefore, when the incident optical signal is relatively weak, the photoelectric detection device can still respond, thereby improving the sensitivity of the detector. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Fig. 1 is a schematic diagram of the three-dimensional structure of the photoelectric detection device of the present application (taking the case where the GeSn layer 2 and the SiGeSn layer 3 are both P-type materials as an example).

[0025] Figure 2 Fig. 2 is a schematic diagram of the cross-sectional structure of the photoelectric detection device shown in Fig. 1. Figure 1

[0026] Figure 3 Fig. 3 is a schematic diagram of the detection principle of the photoelectric detection device of the present application.

[0027] Figure 4 Fig. 4 is a schematic diagram of the polarization response of the photoelectric detection device of the present application under light and dark conditions.

[0028] Figure 5 Fig. 5 is a schematic diagram of the process of effectively separating photo-generated carriers by the built-in electric field inside the heterostructure in the photoelectric detection device of the present application.

[0029] Figure 6 Fig. 6 is a schematic diagram of the preparation process of the photoelectric detection device of the present application.

[0030] In the figure: 1, bottom electrode, 2, GeSn layer, 3, SiGeSn layer, 4, ferroelectric dielectric layer, 5, top electrode. DETAILED DESCRIPTION

[0031] ​The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art belong to the scope of protection of the present application.

[0032] The present application is a ferroelectric capacitor type photoelectric detection device based on heterojunction, as shown in FIGS. Figure 1 and Figure 2 The device includes a bottom electrode 1, a semiconductor layer, a ferroelectric dielectric layer 4 and a top electrode 5 arranged in sequence. The semiconductor layer is composed of a GeSn layer 2 and a SiGeSn layer 3.

[0033] In the present application, the GeSn layer 2 and the SiGeSn layer 3 can both be P-type materials, that is, the GeSn layer 2 is P-type GeSn and the SiGeSn layer 3 is P-type SiGeSn. In this case, the GeSn layer 2 is below the SiGeSn layer 3, the GeSn layer 2 is attached to the bottom electrode 1, the SiGeSn layer 3 is attached to the ferroelectric dielectric layer 4, the GeSn layer 2 and the SiGeSn layer 3 form a SiGeSn / GeSn heterojunction, and the top electrode 5 applies a positive voltage. Alternatively, the GeSn layer 2 and the SiGeSn layer 3 can both be N-type materials, that is, the GeSn layer 2 is N-type GeSn and the SiGeSn layer 3 is N-type SiGeSn. In this case, the GeSn layer 2 is above the SiGeSn layer 3, the SiGeSn layer 3 is attached to the bottom electrode 1, the GeSn layer 2 is attached to the ferroelectric dielectric layer 4, the GeSn layer 2 and the SiGeSn layer 3 form a GeSn / SiGeSn heterojunction, and the top electrode 5 applies a negative voltage.

[0034] The number of carriers in the semiconductor layer is regulated by light and responds to the polarization charge in the ferroelectric dielectric layer 4, and changes the depletion layer capacitance state of the semiconductor layer. In the presence of light, the built-in electric field formed by the heterojunction can effectively separate the photo-generated carriers, so that the minority carrier concentration in the semiconductor near the ferroelectric dielectric layer 4 rises sharply, increasing the response strength of the polarization charge in the ferroelectric dielectric layer 4. Therefore, when the incident light signal is relatively weak, the photoelectric detection device can still respond, greatly improving the sensitivity of the photoelectric detection device.

[0035] In order to capture the light signal, in the present application, the top electrode 5 is preferably made of transparent conductive material, such as ITO or PEDOT, etc.

[0036] Through the above structure, the present application can represent photoelectric detection information by the depletion layer capacitance state, that is, in the absence of light signal, there is no polarization reversal current, and the depletion layer capacitance is in a low capacitance state; in the presence of light signal, a polarization reversal current is generated, and the depletion layer capacitance is in a high capacitance state.

[0037] In the present application, the depletion layer capacitance refers to the capacitance generated by the depletion layer at the contact interface between the semiconductor layer and the ferroelectric dielectric layer 4. Specifically, as shown in Figure 3 As shown in the figure, after the voltage is applied to the ferroelectric dielectric layer 4 through the top electrode 5, when the semiconductor layer cannot provide enough carriers to respond to the polarization charges in the ferroelectric dielectric layer 4, most of the polarization charges in the ferroelectric dielectric layer 4 cannot be flipped, the polarization state does not change, and the depletion layer capacitance is in a low capacitance state; when the semiconductor layer has enough carriers to respond to the polarization charges in the ferroelectric dielectric layer 4, the polarization charges are fully flipped, the polarization state is fully changed, and the depletion layer capacitance is in a high capacitance state. That is, the depletion layer capacitance state can be obtained by observing whether a polarization flipping current is generated when a voltage is applied to the ferroelectric dielectric layer 4, if the polarization flipping current is generated, it is in a high capacitance state, otherwise, it is in a low capacitance state.

[0038] In the present application, the photoelectricity refers to the light signal, which in the present application can be specifically a mid-infrared waveband light signal or contain a mid-infrared waveband light signal. The electricity refers to the polarization flipping current generated after the voltage is applied to the ferroelectric dielectric layer 4, i.e. the current signal. After the light signal is incident on the semiconductor layer, photo-generated carriers, i.e. photo-generated electrons and photo-generated holes, are generated, which in turn affect the carrier concentration of the semiconductor layer, thereby regulating the electric polarization state of the ferroelectric dielectric layer.

[0039] In the present application, the depletion layer capacitance state of the semiconductor layer represents the detection information of the photoelectric detection device; the number of carriers in the semiconductor layer is regulated by the light and responds to the polarization charges in the ferroelectric dielectric layer 4, and changes the depletion layer capacitance state of the semiconductor layer when the top electrode 5 applies a positive voltage or a negative voltage; the built-in electric field formed by the heterojunction effectively separates the photo-generated carriers, so that the minority carrier concentration in the semiconductor near the ferroelectric dielectric layer sharply rises, and the response strength of the polarization charges in the ferroelectric dielectric layer increases. Therefore, when the incident light signal is relatively weak, the photoelectric detection device can still respond, thereby improving the detection sensitivity.

[0040] With the P-type material for both the GeSn layer 2 and the SiGeSn layer 3 as an example, the top electrode 5 applies a positive voltage, and the semiconductor layer can control the polarization state of the ferroelectric layer 4 through the concentration change of the minority carriers (electrons). Specifically, after the top electrode 5 applies a positive voltage to the ferroelectric layer 4, in the case of no light (darkness), that is, in the case of no optical signal, the semiconductor layer cannot provide enough carriers (electrons) to respond to the polarization charge in the ferroelectric layer 4, at this time, most of the polarization charge in the ferroelectric layer 4 cannot be flipped, the polarization state does not change, the depletion layer capacitance is in a low capacitance state, and there is no polarization flipping current. In the case of light, that is, in the case of optical signal, when the photon energy is equal to or greater than the band gap of the semiconductor layer, the carriers (electrons) in the valence band of the semiconductor layer absorb the photon energy and enter the conduction band to generate electron-hole pairs. This carrier is a photo-generated carrier, that is, the concentration of the photo-generated carrier in the semiconductor layer is increased, thereby increasing the concentration of the minority carriers (electrons) in the semiconductor layer to a certain scale, increasing the response intensity of the polarization charge in the ferroelectric layer 4, making the polarization charge in the ferroelectric layer 4 fully flip, and the polarization state changes. At this time, the depletion layer capacitance of the semiconductor layer is in a high capacitance state, and a polarization flipping current is generated. That is, when the ferroelectric layer flips, the depletion layer capacitance changes from a "low capacitance state" to a "high capacitance state", and a polarization flipping current is generated. At this time, the photodetector can detect the light wave. Therefore, the depletion layer capacitance state can be used to represent the detection information, such as Figure 4 When a negative voltage is applied to the top electrode 5, in the case of light or no light, there are enough holes in the semiconductor layer to respond to the polarization charge in the ferroelectric layer 4, the polarization charge is fully flipped, the polarization state is fully changed, and the depletion layer capacitance of the semiconductor layer is in a high capacitance state. The photodetector cannot detect the light wave.

[0041] Similarly, when the GeSn layer 2 and the SiGeSn layer 3 are both N-type materials, the top electrode 5 applies a negative voltage, and the semiconductor layer can control the polarization state of the ferroelectric layer 4 through the concentration change of the minority carriers (holes).

[0042] The "low capacitance state" and "high capacitance state" of the present application can refer to Figure 3 When there is no optical signal, the charge per unit area at the interface between the semiconductor layer and the ferroelectric layer 4 is small, so the depletion layer capacitance generated is small, which is defined as a low capacitance. When there is an optical signal, the charge per unit area at the interface between the semiconductor layer and the ferroelectric layer 4 is large, so the depletion layer capacitance generated is large, which is defined as a high capacitance. That is, the "low capacitance state" and "high capacitance state" of the present application are relative concepts.

[0043] The depletion region formed at the interface of the SiGeSn / GeSn heterojunction is as shown in Figure 5As shown, in the absence of light signal, a depletion region is formed at the interface of the SiGeSn / GeSn heterojunction. When both GeSn layer 2 and SiGeSn layer 3 are made of P-type material, a built-in electric field is eventually formed from P-type SiGeSn to P-type GeSn. When both GeSn layer 2 and SiGeSn layer 3 are made of N-type material, a built-in electric field is eventually formed from N-type GeSn to N-type SiGeSn.

[0044] Under illumination, photogenerated carriers exhibit efficient directional separation under the influence of the built-in electric field, thereby increasing the minority carrier concentration in the semiconductor layer and consequently enhancing the response intensity of polarization charges in the ferroelectric layer 4. Specifically, when both GeSn layer 2 and SiGeSn layer 3 are made of P-type materials, the electron concentration in the semiconductor layer increases; when both GeSn layer 2 and SiGeSn layer 3 are made of N-type materials, the hole concentration in the semiconductor layer increases.

[0045] Taking the example of semiconductor layers using P-type GeSn and P-type SiGeSn materials respectively, the figure shows that in darkness, when the P-type GeSn and P-type SiGeSn materials are in close contact, holes diffuse from the P-type GeSn to the P-type SiGeSn material until thermal equilibrium is reached, forming a depletion region at the interface of the heterostructure. As charge transfer continues, the energy levels near the GeSn surface bend upwards, and the energy levels near the SiGeSn surface bend downwards. Ultimately, a built-in electric field is formed at the heterojunction interface, pointing from the P-type SiGeSn to the P-type GeSn.

[0046] When light shines on the effective working area of ​​the heterojunction, a large number of photogenerated carriers (electron-hole pairs) will be generated in and around the depletion region. These photogenerated electron-hole pairs will be rapidly and effectively separated in the existing built-in electric field (photogenerated electrons move directionally towards P-type SiGeSn, and photogenerated holes move directionally towards P-type GeSn), thereby greatly increasing the electron concentration in the SiGeSn layer adjacent to the ferroelectric layer 4. This, in turn, increases the response intensity of the polarization charge in the ferroelectric layer 4. Therefore, even when the incident light signal is relatively weak, the photodetector can still react, thus improving the detection sensitivity.

[0047] In embodiments of the present invention, the material of the bottom electrode 1 may be any one of tungsten, titanium, copper, aluminum, platinum, iridium, ruthenium, tungsten nitride, titanium nitride, tantalum nitride, iridium oxide, ruthenium oxide, tungsten carbide, titanium carbide, tungsten silicide, titanium silicide, and tantalum silicide.

[0048] The material of the ferroelectric layer 4 can be any one of HYO, HZO, HSO, HAO, BFO, PZT, BST, and ZnSnO3. Among them, HZO is zirconium-doped hafnium oxide, BFO is bismuth ferrite, PZT is lead zirconate titanate, ZnSnO3 is zinc stannate, HSO is silicon-doped hafnium oxide, HAO is aluminum-doped hafnium oxide, BST is barium strontium titanate, and HYO is yttrium-doped hafnium oxide.

[0049] In this invention, the thickness of GeSn layer 2 and SiGeSn layer 3 can both be in the range of 200-250nm, and the thickness of ferroelectric layer 4 can be in the range of 50-70nm. Obviously, this thickness is small and meets the requirements of miniaturization.

[0050] See Figure 6 The present invention also includes a method for fabricating an infrared ferroelectric capacitive photodetector in a heterojunction, comprising the following specific steps:

[0051] 1) Semiconductor layers are prepared using atomic layer deposition (ALD) technology.

[0052] When both GeSn layer 2 and SiGeSn layer 3 are made of P-type material, SiGeSn layer 3 is deposited on top of GeSn layer 2 to form a semiconductor layer; when both GeSn layer 2 and SiGeSn layer 3 are made of N-type material, GeSn layer 2 is deposited on top of SiGeSn layer 3 to form a semiconductor layer.

[0053] 2) A ferroelectric material layer is deposited on top of the semiconductor layer using magnetron sputtering or atomic layer deposition processes to form a ferroelectric dielectric layer 4.

[0054] 3) Using a sputtering process, a layer of transparent conductive material is grown on top of the ferroelectric dielectric layer 4 to form the top electrode 5.

[0055] 4) Using a sputtering process, an electrode material is grown under the semiconductor layer to form the bottom electrode 1.

[0056] In steps 3) and 4), the sputtering process involves first evacuating the reaction chamber using a molecular pump or cold pump until the vacuum pressure in the reaction chamber reaches 0.02 millitor. Then, the top electrode 5 and the bottom electrode 1 are formed by sputtering under conditions of a sputtering power of 300W-400W (preferably 350W) and an argon pressure of 5 millitor.

[0057] In this invention, the preparation process of p-type GeSn material is as follows: SnD4 is used as the gas source for Sn atoms, GeH4 is used as the gas source for Ge atoms, and GeSn is grown using ultra-high vacuum chemical vapor deposition. Ion implantation is then used to dope the material. The preparation process of p-type SiGeSn material is as follows: Si2H6, Ge2H6, SnCl4, and N2 are used as carrier gases, and SiGeSn is grown using reduced pressure chemical vapor deposition. Ion implantation is then used to dope the material. The preparation process of N-type material is similar.

[0058] The following are specific embodiments of two methods for fabricating a heterojunction mid-infrared ferroelectric capacitive photodetector based on different materials.

[0059] Example 1:

[0060] With Hf 0.5 Zr 0.5 O2 is used to fabricate the ferroelectric dielectric layer 4, P-type GeSn and P-type SiGeSn materials are used as semiconductor layers, ITO transparent conductive material is used as the top electrode 5, and tungsten metal is used as the bottom electrode 1. The specific fabrication method is as follows:

[0061] Step 1: Deposit a P-type semiconductor-doped SiGeSn layer 3 on top of the GeSn layer 2 using atomic layer deposition (ALD) to form a semiconductor layer.

[0062] Step 2: Ferroelectric material is deposited on top of the semiconductor layer using atomic layer deposition (ALD) to form ferroelectric dielectric layer 4.

[0063] In this step, atomic layer deposition (ALD) is used. First, deionized water is used as the oxygen source, tetraethylmethylaminohafnium (TEMAHf) as the hafnium precursor source, and tetraethylmethylaminozirconium (TEMAZr) as the zirconium precursor source. The temperature is raised to 573 K. Then, by adjusting the pulse ratio of the hafnium and zirconium precursor sources, Hf with a Zr composition of 0.5 is grown on the upper surface of semiconductor layer 2. 0.5 Zr 0.5 O2 ferroelectric material thin film, forming ferroelectric dielectric layer 4.

[0064] Step 3: Using a sputtering process, a layer of transparent conductive material is grown on top of the ferroelectric layer 4 to form the top electrode 5.

[0065] In this step, a sputtering process is used. First, a molecular pump or cold pump is used to evacuate the reaction chamber until the vacuum pressure in the reaction chamber reaches 0.02 Torr. Then, under the conditions of sputtering power of 350W and argon pressure of 5 millitor, ITO is used as the target material to uniformly sputter the upper surface of the ferroelectric layer 4, depositing a layer of transparent electrode material on its surface, thereby forming the top electrode 5.

[0066] Step 4: Using a sputtering process, grow an electrode material layer under the semiconductor layer to form the bottom electrode 1.

[0067] In this step, a sputtering process is used. First, a molecular pump or cold pump is used to evacuate the reaction chamber until the vacuum pressure in the reaction chamber reaches 0.02 Torr. Then, under the conditions of sputtering power of 350W and argon pressure of 5 mTorr, tungsten metal is used as a target to uniformly sputter the surface below the semiconductor layer, depositing a layer of tungsten metal on its surface to form the bottom electrode 1, and completing the fabrication of a heterojunction mid-infrared ferroelectric capacitive photodetector.

[0068] Example 2:

[0069] The ferroelectric dielectric layer 3 is fabricated using HYO ferroelectric material, the semiconductor layers are N-type GeSn and N-type SiGeSn materials, the top electrode 5 is made of transparent conductive material ITO, and the bottom electrode 1 is made of metallic titanium. The specific fabrication method is as follows:

[0070] Step 1: Deposit an N-type semiconductor-doped GeSn layer 2 on top of the SiGeSn layer 3 using atomic layer deposition (ALD) to form a semiconductor layer;

[0071] Step 2: Ferroelectric material is deposited on top of the semiconductor layer using atomic layer deposition (ALD) to form ferroelectric dielectric layer 4;

[0072] Using pulsed laser sputtering deposition, a thin film of HYO material is formed on the upper surface of the semiconductor layer by alternating sputtering deposition with dual targets (99.99% HfO2 ceramic target and 99.99% Y2O3 ceramic target). The HYO material is then crystallized by annealing to form a ferroelectric dielectric layer 4.

[0073] Step 3: Using a sputtering process, a layer of transparent conductive material is grown on top of the ferroelectric dielectric layer 4 to form the top electrode 5;

[0074] In this step, a sputtering process is used. First, a molecular pump or cold pump is used to evacuate the reaction chamber until the vacuum pressure in the reaction chamber reaches 0.02 Torr. Then, under the conditions of sputtering power of 350W and argon pressure of 5 millitor, ITO is used as the target material to uniformly sputter the upper surface of the ferroelectric layer 4, depositing a layer of transparent electrode material on its surface, thereby forming the top electrode 5.

[0075] Step 4: Using a sputtering process, grow an electrode material layer under the semiconductor layer to form the bottom electrode 1;

[0076] In this step, using reactive sputtering technology, the reaction chamber is first evacuated using a molecular pump or cold pump until the vacuum pressure in the reaction chamber reaches 0.02 Torr. Then, under the conditions of sputtering power of 350W and argon pressure of 5 millitor, titanium metal is used as a target to uniformly sputter the surface below the semiconductor layer, depositing a layer of titanium metal on its surface to form the bottom electrode 1, and completing the fabrication of the photoelectric capacitive ferroelectric memory.

[0077] This invention utilizes photoelectric modulation of the polarization state of the ferroelectric dielectric layer to edit the depletion layer capacitance state of the semiconductor layer. The depletion layer capacitance state of the semiconductor layer characterizes the detection information of the photodetector. Furthermore, the built-in electric field of the heterostructure formed by the semiconductor layers effectively separates photogenerated carriers, causing a sharp increase in the minority carrier concentration in the semiconductor near the ferroelectric dielectric layer, thus increasing the polarization charge response intensity and improving detector sensitivity. Moreover, this photodetector is a capacitive detector with the significant advantage of zero static power consumption. Therefore, this photodetector, with its low power consumption and high sensitivity, can be applied to night vision imaging equipment in extreme environments such as remote areas, mountains, jungles, and military battlefields. It can achieve self-sufficiency and long-endurance when used in conjunction with solar, wind, and hydropower generation devices.

[0078] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A heterojunction-based ferroelectric capacitive photodetector device, comprising: The bottom electrode (1), the semiconductor layer, the ferroelectric dielectric layer (4) and the top electrode (5) are sequentially arranged from bottom to top; the top electrode (5) is made of transparent conductive material; the semiconductor layer is composed of a GeSn layer (2) and a SiGeSn layer (3) arranged in sequence; The transparent conductive material is ITO or PEDOT, the GeSn layer (2) and the SiGeSn layer (3) are both made of P-type material, the GeSn layer (2) is located below the SiGeSn layer (3) and forms a SiGeSn / GeSn heterojunction with the SiGeSn layer (3), and the top electrode (5) applies a positive voltage; or, the GeSn layer (2) and the SiGeSn layer (3) are both made of N-type material, the GeSn layer (2) is located above the SiGeSn layer (3) and forms a GeSn / SiGeSn heterojunction with the SiGeSn layer (3), and the top electrode (5) applies a negative voltage. The photoelectric detection information is represented by the state of the depletion layer capacitor: in the case of no light signal, there is no polarization reversal current, and the depletion layer capacitor is in a low-capacitance state; in the case of light signal, a polarization reversal current is generated, and the depletion layer capacitor is in a high-capacitance state; the depletion layer capacitor is the capacitor generated by the depletion layer at the contact interface between the semiconductor layer and the ferroelectric dielectric layer (4). 2.The heterojunction-based ferroelectric capacitor photodetector device of claim 1, wherein, The light signal is a mid-infrared waveband light signal or contains a mid-infrared waveband light signal. 3.The heterojunction-based ferroelectric capacitor photodetector device of claim 1, wherein, The material of the bottom electrode (1) is any one of tungsten, titanium, copper, aluminum, platinum, iridium, ruthenium, tungsten nitride, titanium nitride, tantalum nitride, iridium oxide, ruthenium oxide, tungsten carbide, titanium carbide, tungsten silicide, titanium silicide and tantalum silicide; the material of the ferroelectric dielectric layer (4) is any one of HYO, HZO, HSO, HAO, BFO, PZT, BST and ZnSnO3. 4.The heterojunction-based ferroelectric capacitor photodetector device of claim 1, wherein, The thickness of the GeSn layer (2) and the SiGeSn layer (3) is in the range of 200-250 nm, and the thickness of the ferroelectric dielectric layer (4) is in the range of 50-70 nm. 5.The heterojunction-based ferroelectric capacitor photodetector device of claim 1, wherein, In the case of no light signal, a depletion region is formed at the interface of the SiGeSn / GeSn heterojunction, and when the GeSn layer (2) and the SiGeSn layer (3) are both made of P-type material, a built-in electric field is finally formed from P-type SiGeSn to P-type GeSn; when the GeSn layer (2) and the SiGeSn layer (3) are both made of N-type material, a built-in electric field is finally formed from N-type GeSn to N-type SiGeSn; the built-in electric field is configured to directionally separate photo-generated carriers under light conditions, so as to increase the concentration of minority carriers in the semiconductor layer and further increase the response strength of the polarization charge in the ferroelectric dielectric layer (4). 6.The heterojunction-based ferroelectric capacitor photodetector device of claim 1, wherein, When the GeSn layer (2) and the SiGeSn layer (3) are both P-type materials, the doping element of GeSn and SiGeSn is boron, and the doping concentration is 10 18 cm -3 ; when the GeSn layer (2) and the SiGeSn layer (3) are both N-type materials, the doping element is phosphorus, and the doping concentration is 10 18 cm -3 .

7. The method for fabricating the ferroelectric capacitive photodetector based on a heterojunction as described in claim 1, characterized in that, The method comprises the following specific steps: 1) using atomic layer deposition process, when the GeSn layer (2) and SiGeSn layer (3) are both P-type material, depositing SiGeSn layer (3) above GeSn layer (2) to form a semiconductor layer; when the GeSn layer (2) and SiGeSn layer (3) are both N-type material, depositing GeSn layer (2) above SiGeSn layer (3) to form a semiconductor layer; 2) using magnetron sputtering or atomic layer deposition process, depositing a layer of ferroelectric material above the semiconductor layer to form a ferroelectric dielectric layer (4); 3) using sputtering process, growing a layer of transparent conductive material above the ferroelectric dielectric layer (4) to form a top electrode (5); 4) using sputtering process, growing a layer of electrode material below the semiconductor layer to form a bottom electrode (1).

8. The preparation method according to claim 7, characterized in that, The sputtering process in step 3) and step 4) is to first vacuum the reaction chamber until the vacuum pressure in the reaction chamber reaches 0.02 Torr, and then perform sputtering to form the top electrode (5) and the bottom electrode (1) under the conditions of a sputtering power of 300-400 W and an argon pressure of 5 mTorr.

9. Use of the heterojunction-based ferroelectric capacitor type photodetector device of claim 1 for night vision imaging equipment.

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