Carbon nanotube Schottky diode and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor integration, in particular to a carbon nanotube Schottky diode and a preparation method thereof. A carbon nanotube active layer is arranged on a substrate; the Schottky contact anode is arranged on the carbon nanotube active layer and forms an anode leading-out end; the cathode ohmic contact layer is arranged on the carbon nanotube active layer, and the cathode ohmic contact layer and the Schottky contact anode are arranged at intervals; the conductive cathode is arranged on the cathode ohmic contact layer and forms a cathode leading-out end; the dielectric layer is located between the Schottky contact anode and the cathode ohmic contact layer and extends to cover the cathode ohmic contact layer. The Schottky diode prepared from the carbon nanotubes can work at a higher frequency, possibility is provided for terahertz communication, radar and other applications, and compared with a traditional silicon or III-V semiconductor Schottky diode, due to the fact that the carbon nanotubes have lower intrinsic capacitance and lower substrate loss, the Schottky diode prepared from the carbon nanotubes can be applied to terahertz communication, radar and other applications. The Schottky diode is prepared by using the carbon nanotubes as the active layer, so that the terahertz signal generation and detection capability can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor integration technologies, and particularly to a carbon nanotube Schottky diode and a preparation method thereof. Background Art

[0002] Terahertz technology has important scientific and economic values and has broad application prospects in the fields of terahertz communication, terahertz radar, terahertz imaging, and astronomical observation. The Schottky diode based on semiconductor technology has the characteristics of strong nonlinearity, high speed, small switching loss, normal temperature operation, and easy system integration, and can achieve frequency doubling and frequency mixing in the terahertz frequency band, thereby obtaining a terahertz signal source and a signal detector with excellent performance.

[0003] As the signal frequency increases to above 100 GHz, the Schottky devices based on silicon and III-V semiconductors have serious substrate losses, small emission power, low frequency conversion efficiency, high costs, and increasingly serious reliability problems. Therefore, it is necessary to propose terahertz devices based on new materials and new structures to meet the development needs of terahertz technology. Summary of the Invention

[0004] The present invention provides a carbon nanotube Schottky diode and a preparation method thereof, which are used to solve the defects that the Schottky devices based on silicon and III-V semiconductors in the prior art have serious substrate losses, small emission power, low frequency conversion efficiency, high costs, and increasingly serious reliability problems, and to achieve higher cut-off frequencies and frequency conversion efficiencies and lower power consumption.

[0005] The present invention provides a carbon nanotube Schottky diode, including a substrate, a carbon nanotube active layer, a Schottky contact anode, a cathode ohmic contact layer, a conductive cathode, and a dielectric layer. Among them, the carbon nanotube active layer is disposed on the substrate to form a carbon nanotube channel on the substrate; the Schottky contact anode is disposed on the carbon nanotube active layer, and the Schottky contact anode is formed with an anode lead-out end; the cathode ohmic contact layer is disposed on the carbon nanotube active layer and is arranged at an interval from the Schottky contact anode; the conductive cathode is disposed on the cathode ohmic contact layer, and the conductive cathode is formed with a cathode lead-out end; the dielectric layer is disposed on the carbon nanotube active layer, the dielectric layer is located in the region between the Schottky contact anode and the cathode ohmic contact layer, and extends to cover the cathode ohmic contact layer.

[0006] According to a carbon nanotube Schottky diode provided by the present invention, the cathode ohmic contact layer includes a first cathode ohmic contact layer and a second cathode ohmic contact layer, the conductive cathode includes a first conductive cathode and a second conductive cathode, and the dielectric layer includes a first dielectric layer and a second dielectric layer.

[0007] The first cathode ohmic contact layer and the second cathode ohmic contact layer are symmetrically arranged on both sides of the Schottky contact anode. The first conductive cathode is arranged on the first cathode ohmic contact layer, and the second conductive cathode is arranged on the second cathode ohmic contact layer. One end of the first conductive cathode and the second conductive cathode are connected to form the cathode lead-out end. A first dielectric layer is arranged between the first cathode ohmic contact layer and the Schottky contact anode, and a second dielectric layer is arranged between the second cathode ohmic contact layer and the Schottky contact anode.

[0008] According to a carbon nanotube Schottky diode provided by the present invention, the width of the upper electrode of the Schottky contact anode away from the upper electrode of the carbon nanotube active layer is greater than the width of the lower electrode close to the carbon nanotube active layer to form a T-shaped electrode structure. The lower end face of the edge of the upper electrode of the Schottky contact anode covers the dielectric layer to form a field plate structure. The lower electrode of the Schottky contact anode is in contact with the carbon nanotube active layer, and the side wall of the lower electrode of the Schottky contact anode forms an angle less than 90 degrees with the surface of the carbon nanotube channel of the carbon nanotube active layer.

[0009] According to a carbon nanotube Schottky diode provided by the present invention, the material of the Schottky contact anode includes one of titanium, aluminum, titanium nitride, aluminum nitride, tungsten nitride, gold, copper, or a combination of at least any two of titanium, aluminum, titanium nitride, aluminum nitride, tungsten nitride, gold, copper.

[0010] According to a carbon nanotube Schottky diode provided by the present invention, the distance between the lower electrode of the Schottky contact anode and the cathode ohmic contact layer is less than 300 nanometers, and the conductive cathode is away from the upper electrode of the Schottky contact anode.

[0011] According to a carbon nanotube Schottky diode provided by the present invention, the cathode ohmic contact layer is formed of a material with a work function less than 4.5 electron volts to form an N-type ohmic contact. The material of the cathode ohmic contact layer includes one of scandium, titanium, yttrium, hafnium, tantalum, titanium nitride, tantalum nitride, or a combination of at least any two of scandium, titanium, yttrium, hafnium, tantalum, titanium nitride, tantalum nitride.

[0012] According to a carbon nanotube Schottky diode provided by the present invention, the cathode ohmic contact layer is formed of a material with a work function greater than 4.5 electron volts to form a P-type ohmic contact. The material of the cathode ohmic contact layer includes one of palladium, molybdenum, nickel, tungsten, titanium nitride, or a combination of at least any two of palladium, molybdenum, nickel, tungsten, titanium nitride.

[0013] A carbon nanotube Schottky diode provided by the present invention, wherein the carbon nanotube active layer includes a randomly arranged carbon nanotube network or an oriented carbon nanotube array, and the bandgap of the carbon nanotube active layer is less than 1.2 electron volts.

[0014] A carbon nanotube Schottky diode provided by the present invention, wherein the material of the substrate includes at least one of quartz, glass, sapphire, alumina, gallium oxide, silicon carbide, gallium arsenide, gallium nitride, aluminum nitride, silicon nitride, indium phosphide, diamond, polyimide, and benzocyclobutene.

[0015] The present invention also provides a method for manufacturing a carbon nanotube Schottky diode, which is suitable for manufacturing the carbon nanotube Schottky diode described in any one of the above, and the method for manufacturing the carbon nanotube Schottky diode includes: Depositing a carbon nanotube active layer on a substrate.

[0016] Forming a first cathode ohmic contact layer and a second cathode ohmic contact layer at two side positions on the carbon nanotube active layer.

[0017] Depositing a dielectric layer on the first cathode ohmic contact layer, the second cathode ohmic contact layer, and the carbon nanotube active layer.

[0018] Etching the deposited dielectric layer, etching an anode contact hole at a position corresponding to the middle of the first cathode ohmic contact layer and the second cathode ohmic contact layer, and etching cathode contact holes at positions corresponding to directly above the first cathode ohmic contact layer and the second cathode ohmic contact layer, respectively.

[0019] Depositing a Schottky contact anode in the anode contact hole and forming an anode lead-out terminal, depositing conductive cathodes in the two cathode contact holes respectively, and connecting the two conductive cathodes to form a cathode lead-out terminal.

[0020] The carbon nanotube Schottky diode provided by the present invention forms a Schottky barrier at the contact between the Schottky contact anode and the carbon nanotube active layer based on the difference in work function between them. When a forward bias is applied, electrons can cross this barrier to generate current; while under a reverse bias, the current is significantly suppressed, thus forming a diode structure using the Schottky barrier. The present invention uses a carbon nanotube active layer as the semiconductor active layer of the diode. Semiconducting carbon nanotubes have a series of advantages such as extremely high carrier mobility, extremely low intrinsic capacitance, ultra-high thermal conductivity, and easy integration with low-loss substrates such as quartz. The theoretical cut-off frequency of a terahertz Schottky diode fabricated using carbon nanotube semiconductor materials can exceed 10 THz, and it has a higher frequency conversion efficiency and lower power consumption. By utilizing the unique electrical properties of carbon nanotubes, the fabricated Schottky diode can operate at higher frequencies, especially in the terahertz frequency band, which provides possibilities for applications such as terahertz communication and radar. Compared with traditional silicon or III-V semiconductor Schottky diodes, since carbon nanotubes have lower intrinsic capacitance and smaller substrate losses, using carbon nanotubes as the active layer to fabricate terahertz Schottky diodes can significantly improve the ability to generate and detect terahertz signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 It is a schematic plan view of the carbon nanotube Schottky diode provided by the present invention.

[0023] Figure 2 is Figure 1 the schematic cross-sectional structure view taken along A-A of

[0024] Figure 3 It is a schematic flow chart of the preparation method of the carbon nanotube Schottky diode provided by the present invention.

[0025] Reference Numerals: 1, substrate; 2, carbon nanotube active layer; 3, Schottky contact anode; 301, anode lead-out terminal; 4, cathode ohmic contact layer; 4a, first cathode ohmic contact layer; 4b, second cathode ohmic contact layer; 5, conductive cathode; 501, cathode lead-out terminal; 5a, first conductive cathode; 5b, second conductive cathode; 6, dielectric layer; 6a, first dielectric layer; 6b, second dielectric layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] To make the objectives, technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention in conjunction with the accompanying drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the embodiments of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and should not be construed as indicating or implying relative importance.

[0028] In the description of the embodiments of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "connected" and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0029] In the embodiments of the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or simply means that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature has a lower horizontal height than the second feature.

[0030] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0031] The following will describe Figures 1 to 3 the carbon nanotube Schottky diode of the present invention and its manufacturing method.

[0032] One embodiment of the present invention provides a carbon nanotube Schottky diode. As shown in combination with Figure 1 and Figure 2 , it includes a substrate 1, a carbon nanotube active layer 2, a Schottky contact anode 3, a cathode ohmic contact layer 4, a conductive cathode 5, and a dielectric layer 6. Among them, the carbon nanotube active layer 2 is disposed on the substrate 1 to form a carbon nanotube channel on the substrate 1; the Schottky contact anode 3 is disposed on the carbon nanotube active layer 2, and the Schottky contact anode 3 is formed with an anode lead-out end 301; the cathode ohmic contact layer 4 is disposed on the carbon nanotube active layer 2 and is arranged at an interval from the Schottky contact anode 3; the conductive cathode 5 is disposed on the cathode ohmic contact layer 4, and the conductive cathode 5 is formed with a cathode lead-out end 501; the dielectric layer 6 is disposed on the carbon nanotube active layer 2, and the dielectric layer 6 is located in the region between the Schottky contact anode 3 and the cathode ohmic contact layer 4 and extends to cover the cathode ohmic contact layer 4.

[0033] It can be understood that for this carbon nanotube Schottky diode of this embodiment, based on the difference in work function between the metal (Schottky contact anode 3) and the semiconductor (carbon nanotube active layer 2), the contact between the Schottky contact anode 3 and the carbon nanotube active layer 2 forms a Schottky barrier. When a forward bias is applied, electrons can cross this barrier to generate current; while under a reverse bias, the current is significantly suppressed, and a diode structure is formed using the Schottky barrier. Among them, the cathode ohmic contact layer 4 and the conductive cathode 5 ensure good electrical contact, reduce the contact resistance, and improve the overall performance of the device. The dielectric layer 6 not only plays a role in isolating the Schottky contact anode 3 and the cathode ohmic contact layer 4, but also helps to increase the breakdown voltage and reduce the leakage current.

[0034] It should be understood that in this carbon nanotube Schottky diode of this embodiment, the carbon nanotube active layer 2 is used as the semiconductor active layer of the diode. Semiconducting carbon nanotubes have a series of advantages such as extremely high carrier mobility, extremely low intrinsic capacitance, ultra-high thermal conductivity, and easy integration with low-loss substrates such as quartz. For a terahertz Schottky diode fabricated using carbon nanotube semiconductor materials, its theoretical cut-off frequency can exceed 10 THz, and it has a higher frequency conversion efficiency and lower power consumption. By utilizing the unique electrical properties of carbon nanotubes, the fabricated Schottky diode can operate at higher frequencies, especially in the terahertz frequency band, which provides possibilities for applications such as terahertz communication and radar. Compared with traditional silicon or III-V semiconductor Schottky diodes, since carbon nanotubes have lower intrinsic capacitance and smaller substrate losses, using carbon nanotubes as the active layer to fabricate terahertz Schottky diodes can significantly improve the ability to generate and detect terahertz signals.

[0035] In some embodiments of the carbon nanotube Schottky diode of the present invention, referring again to Figure 1 as shown, the cathode ohmic contact layer 4 includes a first cathode ohmic contact layer 4a and a second cathode ohmic contact layer 4b, the conductive cathode 5 includes a first conductive cathode 5a and a second conductive cathode 5b, and the dielectric layer 6 includes a first dielectric layer 6a and a second dielectric layer 6b.

[0036] The first cathode ohmic contact layer 4a and the second cathode ohmic contact layer 4b are symmetrically arranged on both sides of the Schottky contact anode 3. The first conductive cathode 5a is disposed on the first cathode ohmic contact layer 4a, and the second conductive cathode 5b is disposed on the second cathode ohmic contact layer 4b. One end of the first conductive cathode 5a and the second conductive cathode 5b that correspond to each other are connected to form a cathode lead-out terminal 501. A first dielectric layer 6a is disposed between the first cathode ohmic contact layer 4a and the Schottky contact anode 3, and a second dielectric layer 6b is disposed between the second cathode ohmic contact layer 4b and the Schottky contact anode 3.

[0037] It can be understood that the Schottky contact anode 3 forms a Schottky barrier with the carbon nanotube active layer 2 to control forward conduction and reverse cut-off; the cathode ohmic contact layer 4 forms a low-resistance contact with the carbon nanotube active layer 2 to ensure efficient current outflow and reduce energy loss; the conductive cathode 5 provides a current extraction path, reduces the contact resistance and evenly distributes the current, and improves the high-frequency response ability; the dielectric layer 6 isolates the anode and cathode contact layers to prevent short-circuiting between the electrodes, and at the same time optimizes the electric field distribution, suppresses electric field spikes, and increases the breakdown voltage. In this embodiment, the symmetrically arranged cathode ohmic contact layers 4 (the first cathode ohmic contact layer 4a and the second cathode ohmic contact layer 4b) and the conductive cathode 5 (the first conductive cathode 5a and the second conductive cathode 5b) are adopted. By symmetrically arranging the first cathode ohmic contact layer 4a and the second cathode ohmic contact layer 4b, and the corresponding first conductive cathode 5a and the second conductive cathode 5b, and connecting one end of them to form the cathode lead-out terminal 501, this layout helps to reduce the parasitic resistance and capacitance of the cathode, thereby improving the overall performance of the Schottky diode.

[0038] Among them, the first cathode ohmic contact layer 4a and the second cathode ohmic contact layer 4b are symmetrically distributed on both sides of the Schottky contact anode 3, which can evenly disperse the current path and reduce the phenomenon of local current congestion, thereby reducing the contact resistance. One end of the first conductive cathode 5a and the second conductive cathode 5b is connected to form the cathode lead-out terminal 501. This symmetric layout makes the current distribution more uniform, improves the conduction efficiency, and especially reduces signal loss at high frequencies. The design of the first dielectric layer 6a and the second dielectric layer 6b not only effectively isolates the Schottky contact anode 3 and the cathode ohmic contact layer 4, but also provides additional protection, which helps to increase the breakdown voltage and reduce the leakage current, which is crucial for maintaining the stability and reliability of the diode at high frequencies.

[0039] In some embodiments of the carbon nanotube Schottky diode of the present invention, the width of the upper electrode of the Schottky contact anode 3 away from the carbon nanotube active layer 2 is greater than the width of the lower electrode close to the carbon nanotube active layer 2 to form a T-shaped electrode structure. The lower end surface of the upper electrode edge of the Schottky contact anode 3 covers the dielectric layer 6 to form a field plate structure. The lower electrode of the Schottky contact anode 3 contacts the carbon nanotube active layer 2, and the side wall of the lower electrode of the Schottky contact anode 3 forms an angle less than 90 degrees with the surface of the carbon nanotube channel of the carbon nanotube active layer 2.

[0040] It can be understood that the Schottky contact anode 3 in this embodiment adopts a T-shaped electrode structure that is wider at the top and narrower at the bottom. The wider upper electrode of the Schottky contact anode 3 provides a larger cross-sectional area, reduces the current density, and lowers the resistance. The lower end surface of the edge of the upper electrode covers the dielectric layer 6 to form a field plate structure, which adjusts the electric field distribution and suppresses the electric field peak. Specifically, by covering the dielectric layer 6, the electric field is transferred from the anode edge to below the field plate, avoiding the concentration of the electric field at the anode tip, which may cause an overly strong local electric field leading to breakdown, reducing the breakdown risk, and improving the breakdown voltage resistance of the device. The lower electrode of the Schottky contact anode 3 is in direct contact with the carbon nanotube active layer 2 to form a Schottky barrier. The angle between the side wall and the surface of the carbon nanotube channel is less than 90°, avoiding the electric field sharpening effect caused by sharp edges and further reducing the leakage current. The structure design of the Schottky contact anode 3 that is wider at the top and narrower at the bottom reduces the parasitic capacitance between the electrode and the carbon nanotubes. Combining with the low intrinsic capacitance characteristics of the carbon nanotubes, the maximum oscillation frequency of the diode device is further increased to above 10 THz, meeting the requirements of terahertz applications.

[0041] Furthermore, the material of the Schottky contact anode 3 includes one of titanium, aluminum, titanium nitride, aluminum nitride, tungsten nitride, gold, and copper, or is composed of at least any two combinations of titanium, aluminum, titanium nitride, aluminum nitride, tungsten nitride, gold, and copper.

[0042] It can be understood that titanium (Ti) has good adhesion and can adhere well to various substrates. At the same time, its work function is moderate, making it suitable for forming a Schottky barrier with carbon nanotubes; materials such as aluminum (Al), gold (Au), and copper (Cu) have excellent electrical conductivity, which can effectively reduce the parasitic resistance of the anode and also reduce the transmission loss of the anode lead at high frequencies; titanium nitride (TiN) has high hardness and thermal stability, as well as good electrical conductivity, and is commonly used in occasions that require high heat resistance; aluminum nitride (AlN) and titanium nitride (TiN) can form a TiAlN alloy to achieve continuous adjustment of the work function of the anode contact for precise control of the Schottky barrier height; tungsten nitride (WN) has a high melting point and good electrical conductivity and can remain stable under extreme conditions. By using a combination of at least two of the above materials, better comprehensive performance can be obtained. For example, titanium can be used as the bottom layer to enhance the adhesion to the carbon nanotube active layer 2, and then a layer of titanium nitride can be deposited on it to increase the structural stability; or copper or gold can be used at the top to reduce the resistivity, while using a nitride layer to improve the corrosion resistance and thermal stability. It should be understood that different metals and their compounds have different work functions, and by reasonably matching them, the height of the Schottky barrier can be precisely controlled, thereby optimizing key parameters such as the turn-on voltage and reverse leakage current of the device.

[0043] In some embodiments of the carbon nanotube Schottky diode of the present invention, the distance between the lower electrode of the Schottky contact anode 3 and the cathode ohmic contact layer 4 is less than 300 nanometers, and the conductive cathode 5 is far from the upper electrode of the Schottky contact anode 3.

[0044] It can be understood that in this embodiment, by controlling the distance between the lower electrode of the Schottky contact anode 3 and the cathode ohmic contact layer 4 within 300 nanometers, the channel resistance of the carbon nanotubes can be effectively reduced, which helps to increase the forward conduction current and reduce the on-state resistance of the Schottky diode.

[0045] The conductive cathode 5 being far from the upper electrode of the Schottky contact anode 3 can reduce the parasitic capacitance and resistance between the two, thereby improving the overall performance of the device. The design of the conductive cathode 5 being far from the upper electrode of the Schottky contact anode 3 reduces unnecessary parasitic effects and high-frequency signal crosstalk, making the signal transmission more pure and efficient. Combined with the high carrier mobility characteristics of the carbon nanotube active layer 2, it further enhances the response speed and efficiency of the diode at high frequencies, making it suitable for applications in the terahertz frequency band.

[0046] In some specific examples, the cathode ohmic contact layer 4 is formed of a material with a work function less than 4.5 electron volts to form an N-type ohmic contact. The material of the cathode ohmic contact layer 4 includes one of scandium, titanium, yttrium, hafnium, tantalum, titanium nitride, tantalum nitride or a combination of at least any two of scandium, titanium, yttrium, hafnium, tantalum, titanium nitride, and tantalum nitride.

[0047] Due to their relatively low work functions, materials such as scandium, titanium, yttrium, hafnium, tantalum, titanium nitride, and tantalum nitride enable the cathode ohmic contact layer 4 to form a good N-type ohmic contact with the carbon nanotube active layer 2, reducing the contact resistance and improving the current injection efficiency. For example, titanium nitride (TiN) and tantalum nitride (TaN) not only have low work functions but also exhibit excellent thermal stability and mechanical strength, making them suitable for high-temperature or high-power applications.

[0048] In other specific examples, the cathode ohmic contact layer 4 is formed of a material with a work function greater than 4.5 electron volts to form a P-type ohmic contact. The material of the cathode ohmic contact layer 4 includes one of palladium, molybdenum, nickel, tungsten, titanium nitride or a combination of at least any two of palladium, molybdenum, nickel, tungsten, and titanium nitride.

[0049] These high-work-function materials such as palladium, molybdenum, nickel, tungsten, and titanium nitride can form an effective P-type ohmic contact with the carbon nanotube active layer 2 and are suitable for application scenarios where holes are the main carriers. It should be understood that although titanium nitride (TiN) also appears in the P-type ohmic contact materials, in this case, its role is to combine with other high-work-function metals to adjust the overall work function or improve physical properties.

[0050] The cathode ohmic contact layer 4 forms a good ohmic contact with the carbon nanotube active layer 2 by selecting appropriate materials (work function less than 4.5 electron volts for N-type or greater than 4.5 electron volts for P-type), which helps to significantly reduce the contact resistance, ensure that current can efficiently enter and exit the device, and reduce energy loss. Through the selection of the material for the cathode ohmic contact layer 4, whether for N-type or P-type contacts, the present invention aims to utilize the unique properties of specific metals and their compounds to achieve optimal electrical performance. These designs not only solve key problems in traditional Schottky diodes, such as high contact resistance and high power consumption, but also demonstrate excellent potential in high-frequency applications. In addition, a reasonable selection of material combinations can further optimize the thermal stability and mechanical strength of the device to meet the requirements of various complex application scenarios.

[0051] In some embodiments of the carbon nanotube Schottky diode of the present invention, the carbon nanotube active layer 2 includes a randomly arranged carbon nanotube network or an oriented carbon nanotube array, and the bandgap of the carbon nanotube active layer 2 is less than 1.2 electron volts. It can be understood that in this embodiment, the carbon nanotube active layer 2 can be a randomly arranged carbon nanotube network or an oriented carbon nanotube array. Among them, the randomly arranged carbon nanotube network structure provides lower cost and better uniformity, and is suitable for application scenarios with medium current density and millimeter wave frequency band. The oriented carbon nanotube array can provide higher current density and lower on-resistance, and is suitable for very high-frequency terahertz applications, such as terahertz communication, radar, etc. The bandgap of the carbon nanotube active layer 2 is less than 1.2 electron volts (eV), which makes it very suitable for fabricating high-speed electronic devices. The smaller bandgap means lower energy loss and higher carrier mobility, thus achieving higher operating frequency and better frequency conversion efficiency.

[0052] In some embodiments of the carbon nanotube Schottky diode of the present invention, the material of the substrate 1 includes at least one of quartz, glass, sapphire, alumina, gallium oxide, silicon carbide, gallium arsenide, gallium nitride, aluminum nitride, silicon nitride, indium phosphide, diamond, polyimide, and benzocyclobutene. Quartz and glass have low dielectric constants, good insulation properties, and thermal stability, and are suitable for terahertz Schottky diodes; sapphire, alumina, and gallium oxide have high thermal stability and mechanical strength, and are suitable for high-temperature and high-frequency applications; gallium arsenide, indium phosphide, gallium nitride, and silicon nitride have excellent electrical properties and thermal stability, and are suitable for high-performance electronic devices; silicon carbide, aluminum nitride, and diamond have extremely high thermal conductivity and excellent mechanical strength, and are suitable for applications in extreme environments; polyimide and benzocyclobutene have good flexibility and insulation properties, and are suitable for flexible electronic devices.

[0053] It can be understood that using a high thermal conductivity material such as silicon carbide or diamond as the substrate 1 can effectively dissipate heat and prevent performance degradation or failure caused by overheating; materials such as sapphire and alumina provide high-strength support for the substrate 1, increasing the durability of the diode. Different substrate 1 materials are suitable for different application requirements. For example, quartz and glass are suitable for terahertz devices, while polyimide and benzocyclobutene are suitable for flexible electronic devices. By selecting a suitable low dielectric constant material as the substrate 1, parasitic capacitance can be reduced and high-frequency performance can be improved.

[0054] On the other hand, the present invention also provides a method for manufacturing a carbon nanotube Schottky diode, which is suitable for manufacturing the carbon nanotube Schottky diode in any of the above embodiments. Refer to Figure 3 As shown, the method for manufacturing a carbon nanotube Schottky diode includes the following steps S1 to S5.

[0055] S1. Deposit a carbon nanotube active layer 2 on the substrate 1.

[0056] The purpose of this step is to construct the basic semiconductor layer of the Schottky diode. Select a substrate 1 material suitable for the application requirements (such as quartz, glass, sapphire, etc.), and deposit a layer of carbon nanotubes (which can be randomly arranged or directionally arranged) as the active layer on it by chemical vapor deposition (CVD), physical vapor deposition (PVD) or other suitable methods.

[0057] S2. Form a first cathode ohmic contact layer 4a and a second cathode ohmic contact layer 4b at both sides of the carbon nanotube active layer 2.

[0058] The purpose of this step is to establish a low-resistance path to ensure effective current injection. By means of photolithography, evaporation or sputtering techniques, a first cathode ohmic contact layer 4a and a second cathode ohmic contact layer 4b are respectively formed at the designated positions on both sides of the carbon nanotube active layer 2. The first cathode ohmic contact layer 4a and the second cathode ohmic contact layer 4b are made of a metal or alloy with a work function less than 4.5 electron volts (for N-type) or greater than 4.5 electron volts (for P-type).

[0059] S3. Deposit a dielectric layer 6 on the first cathode ohmic contact layer 4a, the second cathode ohmic contact layer 4b and the carbon nanotube active layer 2.

[0060] The purpose of this step is to provide electrical isolation and optimize the electric field distribution. Use methods such as atomic layer deposition (ALD), chemical vapor deposition (CVD), etc. to cover the entire structure with an insulating dielectric (such as SiO2, Al2O3, etc.), including the first cathode ohmic contact layer 4a, the second cathode ohmic contact layer 4b and the part of the carbon nanotube active layer 2 that is not covered.

[0061] S4. Etch the deposition medium layer 6 to etch out an anode contact hole at a position corresponding to the middle of the first cathode ohmic contact layer 4a and the second cathode ohmic contact layer 4b, and etch out cathode contact holes at positions directly above the first cathode ohmic contact layer 4a and the second cathode ohmic contact layer 4b respectively.

[0062] The purpose of this step is to prepare channels for subsequent electrode deposition. Dry etching (such as reactive ion etching RIE) or wet etching techniques are used to precisely open holes in the dielectric layer 6 to expose the underlying carbon nanotube active layer 2 for anode connection and to expose the first cathode ohmic contact layer 4a and the second cathode ohmic contact layer 4b for cathode connection.

[0063] S5. Deposit a Schottky contact anode 3 in the anode contact hole and form an anode lead 301. Deposit conductive cathodes 5 in the two cathode contact holes respectively, and connect the two conductive cathodes 5 to form a cathode lead 501.

[0064] The purpose of this step is to complete the electrode fabrication and ensure circuit connection. The Schottky contact anode 3 material (such as Ti, TiN, Au, etc.) is filled in the anode contact hole by evaporation, sputtering, etc., and at the same time, the conductive cathode 5 material (such as Au, Cu, etc.) is filled in the two cathode contact holes. Finally, the two conductive cathodes are connected to form a cathode lead 501, and a lead 301 is set for the anode to connect to the external circuit.

[0065] Through the above steps S1 - S5, a carbon nanotube Schottky diode with excellent performance can be successfully fabricated, which is applicable to fields such as high - frequency communication, radar, and imaging systems. This method not only considers how to effectively realize the functions of each component, but also pays attention to the rationality and operability of the process flow, aiming to improve production efficiency and yield. The theoretical cut - off frequency of the fabricated carbon nanotube Schottky diode can exceed 10 THz, and it has higher frequency conversion efficiency, lower power consumption, and can be used in terahertz devices and application systems.

[0066] In some specific examples, the following steps can be adopted to fabricate a carbon nanotube Schottky diode: deposit aligned carbon nanotubes on an insulating quartz (substrate 1) to form a carbon nanotube active layer 2; form a first cathode ohmic contact layer 4a and a second cathode ohmic contact layer 4b on the deposited carbon nanotube active layer 2. Specifically, use 40-nanometer Pd metal to form a P-type ohmic contact layer; deposit 10 nanometers of alumina and 10 nanometers of silicon oxide on the carbon nanotube active layer 2 to form a dielectric layer 6, which is placed above the carbon nanotube active layer 2, the first cathode ohmic contact layer 4a, and the second cathode ohmic contact layer 4b; etch the dielectric layer 6 to form a first cathode contact hole and a second cathode contact hole (corresponding to the positions directly above the first cathode ohmic contact layer 4a and the second cathode ohmic contact layer 4b respectively) and an anode contact hole (corresponding to the position between the first cathode ohmic contact layer 4a and the second cathode ohmic contact layer 4b); use a photolithography process to fabricate a Schottky contact anode 3, deposit 300-nanometer Ti / Au metal to form the Schottky contact anode 3 and an anode lead 301, and at the same time form the first cathode ohmic contact layer 4a, the second cathode ohmic contact layer 4b, and a cathode lead 501, thus completing the fabrication of the carbon nanotube Schottky diode.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A carbon nanotube Schottky diode, characterized in that: include: Substrate (1); A carbon nanotube active layer (2) is arranged on the substrate (1) to form a carbon nanotube channel on the substrate (1); A Schottky contact anode (3) is arranged on the carbon nanotube active layer (2), and the Schottky contact anode (3) is formed with an anode lead-out terminal (301); A cathode ohmic contact layer (4) is disposed on the carbon nanotube active layer (2) and is spaced apart from the Schottky contact anode (3); A conductive cathode (5) is arranged on the cathode ohmic contact layer (4), and the conductive cathode (5) is formed with a cathode lead-out terminal (501); A dielectric layer (6) is arranged on the carbon nanotube active layer (2), wherein the dielectric layer (6) is located in a region between the Schottky contact anode (3) and the cathode ohmic contact layer (4), and extends to cover the cathode ohmic contact layer (4).

2. The carbon nanotube Schottky diode according to claim 1, characterized in that: The cathode ohmic contact layer (4) comprises a first cathode ohmic contact layer (4a) and a second cathode ohmic contact layer (4b); the conductive cathode (5) comprises a first conductive cathode (5a) and a second conductive cathode (5b); and the dielectric layer (6) comprises a first dielectric layer (6a) and a second dielectric layer (6b); The first cathode ohmic contact layer (4a) and the second cathode ohmic contact layer (4b) are symmetrically arranged on both sides of the Schottky contact anode (3); the first conductive cathode (5a) is arranged on the first cathode ohmic contact layer (4a); the second conductive cathode (5b) is arranged on the second cathode ohmic contact layer (4b); corresponding ends of the first conductive cathode (5a) and the second conductive cathode (5b) are connected to form the cathode lead-out terminal (501); the first dielectric layer (6a) is arranged between the first cathode ohmic contact layer (4a) and the Schottky contact anode (3); and the second dielectric layer (6b) is arranged between the second cathode ohmic contact layer (4b) and the Schottky contact anode (3).

3. The carbon nanotube Schottky diode according to claim 1 or 2, characterized in that: The width of the upper electrode of the Schottky contact anode (3) away from the carbon nanotube active layer (2) is greater than the width of the lower electrode close to the carbon nanotube active layer (2), so as to form a T-shaped electrode structure; the lower end surface of the edge of the upper electrode of the Schottky contact anode (3) covers the dielectric layer (6) to form a field plate structure; the lower electrode of the Schottky contact anode (3) contacts the carbon nanotube active layer (2), and the side wall of the lower electrode of the Schottky contact anode (3) forms an angle less than 90 degrees with the carbon nanotube channel surface of the carbon nanotube active layer (2).

4. The carbon nanotube Schottky diode according to claim 3, characterized in that: The material of the Schottky contact anode (3) includes one of titanium, aluminum, titanium nitride, aluminum nitride, tungsten nitride, gold, and copper, or is a combination of at least any two of titanium, aluminum, titanium nitride, aluminum nitride, tungsten nitride, gold, and copper.

5. The carbon nanotube Schottky diode according to claim 3, characterized in that: The distance between the lower electrode of the Schottky contact anode (3) and the cathode ohmic contact layer (4) is less than 300 nanometers, and the conductive cathode (5) is far away from the upper electrode of the Schottky contact anode (3).

6. The carbon nanotube Schottky diode according to claim 1 or 2, characterized in that: The cathode ohmic contact layer (4) uses a material with a work function less than 4.5 electron volts to form an N-type ohmic contact, and the material of the cathode ohmic contact layer (4) includes one of scandium, titanium, yttrium, hafnium, tantalum, titanium nitride, and tantalum nitride, or is composed of a combination of at least any two of scandium, titanium, yttrium, hafnium, tantalum, titanium nitride, and tantalum nitride.

7. The carbon nanotube Schottky diode according to claim 1 or 2, characterized in that: The cathode ohmic contact layer (4) uses a material with a work function greater than 4.5 electron volts to form a P-type ohmic contact, and the material of the cathode ohmic contact layer (4) includes one of palladium, molybdenum, nickel, tungsten, and titanium nitride, or a combination of at least any two of palladium, molybdenum, nickel, tungsten, and titanium nitride.

8. The carbon nanotube Schottky diode according to claim 1 or 2, characterized in that: The carbon nanotube active layer (2) comprises a randomly arranged carbon nanotube network or a directionally arranged carbon nanotube array, and the band gap width of the carbon nanotube active layer (2) is less than 1.2 electron volts.

9. The carbon nanotube Schottky diode according to claim 1 or 2, characterized in that: The material of the substrate (1) includes at least one of quartz, glass, sapphire, aluminum oxide, gallium oxide, silicon carbide, gallium arsenide, gallium nitride, aluminum nitride, silicon nitride, indium phosphide, diamond, polyimide, and phenylcyclobutene.

10. A method for preparing a carbon nanotube Schottky diode, characterized in that: Suitable for preparing the carbon nanotube Schottky diode according to any one of claims 1 to 9, the preparation method of the carbon nanotube Schottky diode comprising: Depositing a carbon nanotube active layer (2) on a substrate (1); Forming a first cathode ohmic contact layer (4a) and a second cathode ohmic contact layer (4b) at two sides of the carbon nanotube active layer (2); Depositing a dielectric layer (6) on the first cathode ohmic contact layer (4a), the second cathode ohmic contact layer (4b) and the carbon nanotube active layer (2); Etching the deposited dielectric layer (6) to form an anode contact hole at a position corresponding to the middle of the first cathode ohmic contact layer (4a) and the second cathode ohmic contact layer (4b), and etching cathode contact holes at positions corresponding to directly above the first cathode ohmic contact layer (4a) and the second cathode ohmic contact layer (4b); A Schottky contact anode (3) is deposited in the anode contact hole to form an anode lead-out terminal (301), and a conductive cathode (5) is deposited in each of the two cathode contact holes, and the two conductive cathodes (5) are connected to form a cathode lead-out terminal (501).

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