Schottky diode, preparation method and application
By designing a Schottky diode structure that does not contain a two-dimensional electron gas, the source of junction capacitance is eliminated, solving the problems of high switching losses and large junction capacitance in existing technologies, and achieving ultra-high frequency and ultra-high efficiency application effects.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SUZHOU INST OF NANO TECH & NANO BIONICS CHINESE ACEDEMY OF SCI
- Filing Date
- 2026-03-03
- Publication Date
- 2026-05-15
AI Technical Summary
Existing silicon-based fast recovery diodes, silicon carbide Schottky diodes, and conventional gallium nitride Schottky diodes suffer from problems such as high switching losses and large junction capacitance in ultra-high frequency and ultra-high efficiency applications, which limits their further application.
Design a Schottky diode including a stacked channel layer and a barrier layer, configured to not contain two-dimensional electron gas (2DEG) in its natural state. By setting a two-dimensional electron gas generation layer and an electrode structure on the semiconductor structure layer, ohmic contacts and Schottky contacts are formed, eliminating the source of junction capacitance. A thin barrier layer and a specific material combination are used to adjust the polarization intensity to ensure that there is no 2DEG charging and discharging process during reverse cutoff.
It achieves ultra-low reverse recovery charge and extremely low junction capacitance, making it suitable for ultra-high frequency and ultra-high efficiency applications, and features extremely high switching speed and low loss performance.
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Figure CN122054613A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of micro / nano manufacturing technology, and more specifically, to a Schottky diode, its fabrication method, and its application. Background Technology
[0002] In radio frequency front-end systems such as radar, electronic warfare, and high-speed communications, the receiving channel is highly susceptible to damage from high-power pulse signals (such as radar transmission leakage, electromagnetic interference, etc.) originating from the antenna or internal components. As a critical passive protection device, the limiter is placed before sensitive components such as low-noise amplifiers. Its function is to transmit signals losslessly when the input power is low, and to quickly activate when a high-power pulse is input, clamping the output power to a safe level, thereby protecting subsequent circuitry.
[0003] Another application of Schottky diodes is in microwave rectifier circuits. A microwave rectifier circuit is a device that converts high-frequency microwave energy into direct current (DC) energy. Its core utilizes high-speed nonlinear components such as Schottky diodes to rectify the microwave signal, achieves maximum power transmission through a precision impedance matching network, and finally outputs stable DC power after a filter circuit. This technology is widely used in radio frequency energy harvesting and wireless power transmission systems.
[0004] The relevant technologies mainly provide the following implementation schemes: (1) Silicon-based fast recovery diode: By artificially introducing lattice defects into silicon material, the minority carrier lifetime is shortened, thereby greatly accelerating the switching speed of the diode from the on state to the off state.
[0005] (2) Silicon carbide Schottky diode: Unlike silicon-based fast recovery diodes, silicon carbide Schottky diodes rely on majority carriers for conduction and theoretically do not have a reverse recovery effect. They have fast switching performance and have become the main choice for high-frequency applications.
[0006] (3) Conventional gallium nitride Schottky diode: It adopts a lateral structure and has a relatively high theoretical breakdown field strength.
[0007] However, for silicon-based fast recovery diodes, due to their minority carrier conduction mechanism, the inherent reverse recovery effect cannot be completely eliminated. In high-frequency applications at MHz and above, problems such as reverse recovery loss and reverse recovery current spikes are unavoidable, further inhibiting the improvement of overall circuit performance.
[0008] For silicon carbide Schottky diodes, the inherent junction capacitance of silicon carbide Schottky diodes further limits their application in ultra-high frequency scenarios.
[0009] Conventional gallium nitride Schottky diodes, similar to silicon carbide diodes, rely on majority carrier conduction for power delivery. However, they also possess inherent junction capacitance, limiting their application at higher frequencies.
[0010] In summary, silicon-based fast recovery diodes, silicon carbide Schottky diodes, and conventional gallium nitride Schottky diodes suffer from high switching losses and large junction capacitances in ultra-high frequency and ultra-high efficiency applications. Therefore, there is an urgent need to provide a Schottky diode, its fabrication method, and its applications. Summary of the Invention
[0011] This application provides a Schottky diode, its fabrication method, and its application, thereby solving the technical problems in related technologies.
[0012] According to one aspect of this application, a Schottky diode is provided, comprising: A semiconductor structure layer, comprising a channel layer and a barrier layer stacked thereon, wherein the semiconductor structure layer is configured not to contain a two-dimensional electron gas (2DEG) in its natural state. A two-dimensional electron gas generating layer is stacked on the semiconductor structure layer and is used to generate two-dimensional electron gas in a selected area of the semiconductor structure layer. The selected area is located between the first electrode contact area and the second electrode contact area of the semiconductor structure layer. The first electrode structure forms an ohmic contact with the first electrode contact region of the semiconductor structure layer; The second electrode structure forms a Schottky contact with the second electrode contact region of the semiconductor structure layer, and the second electrode structure is electrically connected to the first electrode structure via the two-dimensional electron gas.
[0013] Furthermore, the Al atom percentage content of the barrier layer is 1%~30%, and the thickness is 1nm~30nm. The barrier layer is configured such that the semiconductor structure layer does not contain two-dimensional electron gas in its natural state.
[0014] Furthermore, the first electrode structure includes an anode metal, which is in contact with at least the barrier layer.
[0015] Furthermore, the second electrode structure includes a cathode disposed on the barrier layer and undergoes an alloying reaction with the barrier layer and the channel layer.
[0016] Furthermore, the first electrode contact region of the semiconductor structure layer has a stepped structure, wherein the upper step surface and the lower step surface of the stepped structure are the surface of the barrier layer and the surface of the channel layer, respectively, and the anode metal continuously covers the upper step surface and the lower step surface of the stepped structure.
[0017] Furthermore, the anode metal is disposed on the barrier layer, and the cathode is configured as one or more.
[0018] For example, the first electrode structure is disposed on the barrier layer, and multiple second electrode structures are configured, with the first electrode structure disposed between the multiple second electrode structures.
[0019] Furthermore, the anode metal is disposed on the channel layer and in contact with the side of the barrier layer.
[0020] Furthermore, the first electrode structure includes an anode metal and a field plate terminal stacked sequentially.
[0021] Furthermore, the two-dimensional electron gas generating layer continuously covers a selected area of the semiconductor structure layer and the second electrode structure.
[0022] Furthermore, the two-dimensional electron gas generating layer and the second electrode structure are also covered with an insulating dielectric layer.
[0023] Furthermore, the Schottky diode also includes a substrate, and the semiconductor structure layer is disposed on the substrate.
[0024] Furthermore, the semiconductor structure layer is made of group III nitrides.
[0025] Furthermore, the material of the two-dimensional electron gas generating layer includes a material whose surface potential is lower than the energy level position of oxygen at the surface of the barrier layer.
[0026] According to another aspect of this application, a method for fabricating the aforementioned Schottky diode is provided, comprising: A channel layer and a barrier layer are sequentially grown on a substrate to form a semiconductor structure layer; A two-dimensional electron gas generating layer is disposed on at least a selected region of the semiconductor structure layer to generate a two-dimensional electron gas in the selected region of the semiconductor structure layer. A first electrode structure and a second electrode structure are disposed on the semiconductor structure layer, such that the first electrode structure forms an ohmic contact with the first electrode contact area of the semiconductor structure layer, and the second electrode structure forms a Schottky contact with the second electrode contact area of the semiconductor structure layer, and the first electrode structure is electrically connected to the second electrode structure via the two-dimensional electron gas.
[0027] Furthermore, specifically including: The first electrode contact area of the semiconductor structure layer is etched to form a stepped structure, and the upper step surface and the lower step surface of the stepped structure are respectively the barrier layer surface and the channel layer surface. Then, a first electrode structure is set on the first electrode contact area, so that the anode metal therein continuously covers the upper step surface and the lower step surface of the stepped structure. In addition, the second electrode contact area of the semiconductor structure layer is etched to expose at least partially the channel layer therein, and then a second electrode structure is formed on the exposed channel layer and the second electrode structure is made to contact the side of the barrier layer. Alternatively, the second electrode contact area of the semiconductor structure layer can be set as a plurality, and each second electrode contact area can be etched to expose at least partially the channel layer therein, and then a second electrode structure can be set on the exposed channel layer and the second electrode structure can be made to contact the side of the barrier layer. The first electrode structure is disposed on the barrier layer and positioned between multiple second electrode structures. Alternatively, the first electrode contact area of the semiconductor structure layer can be etched to expose at least part of the channel layer therein, and then the first electrode structure can be disposed on the exposed channel layer and the first electrode structure can be made to contact the side of the barrier layer. Furthermore, the second electrode contact area of the semiconductor structure layer is etched to expose at least partially the channel layer therein, and a second electrode structure is then formed on the exposed channel layer, with the second electrode structure in contact with the side of the barrier layer.
[0028] Furthermore, specifically including: The two-dimensional electron gas generation layer is continuously covered in a selected area of the semiconductor structure layer and on the second electrode structure; Furthermore, an insulating dielectric layer is continuously covered on the two-dimensional electron gas generating layer.
[0029] According to another aspect of this application, the aforementioned Schottky diode is provided for use in limiting networks, rectifier networks, limiters, rectifiers, radio frequency systems, or wireless power transmission systems.
[0030] Based on the above technical solutions and the technical problems solved, this application provides a Schottky diode, its fabrication method, and its application. Because it naturally lacks a 2DEG below the anode, it eliminates the source of junction capacitance found in traditional Schottky diodes. Since there is no 2DEG charging and discharging process during reverse cutoff, it exhibits ultra-low reverse recovery charge. In summary, it is suitable for ultra-high frequency and ultra-high efficiency applications. Attached Figure Description
[0031] Figure 1 This is a schematic diagram of the CV test results for a low-capacitance, ultra-fast recovery Schottky diode; Figure 2 This is a schematic diagram illustrating the principle of silicon deposition on the surface and generation of 2DEG in a thin barrier layer AlGaN / GaN heterojunction structure. Figure 3 This is a schematic diagram of a Schottky diode with a grooved contact anode structure provided in this application; Figure 4 This is a schematic diagram of a Schottky diode with a horizontal contact anode structure provided in this application; Figure 5 This is a schematic diagram of a Schottky diode with a vertical contact anode structure provided in this application; Figure 6 This is a schematic diagram of the structure of a Schottky diode with an interdigitated hybrid anode structure provided in this application; Figure 7 This is a schematic diagram of a Schottky diode with a ring-shaped hybrid anode structure provided in this application; Figure 8 This is a schematic diagram of the application of a Schottky diode in a limiting circuit provided in this application; Figure 9 This is a schematic diagram of the application of a Schottky diode in a rectifier circuit provided in this application; Figure 10 This is a schematic diagram of the groove contact anode structure of a Schottky diode provided in this application; Figure 11 This is a schematic diagram of the IV characteristics of a grooved contact anode structure of a Schottky diode provided in this application; Figure 12 This is a schematic diagram of the IV characteristics of a Schottky diode before and after PECVD_Si provided in this application; Figure 13 This is a schematic diagram of the CV test results of a horizontal contact anode structure of a Schottky diode provided in this application; Figure 14 This is a schematic diagram of the carrier distribution of a Schottky diode provided in this application; Figure 15 This is a schematic diagram of the CV characteristics of a conventional Schottky diode provided in this application; Figure 16 This is a schematic diagram of the carrier distribution in a conventional Schottky diode provided in this application; Figure 17 This is a schematic diagram of the CV test results of the SiC Schottky diode provided in this application.
[0032] Illustration: 101, Substrate layer; 102, Channel layer; 103, Barrier layer; 104, Ohmic contact layer; 105, Two-dimensional electron gas generation layer; 106, Insulating dielectric layer; 107, Schottky contact layer. Detailed Implementation
[0033] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed to enable those skilled in the art to better understand and implement the subject matter described herein. Changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.
[0034] To facilitate understanding, the principle of the low-capacitance ultrafast recovery Schottky diode will first be explained: A Schottky diode is a device that uses the potential barrier formed by the contact between a metal and a semiconductor for rectification. When a metal contacts an N-type semiconductor, electrons in the semiconductor spontaneously flow to the lower-energy metal because the Fermi level of the semiconductor is higher than that of the metal, until the Fermi levels of the two are leveled. Under forward bias, the direction of the external electric field is opposite to the direction of the built-in electric field, thus weakening the built-in electric field and the Schottky barrier. With the barrier lowered, a large number of charge carriers in the semiconductor can cross the barrier, forming a large forward current. Under reverse bias, the direction of the external electric field is the same as that of the built-in electric field, thus increasing the built-in electric field and the Schottky barrier. With the barrier increased, it is difficult for charge carriers in the semiconductor to cross the barrier, therefore the reverse current is very small.
[0035] According to the thermionic emission model, the voltage-current formula for a Schottky contact can be expressed as: in, For the area of the Schottky contact, For an effective Richardson constant, For unit charge, For the height of the barrier, Boltzmann's constant, Absolute temperature For series resistance, It is the ideal factor.
[0036] For structures such as Schottky barrier, MIS junction, and pn junction, the width and charge number of their space charge region change when different voltages are applied. Therefore, we can use CV testing to measure the charge concentration and distribution of Schottky diodes.
[0037] In low-capacitance ultrafast recovery Schottky diodes, when the device is forward biased, the direction of the applied electric field is opposite to the direction of the built-in electric field, allowing electrons to pass through the potential barrier smoothly. When the device is reverse biased, for conventional gallium nitride Schottky diodes, under reverse bias, a charging and discharging process inevitably occurs due to the junction capacitance. Low-capacitance ultrafast recovery Schottky diodes naturally lack a two-dimensional electron gas below the anode, thus eliminating junction capacitance and resulting in a very short charging and discharging time. Therefore, low-capacitance ultrafast recovery Schottky diodes can operate in ultra-high frequency applications. See also Figure 1 This is a schematic diagram of the CV test results for a low-capacitance, ultra-fast recovery Schottky diode. It can be clearly seen that the junction capacitance is very small and can be ignored.
[0038] Then, the principle of 2DEG generation in the thin-barrier AlGaN / GaN heterojunction structure is explained: Due to the significant difference in spontaneous and piezoelectric polarization between AlGaN and GaN, a highly concentrated two-dimensional electron gas is generated at their interface. The GaN layer containing this two-dimensional electron gas is typically unintentionally doped, thus electrons are almost unaffected by impurities at the interface, resulting in extremely high mobility. The concentration of the two-dimensional electron gas can be adjusted by weakening the intensity of the spontaneous and piezoelectric polarization of the AlGaN layer, which is usually achieved by changing the Al composition and thickness of the barrier layer. The following formula gives the calculation formula for the concentration of the two-dimensional electron gas.
[0039] In the formula, For two-dimensional electron gas concentration, For charge quantity, The polarization charge density of the corresponding material. For the thickness of the corresponding material, Where is the dielectric constant of the corresponding material. The surface potential of the barrier layer is denoted as . The energy difference between the two-dimensional electron gas quantum well and the Fermi level. This corresponds to the difference in conduction band between the two materials.
[0040] The surface potential is reduced by depositing a 2DEG layer on the surface, thereby achieving the purpose of generating a two-dimensional electron gas. Figure 2 This is a schematic diagram illustrating the principle of generating 2DEG by depositing silicon on the surface of a thin barrier layer AlGaN / GaN heterojunction structure.
[0041] The purpose of this application is to address the shortcomings of existing silicon-based and complex GaN limiters in terms of power, speed, loss and integration by providing a novel limiter based on gallium nitride diodes to meet the needs of high-frequency and high-efficiency applications, and to realize a novel low-capacitance ultrafast recovery Schottky diode with ultra-low reverse recovery charge, extremely low junction capacitance and high reliability.
[0042] The following description, in conjunction with the accompanying drawings and specific embodiments, illustrates how to solve the aforementioned technical problems by describing the structure, fabrication method, and applications of Schottky diodes. It should be noted that the various embodiments or technical features described below can be arbitrarily combined to form new embodiments, and the same or similar concepts or processes may not be repeated in some embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them.
[0043] Example 1 This embodiment provides a Schottky diode, including: A semiconductor structure layer, including a channel layer and a barrier layer stacked thereon, wherein the semiconductor structure layer is configured not to contain a two-dimensional electron gas in its natural state; A two-dimensional electron gas generating layer is stacked on the semiconductor structure layer and is used to generate two-dimensional electron gas in a selected area of the semiconductor structure layer. The selected area is located between the first electrode contact area and the second electrode contact area of the semiconductor structure layer. The first electrode structure forms an ohmic contact with the first electrode contact region of the semiconductor structure layer; The second electrode structure forms a Schottky contact with the second electrode contact region of the semiconductor structure layer, and the second electrode structure is electrically connected to the first electrode structure via the two-dimensional electron gas.
[0044] Furthermore, the Al atom percentage content of the barrier layer is 1%~30% and the thickness is 1nm~30nm. The barrier layer is configured such that the semiconductor structure layer does not contain two-dimensional electron gas (2DEG) in its natural state.
[0045] As an example, by configuring the thickness (e.g., 1nm-30nm) and composition (AlGaN, InAlN, AlN, AlScN, AlInGaN) of the barrier layer, the spontaneous polarization and piezoelectric polarization intensity at the heterojunction interface are weakened, so that the channel layer intrinsically lacks two-dimensional electron gas without external induction. In particular, through this thin barrier layer design, two-dimensional electron gas does not exist in the region below the anode metal in its natural state, fundamentally eliminating the source of junction capacitance in traditional Schottky diodes. At the same time, a two-dimensional electron gas generation layer is covered on the surface of the semiconductor epitaxial structure between the cathode and anode, forming a low-resistance conductive channel connecting the cathode (ohmic contact) and the anode (Schottky contact).
[0046] Furthermore, the first electrode structure includes an anode metal, which is in contact with at least the barrier layer.
[0047] Furthermore, the second electrode structure includes a cathode disposed on the barrier layer and undergoes an alloying reaction with the barrier layer and the channel layer.
[0048] Furthermore, the Schottky diode also includes a substrate, on which the semiconductor structure layer is disposed.
[0049] Furthermore, the semiconductor structure layer is made of group III nitrides.
[0050] Furthermore, the material of the two-dimensional electron gas generating layer includes a material whose surface potential is lower than the energy level position of oxygen at the surface of the barrier layer.
[0051] In this embodiment, the beneficial effect of the Schottky diode device structure design is that, in ultra-high frequency and ultra-high efficiency applications, the Schottky diode provided in this embodiment eliminates the source of junction capacitance in traditional Schottky diodes because there is naturally no two-dimensional electron gas below the anode. Furthermore, since there is no 2DEG charging and discharging process during reverse cutoff, it exhibits ultra-low reverse recovery charge.
[0052] In specific applications, the Schottky diode can have a grooved contact anode structure. In this case, the first electrode contact region of the semiconductor structure layer has a stepped structure, wherein the upper and lower stepped surfaces of the stepped structure are the surface of the barrier layer and the surface of the channel layer, respectively, and the anode metal continuously covers the upper and lower stepped surfaces of the stepped structure. The first electrode structure may include anode metal and field plate terminals stacked sequentially.
[0053] See Figure 3As an example, a Schottky diode with a grooved contact anode structure is provided, which, from top to bottom, comprises: a. a substrate layer 101, including any one of SiC, Si, sapphire, GaN, AlN, and diamond; b. a channel layer 102, including any one of GaN, InGaN, AlGaN, and AlInGaN; a barrier layer 103, including any one of AlGaN, InAlN, AlN, AlScN, and AlInGaN; and d. an ohmic contact layer 10. 4; e. 2DEG generation layer (two-dimensional electron gas generation layer 105), including any one of the following materials with low surface potential: silicon, germanium, silicon-germanium hybrid materials, silicon nitride, silicon oxide, aluminum nitride, aluminum oxynitride, etc.; f. Schottky contact layer 107; g. Insulating dielectric layer 106, including any one of Si3N4, SiO2, Al2O3, HfO2; h. Anode field plate (field plate terminal). In specific applications, different device structures (by adding field plates, etc.) can be designed to cope with different voltages and application environments. The red dashed line represents the two-dimensional electron gas 2DEG. The field plate terminal of the anode is located above the Schottky contact layer. It can be considered that in the groove contact anode structure, since the anode metal is in direct contact with the heterojunction channel, it is beneficial to reduce the turn-on voltage.
[0054] It is worth noting that the thin barrier epitaxial wafer used in the structure, by adjusting the composition and thickness of the barrier layer, naturally eliminates the presence of a two-dimensional electron gas. In the diode structure protected in this embodiment, the key to generating low capacitance lies in the absence of a two-dimensional electron gas beneath the anode metal. By covering the active region with a 2DEG generation layer, the connection between the anode and cathode is achieved. The specific composition and thickness of the barrier layer will be explained in subsequent embodiments or examples.
[0055] In specific applications, the Schottky diode can also have a horizontal contact anode structure. In this case, the anode metal is disposed on the barrier layer, and more than one cathode is configured. The first electrode structure may include anode metal and field plate terminals stacked sequentially.
[0056] Correspondingly, the first electrode structure is disposed on the barrier layer, and multiple second electrode structures are configured, with the first electrode structure disposed between the multiple second electrode structures.
[0057] See Figure 4As an example, a Schottky diode with a horizontal contact anode structure is provided, comprising, from top to bottom: a. a substrate layer 101, including any one of SiC, Si, sapphire, GaN, AlN, and diamond; b. a channel layer 102, including any one of GaN, InGaN, AlGaN, and AlInGaN; c. a barrier layer 103, including any one of AlGaN, InAlN, AlN, AlScN, and AlInGaN; d. an ohmic contact layer 104; e. a 2DEG generation layer (two-dimensional electron gas generation layer 105), which is any one of materials with low surface potential such as silicon, germanium, silicon-germanium mixture, silicon nitride, silicon oxide, aluminum nitride, and aluminum oxynitride; f. a Schottky contact layer 107; g. an insulating dielectric layer 106, including any one of Si3N4, SiO2, Al2O3, and HfO2; h. an anode field plate, which may be added or omitted depending on the specific application. The red dashed line represents the two-dimensional electron gas (2DEG). The field plate terminal of the anode is located above the Schottky contact layer. It can be considered that in the horizontal contact anode structure, this structure effectively avoids damage to the barrier layer, reduces the series resistance of the device, and thus obtains a larger saturation current.
[0058] In specific applications, this Schottky diode can also have a vertically contacted anode structure. In this case, the anode metal is disposed on the channel layer and contacts the side of the barrier layer. The first electrode structure may include anode metal and field plate terminals stacked sequentially.
[0059] See Figure 5 As an example, a Schottky diode with a vertical contact anode structure is provided, which, from top to bottom, comprises: a. a substrate layer 101, including any one of SiC, Si, sapphire, GaN, AlN, and diamond; b. a channel layer 102, including any one of GaN, InGaN, AlGaN, and AlInGaN; c. a barrier layer 103, including any one of AlGaN, InAlN, AlN, AlScN, and AlInGaN; d. an ohmic contact layer 104; e. a 2DEG generation layer (two-dimensional electron gas generation layer 105), including any one of materials with low surface potential such as silicon, germanium, silicon-germanium hybrid materials, silicon nitride, silicon oxide, aluminum nitride, and aluminum oxynitride; f. a Schottky contact layer 107; g. an insulating dielectric layer 106, including any one of Si3N4, SiO2, Al2O3, and HfO2; and h. an anode field plate, which may be added or omitted depending on the specific application. The red dashed line represents the two-dimensional electron gas (2DEG). The field plate terminal of the anode is located above the Schottky contact layer. It can be considered that in the vertical contact anode structure, the anode metal and the etched area of the barrier layer form a self-aligned process, which can reduce the device size and achieve higher power density.
[0060] See Figure 6 and Figure 7 As an example, a Schottky diode with a hybrid anode structure is provided, which, from top to bottom, comprises: a. a substrate layer 101, including any one of SiC, Si, sapphire, GaN, AlN, and diamond; b. a channel layer 102, including any one of GaN, InGaN, AlGaN, and AlInGaN; c. a barrier layer 103, including any one of AlGaN, InAlN, AlN, AlScN, and AlInGaN; d. an ohmic contact layer 104; e. a 2DEG generation layer (two-dimensional electron gas generation layer 105), including any one of materials with low surface potential such as silicon, germanium, silicon-germanium hybrid materials, silicon nitride, silicon oxide, aluminum nitride, and aluminum oxynitride; f. a Schottky contact layer 107; g. an insulating dielectric layer 106, including any one of Si3N4, SiO2, Al2O3, and HfO2; and h. an anode field plate, which may be added or omitted depending on the specific application. The red dashed line represents the two-dimensional electron gas (2DEG). The field plate terminal of the anode is located above the Schottky contact layer. It can be considered that in a hybrid anode structure, this structure can reduce the device's turn-on voltage without damaging the barrier layer. Specifically, Figure 6 This is a Schottky diode with an interdigitated hybrid anode structure. Figure 7 This is a Schottky diode with a ring-shaped hybrid anode structure.
[0061] Furthermore, the two-dimensional electron gas generating layer continuously covers a selected area of the semiconductor structure layer and the second electrode structure.
[0062] Furthermore, the two-dimensional electron gas generating layer and the second electrode structure are also covered with an insulating dielectric layer.
[0063] Example 2 This application also provides a method for fabricating a Schottky diode, the beneficial effects of which are further illustrated below by comparison with comparative examples. The method is used to fabricate the Schottky diode described in any one of Examples 1, and the method includes: A channel layer and a barrier layer are sequentially grown on a substrate to form a semiconductor structure layer; A two-dimensional electron gas generating layer is disposed on at least a selected region of the semiconductor structure layer to generate a two-dimensional electron gas in the selected region of the semiconductor structure layer. A first electrode structure and a second electrode structure are disposed on the semiconductor structure layer, such that the first electrode structure forms an ohmic contact with the first electrode contact area of the semiconductor structure layer, and the second electrode structure forms a Schottky contact with the second electrode contact area of the semiconductor structure layer, and the first electrode structure is electrically connected to the second electrode structure via the two-dimensional electron gas.
[0064] In practical applications, it is not limited to AlGaN / GaN heterojunction substrates; other semiconductors such as GaAs can also be used. Furthermore, for conventional epitaxial layer structures, the area below the anode can be etched to achieve a state critical to the generation of a two-dimensional electron gas. Additionally, it can reduce costs, addressing the issue of expensive silicon carbide substrates and high manufacturing costs associated with silicon carbide Schottky diodes.
[0065] In one embodiment, it specifically includes: The first electrode contact area of the semiconductor structure layer is etched to form a stepped structure, and the upper step surface and the lower step surface of the stepped structure are respectively the barrier layer surface and the channel layer surface. Then, a first electrode structure is set on the first electrode contact area, so that the anode metal therein continuously covers the upper step surface and the lower step surface of the stepped structure. In addition, the second electrode contact area of the semiconductor structure layer is etched to expose at least partially the channel layer therein, and then a second electrode structure is formed on the exposed channel layer and the second electrode structure is made to contact the side of the barrier layer. Alternatively, the second electrode contact area of the semiconductor structure layer can be set as a plurality, and each second electrode contact area can be etched to expose at least partially the channel layer therein, and then a second electrode structure can be set on the exposed channel layer and the second electrode structure can be made to contact the side of the barrier layer. The first electrode structure is disposed on the barrier layer and positioned between multiple second electrode structures. Alternatively, the first electrode contact area of the semiconductor structure layer can be etched to expose at least part of the channel layer therein, and then the first electrode structure can be disposed on the exposed channel layer and the first electrode structure can be made to contact the side of the barrier layer. Furthermore, the second electrode contact area of the semiconductor structure layer is etched to expose at least partially the channel layer therein, and a second electrode structure is then formed on the exposed channel layer, with the second electrode structure in contact with the side of the barrier layer.
[0066] In one embodiment, it specifically includes: The two-dimensional electron gas generation layer is continuously covered in a selected area of the semiconductor structure layer and on the second electrode structure; Furthermore, an insulating dielectric layer is continuously covered on the two-dimensional electron gas generating layer.
[0067] As an example, a method for fabricating a low-capacitance, ultrafast recovery Schottky diode is provided, comprising the following steps: S1. A semiconductor epitaxial structure is formed by sequentially growing a Fe-GaN buffer layer with a thickness of 100nm-500nm, an unintentionally doped GaN layer with a thickness of 100nm-600nm, a GaN channel layer with a thickness of 10nm-100nm, an AlN space layer with a thickness of 1nm-10nm, an AlGaN barrier layer with a thickness of 1nm-30nm, and a GaN capping layer with a thickness of 1nm-5nm on a silicon carbide substrate using MOCVD process.
[0068] S2. The semiconductor epitaxial structure is isolated by means of ICP etching process, etc., with an etching depth of 30nm-300nm.
[0069] S3. Define the ohmic region using photolithography, deposit ohmic metals such as Ti, Al, Ni, or Au in the ohmic region, and then anneal in a nitrogen atmosphere. This creates an ohmic contact between the transistor cathode and the semiconductor layer.
[0070] S4. Anode patterns are created using photolithography and other processes, and then anode metal Ni or Au is deposited by vapor deposition.
[0071] S5. Amorphous silicon with a thickness of 1nm-20nm is grown on the semiconductor epitaxial structure using PECVD process to serve as a two-dimensional electron gas generation layer for transistors.
[0072] To verify the Schottky diode protected in this application, the IV characteristics of a low-capacitance, ultra-fast recovery Schottky diode structure (groove contact anode structure) were first tested. See [link to relevant documentation]. Figure 10 Define some dimensional characteristics of the groove contact anode structure. The length of the anode metal, It represents the distance between the yin and yang poles.
[0073] See Figure 11 The IV characteristics of the device were displayed, with the distance between the anode and cathode fixed at 10 μm. The results showed that different anode metal lengths ( The IV characteristics of devices with anode lengths of 1, 3, 5, 6, 10, 12, and 14 μm are almost identical, meaning the anode metal length does not affect the current. Therefore, higher power density can be achieved by minimizing the anode metal length as much as possible. The device has a turn-on voltage of 0.59 V@1 mA / mm and a current density of 139 mA / mm@2 V.
[0074] See Figure 12 The figure shows the IV characteristics before and after the PECVD process. Without PECVD_Si, a resistor with an ohmic contact distance of 8µm draws a current of 300pA at 1V. After PECVD_Si, with the same device structure, the current is 15mA. This indicates that PECVD_Si can effectively generate 2DEG.
[0075] Then, CV tests were performed on the low-capacitance ultrafast recovery Schottky diode structure (horizontal contact anode structure), such as... Figure 13 As shown in the figure. The CV test results show that the device has a relatively low unit capacitance; at a test frequency of 2MHz, the normalized capacitance is only 6nF / cm²@0V. Integrating the capacitance over the CV from -3V to 0V yields the stored charge under reverse bias, approximately 5.49nC, for an area of 1cm². 2 .
[0076] See Figure 13 Next, CV calculations are performed to obtain the carrier distribution in the semiconductor below the anode. The results show no accumulation and depletion process of 2DEG. s It refers to the surface density of two-dimensional electron gas (2DEG).
[0077] The following provides further explanation for Comparative Examples 1 and 2: Comparative Example 1 This invention provides a method for fabricating gallium nitride Schottky diodes, which is consistent with the method and process for fabricating low-capacitance ultrafast recovery Schottky diodes. The only difference is the epitaxial wafer used. Using MOCVD, a semiconductor epitaxial layer is formed by sequentially growing the following layers on a silicon carbide substrate: a 100nm-500nm thick Fe-GaN buffer layer, a 100nm-400nm thick unintentionally doped GaN layer, a 20nm-200nm thick GaN channel layer, a 0.5nm-5nm thick AlN space layer, a 10nm-30nm thick AlGaN barrier layer, and a 1nm-3nm thick GaN capping layer.
[0078] The difference between this and the technical solution provided in Example 2 lies in the epitaxial wafer, which results in a different structure for the final Schottky diode. Conventional gallium nitride Schottky diodes have a two-dimensional electron gas beneath the anode metal; therefore, when a conventional Schottky diode operates under reverse bias, it inevitably undergoes a charging and discharging process of its capacitor.
[0079] Figure 15 The CV characteristics of a conventional Schottky diode are shown. The CV test results indicate that under reverse bias, the device exhibits junction capacitance and a charge charging / discharging process. Integrating the CV capacitance from -4V to 0V yields the stored charge under reverse bias, approximately 791.2 nC, for a 1 cm² area. 2 It has approximately 144 times the charge stored in a low-capacitance ultrafast recovery Schottky diode. Therefore, low-capacitance ultrafast recovery Schottky diodes can handle higher frequency applications. Figure 16The distribution of charge carriers in the anode metal obtained by CV testing is shown, and the distribution in the semiconductor of 2DEG can be seen. Figure 17 The CV test results of the SiC Schottky diode are shown.
[0080] Comparative Example 2 The method for fabricating a 4H-SiC Schottky diode provided in this comparative example includes the following steps: S1. The doping concentration of the n-type 4H-SiC substrate used in the experiment is: The epitaxial layer grown has a thickness of 12 μm and a doping concentration of [missing information]. First, the wafer is cleaned according to the RCA standard.
[0081] S2. Sputter Ni metal to the back of the SiC wafer to a thickness of 200 nm, and anneal at 950 °C for 2 minutes in a nitrogen atmosphere to form an ohmic contact.
[0082] S3. Anode patterns are created using photolithography and other processes, and then anode metal Ni / Au (thickness approximately 50 / 200nm) is deposited by vapor deposition to form Schottky contacts.
[0083] Figure 14 The CV characteristics of the fabricated SiC Schottky diode are shown. Integrating the CV capacitance from -4V to 0V yields the stored charge under reverse bias, which is approximately 64.8 nC, for a device with an area of 1 cm². 2 It has approximately 12 times the charge stored in a low-capacitance ultrafast recovery Schottky diode.
[0084] As can be seen from the above examples, compared with related technologies, the technical solution provided in this application offers a Schottky diode with extremely low reverse capacitance, and a forward current density comparable to that of a conventional Schottky diode. It exhibits excellent high-frequency performance and signal integrity, ultra-high switching speed, and low loss. It also features lower reverse recovery charge and lower noise.
[0085] Example 3 This application also provides an application of the Schottky diode described in any one of Embodiment 1 in a limiting network, rectifier network, limiter, rectifier, radio frequency system, or wireless power transmission system.
[0086] See Figure 8 As an example, this illustrates the application of low-capacitance, ultra-fast recovery Schottky diodes in limiting circuits. When the input signal does not exceed the diode's turn-on voltage, the input RF signal can pass through the limiting network without loss. By increasing the amplitude of the input RF signal, the output voltage is limited to a certain range after the diode turns on, protecting downstream components. The schematic diagram shows a three-stage limiting network, with each stage connected back-to-back to achieve full-cycle limiting.
[0087] See Figure 9 As an example, this section illustrates the application of low-capacitance ultrafast recovery Schottky diodes in microwave rectifier circuits. The working principle of a microwave rectifier circuit is essentially the process of efficiently converting high-frequency AC microwave signals into DC current. Its core can be summarized in four key steps: Signal reception: The antenna captures microwave electromagnetic waves in space and converts them into high-frequency alternating voltage / current signals. Impedance matching: This is crucial for efficiency. The matching network precisely transforms the antenna impedance to the optimal impedance required by the rectifier diode, ensuring that microwave energy is transferred to the rectifier element to the maximum extent possible, rather than being lost through reflection. Nonlinear rectification: This is the core conversion step. Utilizing the unidirectional conductivity of the Schottky diode (due to its extremely fast switching speed and low turn-on voltage), the high-frequency AC signal is "clipping" or "detected," causing the current / voltage to flow primarily in one direction, thus generating a pulsating signal containing a DC component. Filtered output: A low-pass filter composed of capacitors, inductors, etc., filters out residual high-frequency AC components from the pulsating signal, outputting a smooth and stable DC voltage to power the downstream load.
[0088] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are configured to distinguish similar objects and are not necessarily configured to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0089] This application describes the invention from the perspectives of purpose, performance, progress, and novelty, and it meets the functional enhancement and use requirements emphasized by the Patent Law. The above description and drawings are merely preferred embodiments of this application and are not intended to limit this application. Therefore, all structures, devices, features, etc., that are similar to or identical to those of this application, i.e., all equivalent substitutions or modifications made in accordance with the scope of this patent application, shall fall within the scope of protection of this patent application.
Claims
1. A Schottky diode, characterized in that, include: A semiconductor structure layer, including a channel layer and a barrier layer stacked thereon, wherein the semiconductor structure layer is configured not to contain a two-dimensional electron gas in its natural state; A two-dimensional electron gas generating layer is stacked on the semiconductor structure layer and is used to generate two-dimensional electron gas in a selected area of the semiconductor structure layer. The selected area is located between the first electrode contact area and the second electrode contact area of the semiconductor structure layer. The first electrode structure forms an ohmic contact with the first electrode contact region of the semiconductor structure layer; The second electrode structure forms a Schottky contact with the second electrode contact region of the semiconductor structure layer, and the second electrode structure is electrically connected to the first electrode structure via the two-dimensional electron gas.
2. The Schottky diode according to claim 1, characterized in that: The barrier layer has an Al atom percentage content of 1% to 30% and a thickness of 1 nm to 30 nm. The barrier layer is configured such that the semiconductor structure layer does not contain a two-dimensional electron gas in its natural state.
3. The Schottky diode according to claim 1, characterized in that: The first electrode structure includes an anode metal, which is in contact with at least the barrier layer; And / or, the second electrode structure includes a cathode disposed on a barrier layer and undergoing an alloying reaction with the barrier layer and the channel layer.
4. The Schottky diode according to claim 3, characterized in that: The first electrode contact region of the semiconductor structure layer has a stepped structure, wherein the upper step surface and the lower step surface of the stepped structure are the surface of the barrier layer and the surface of the channel layer, respectively, and the anode metal continuously covers the upper step surface and the lower step surface of the stepped structure. Alternatively, the anode metal may be disposed on the barrier layer, and more than one cathode may be configured. Alternatively, the anode metal is disposed on the channel layer and in contact with the side of the barrier layer.
5. The Schottky diode according to claim 4, characterized in that: The first electrode structure is disposed on the barrier layer, and multiple second electrode structures are configured, with the first electrode structure disposed between the multiple second electrode structures. And / or, the first electrode structure includes an anode metal and a field plate terminal stacked sequentially.
6. The Schottky diode according to any one of claims 1-5, characterized in that: The two-dimensional electron gas generating layer continuously covers a selected area of the semiconductor structure layer and the second electrode structure; And / or, the two-dimensional electron gas generating layer and the second electrode structure are further covered with an insulating dielectric layer; And / or, the Schottky diode further includes a substrate, and the semiconductor structure layer is disposed on the substrate; And / or, the material of the semiconductor structure layer includes group III nitrides; And / or, the material of the two-dimensional electron gas generating layer includes a material that makes the surface potential lower than the energy level position of oxygen at the surface of the barrier layer.
7. The method for fabricating a Schottky diode according to any one of claims 1-6, characterized in that, include: A channel layer and a barrier layer are sequentially grown on a substrate to form a semiconductor structure layer; A two-dimensional electron gas generating layer is disposed on at least a selected region of the semiconductor structure layer to generate a two-dimensional electron gas in the selected region of the semiconductor structure layer. A first electrode structure and a second electrode structure are disposed on the semiconductor structure layer, such that the first electrode structure forms an ohmic contact with the first electrode contact area of the semiconductor structure layer, and the second electrode structure forms a Schottky contact with the second electrode contact area of the semiconductor structure layer, and the first electrode structure is electrically connected to the second electrode structure via the two-dimensional electron gas.
8. The preparation method according to claim 7, characterized in that, Specifically, it includes: The first electrode contact area of the semiconductor structure layer is etched to form a stepped structure, and the upper step surface and the lower step surface of the stepped structure are respectively the barrier layer surface and the channel layer surface. Then, a first electrode structure is set on the first electrode contact area, so that the anode metal therein continuously covers the upper step surface and the lower step surface of the stepped structure. In addition, the second electrode contact area of the semiconductor structure layer is etched to expose at least partially the channel layer therein, and then a second electrode structure is formed on the exposed channel layer and the second electrode structure is made to contact the side of the barrier layer. Alternatively, the second electrode contact area of the semiconductor structure layer can be set as a plurality, and each second electrode contact area can be etched to expose at least partially the channel layer therein, and then a second electrode structure can be set on the exposed channel layer and the second electrode structure can be made to contact the side of the barrier layer. The first electrode structure is disposed on the barrier layer and positioned between multiple second electrode structures. Alternatively, the first electrode contact area of the semiconductor structure layer can be etched to expose at least part of the channel layer therein, and then the first electrode structure can be disposed on the exposed channel layer and the first electrode structure can be made to contact the side of the barrier layer. Furthermore, the second electrode contact area of the semiconductor structure layer is etched to expose at least partially the channel layer therein, and a second electrode structure is then formed on the exposed channel layer, with the second electrode structure in contact with the side of the barrier layer.
9. The preparation method according to claim 7, characterized in that, Specifically, it includes: The two-dimensional electron gas generation layer is continuously covered in a selected area of the semiconductor structure layer and on the second electrode structure; Furthermore, an insulating dielectric layer is continuously covered on the two-dimensional electron gas generating layer.
10. The application of the Schottky diode according to any one of claims 1-6 in a limiting network, rectifier network, limiter, rectifier, radio frequency system or wireless power transmission system.