Gallium oxide schottky barrier diode with ferroelectric field plate structure

Abstract

The present invention relates to a Schottky barrier diode in which current characteristics and breakdown voltage are simultaneously improved by utilizing a ferroelectric field plate structure. The Schottky barrier diode incorporating the ferroelectric field plate structure of the present invention exhibits reduced on-resistance and a breakdown voltage that is more than 2.5 times higher compared to conventional structures, while maintaining stable characteristics under various anode sizes and temperature conditions. In particular, the Power Performance Index (BFOM) is improved by approximately 10 times, demonstrating high potential as a next-generation power semiconductor device. These characteristics make it suitable for applications requiring high efficiency and high voltage resistance, such as automobiles and industrial power conversion systems.

Description

Technology Field

[0001] The present invention relates to power semiconductor devices, and more specifically, to a gallium oxide-based Schottky barrier diode with improved current characteristics and breakdown voltage using a ferroelectric field plate structure. In particular, the present invention relates to a next-generation power semiconductor device structure capable of simultaneously improving current driving capability and breakdown voltage by utilizing polarization field alignment. Background Technology

[0003] Gallium oxide (Ga2O3), which is attracting attention as a next-generation power semiconductor material, is receiving much interest for high-voltage, high-efficiency power device applications due to its excellent characteristics, such as a wide bandgap (4.8-4.9 eV) and a high dielectric breakdown electric field (8 MV / cm).

[0004] In particular, gallium oxide-based Schottky barrier diodes (SBDs) are evaluated as devices capable of playing an important role in power conversion systems due to their fast switching characteristics and low forward voltage drop.

[0005] For gallium oxide Schottky barrier diodes to be commercialized as power semiconductor devices, high current characteristics and high breakdown voltage are required simultaneously.

[0006] High current driving capability is essential, especially in structures utilizing large-area anode electrodes. However, conventional Schottky barrier diodes exhibit a trade-off between current characteristics and breakdown voltage, which has limited the ability to simultaneously improve both characteristics.

[0007] To overcome these limitations, a field plate structure was introduced. This structure is a technology that improves breakdown voltage by extending a metal electrode from the Schottky electrode to the semiconductor surface to alleviate electric field concentration.

[0008] However, when the conventional field plate structure was applied to a gallium oxide Schottky barrier diode, there was a limitation in that while the breakdown voltage improved due to the electric field dispersion effect, the current value remained unchanged.

[0009] In other words, when a field plate structure was applied to obtain a high breakdown voltage, the current characteristics remained unchanged, making it difficult to achieve high current and high voltage simultaneously.

[0010] Therefore, there has been a demand for the development of a new gallium oxide Schottky barrier diode structure capable of simultaneously improving current characteristics while maintaining the effect of enhancing breakdown voltage. Prior art literature

[0011] Korean Published Patent No. 10-2023-0018646, "Nanoparticles for X-ray attenuation-based bioimaging comprising organic-inorganic composites, method for manufacturing the same, and composition using the same" Korean Registered Patent No. 2320367, "Method for manufacturing a Schottky barrier diode with improved breakdown voltage through field plate layer deposition" US Published Patent No. 2023-0420542, "Method for producing a transistor with a high degree of electron mobility, and produced transistor" Korean Published Patent No. 2023-066609, "Side-gate type transistors and side-Schottky diodes having integrated side-field plate structures" The problem to be solved

[0012] The present invention aims to simultaneously improve the current characteristics and breakdown voltage of a gallium oxide Schottky barrier diode.

[0013] The present invention aims to provide a Schottky barrier diode of a novel structure that improves current driving capability while maintaining the breakdown voltage enhancement effect provided by the field plate structure.

[0014] The present invention aims to improve current characteristics by controlling the distribution of charge carriers within a semiconductor layer using the polarization electric field of a ferroelectric material.

[0015] The present invention aims to reduce the on-resistance (Ron) of a Schottky barrier diode through a ferroelectric field plate structure.

[0016] The present invention aims to provide a Schottky barrier diode capable of maintaining excellent current characteristics and breakdown voltage even in a large-area anode electrode structure.

[0017] The present invention aims to optimize the properties of aluminum scandium nitride (AlScN), a ferroelectric material, by applying it to a field plate structure. means of solving the problem

[0019] A Schottky barrier diode according to one embodiment comprises a semiconductor substrate, a semiconductor epitaxial layer formed on the semiconductor substrate, an anode electrode formed on the upper surface of the semiconductor epitaxial layer, a cathode electrode formed on the lower surface of the semiconductor epitaxial layer, and a ferroelectric layer formed on the anode electrode and the semiconductor epitaxial layer, extending laterally from the anode electrode to disperse an electric field, wherein the polarized electric field of the ferroelectric layer induces additional charge carriers within the semiconductor epitaxial layer to improve current driving capability.

[0020] The polarization electric field of the above ferroelectric layer can increase the concentration of electrons in the semiconductor epitaxial layer, thereby improving the current density.

[0021] The on-resistance of the Schottky barrier diode can be reduced by the ferroelectric layer.

[0022] The breakdown voltage of the Schottky barrier diode can be improved by the ferroelectric layer.

[0023] The above ferroelectric layer can form an electric field through spontaneous polarization without the application of an external voltage.

[0024] The ferroelectric layer can extend laterally from the anode electrode to alleviate electric field concentration in the semiconductor epitaxial layer.

[0025] The semiconductor substrate and the semiconductor epitaxial layer may include gallium oxide (Ga2O3).

[0026] The ferroelectric layer may include aluminum scandium nitride (AlScN).

[0027] The above aluminum scandium nitride (AlScN) is Al x Sc (1-x) It has a composition of N (0 < x < 1), and the above (1-x) may be 0.20 to 0.45.

[0028] The above anode electrode has a circular pattern and can have a radius of 50 μm to 1000 μm.

[0029] The ferroelectric layer can be extended from the anode electrode by 10 μm to 50 μm.

[0030] It may further include a region extending 20 μm to 50 μm from the end of the ferroelectric layer.

[0031] The anode electrode and the ferroelectric layer may have a thickness ratio of 1:1.5 to 1:3. Effects of the invention

[0032] According to one embodiment, the current characteristics and breakdown voltage of a Ga2O3 Schottky barrier diode can be simultaneously improved by using a ferroelectric field plate structure.

[0033] According to one embodiment, the polarization electric field of AlScN, a ferroelectric material, can increase the charge carrier concentration within the Ga2O3 epitaxial layer, thereby improving current driving capability.

[0034] According to one embodiment, the breakdown voltage can be improved by the electric field dispersion effect provided by the field plate structure, while the on-resistance (Ron) can be reduced by the polarization effect of the ferroelectric material.

[0035] According to one embodiment, a diode suitable for high-power applications can be realized by securing stable electrical characteristics even in a large-area anode electrode structure.

[0036] According to one embodiment, an additional electric field effect can be obtained through the spontaneous polarization of the ferroelectric material without the application of an external voltage, thereby enabling the realization of an energy-efficient device.

[0037] According to one embodiment, consistent performance improvement can be obtained even with anode electrodes of a circular pattern having various sizes ranging from a radius of 50 μm to 1000 μm.

[0038] According to one embodiment, improved characteristics of current characteristics and breakdown voltage can be maintained even in a high-temperature environment (300K to 550K), thereby providing a device suitable for power electronic applications requiring high-temperature operation. Brief explanation of the drawing

[0040] FIG. 1 illustrates a cross-sectional structure of a Schottky barrier diode using a ferroelectric field plate structure according to one embodiment of the present invention. FIG. 2 is a top view of a Schottky barrier diode using a ferroelectric field plate structure according to one embodiment of the present invention. Figure 3 shows the polarization-electric field measurement results of a metal-AlScN-metal structure for confirming ferroelectric properties according to one embodiment of the present invention. Figure 4 illustrates the simulation results of a Schottky barrier diode using a ferroelectric field plate structure according to one embodiment of the present invention. Figure 5 is a graph showing a comparison of characteristics with and without a ferroelectric field plate structure according to one embodiment of the present invention. Figure 6 is a graph showing a comparison of current-voltage characteristics according to the field plate length according to one embodiment of the present invention. FIG. 7 is a graph showing a comparison of high-temperature characteristics with and without a ferroelectric field plate structure according to one embodiment of the present invention. FIG. 8 is a graph showing a comparison of characteristics according to the radius size of a Schottky barrier diode to which a ferroelectric field plate structure according to one embodiment of the present invention is applied. FIG. 9 is a graph showing the change in on-resistance according to the anode radius and temperature of a Schottky barrier diode with a ferroelectric field plate structure applied according to one embodiment of the present invention. FIG. 10 is a graph showing the yield characteristics according to a ferroelectric field plate structure according to one embodiment of the present invention. FIG. 11 is a graph comparing the on-resistance characteristics of a Schottky barrier diode with a ferroelectric field plate structure according to one embodiment of the present invention and previously reported gallium oxide Schottky barrier diodes. Specific details for implementing the invention

[0041] Embodiments of the present invention will be described in detail below with reference to the attached drawings and the contents described therein, but the present invention is not limited or restricted by the embodiments.

[0042] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, “comprises” and / or “comprising” do not exclude the presence or addition of one or more other components or steps mentioned in the description.

[0043] As used herein, terms such as “examples,” “examples,” “aspects,” “examples,” etc., are not to be interpreted as implying that any described aspect or design is superior or advantageous to other aspects or designs.

[0044] Furthermore, the term 'or' refers to an inclusive or rather an exclusive or. That is, unless otherwise noted or is clear from the context, the expression 'x uses a or b' refers to any one of the natural inclusive permutations.

[0045] Additionally, singular expressions (“a” or “an”) used in this specification and claims should generally be interpreted to mean “one or more” unless otherwise stated or it is clear from the context that they relate to the singular form.

[0046] The terms used in the following description have been selected as common and universal in the relevant technical field, but other terms may exist depending on technological development and / or changes, conventions, preferences of the skilled technician, etc. Therefore, the terms used in the following description should not be understood as limiting the technical concept, but as illustrative terms to explain the embodiments.

[0047] In addition, in specific cases, there are terms arbitrarily selected by the applicant, and in such cases, their detailed meanings will be described in the relevant explanatory section. Therefore, the terms used in the description below must be understood not merely as their names, but based on their meanings and the content throughout the specification.

[0048] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning that is commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0049] Meanwhile, in describing the present invention, if it is determined that a detailed description of related known functions or configurations could unnecessarily obscure the essence of the invention, such detailed description will be omitted. Furthermore, the terminology used in this specification is used to appropriately express embodiments of the present invention, and such terminology may vary depending on the intent of the user or operator, or the conventions of the field to which the invention belongs. Accordingly, the definitions of these terms should be based on the content throughout this specification.

[0051] FIG. 1 illustrates a cross-sectional structure of a Schottky barrier diode using a ferroelectric field plate structure according to one embodiment of the present invention.

[0052] Referring to FIG. 1, a Schottky barrier diode using a ferroelectric field plate structure according to one embodiment of the present invention is illustrated.

[0053] The Schottky barrier diode (100) according to the present embodiment includes a cathode electrode (140), a semiconductor substrate (110), a semiconductor epitaxial layer (120), an anode electrode (130), and a ferroelectric layer (150).

[0054] A semiconductor epitaxial layer (120) can be formed on a semiconductor substrate (110).

[0055] The semiconductor substrate (110) and the semiconductor epitaxial layer (120) may preferably include gallium oxide (Ga2O3), but are not limited thereto and may use various wide bandgap semiconductor materials according to embodiments of the present invention.

[0056] For example, the semiconductor substrate (110) and the semiconductor epitaxial layer (120) may include at least one of silicon carbide (SiC, particularly 4H-SiC or 6H-SiC polytype), gallium nitride (GaN), aluminum nitride (AlN), aluminum gallium nitride (AlGaN), diamond (C), zinc oxide (ZnO), aluminum oxide (Al2O3), hafnium oxide (HfO2), indium oxide (In2O3), aluminum gallium oxide (AlGaO), and indium gallium oxide (InGaO).

[0057] The above wide bandgap semiconductor materials each possess unique bandgap energy, electron mobility, thermal conductivity, and dielectric breakdown electric field characteristics, allowing them to be selectively utilized for specific applications. In particular, the above wide bandgap semiconductor materials have characteristics suitable for use as substrates and epitaxial layers of power semiconductor devices operating in high-voltage and high-temperature environments.

[0058] According to the embodiment, the thickness of the semiconductor epitaxial layer (120) is approximately 8.7 μm, and the doping concentration is 2 × 10⁻⁶ 16 cm -3 It may be to some extent. In addition, depending on the embodiment, the semiconductor epitaxial layer (120) may have a crystal structure of the beta phase (β-phase).

[0059] An anode electrode (130) may be formed on the upper surface of the semiconductor epitaxial layer (120). The anode electrode (130) may be deposited with a thickness of 100 nm to 150 nm using an E-gun. The anode electrode (130) may be formed in a circular pattern shape, and its radius (RA) may be designed to vary within the range of 50 μm to 1000 μm.

[0060] A cathode electrode (140) can be formed on the lower surface of the semiconductor epitaxial layer (120). The cathode electrode (140) can also be deposited with a thickness of 100 nm to 150 nm using an electron gun evaporator (E-gun evaporator).

[0061] A ferroelectric layer (150) may be formed on the anode electrode (130) and the semiconductor epitaxial layer (120). In one embodiment, the ferroelectric layer (150) may include aluminum scandium nitride (AlScN) and may be deposited with a thickness of 40 nm to 400 nm using a sputtering technique.

[0062] The ferroelectric layer (150) is Al x Sc (1-x) N (0 <x<1)의 조성을 갖는 AlScN을 포함하고, 여기서 (1-x)는 0.20 내지 0.45일 수 있다.

[0063] The ferroelectric layer (150) can extend laterally from the anode electrode (130) to form a structure that disperses the electric field. The length (LFP) of this extended structure can be designed within the range of 10 μm to 50 μm. Additionally, the length (LFE) from the end of the extended structure to the end of the ferroelectric layer (150) can be designed within the range of 20 μm to 50 μm.

[0064] The ferroelectric layer (150) and the anode electrode (130) may have a thickness ratio of 1:1.5 to 1:3. Etching for forming the ferroelectric layer (150) may be performed using an inductive etching technique (ICP).

[0065] According to an embodiment of the present invention, the polarization electric field of the ferroelectric layer (150) can induce additional charge carriers within the semiconductor epitaxial layer (120) to improve current driving capability. This polarization electric field can be formed spontaneously without the application of an external voltage.

[0066] In addition, a structure in which the ferroelectric layer (150) extends laterally from the anode electrode (130) can improve the breakdown voltage by mitigating electric field concentration around the electrode. Through this, the breakdown voltage can be improved by the electric field dispersion effect, while the on-resistance (Ron) can be reduced due to the polarization effect of the ferroelectric material.

[0067] The structure according to the embodiment of the present invention can maintain excellent current characteristics and breakdown voltage even when a large-area anode electrode is applied, thereby enabling the realization of a Schottky barrier diode suitable for high-power applications.

[0069] FIG. 2 is a top view of a Schottky barrier diode using a ferroelectric field plate structure according to one embodiment of the present invention.

[0070] Referring to FIG. 2, a top view of a Schottky barrier diode using a ferroelectric field plate structure according to one embodiment of the present invention is shown.

[0071] In an embodiment of the present invention, the ferroelectric layer (150) may cover an anode electrode (130) formed in a circular pattern and extend around it to form a field plate structure. The anode electrode (130) has a boundary indicated by a dotted line, and its radius (RA) may be designed to be within the range of 50 μm to 1000 μm.

[0072] The length (LFP) of the field plate portion extending outward from the boundary of the anode electrode (130) can be designed within the range of 10 μm to 50 μm. Additionally, the length (LFE) from the end of the field plate to the end of the ferroelectric layer (150) can be designed within the range of 20 μm to 50 μm.

[0073] A Schottky barrier diode according to one embodiment of the present invention can effectively disperse electric field concentration occurring at the edge of the anode electrode (130) through a field plate structure formed by a ferroelectric layer (150) extending laterally from the anode electrode (130). When the electric field strength decreases in the region where the electric field is concentrated, the breakdown voltage is improved, which can be an important characteristic of a power semiconductor device.

[0074] In addition, a Schottky barrier diode according to one embodiment of the present invention may have a polarization electric field effect due to the ferroelectric properties of the ferroelectric layer (150).

[0075] For example, a ferroelectric material such as aluminum scandium nitride (AlScN) can maintain spontaneous polarization even in the absence of an external voltage. This spontaneous polarization induces a charge at the interface between the ferroelectric layer (150) and the semiconductor epitaxial layer, thereby generating additional charge carriers (electrons) within the semiconductor epitaxial layer.

[0076] The aforementioned additional charge carriers can expand the current path and increase the carrier concentration, thereby improving current density; consequently, the diode's on-resistance (Ron) decreases and current driving capability is improved.

[0077] In particular, in a structure having a large-area anode electrode (130) with a circular pattern, this effect occurs along the entire periphery, so current characteristics can be improved more effectively as the device size increases.

[0078] The circular ferroelectric field plate shown in Fig. 2 utilizes two mechanisms simultaneously—the electric field dispersion effect and the polarization electric field effect—thereby providing the advantage of simultaneously improving current characteristics while maintaining the breakdown voltage enhancement effect of the existing field plate structure.

[0079] This can be considered an innovative approach to overcoming significant trade-off relationships in power device design.

[0081] Figure 3 shows the polarization-electric field measurement results of a metal-AlScN-metal structure for confirming ferroelectric properties according to one embodiment of the present invention.

[0082] Referring to FIG. 3, the polarization-electric field (PE) characteristic curve of the aluminum scandium nitride (AlScN) ferroelectric material used in the present invention is shown. The measurements shown in FIG. 3 were performed using a sample with a metal-AlScN-metal structure to confirm the characteristics of AlScN as a ferroelectric.

[0083] The horizontal axis of the graph represents the applied electric field strength, with units of MV / cm (megavolt / centimeter). The vertical axis represents polarization, with units of μC / cm² (microcoulomb / square centimeter). "PUND" displayed at the top of the graph stands for Positive Up Negative Down and may refer to a standard measurement method for measuring ferroelectric properties.

[0084] As shown in Fig. 3, the polarization-electric field curve illustrates the hysteresis characteristics of a typical ferroelectric material. Multiple superimposed curves represent measurement results under various conditions.

[0085] According to an embodiment of the present invention, a residual polarization value of approximately ±80 μC / cm² can be exhibited when the electric field is zero. According to an embodiment of the present invention, the coercive electric field strength at which the direction of polarization changes can have a value between approximately -2 MV / cm and -3 MV / cm, and between 2 MV / cm and 3 MV / cm.

[0086] In addition, according to an embodiment of the present invention, the saturation polarization value at a high electric field can exhibit a value of approximately ±110 μC / cm².

[0087] The characteristics shown in Fig. 3 confirm that AlScN actually possesses ferroelectric properties. In particular, the presence of residual polarization may mean that the ferroelectric layer can provide a continuous electric field effect to the semiconductor epitaxial layer even without an external voltage.

[0088] The AlScN ferroelectric layer applied to the Schottky barrier diode of the present invention can induce additional charge carriers within the semiconductor epitaxial layer through these polarization characteristics. This can serve as a key mechanism for improving the current characteristics of the diode.

[0089] Specifically, the electric field formed by the polarization of the ferroelectric layer increases the concentration of electrons within the semiconductor, thereby increasing the current density and consequently reducing the on-resistance (Ron), which can improve the performance of the diode.

[0090] In addition, these characteristics confirm that AlScN actually possesses ferroelectric properties. Of particular importance is the presence of remanent polarization, which means that the ferroelectric layer can provide a continuous electric field effect to the semiconductor epitaxial layer even without an external voltage.

[0091] The AlScN ferroelectric layer applied to the Schottky barrier diode of the present invention induces additional charge carriers within the semiconductor epitaxial layer through these polarization characteristics. This acts as a key mechanism for improving the current characteristics of the diode.

[0092] Specifically, the electric field formed by the polarization of the ferroelectric layer increases the concentration of electrons within the semiconductor, thereby increasing the current density and consequently reducing the on-resistance (Ron), which can improve the performance of the diode.

[0094] Figure 4 illustrates the simulation results of a Schottky barrier diode using a ferroelectric field plate structure according to one embodiment of the present invention.

[0095] More specifically, FIG. 4 shows the results of a Physics-based TCAD (Technology Computer Aided Design) simulation of a Schottky barrier diode using a ferroelectric field plate structure according to one embodiment of the present invention.

[0096] Figure 4(a) shows the current density distribution inside a Schottky barrier diode.

[0097] Referring to Figure 4(a), in the simulation results, the x-axis and y-axis represent the position coordinates within the device, and the color represents the current density, with the unit being A / cm². An anode electrode is located at the top, and a field plate (FP) structure extends to the right of it, with a β-Ga₂O₃ layer formed below it.

[0098] The current density shows the highest value (1.35 × 10³ A / cm²) around the anode electrode and can be seen to decrease as it moves toward the field plate region.

[0099] In addition, according to an embodiment of the present invention, carrier depletion can be extended in the region below the field plate due to the polarization of the ferroelectric AlScN. On the other hand, a phenomenon can be observed in which the carrier concentration around the anode electrode is relatively higher. This mechanism can be manifested as a high current density around the anode electrode in FIG. 4 (a).

[0100] Figure 4(b) shows the change in current density according to position at various depths (0.3μm, 1μm, 3μm).

[0101] Referring to Figure 4(b), the solid line shows a Schottky barrier diode (FP SBD) with a ferroelectric field plate structure, and the dotted line shows a standard Schottky barrier diode (Ref SBD).

[0102] As shown in Figure 4(b), the current density of the diode with the ferroelectric field plate structure applied at all depths is higher than that of a general diode.

[0103] In particular, the current density increases sharply at the edge of the anode electrode (at a position of about 200 μm), and at a depth of 0.3 μm close to the surface, it shows a current density of up to 1300 A / cm² or more, which can be significantly higher than that of a general structure.

[0104] Figures 4(c) and 4(d) respectively compare the electron density distribution of a diode with a ferroelectric field plate structure and a general diode.

[0105] Referring to Figures 4 (c) and (d), it can be seen that in a diode with a ferroelectric field plate structure, a characteristic charge distribution appears in the region below the field plate (FP) due to the polarization effect. The part marked with a "+-+-+-" pattern on the surface of the field plate represents the polarization charge of the ferroelectric material, which can increase the electron density around the anode electrode.

[0106] According to an embodiment of the present invention, these simulation results clearly demonstrate the mechanism by which a ferroelectric field plate structure improves current characteristics. Charge redistribution due to ferroelectric polarization increases the electron density around the anode electrode, which can lead to an improvement in the current driving capability of the diode.

[0107] In addition, the present invention can overcome the limitations of conventional Schottky barrier diodes through the dual effect of the field plate structure dispersing the electric field to improve breakdown voltage, and the ferroelectric polarization improving current characteristics.

[0109] Figure 5 shows a graph illustrating a comparison of characteristics with and without a ferroelectric field plate structure according to one embodiment of the present invention.

[0110] Referring to FIG. 5, the results of comparing the electrical characteristics of a Schottky barrier diode (FP SBD) with a ferroelectric field plate structure according to one embodiment of the present invention and a general Schottky barrier diode (Ref SBD) are shown.

[0111] Figure 5(a) shows the current density characteristics according to the forward voltage. The horizontal axis represents the forward voltage (V), and the vertical axis represents the current density (A / cm²).

[0112] In the graph shown in Fig. 5(a), the solid line represents a Schottky barrier diode (FP SBD) with a ferroelectric field plate structure, and the dotted line represents a standard Schottky barrier diode (Ref SBD). The lines of different colors represent the characteristics of devices with various anode radii ranging from 50 μm to 200 μm.

[0113] According to an embodiment of the present invention, it can be confirmed that the current density of a Schottky barrier diode with a ferroelectric field plate structure applied at all anode radius sizes is higher than that of a general Schottky barrier diode.

[0114] In particular, at a forward voltage of 3V, a Schottky barrier diode with a ferroelectric field plate structure exhibits a current density of approximately 650 A / cm² when the anode radius is smallest (blue line), showing current characteristics that are about 18% better than a standard diode of the same size (approx. 550 A / cm²).

[0115] In addition, as shown in Figure 5 (a), the current density decreases as the anode radius increases, but the diode with a ferroelectric field plate structure can maintain superior current characteristics compared to a general diode at all sizes.

[0116] Figure 5(b) shows the change in on-resistance (Ron) and ideality factor according to the anode radius. The horizontal axis represents the anode radius (μm), the left vertical axis represents the on-resistance (mΩ·cm²), and the right vertical axis represents the ideality factor (η). The on-resistance is displayed as a colored bar graph, and the ideality factor is displayed as a line graph.

[0117] According to an embodiment of the present invention, it can be confirmed that the on-resistance (Ron) of a Schottky barrier diode with a ferroelectric field plate structure applied at all anode radius sizes is lower than that of a general Schottky barrier diode.

[0118] For example, when the anode radius is 50 μm, the on-resistance of the diode with a ferroelectric field plate structure is about 3.1 mΩ·cm², which is about 16% lower than the about 3.7 mΩ·cm² of a general diode.

[0119] In addition, as shown in Figure 5 (b), the on-resistance increases as the anode radius increases, but a diode with a ferroelectric field plate structure applied at all sizes can maintain a lower on-resistance than a general diode.

[0120] Meanwhile, the ideality factor (η) shows a similar value of about 1.0 at all anode radii, regardless of whether a ferroelectric field plate structure is applied. This may mean that the ferroelectric field plate structure improves current characteristics without affecting the basic operating mechanism of the diode.

[0121] According to an embodiment of the present invention, the graphs shown in FIG. 5 (a) and (b) experimentally demonstrate that a ferroelectric field plate structure can effectively improve the current characteristics of a Schottky barrier diode. This can be achieved through a mechanism in which the polarization electric field of the ferroelectric material AlScN induces additional charge carriers within the semiconductor epitaxial layer, thereby increasing current density and decreasing on-resistance.

[0123] Figure 6 is a graph showing a comparison of current-voltage characteristics according to the field plate length according to one embodiment of the present invention.

[0124] Referring to FIG. 6, current-voltage characteristics according to field plate length (LFP) are shown in a Schottky barrier diode to which a ferroelectric field plate structure according to one embodiment of the present invention is applied.

[0125] More specifically, Figures 6 (a), (b), and (c) show the current density characteristics according to the forward voltage when the field plate length (LFP) is 10 μm, 20 μm, and 50 μm, respectively.

[0126] In each graph of Figures 6 (a), (b), and (c), the horizontal axis represents the forward voltage (V), and the vertical axis represents the current density (A / cm²). The lines of different colors represent the characteristics of devices with different anode radii (50 μm, 100 μm, 150 μm, 200 μm).

[0127] Referring to FIG. 6 (a), (b) and (c), it can be seen that, according to an embodiment of the present invention, similar current-voltage characteristic trends are observed at three different field plate lengths (10 μm, 20 μm, 50 μm).

[0128] As shown in Figures 6 (a), (b), and (c), it can be seen that there is not a significant difference in current density even when the field plate length changes. For example, in the case of a device with an anode radius of 50 μm at a forward voltage of 3 V, it can be confirmed that there is no significant difference, as the current density is approximately 550 A / cm² when the field plate length is 10 μm, approximately 540 A / cm² when it is 20 μm, and approximately 530 A / cm² when it is 50 μm.

[0129] In addition, as shown in Figures 6 (a), (b), and (c), the current density tends to be higher as the anode radius decreases under all field plate length conditions. This may be because as the anode radius decreases, the current flow is concentrated in a narrow area, increasing the current per unit area.

[0130] The highest current density is observed when the anode radius is 50 μm, and the current density tends to gradually decrease as the radius increases.

[0131] According to an embodiment of the present invention, the fact that the field plate length does not have a significant effect on current characteristics may suggest that the current enhancement effect in a ferroelectric field plate structure is mainly determined by the polarization characteristics of the ferroelectric material, and that the length of the field plate does not significantly affect this effect.

[0132] This can provide the flexibility to optimize the field plate length for improved breakdown voltage during device design.

[0133] It can be observed that while the field plate length does not significantly affect the current characteristics, the change in current density according to the anode radius is distinct. This implies that the device's current driving capability is primarily determined by the size of the anode electrode.

[0134] Therefore, when applying a ferroelectric field plate structure according to an embodiment of the present invention, it may be more important to design the anode size to meet current requirements rather than the field plate length.

[0135] The results of FIG. 6 (a), (b), and (c) can provide important guidelines for the design of a Schottky barrier diode with a ferroelectric field plate structure according to an embodiment of the present invention. An optimized device design considering both current characteristics and breakdown voltage is possible, thereby maximizing performance as a power semiconductor device.

[0137] FIG. 7 is a graph showing a comparison of high-temperature characteristics with and without a ferroelectric field plate structure according to one embodiment of the present invention.

[0138] More specifically, referring to FIG. 7, the change in electrical characteristics according to temperature of a Schottky barrier diode (FP SBD) with a ferroelectric field plate structure according to one embodiment of the present invention and a general Schottky barrier diode (Ref SBD) is illustrated.

[0139] Figure 7(a) shows the change in current density with temperature. The horizontal axis represents temperature (K), and the vertical axis represents current density (A / cm²). In the graph, the solid line represents a Schottky barrier diode with a ferroelectric field plate structure (FP SBD), and the dotted line represents a standard Schottky barrier diode (Ref SBD). The lines of different colors represent the characteristics of devices with various anode radii ranging from 50 μm to 200 μm.

[0140] According to the embodiment of the present invention in FIG. 7(a), measurements were taken at a forward voltage of 3 V (@3 V) and in a temperature range from 300 K (approx. 27°C) to 550 K (approx. 277°C). As the temperature increases, the current density of all devices tends to decrease. This is a phenomenon generally observed in semiconductor devices, and the decrease in carrier mobility with increasing temperature may be the main cause.

[0141] As shown in Figure 7(a), it can be seen that the current density of the Schottky barrier diode with a ferroelectric field plate structure is maintained higher than that of a standard Schottky barrier diode across all temperature ranges.

[0142] In particular, for a device with an anode radius of 50 μm (blue line), the diode with a ferroelectric field plate structure at 300 K exhibits a current density of approximately 650 A / cm², which is about 8% higher than that of a standard Schottky barrier diode (approx. 600 A / cm²).

[0143] This current density enhancement effect is maintained even at a high temperature of 550K, so the diode with the ferroelectric field plate structure exhibits a current density of about 320 A / cm², while the general diode exhibits about 280 A / cm².

[0144] Figure 7(b) illustrates the change in on-voltage (Von) and ideality factor according to temperature change. The horizontal axis represents temperature (K), the left vertical axis represents on-voltage (V), and the right vertical axis represents the ideality factor (η). The graph shown in Figure 7(b) illustrates the results for a device with an anode radius of 50 μm.

[0145] As shown in Fig. 7(b), according to an embodiment of the present invention, the on voltage (Von) tends to decrease as the temperature increases.

[0146] In addition, as shown in Fig. 7(b), the on-voltage of the Schottky barrier diode with a ferroelectric field plate structure is lower than that of a standard Schottky barrier diode across all temperature ranges.

[0147] For example, at 300K, the on-voltage of a diode with a ferroelectric field plate structure according to an embodiment of the present invention is about 0.95V, which is about 0.1V lower than that of a general Schottky barrier diode, about 1.05V. This reduction in on-voltage means that current flow is improved, which can lead to a reduction in power loss.

[0148] As shown in Fig. 7(b), the ideality factor (η) maintains a relatively stable value with respect to temperature changes and shows a value close to 1.0 regardless of whether a ferroelectric field plate structure is applied. This may mean that the basic operating mechanism of the diode is maintained even when the temperature changes.

[0149] According to an embodiment of the present invention, the results of FIG. 7 (a) and (b) show that a Schottky barrier diode with a ferroelectric field plate structure can stably maintain improved current characteristics even in a high-temperature environment.

[0150] This characteristic is suitable for applications requiring high-temperature operation, such as automobiles, aerospace, and industrial power conversion systems. By maintaining the polarization effect of the ferroelectric layer even at high temperatures and effectively inducing charge carriers, performance degradation in high-temperature environments can be minimized.

[0152] FIG. 8 is a graph showing a comparison of characteristics according to the radius size of a Schottky barrier diode to which a ferroelectric field plate structure according to one embodiment of the present invention is applied.

[0153] Referring to FIG. 8, changes in electrical characteristics according to the size of the anode radius are illustrated in a Schottky barrier diode (FP SBD) to which a ferroelectric field plate structure according to one embodiment of the present invention is applied.

[0154] Figure 8(a) shows the current density characteristics as a function of forward voltage for devices with various anode radii. The horizontal axis represents the forward voltage (V), and the vertical axis represents the current density (A / cm²). As shown in Figure 8(a), the anode radii were fabricated over a wide range from 50 μm to 1000 μm.

[0155] As shown in Fig. 8(a), according to an embodiment of the present invention, the current density tends to decrease as the anode radius increases.

[0156] The device with the smallest radius of 50 μm (top line) exhibits a current density of approximately 650 A / cm² at a forward voltage of 3 V, whereas the device with the largest radius of 1000 μm (bottom line) exhibits a current density of approximately 50 A / cm² at the same voltage. It can be observed that as the anode radius increases, the current is distributed over a wider area, resulting in a decrease in current density per unit area.

[0157] Figure 8(b) shows the change in on-resistance (Ron) and ideality factor according to the anode radius. The horizontal axis represents the anode radius (μm), the left vertical axis represents the on-resistance (mΩ·cm²), and the right vertical axis represents the ideality factor (η).

[0158] As shown in FIG. 8(b), according to an embodiment of the present invention, the on-resistance (Ron) tends to increase as the anode radius increases. A device with an anode radius of 50 μm exhibits a low on-resistance of about 3 mΩ·cm², but a large-area device of 1000 μm increases to about 30 mΩ·cm².

[0159] The increase in on-resistance shown in Fig. 8(b) may be due to the current path becoming longer and resistance increasing as the radius increases.

[0160] In addition, as shown in Figure 8 (b), the on-resistance increases in proportion to the anode radius, but it can be seen that it shows a gradual increasing trend up to a range of about 300-400 μm, and then increases at a faster rate at larger sizes. This suggests that the effect of the ferroelectric field plate structure works efficiently from small to medium-sized anodes, but the effect may be relatively reduced at very large sizes.

[0161] In addition, as shown in Fig. 8(b), it can be confirmed that the ideality factor (η) maintains a stable value close to about 1.0 regardless of the anode radius, which means that the Schottky barrier diode with the ferroelectric field plate structure according to the embodiment of the present invention maintains operating characteristics close to an ideal diode even in various sizes.

[0162] According to an embodiment of the present invention, FIGS. 8(a) and (b) show that a Schottky barrier diode with a ferroelectric field plate structure can be implemented over a wide range of device sizes. This provides flexibility to design devices for applications with various current requirements. In particular, by considering the relationship between on-resistance and current density, an anode size optimized for a specific application can be selected.

[0163] Small devices (in the range of 50–200 μm) may be suitable for applications requiring high-speed switching due to their low on-resistance and high current density, while large devices (in the range of 500–1000 μm) may be suitable for high-power applications where the total current is important.

[0164] The scalability of the Schottky barrier diode according to an embodiment of the present invention demonstrates the possibility of being applied to various power electronic systems.

[0166] FIG. 9 is a graph showing the change in on-resistance according to the anode radius and temperature of a Schottky barrier diode with a ferroelectric field plate structure applied according to one embodiment of the present invention.

[0167] More specifically, FIG. 9 illustrates the change in on-resistance (Ron) according to temperature and the anode radius of a Schottky barrier diode (FP SBD) to which a ferroelectric field plate structure according to one embodiment of the present invention is applied.

[0168] Referring to Fig. 9, the horizontal axis of the graph represents the anode radius (μm) on a logarithmic scale, showing a range from 50 μm to 1000 μm. The vertical axis represents the on-resistance (Ron) on a logarithmic scale, with units of mΩ·cm². The dots of various colors represent results measured at different temperatures (300K, 350K, 400K, 450K, 500K, 550K).

[0169] As shown in FIG. 9, according to an embodiment of the present invention, as the anode radius increases under all temperature conditions, the on-resistance tends to increase.

[0170] For example, looking at the results measured at 300K (about 27°C) (blue dot), the on-resistance is about 2.5 mΩ·cm² when the anode radius is 50 μm, whereas when it increases to 1000 μm, the on-resistance increases to about 20 mΩ·cm².

[0171] In addition, as shown in Fig. 9, it can be observed that the on-resistance also tends to increase with increasing temperature at the same anode radius. For example, for a device with an anode radius of 100 μm, the on-resistance at 300 K is approximately 3.5 mΩ·cm², but increases to approximately 8 mΩ·cm² at 550 K (approx. 277°C). This increase in on-resistance with temperature is a phenomenon generally observed in semiconductor devices, and the decrease in carrier mobility with increasing temperature may be the main cause.

[0172] As shown in Fig. 9, when the anode radius changes from 50 μm to 1000 μm across all temperature ranges, the on-resistance increases at a ratio of approximately 1:10, which means that when the device size is expanded 20 times, the on-resistance increases by about 10 times, suggesting that the ferroelectric field plate structure operates effectively even in large-area devices.

[0173] In addition, when the temperature increases from 300K to 550K, the rate of increase in on-resistance is approximately twofold, showing relatively stable characteristics with respect to temperature changes. This may mean that a Schottky barrier diode with a ferroelectric field plate structure can maintain stable operating characteristics even in high-temperature environments.

[0174] The results illustrated in Fig. 9 show the possibility that a Schottky barrier diode with a ferroelectric field plate structure of the present invention can be applied under various sizes and temperature conditions.

[0175] In particular, small devices may be suitable for applications requiring high-efficiency power conversion due to their low on-resistance, while large devices may be suitable for high-power applications due to their increased total current capacity, even if the on-resistance increases slightly.

[0176] Furthermore, the fact that it exhibits stable operating characteristics even at high temperatures suggests the possibility of application in high operating temperature environments, such as automobiles, aerospace, and industrial power conversion systems. A Schottky barrier diode with a ferroelectric field plate structure according to one embodiment of the present invention can provide excellent performance under various conditions, which can make a significant contribution to the practical application of gallium oxide-based power semiconductor devices.

[0178] FIG. 10 is a graph showing the yield characteristics according to a ferroelectric field plate structure according to one embodiment of the present invention.

[0179] Referring to FIG. 10, the results of comparing the breakdown characteristics of a Schottky barrier diode (FP SBD) with a ferroelectric field plate structure according to one embodiment of the present invention and a general Schottky barrier diode (Ref SBD) are shown.

[0180] Figure 10 (a) shows the current density characteristics according to reverse voltage. The horizontal axis represents the reverse voltage (V), and the vertical axis represents the current density (A / cm²) on a logarithmic scale.

[0181] The curves in the left group of Fig. 10 (a) represent Schottky barrier diodes with a ferroelectric field plate structure (FP SBD), and the curves in the right group represent general Schottky barrier diodes (Ref SBD). The lines of different colors represent the characteristics of devices with various anode radii ranging from 50 μm to 200 μm.

[0182] Referring to FIG. 10(a), it can be seen that a Schottky barrier diode with a ferroelectric field plate structure according to an embodiment of the present invention breaks down at a reverse voltage between approximately -500V and -600V, whereas a general Schottky barrier diode breaks down at approximately -200V. This demonstrates that the ferroelectric field plate structure improves the breakdown voltage by more than 2.5 times through the electric field dispersion effect.

[0183] Figure 10(b) shows the relationship between breakdown voltage and on-resistance (Ron). The horizontal axis represents breakdown voltage (V), and the vertical axis represents on-resistance (mΩ·cm²). The blue squares represent Schottky barrier diodes with a ferroelectric field plate structure, and the green squares represent standard Schottky barrier diodes. The arrows indicate the direction in which the anode radius increases (from 50 μm to 200 μm).

[0184] Referring to FIG. 10(b), a Schottky barrier diode with a ferroelectric field plate structure according to an embodiment of the present invention exhibits a higher breakdown voltage and a lower on-resistance value than a general Schottky barrier diode of the same size.

[0185] For example, as shown in Fig. 10(b), when the anode radius is 50 μm, the diode with a ferroelectric field plate structure exhibits a breakdown voltage of about 600 V and an on-resistance of 3 mΩ·cm², whereas a standard Schottky barrier diode exhibits a breakdown voltage of about 100 V and an on-resistance of 3.5 mΩ·cm².

[0186] Figure 10 (c) shows Baliga's Figure of Merit (BFOM) as a function of anode radius. The horizontal axis represents the anode radius (μm), and the vertical axis represents the BFOM (MW / cm²) on a logarithmic scale. A blue asterisk indicates a Schottky barrier diode with an AlScN ferroelectric field plate structure, and a green asterisk indicates a standard Schottky barrier diode.

[0187] Referring to Fig. 10(c), according to an embodiment of the present invention, the BFOM of a Schottky barrier diode with a ferroelectric field plate structure applied at all anode radii is about 10 times higher than that of a general diode.

[0188] For example, as shown in Fig. 10(c), when the anode radius is 50 μm, the BFOM of the diode with a ferroelectric field plate structure is about 120 MW / cm², whereas that of a general diode is about 12 MW / cm². The BFOM is calculated as VB² / Ron (the square of the breakdown voltage divided by the on-resistance) and is an indicator that comprehensively evaluates the performance of a power device.

[0189] According to an embodiment of the present invention, the results of FIG. 10 (a) to (c) show that a ferroelectric field plate structure can improve overall power performance by significantly improving the breakdown voltage of a Schottky barrier diode while reducing the on-resistance.

[0190] This can be seen as the result of the electric field dispersion effect of the field plate and the polarization effect of the ferroelectric material acting simultaneously.

[0191] In particular, the significant improvement in BFOM implies that the Schottky barrier diode of the present invention can provide high efficiency and reliability in power conversion systems. Although a trade-off generally exists between breakdown voltage and on-resistance in power devices, this demonstrates that these limitations can be overcome through a ferroelectric field plate structure.

[0193] FIG. 11 is a graph comparing the on-resistance characteristics of a Schottky barrier diode with a ferroelectric field plate structure according to one embodiment of the present invention and previously reported gallium oxide Schottky barrier diodes.

[0194] Referring to FIG. 11, the results of comparing the on-resistance characteristics of a Schottky barrier diode (This work) with a ferroelectric field plate structure according to one embodiment of the present invention and various gallium oxide Schottky barrier diodes reported in the literature are shown.

[0195] The horizontal axis of the graph represents the anode radius (μm) on a logarithmic scale, and the vertical axis represents the on-resistance (Ron, mΩ·cm²) on a logarithmic scale. Red asterisks represent Schottky barrier diodes with the ferroelectric field plate structure of the present invention, and blue circles represent conventional gallium oxide Schottky barrier diodes reported by various research institutions.

[0196] According to an embodiment of the present invention, a Schottky barrier diode with a ferroelectric field plate structure exhibits lower on-resistance values ​​than other previously reported gallium oxide Schottky barrier diodes at various anode radius sizes (from 50 μm to 1000 μm).

[0197] For example, as shown in FIG. 11, when the anode radius is about 200 μm, the device of the present invention exhibits an on-resistance of about 4 mΩ·cm², whereas conventional devices of similar size (NICT.17, XDU.20, etc.) exhibit an on-resistance of about 7 to 10 mΩ·cm².

[0198] The institutions and research results shown in the graph (ORNL.21, USTC.22, USTC.23, NICT.17, XDU.20, SYSU.19, DTU.24, XDU.23, etc.) represent the performance of gallium oxide Schottky barrier diodes developed by various research groups. Although these devices were fabricated using various structures and process technologies, they generally exhibit higher on-resistance values ​​compared to devices with the ferroelectric field plate structure of the present invention.

[0199] As shown in FIG. 11, it can be confirmed that the rate of increase in on-resistance with increasing anode radius is gentler in the device of the present invention for a Schottky barrier diode with a ferroelectric field plate structure.

[0200] This suggests that the effect of the ferroelectric field plate structure operates effectively even in large-area devices. While many existing devices tend to show a rapid increase in on-resistance as the anode radius increases, the device of the present invention can maintain a relatively gradual increase trend.

[0201] In addition, the results illustrated in FIG. 11 show that the ferroelectric field plate structure according to an embodiment of the present invention can significantly improve the on-resistance characteristics of a gallium oxide Schottky barrier diode.

[0202] This can be attributed to a mechanism in which the polarization effect of the ferroelectric material AlScN induces additional charge carriers within the semiconductor epitaxial layer, thereby expanding the current path and increasing the current density.

[0203] The comparison results shown in Figure 11 demonstrate that the technology of the present invention can achieve state-of-the-art performance in the field of gallium oxide-based power semiconductor devices.

[0204] Since low on-resistance is a critical factor in reducing conduction losses and improving energy efficiency in power devices, the Schottky barrier diode of the present invention has great potential for application in high-efficiency power conversion systems.

[0206] As described above, although the present invention has been explained by limited embodiments and drawings, the present invention is not limited to the above embodiments, and various modifications and variations are possible from this description by those skilled in the art to which the present invention belongs. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof.

Claims

Claim 1 A Schottky barrier diode comprising: a semiconductor substrate; a semiconductor epitaxial layer formed on the semiconductor substrate; an anode electrode formed on the upper surface of the semiconductor epitaxial layer; a cathode electrode formed on the lower surface of the semiconductor epitaxial layer; and a ferroelectric layer formed on the anode electrode and the semiconductor epitaxial layer, extending laterally from the anode electrode to disperse an electric field, wherein the ferroelectric layer comprises aluminum scandium nitride (AlScN), forms an electric field through spontaneous polarization without the application of an external voltage, induces an interfacial charge at the interface with the semiconductor epitaxial layer through the spontaneous polarization, and the polarized electric field formed by the spontaneous polarization induces additional charge carriers within the semiconductor epitaxial layer to improve current driving capability. Claim 2 In claim 1, the polarization electric field of the ferroelectric layer increases the concentration of electrons in the semiconductor epitaxial layer, thereby improving the current density. Schottky barrier diode. Claim 3 A Schottky barrier diode according to claim 1, wherein the on-resistance of the Schottky barrier diode is reduced by the ferroelectric layer. Claim 4 A Schottky barrier diode according to claim 1, wherein the breakdown voltage of the Schottky barrier diode is improved by the ferroelectric layer. Claim 5 delete Claim 6 In claim 1, the ferroelectric layer extends laterally from the anode electrode to alleviate electric field concentration in the semiconductor epitaxial layer, forming a Schottky barrier diode. Claim 7 In claim 1, the semiconductor substrate and the semiconductor epitaxial layer comprise gallium oxide (Ga2O3) in a Schottky barrier diode. Claim 8 delete Claim 9 In claim 1, the aluminum scandium nitride (AlScN) is Al x Sc (1-x) A Schottky barrier diode having a composition of N (0 < x < 1), wherein (1-x) is 0.20 to 0.

45. Claim 10 In claim 1, the anode electrode has a circular pattern and is a Schottky barrier diode having a radius of 50 μm to 1000 μm. Claim 11 In claim 1, the ferroelectric layer is a Schottky barrier diode extending 10 μm to 50 μm outward from the boundary of the anode electrode. Claim 12 In claim 11, the ferroelectric layer is a Schottky barrier diode that extends 20 μm to 50 μm further from the end of the structure extending outward from the boundary of the anode electrode. Claim 13 In claim 1, the anode electrode and the ferroelectric layer have a thickness ratio of 1:1.5 to 1:3, forming a Schottky barrier diode.

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