Schottky Diode and Its Preparation Method

Abstract

A Schottky diode and a method for manufacturing the same are provided. A Schottky diode is provided. The Schottky diode includes: a gallium oxide layer, which is a semiconductor layer doped with a first-type dopant; a cathode, which forms an ohmic contact with the gallium oxide layer; and an anode, which has a Schottky contact metal layer that forms a Schottky contact with the gallium oxide layer. The gallium oxide layer includes an intermediate layer, which is in contact with the interface of the Schottky contact metal layer and contains a second-type dopant whose conductivity is opposite to that of the first-type dopant, wherein the concentration of the second-type dopant gradually decreases in a direction away from the interface of the Schottky contact metal layer.

Description

Technical Field

[0001] The present invention relates to a semiconductor device, and more particularly, to a Schottky diode. Background Art

[0002] A Schottky diode or Schottky barrier diode is a device that uses a Schottky barrier generated by a junction of a metal and a semiconductor, and has a relatively low forward conduction voltage and a fast switching speed compared to a diode having a PN junction. The Schottky diode is used as a switching device of a power semiconductor device.

[0003] As such a Schottky diode, a SiC Schottky diode formed by epitaxially growing SiC on a Si wafer, or a GaN Schottky diode formed by epitaxially growing GaN on a Si wafer has been developed.

[0004] However, since the SiC Schottky diode has a large lattice mismatch with the Si wafer, it is difficult to grow a single crystal layer with few defects on the Si wafer. The problem of the GaN Schottky diode is that crystal growth is difficult without a buffer layer such as AlN, and thus mass productivity is poor.

[0005] To solve this problem, a Schottky diode using gallium oxide is being developed. The advantage of gallium oxide is that an ingot can be manufactured at low cost while providing a sufficiently high breakdown voltage. Summary of the Invention

[0006] An object of the present invention is to provide a gallium oxide-based Schottky diode in which the conduction voltage is increased and the leakage current is stabilized by increasing the Schottky barrier height.

[0007] The object of the present invention is not limited to the above object, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

[0008] To achieve the above technical object, an embodiment of the present invention provides a Schottky diode. The Schottky diode may include: a gallium oxide layer, which is a semiconductor layer doped with a first-type dopant; a cathode in ohmic contact with the gallium oxide layer; and an anode having a Schottky contact metal layer in Schottky contact with the gallium oxide layer. The gallium oxide layer may be in contact with the interface of the Schottky contact metal layer, contain a second-type dopant having a conductivity opposite to that of the first-type dopant, and have an intermediate layer, which is a region where the concentration of the second-type dopant decreases as it moves away from the interface of the Schottky contact metal layer.

[0009] In one embodiment, the second type of dopant may be the same metal as that contained in the Schottky contact metal layer. The Schottky contact metal layer and the intermediate layer may contain Ni, Co, or a combination thereof. In another embodiment, the Schottky contact metal layer may contain Se, Os, Rh, Co, Cu, Pd, Au, Ir, Pt, W, Ag, Ni, or a combination thereof, and the second type of dopant in the intermediate layer may contain Li, Na, Cs, Rb, Ca, Sr, Ba, Sc, Y, Ti, Zr, Hf, Ta, Fe, Co, Ni, Zn, Al, Nd, Sm, or a combination thereof.

[0010] The width of the intermediate layer may be wider than the width of the Schottky contact metal layer.

[0011] The gallium oxide layer may be a β-Ga 2 O 3 layer. The gallium oxide layer may include a first gallium oxide layer and a second gallium oxide layer. The doping concentration of the second gallium oxide layer is lower than that of the first gallium oxide layer. The cathode may be in ohmic contact with the first gallium oxide layer, the anode may be in Schottky contact with the second gallium oxide layer, and the intermediate layer may be located in the second gallium oxide layer. The second gallium oxide layer may be a layer epitaxially grown from the first gallium oxide layer. The first gallium oxide layer may be a gallium oxide layer doped with Sn, and the second gallium oxide layer may be a gallium oxide layer doped with Si.

[0012] The Schottky diode may have a Schottky barrier height of 1.25 eV to 1.5 eV.

[0013] To achieve the above technical objectives, another embodiment of the present invention provides a method for manufacturing a Schottky diode. The method for manufacturing a Schottky diode may include: providing a gallium oxide layer as a semiconductor layer doped with a first type of dopant; forming a cathode in contact with the gallium oxide layer; forming a Schottky contact metal layer in contact with the gallium oxide layer; and annealing the gallium oxide layer on which the Schottky contact metal layer is formed to form an intermediate layer that is in contact with the Schottky contact metal layer, contains a second type of dopant having a conductivity opposite to that of the first type of dopant, and is a region where the concentration of the second type of dopant decreases as it moves away from the interface with the Schottky contact metal layer.

[0014] In one embodiment, the Schottky contact metal layer may contain the second type of dopant, and the intermediate layer may be formed by diffusing the second type of dopant contained in the Schottky contact metal layer into the gallium oxide layer during annealing. The Schottky contact metal layer may be formed by sputtering. The Schottky contact metal layer contains Ni, Co, or a combination thereof as the second type of dopant. The Schottky contact metal layer is formed using facing target sputtering.

[0015] In another embodiment, before forming the Schottky contact metal layer in contact with the gallium oxide layer, a diffusion doping layer containing a second-type dopant may be formed on the gallium oxide layer, and the Schottky contact metal layer may be formed on the diffusion doping layer. The diffusion doping layer is formed by sputtering. The Schottky contact metal layer may include Se, Os, Rh, Co, Cu, Pd, Au, Ir, Pt, W, Ag, Ni, or a combination thereof, and the second-type dopant in the intermediate layer may include Li, Na, Cs, Rb, Ca, Sr, Ba, Sc, Y, Ti, Zr, Hf, Ta, Fe, Co, Ni, Zn, Al, Nd, Sm, or a combination thereof.

[0016] Annealing may be performed in a vacuum or an inert gas atmosphere. Annealing may be performed at 300 °C to 600 °C. Annealing is performed by using rapid thermal annealing. By annealing, the Schottky barrier height or the turn-on voltage of the Schottky diode can be increased.

[0017] The gallium oxide layer may be a β-Ga 2 O 3 layer.

[0018] To achieve the above technical objectives, another embodiment of the present invention provides a method for manufacturing a Schottky diode. The method may include: providing a gallium oxide layer as an impurity semiconductor layer; forming a cathode in contact with the gallium oxide layer; forming a Schottky contact metal layer in contact with the gallium oxide layer and having magnetism by using opposed target sputtering; and annealing the gallium oxide layer on which the Schottky contact metal layer is formed.

[0019] As described above, in the Schottky diode according to an embodiment of the present invention, by increasing the Schottky barrier height, the turn-on voltage can be increased and the leakage current can be stabilized.

[0020] Hereinafter, preferred examples are given to help understand the present invention. However, the following embodiments are only for helping to understand the present invention, and the present invention is not limited by the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 and Figure 2 are cross-sectional views showing a method for manufacturing a Schottky diode according to an embodiment of the present invention;

[0022] Figure 3 is a cross-sectional view showing a method for manufacturing a Schottky diode according to another embodiment of the present invention;

[0023] Figure 4 、 Figure 5 、 Figure 6 and Figure 7 are graphs showing the current density-voltage (J-V) of the Schottky diodes according to the preparation examples and the comparative examples;

[0024] Figure 8 and Figure 9 and Figure 10 are graphs showing the Schottky barrier height (SBH) (a), the ideality factor (n) (b), and the on-resistance value (c);

[0025] Figure 11 and Figure 12 are graphs showing the current density-voltage (J-V) according to temperature change during the measurement of the Schottky diode of Preparation Example 3;

[0026] Figure 13 and Figure 14 are graphs showing the current density-voltage (J-V) according to temperature change during the measurement of the Schottky diode of Comparative Example 3;

[0027] Figure 15 show the cross-sections of the Schottky diodes according to Preparation Example 1, Preparation Example 3, and Comparative Example 3 taken by a transmission electron microscope (TEM);

[0028] Figure 16 show the cross-sections of the Schottky diodes according to Preparation Example 1, Preparation Example 3, and Comparative Example 3 taken by energy dispersive spectroscopy (EDS). Detailed Description of the Invention

[0029] Hereinafter, to describe the present invention in more detail, embodiments according to the present invention will be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and can be implemented in other forms. When a layer is referred to as being "on" another layer or substrate, it can be formed directly on the other layer or substrate, or a third layer can be interposed therebetween.

[0030] Figure 1 and Figure 2 is a cross-sectional view showing a method of manufacturing a Schottky diode according to an embodiment of the present invention.

[0031] Referring to Figure 1 , a gallium oxide layer can be provided. The gallium oxide layer can be an extrinsic semiconductor layer doped with an n-type or p-type dopant as an example of a first-type dopant, and includes a first gallium oxide layer 10 and a second gallium oxide layer 20 doped at a concentration lower than that of the first gallium oxide layer 10. The second gallium oxide layer 20 can be referred to as a drift layer. The first gallium oxide layer 10 and the second gallium oxide layer 20 are single-crystal gallium oxide layers such as α, β, γ, δ, ε crystal phases, specifically β-Ga 2 O 3 layers.

[0032] Both the first gallium oxide layer 10 and the second gallium oxide layer 20 are layers doped with an n-type dopant, and the concentration of the dopant in the first gallium oxide layer 10 can be about 100 to 500 times higher than that of the second gallium oxide layer 20. As the n-type dopant, Si, Sn, or a combination thereof can be used. Specifically, the first gallium oxide layer 10 can be a gallium oxide layer doped with Sn, and the second gallium oxide layer 20 can be a gallium oxide layer doped with Si.

[0033] The first gallium oxide layer 10 can be a gallium oxide substrate obtained by cutting a bulk crystal formed by a melt growth method or the like. The first gallium oxide layer 10 can have a thickness of several hundred micrometers, specifically, a thickness of about 500 μm to 1000 μm. The second gallium oxide layer 20 is, specifically, a layer epitaxially grown from the upper surface of the first gallium oxide layer 10 by a physical vapor deposition (PVD) method, a pulsed laser deposition (PLD) method, and an MBE (which can be a layer grown by molecular beam epitaxy), a metalorganic chemical vapor deposition (MOCVD) method, or a hydride vapor phase epitaxy (HVPE) method. The second gallium oxide layer 20 can have a thickness of about 5 μm to 10 μm.

[0034] A cathode 30 in ohmic contact with the first gallium oxide layer 10 can be provided. As an example, the cathode 30 can be provided on the lower surface of the first gallium oxide layer 10. The cathode 30 can have a bilayer structure of an ohmic contact metal layer 30a and a cathode low-resistance layer 30b having a lower resistance than that of the ohmic contact metal layer 30a. The ohmic contact metal layer 30a can be made of titanium (Ti), indium (In), or a combination thereof. The cathode low-resistance layer 30b can be gold (Au), aluminum (Al), or a combination thereof.

[0035] An anode 40 in Schottky contact with the second gallium oxide layer 20 can be provided on the second gallium oxide layer 20. The anode 40 can include a Schottky contact metal layer 42, which is a metal layer having a high work function compared to the electron affinity of the second gallium oxide layer 20, for example, 4.4 eV to 6 eV, specifically 5 eV or more. The Schottky contact metal layer 42 can be Se, Os, Rh, Co, Cu, Pd, Au, Ir, Pt, W, Ag, Ni, or a combination thereof. In addition, the anode 40 can further include an anode low-resistance layer 44 having a lower resistance than that of the Schottky contact metal layer 42 on the Schottky contact metal layer 42. The anode low-resistance layer 44 can be gold (Au), aluminum (Al), or a combination thereof. In another example, a diffusion barrier layer 43 can also be interposed between the Schottky contact metal layer 42 and the anode low-resistance layer 44. The diffusion barrier layer 43 can be titanium (Ti) or a TiN layer. The anode 40 can be patterned using a lift-off method or a photolithography method.

[0036] Sputtering can be used, specifically the facing target sputtering method, to form the Schottky contact metal layer 42. In particular, when the Schottky contact metal layer is a magnetic metal, as an example of a ferromagnetic material, such as Ni, Co, or a combination thereof, the facing target sputtering method can be used to form the Schottky contact metal layer. In this case, by minimizing ion bombardment that may occur due to secondary electrons during film formation and by forming magnetic confinement to maintain a high plasma density, a high-quality Schottky contact metal layer can be formed at a high sputtering rate.

[0037] The element formed on the anode 40 can be annealed. This annealing can be carried out in a vacuum or an inert gas atmosphere and can be performed at about 200 °C to 600 °C, specifically 300 °C to 600 °C, more specifically 350 °C to 450 °C. Additionally, a rapid thermal annealing (RTA) method can be used to perform this annealing.

[0038] During annealing, a second-type dopant, for example, a p-type dopant such as Ni, Co, or a combination thereof, can diffuse into the second gallium oxide layer 20 in contact therewith. The second-type dopant constitutes the Schottky contact metal layer 42 included in the anode 40 (the Schottky contact metal layer 42 is formed by using the facing target sputtering method) and has a conductivity type opposite to that of the first-type dopant.

[0039] Reference Figure 2 , the intermediate layer 20a can be formed by the diffusion of the metal constituting the Schottky contact metal layer 42. The intermediate layer 20a can be formed to have a width wider than the width of the anode 40 (i.e., the Schottky contact metal layer 42). In other words, the second gallium oxide layer 20 can include the intermediate layer 20a in interface contact with the Schottky contact metal layer 42, and the intermediate layer 20a is a region in which the same metal as the second-type dopant is diffused, dispersed, or doped. The thickness of the intermediate layer 20a can be about 5 nm to 20 nm, for example, 8 nm to 15 nm. Additionally, in the intermediate layer 20a, the metal, which is the same second dopant as the metal contained in the Schottky contact metal layer 42, can have a lower concentration as it moves away from the interface with the Schottky contact metal layer 42. Therefore, the metal constituting the Schottky contact metal layer 42 in the intermediate layer 20a, that is, the second-type dopant, can have a concentration gradient.

[0040] When the metal constituting the Schottky contact metal layer 42 is Ni, Co, or a combination thereof, that is, the second-type dopant, and also the p-type dopant, due to the formed intermediate layer 20a, the Schottky barrier height will increase. Specifically, the Schottky diode according to this embodiment can exhibit a Schottky barrier height of about 1.25 eV to 1.5 eV, specifically 1.3 eV to 1.4 eV. In addition, due to the formed intermediate layer 20a, the turn-on voltage will increase, the breakdown voltage will increase, and the leakage current will decrease.

[0041] Figure 3 FIG. 2 is a cross-sectional view showing a method of manufacturing a Schottky diode according to another embodiment of the present invention. Except as described hereinafter, the method of manufacturing a Schottky diode according to the present embodiment may be similar to the method of manufacturing a Schottky diode with reference to Figure 1 and Figure 2 described.

[0042] With reference to Figure 3 , an anode 40 in Schottky contact with the second gallium oxide layer 20 may be provided on the second gallium oxide layer 20. As described with reference to Figure 1 , the anode 40 may include a Schottky contact metal layer 42, a diffusion barrier layer 43, and an anode low-resistance layer 44. In some cases, the anode low-resistance layer 44 and / or the diffusion barrier layer 43 may be omitted. The Schottky contact metal layer 42 is a metal layer having a high work function compared to the electron affinity of the second gallium oxide layer 20, for example, 4.4 eV to 6 eV, specifically a metal layer having a work function of more than 5 eV. The Schottky contact metal layer 42 may be Se, Os, Rh, Co, Cu, Pd, Au, Ir, Pt, W, Ag, Ni, or a combination thereof. A diffusion doping layer 41 may be formed under the anode 40, specifically, between the Schottky contact metal layer 42 and the second gallium oxide layer 20. The diffusion doping layer 41 may be a layer formed of a p-type dopant, which is an example of a second dopant, specifically Li, Na, Cs, Rb, Ca, Sr, Ba, Sc, Y, Ti, Zr, Hf, Ta, Fe, Co, Ni, Zn, Al, Nd, Sm, or a combination thereof. The diffusion doping layer 41 may be formed using a sputtering method and may be formed to have a very thin thickness, for example, a few angstroms or a few nanometers. For example, when the diffusion doping layer 41 is a layer formed of Fe, Co, Ni, Nd, Sm, or a combination thereof having magnetism, it may be formed using a facing target sputtering method.

[0043] The element formed to the anode 40 may be annealed. The annealing may be performed in a vacuum or an inert gas atmosphere and may be performed at about 200°C to 600°C, specifically 300°C to 600°C, more specifically 350°C to 450°C. In addition, a rapid thermal annealing (RTA) method may be used to perform the annealing.

[0044] In the annealing process, the metal (i.e., p-type dopant) constituting the diffusion doping layer 41 may be completely diffused (D) into the second gallium oxide layer 20 in contact therewith. Therefore, an intermediate layer ( Figure 2 20a in) may be formed by the diffusion, dispersion, or doping of the metal constituting the diffusion doping layer 41. In addition, since the metal constituting the diffusion doping layer 41 is completely diffused (D) into the second gallium oxide layer 20 in contact therewith, the intermediate layer ( Figure 2In 20a), the Schottky contact metal layer 42 can be contacted to form a Schottky contact.

[0045] In addition, in the intermediate layer ( Figure 2 In 20a), the metal contained in the diffusion doping layer 41, that is, the p-type dopant metal, can have a lower concentration as it moves away from the interface with the Schottky contact metal layer 42. Therefore, the metal contained in the diffusion doping layer 41 in the intermediate layer 20a, that is, the p-type dopant, can have a concentration gradient. In other words, in the intermediate layer ( Figure 2 In 20a), the n-type carrier concentration in the second gallium oxide layer 20 can have a higher concentration as it moves away from the interface with the Schottky contact metal layer 42.

[0046] The Schottky barrier height can be increased by the intermediate layer ( Figure 2 In 20a) formed by the diffusion of the metal contained in the diffusion doping layer 41 into the second gallium oxide layer 20. Specifically, the Schottky diode according to this embodiment can exhibit a Schottky barrier height of about 1.25 eV to 1.5 eV, specifically 1.3 eV to 1.4 eV. In addition, due to the formed intermediate layer ( Figure 2 In 20a), the turn-on voltage will increase, the breakdown voltage will increase, and the leakage current will decrease.

[0047] Hereinafter, preferred experimental examples are provided to help understand the present invention. However, the following examples are only for helping to understand the present invention, and the present invention is not limited by the following examples.

[0048] <Preparation Example 1 of Schottky Diode>

[0049] On the upper surface of a β-gallium oxide wafer doped with Sn at a concentration of about 10 18 atmos / cm -3 and having a thickness of about 650 μm, a β-gallium oxide epitaxial layer doped with Si at a concentration of about 10 16 atmos / cm -3 was grown to a thickness of about 5 μm using HVPE (halide vapor phase epitaxy). A Ti layer of about 10 nm and an Au layer of about 40 nm were laminated on the lower surface of the β-gallium oxide wafer by using an electron beam evaporator to form a Ti / Au electrode. A Ni layer of about 300 nm was deposited on the β-gallium oxide epitaxial layer by using a facing target sputtering method.

[0050] <Preparation Examples 2 to 4 of Schottky Diode>

[0051] After forming the Ni layer, RTA (rapid thermal annealing) was performed on the same Schottky diode as in Preparation Example 1 for 1 minute at 200 °C, 400 °C, or 600 °C in an Ar gas atmosphere of 100 mTorr.

[0052] <Comparative Example 1 of Diode>

[0053] A Schottky diode was fabricated using the same method as in Preparation Example 1 of the Schottky diode, except that a Ni layer of about 300 nm was deposited on the β-gallium oxide epitaxial layer using an electron beam evaporator.

[0054] <Comparative Examples 2 to 4 of Schottky Diode>

[0055] After forming the Ni layer, rapid thermal annealing (RTA) was performed on the same Schottky diode as in Comparative Example 1 for 1 minute at 200 °C (Comparative Example 2), 400 °C (Comparative Example 3), or 600 °C (Comparative Example 4) in an Ar gas atmosphere of 100 mTorr.

[0056] Figure 4 , Figure 5 , Figure 6 and Figure 7 are graphs showing the current density-voltage (J-V) of the Schottky diodes according to the preparation examples and comparative examples. Specifically, (a) is the forward bias J-V graph of the Schottky diodes according to Preparation Examples 1 to 4, (b) is the reverse bias J-V graph of the Schottky diodes according to Preparation Examples 1 to 4, (c) is the forward bias J-V graph of the Schottky diodes according to Comparative Examples 1 to 4, and (b) is the reverse bias J-V graph of the Schottky diodes according to Comparative Examples 1 to 4.

[0057] Referring to Figures 4 to 7 , in the preparation examples, it can be seen that the turn-on voltage in the forward bias region shifts to the right as the annealing temperature increases. In particular, in the Figure 4 showing the J-V of the diode annealed at 400 °C, a large shift in the turn-on voltage can be seen. Additionally, in Figure 6 , it can be seen that in the preparation examples, when the annealing temperature is increased to 400 °C, the leakage current value in the reverse bias region gradually decreases. However, when the annealing temperature is 600 °C, it can be seen that the leakage current value increases again. Conversely, in the case of the Figure 5 comparative examples, the change in the turn-on voltage in the forward bias region according to the annealing temperature is relatively small, and in Figure 7 , it can be seen that the change in the leakage current value in the reverse bias region is also relatively small.

[0058] Figure 8 is a graph showing the Schottky barrier height (SBH) of the preparation examples and comparative examples, Figure 9 is a graph showing the ideality factor (n), Figure 10 is a graph showing the on-resistance value.

[0059] In addition, various characteristics of the Schottky diodes according to Preparation Examples 1 to 4 are summarized in Table 1 below.

[0060] [Table 1]

[0061]

[0062] Reference Figures 8 to 10 and Table 1, in Figure 8 , it can be seen from the preparation examples that the Schottky barrier height (SBH) increases as the annealing temperature rises to 400 °C, but at subsequent temperatures, the increase in the Schottky barrier height is not obvious, with values ranging from approximately 1.25 eV to 1.5 eV, specifically from 1.3 eV to 1.4 eV. In the comparative examples, the SBH hardly changes below 1 eV depending on the annealing temperature. On the other hand, in Figure 9 , as the annealing temperature rises to 400 °C, the ideality factor n approaches the ideal value of 1, and it slightly increases when annealing is performed at 600 °C in the preparation examples, ranging from approximately 1.01 to 1.1, specifically from approximately 1.03 to 1.09. On the other hand, regardless of the annealing temperature, the comparative examples exhibit an ideality factor of approximately 1.05.

[0063] In Figure 10 , in the preparation examples, the on-resistance slightly increases as the annealing temperature rises, but the increase is not obvious. Regardless of the annealing temperature, the comparative examples show similar on-resistances.

[0064] Figures 11 to 14 are the current density-voltage (J-V) curves according to temperature changes during the measurement of the Schottky diodes of Preparation Example 3 and Comparative Example 3, respectively.

[0065] Referring together to Figure 11 and Figure 12 , in the Schottky diode according to Preparation Example 3, the initial leakage current in the reverse bias region increases as the measurement temperature rises, but in Figure 11 , when the measurement temperature is above 175 °C, the increase in the leakage current decreases as the voltage increases. At the same time, in Figure 12 , it can be seen that in the forward bias region, as the measurement temperature rises, the on-voltage shifts to the left and the slope decreases.

[0066] Referring together to Figure 13 and Figure 14 , it can be seen that the Schottky diode according to Comparative Example 3 has poorer temperature characteristics compared to the Schottky diode according to Preparation Example 3, such as the leakage current increasing as the temperature rises.

[0067] Figure 15 Shows the cross-sections of the Schottky diodes according to Preparation Example 1, Preparation Example 3, and Comparative Example 3 taken by a transmission electron microscope (TEM). Figure 16 Shows the cross-sections of the Schottky diodes according to Preparation Example 1, Preparation Example 3, and Comparative Example 3 taken by energy-dispersive spectroscopy (EDS).

[0068] Reference Figure 15 and Figure 16 When the Ni layer is formed by the facing target sputtering method, different from before annealing (Preparation Example 1), after annealing at 400 °C (Preparation Example 3), it can be seen that at the interface between the Ni layer and the gallium oxide epitaxial layer, specifically, an intermediate layer with a thickness of about 10 nm is generated in the gallium oxide epitaxial layer. Referring to the EDS composition analysis results ( Figure 16 ), this intermediate layer is a layer formed by the diffusion of Ni into the gallium oxide epitaxial layer during the annealing process, and it can be seen that Ni has a lower concentration as it penetrates deeper into the gallium oxide epitaxial layer from the surface (interface with the Ni layer). Thus, in a device formed by the facing target sputtering method and annealed at 400 °C, it can be seen that a Ni-doped layer, i.e., an intermediate layer, is formed in the gallium oxide epitaxial layer in contact with the Ni layer, and Ni has a concentration gradient in the intermediate layer. As described above, the intermediate layer can be used to increase the Schottky barrier height and the breakdown voltage, etc.

[0069] On the other hand, it can be seen that even when the Ni layer is formed by an electron beam evaporator and annealed at 400 °C, no diffusion of Ni occurs between the Ni layer and the gallium oxide epitaxial layer, and thus no intermediate layer is formed.

[0070] The present invention has been described in detail above with reference to the preferred embodiments, but the present invention is not limited to the above embodiments, and those skilled in the art can make various modifications and deformations within the spirit and scope of the present invention.

Claims

1. A Schottky diode, comprising: a gallium oxide layer, the gallium oxide layer being a semiconductor layer doped with a first-type dopant; a cathode, the cathode being in ohmic contact with the gallium oxide layer; and an anode, the anode having a Schottky contact metal layer in Schottky contact with the gallium oxide layer, wherein the interface contact between the gallium oxide layer and the gallium oxide layer and the Schottky contact metal layer contains a second-type dopant having a conductivity opposite to that of the first-type dopant, and has an intermediate layer, the intermediate layer containing the second-type dopant, the second-type dopant diffusing from the Schottky contact metal layer into the gallium oxide layer such that the concentration of the second-type dopant decreases as it moves away from the interface between the gallium oxide layer and the Schottky contact metal layer, the intermediate layer forming a Schottky contact with the Schottky contact metal layer, and the intermediate layer increasing the Schottky barrier height at the interface.

2. The Schottky diode according to claim 1, wherein, the second-type dopant is the same metal as the metal contained in the Schottky contact metal layer.

3. The Schottky diode according to claim 2, wherein, the Schottky contact metal layer and the intermediate layer contain Ni, Co or a combination thereof.

4. The Schottky diode according to claim 1, wherein, the Schottky contact metal layer contains Se, Os, Rh, Co, Cu, Pd, Au, Ir, Pt, W, Ag, Ni or a combination thereof, wherein the second-type dopant in the intermediate layer contains Li, Na, Cs, Rb, Ca, Sr, Ba, Sc, Y, Ti, Zr, Hf, Ta, Fe, Co, Ni, Zn, Al, Nd, Sm or a combination thereof.

5. The Schottky diode according to claim 1, wherein, the width of the intermediate layer is wider than the width of the Schottky contact metal layer.

6. The Schottky diode according to claim 1, wherein, The gallium oxide layer is a β-Ga 2 O 3 layer.

7. The Schottky diode according to claim 1, wherein, the gallium oxide layer includes a first gallium oxide layer and a second gallium oxide layer, the doping concentration of the second gallium oxide layer being lower than the doping concentration of the first gallium oxide layer, wherein the cathode is in ohmic contact with the first gallium oxide layer, wherein the anode is in Schottky contact with the second gallium oxide layer, wherein the intermediate layer is located in the second gallium oxide layer.

8. The Schottky diode according to claim 7, wherein, the second gallium oxide layer is a layer epitaxially grown from the first gallium oxide layer.

9. The Schottky diode according to claim 7, wherein, the first gallium oxide layer is a gallium oxide layer doped with Sn, and the second gallium oxide layer is a gallium oxide layer doped with Si.

10. The Schottky diode according to claim 1, wherein, the Schottky diode has a Schottky barrier height of 1.25 eV to 1.5 eV.

11. A method for manufacturing a Schottky diode, the method comprising: providing a gallium oxide layer as a semiconductor layer doped with a first-type dopant; forming a cathode in contact with the gallium oxide layer; Forming a Schottky contact metal layer that is in contact with the gallium oxide layer and has magnetism by using facing target sputtering; and Annealing the gallium oxide layer formed with the Schottky contact metal layer to form an intermediate layer that is in contact with the Schottky contact metal layer, contains a second-type dopant whose conductivity is opposite to that of the first-type dopant, the second-type dopant diffuses from the Schottky contact metal layer into the gallium oxide layer, and the concentration of the second-type dopant decreases as it moves away from the interface between the gallium oxide layer and the Schottky contact metal layer, wherein the intermediate layer forms a Schottky contact with the Schottky contact metal layer, and the intermediate layer increases the Schottky barrier height at the interface.

12. The method according to claim 11, wherein, the Schottky contact metal layer contains the second-type dopant, wherein, during the annealing, the intermediate layer is formed by diffusing the second-type dopant contained in the Schottky contact metal layer into the gallium oxide layer.

13. The method according to claim 12, wherein, the Schottky contact metal layer contains Ni, Co, or a combination thereof as the second-type dopant.

14. The method according to claim 11, further comprising forming a diffusion doping layer containing the second-type dopant on the gallium oxide layer before forming the Schottky contact metal layer in contact with the gallium oxide layer, wherein, the Schottky contact metal layer is formed on the diffusion doping layer.

15. The method according to claim 14, wherein, the diffusion doping layer is formed by sputtering.

16. The method according to claim 14, wherein, the Schottky contact metal layer contains Se, Os, Rh, Co, Cu, Pd, Au, Ir, Pt, W, Ag, Ni, or a combination thereof, wherein the second-type dopant in the intermediate layer contains Li, Na, Cs, Rb, Ca, Sr, Ba, Sc, Y, Ti, Zr, Hf, Ta, Fe, Co, Ni, Zn, Al, Nd, Sm, or a combination thereof.

17. The method according to claim 11, wherein, the annealing is performed in a vacuum or an inert gas atmosphere.

18. The method according to claim 11, wherein, the annealing is performed at 300°C to 600°C.

19. The method according to claim 11, wherein, the annealing is performed by using rapid thermal annealing.

20. The method according to claim 18, wherein, the Schottky barrier height or the turn-on voltage of the Schottky diode is increased by the annealing.

21. The method according to claim 11, wherein, The gallium oxide layer is a β-Ga 2 O 3 layer.

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