Gallium oxide Schottky diode with diffusion barrier structure

Abstract

The invention discloses a gallium oxide Schottky diode with a diffusion barrier structure. The gallium oxide Schottky diode comprises a substrate layer, a conductive layer, a diffusion barrier layer, a drift layer, a first electrode and a second electrode. The conductive layer is arranged on the substrate layer, and the conductive layer is composed of a heavily doped alpha-Ga2O3 film; the diffusion barrier layer covers part of the conductive layer, and the diffusion barrier layer is formed by laminating one or more of an Al2O3 film, a SiO2 film and a Si3N4 film; the drift layer is arranged on the diffusion barrier layer, and the drift layer is composed of a lightly doped alpha-Ga2O3 film; the first electrode and the drift layer form Schottky contact, the second electrode is arranged on the area, not covered by the diffusion barrier layer, of the conducting layer, and the second electrode and the conducting layer form ohmic contact. By introducing the diffusion barrier layer, longitudinal diffusion of doped elements in a high-temperature process can be effectively inhibited, so that the reverse breakdown voltage of the device is improved, and the reverse leakage current is reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor power device technology, and in particular to a gallium oxide Schottky diode with a diffusion barrier structure. Background Technology

[0002] Alpha-phase gallium oxide (α-Ga₂O₃), as an emerging ultra-wide bandgap semiconductor, possesses significant advantages in high-voltage power devices due to its high breakdown field strength and Baliga figure of merit. Schottky diodes are an important device structure type in the field of power electronics, characterized by low turn-on voltage, low on-resistance, and fast response speed. Therefore, α-Ga₂O₃-based Schottky diodes represent an important research direction for the development of power devices. Due to the lack of homogeneous single-crystal substrates for α-Ga₂O₃, multilayer thin films need to be epitaxially grown on heterogeneous substrates such as sapphire. Heavily doped layers serve as ohmic contact regions, while lightly doped layers serve as drift regions. By controlling the carrier concentration and crystal quality of each thin film layer and optimizing the device structure, low-leakage-current Schottky diodes at the kilovolt level can be realized, demonstrating significant application value.

[0003] However, Schottky diodes based on α-Ga₂O₃ thin films currently face the following challenges: high-quality epitaxy and doping activation of α-Ga₂O₃ often require high temperatures, while elements such as Sn, Si, and Ge in the heavily doped layer are prone to volatilization and diffusion into the lightly doped layer at high temperatures. This diffusion not only leads to a significant increase in carrier concentration in the lightly doped layer and a reduction in the depletion region width, but also induces lattice distortion and an increase in interface defect density, ultimately resulting in increased leakage current and a decrease in reverse breakdown voltage. Furthermore, the doping inhomogeneity in the drift region caused by diffusion further degrades the forward conduction characteristics of the device. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is how to suppress the element diffusion between heavily doped and lightly doped α-Ga2O3 films, so as to improve the reverse breakdown and forward conduction performance of α-Ga2O3 Schottky diodes.

[0005] To achieve the above objectives, the present invention provides a gallium oxide Schottky diode with a diffusion barrier structure, comprising a substrate layer, a conductive layer, a diffusion barrier layer, a drift layer, a first electrode, and a second electrode. The conductive layer is disposed on the substrate layer and is composed of a heavily doped α-Ga₂O₃ thin film. The diffusion barrier layer covers a portion of the conductive layer and is composed of one or more stacked layers of Al₂O₃ thin film, SiO₂ thin film, and Si₃N₄ thin film. The drift layer is disposed on the diffusion barrier layer and is composed of a lightly doped α-Ga₂O₃ thin film. The first electrode forms a Schottky contact with the drift layer. The second electrode is disposed on a region of the conductive layer not covered by the diffusion barrier layer and forms an ohmic contact with the conductive layer.

[0006] This invention introduces a diffusion barrier layer between a heavily doped conductive layer and a lightly doped drift layer. By utilizing the high barrier properties of Al2O3 / SiO2 / Si3N4, the longitudinal diffusion of doped elements under high-temperature processes is effectively suppressed, thereby reducing the carrier concentration of the drift layer, expanding the depletion region width, improving the reverse breakdown voltage of the device, and reducing the reverse leakage current.

[0007] Furthermore, the diffusion barrier layer is composed of stacked Al2O3, SiO2, and Si3N4 films. This stacked composite structure further optimizes the diffusion barrier effect through the synergistic effect of each layer. Specifically, the Al2O3 film, with its high chemical stability and density, blocks the migration of dopant elements; the SiO2 layer regulates the interfacial band distribution and optimizes electron tunneling efficiency; and the Si3N4 layer provides an additional barrier, enhancing the ability to suppress diffusion.

[0008] Furthermore, the thickness of the diffusion barrier layer is 3~10 nm. Limiting the thickness of the diffusion barrier layer ensures that charge carriers can tunnel through the barrier layer, reducing the additional increase in on-resistance.

[0009] Furthermore, the carrier concentration of the conductive layer is 10. 18 ~10 20 cm -3 The carrier concentration of the drift layer is 10. 15 ~10 17 cm -3 The heavily doped conductive layer ensures good ohmic contact, while the lightly doped drift layer provides a wide depletion region. When the concentration gradient difference between the two is greater than three orders of magnitude, a steep carrier distribution can be formed, reducing reverse leakage current.

[0010] Furthermore, the doping elements of the conductive layer and the drift layer are selected from one or more of Sn, Si, Ge, Zr, Ir, and Hf. The doping elements can provide the charge carriers required by the device.

[0011] Furthermore, the thickness of the conductive layer is 20~2000 nm, and the thickness of the drift layer is 0.3~50 μm. Limiting the thickness of the conductive and drift layers balances breakdown voltage, on-resistance, and leakage current, optimizing electrical performance.

[0012] Furthermore, the substrate layer is made of sapphire or diamond. Sapphire or diamond substrates have good lattice compatibility with α-Ga₂O₃, ensuring high-quality epitaxial growth of α-Ga₂O₃ thin films.

[0013] Furthermore, the thickness of the substrate layer is 50~1000μm. Limiting the thickness of the substrate layer provides mechanical support and heat dissipation capabilities.

[0014] Furthermore, the material of the first electrode is selected from one or more of Au, Pt, Ni, Cu, W, Zr, and PtO2. The material of the first electrode has a high work function or a protective function to ensure the formation of a good Schottky contact.

[0015] Furthermore, the material of the second electrode is selected from one or more of Au, Ti, Al, Ni, In, and ITO. The material of the second electrode has a low work function or a protective function to ensure the formation of a good ohmic contact.

[0016] In summary, the present invention has the following beneficial effects: (1) Improve reverse breakdown voltage and reduce leakage current: By introducing a diffusion barrier layer, the diffusion of dopants from the heavily doped conductive layer to the lightly doped drift layer is effectively suppressed, maintaining a low carrier concentration in the drift layer, increasing the width of the depletion region, improving the reverse breakdown voltage and reducing leakage current.

[0017] (2) Maintaining low on-resistance and high response speed: The ultrathin diffusion barrier layer allows electrons to tunnel through quantum, which can maintain the device's low on-resistance and fast recovery characteristics. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a gallium oxide Schottky diode in a specific embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of the gallium oxide Schottky diode according to Embodiment 1 of the present invention.

[0020] Figure 3 This is a schematic diagram of the structure of the gallium oxide Schottky diode according to Embodiment 2 of the present invention.

[0021] Figure 4 This is a schematic diagram of the structure of the gallium oxide Schottky diode in Embodiment 3 of the present invention.

[0022] Explanation of reference numerals in the attached figures: 1-Substrate, 2-Conductive layer, 3-Diffusion barrier layer, 31-Al2O3 thin film, 32-SiO2 thin film, 33-Si3N4 thin film, 4-Drift layer, 5-First electrode, 6-Second electrode. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art.

[0026] A specific embodiment of the present invention provides a gallium oxide Schottky diode with a diffusion barrier structure, the structure of which is as follows: Figure 1 As shown, the structure includes a functional layer and an electrode layer. The functional layer includes a substrate layer 1, a conductive layer 2, a diffusion barrier layer 3, and a drift layer 4. The conductive layer 2 is disposed on the substrate layer 1 and is composed of a heavily doped α-Ga₂O₃ thin film. The diffusion barrier layer 3 is disposed on the conductive layer 2, covering a portion of the surface of the conductive layer 2. The drift layer 4 is disposed on the diffusion barrier layer 3 and is composed of a lightly doped α-Ga₂O₃ thin film. This gallium oxide Schottky diode, by inserting a diffusion barrier layer 3 between the heavily doped conductive layer 2 and the lightly doped drift layer 4, in a specific embodiment, the diffusion barrier layer 3 is composed of one or more stacks of Al₂O₃ thin film, SiO₂ thin film, and Si₃N₄ thin film, which can effectively suppress the migration of doped atoms in the conductive layer to the drift layer under high-temperature processes, thereby reducing the carrier concentration of the drift layer, expanding the depletion region width, and improving the reverse breakdown voltage.

[0027] Preferably, the thickness of the diffusion barrier layer 3 is 3~10nm. While blocking diffusion, it allows electrons to penetrate the diffusion barrier layer 3 through the quantum tunneling effect, so that the forward conduction resistance of the device does not increase significantly. While increasing the reverse breakdown voltage of the device, it can maintain the low on-resistance of the device.

[0028] The electrode layer structure includes a first electrode 5 and a second electrode 6. The first electrode 5 is disposed on the drift layer 4 and forms a Schottky contact with the drift layer 4. The second electrode 6 is disposed on the area of ​​the conductive layer 2 that is not covered by the diffusion barrier layer 3 and forms an ohmic contact with the conductive layer 2.

[0029] In gallium oxide Schottky diodes, a reasonable film and interface design is key to improving device performance. In specific embodiments, the substrate layer 1 can be made of sapphire or diamond, with a thickness of 50~1000μm. The substrate layer 1 ensures high-quality epitaxial growth of the α-Ga2O3 thin film and provides mechanical support and heat dissipation capabilities. The doping elements of the conductive layer 2 and drift layer 4 can be Sn, Si, Ge, Zr, Ir, Hf, etc., and the carrier concentration of the conductive layer 2 is in the range of 10. 18 ~10 20 cm -3 Typical thickness is 20~2000nm; carrier concentration range of drift layer 4 is 10 15 ~10 17 cm -3 The typical thickness is 0.3~50μm. The material of the first electrode 5 is selected from materials with high work function or protective function, such as Au, Pt, Ni, Cu, W, Zr, PtO2, etc.; the material of the second electrode 6 is selected from materials with low work function or protective function, such as Au, Ti, Al, Ni, In, ITO, etc.

[0030] The aforementioned gallium oxide Schottky diode achieves carrier concentration gradient control and transport optimization by introducing a diffusion barrier layer 3, providing a key technical path for improving device performance.

[0031] The technical solution and effects of the present invention will be illustrated below with specific embodiments.

[0032] Example 1 This embodiment provides a gallium oxide Schottky diode, with the structure as follows: Figure 2 As shown, the structure includes a functional layer and an electrode layer. The functional layer structure includes: a substrate layer 1, made of (11-20) oriented single-crystal sapphire with a thickness of 500 μm; and a conductive layer 2, disposed on the substrate layer 1, made of heavily doped α-Ga₂O₃ thin film with Sn as the dopant element and a carrier concentration of 1 × 10⁻⁶. 19 cm -3 The conductive layer 2 has a thickness of 200 nm; the diffusion barrier layer 3, disposed on a portion of the conductive layer 2, is an Al2O3 thin film 31 with a thickness of 5 nm; the drift layer 4, disposed on the diffusion barrier layer 3, is a lightly doped α-Ga2O3 thin film with Sn as the dopant element and a carrier concentration of 1 × 10⁻⁶. 16 cm -3The thickness is 5 μm. The electrode layer structure includes: a first electrode 5, which is disposed on the drift layer 4 and forms a Schottky contact with the drift layer 4. The first electrode 5 is a Pt / Au double layer structure; and a second electrode 6, which is disposed on the area of ​​the conductive layer 2 not covered by the diffusion barrier layer 3 and forms an ohmic contact with the conductive layer 2. The second electrode 6 is a Ti / Au double layer structure.

[0033] Example 2 This embodiment provides a gallium oxide Schottky diode, with the structure as follows: Figure 3 As shown, the structure includes a functional layer and an electrode layer. The functional layer includes: a substrate 1, which is a (111) oriented diamond substrate with a thickness of 300 μm; and a conductive layer 2, which is disposed on the substrate 1 and is a heavily doped α-Ga2O3 thin film with Ge as the dopant element and a carrier concentration of 1 × 10⁻⁶. 18 cm -3 The conductive layer 2 has a thickness of 500 nm; a diffusion barrier layer 3, disposed on a portion of the conductive layer 2, has a thickness of 5 nm and is composed of a 3 nm Al2O3 thin film 31 and a 2 nm SiO2 thin film 32; a drift layer 4, disposed on the diffusion barrier layer 3, is a lightly doped α-Ga2O3 thin film with Ge as the dopant element and a carrier concentration of 1 × 10⁻⁶. 15 cm -3 The thickness is 10 μm. The electrode layer structure includes: a first electrode 5, which is disposed on the drift layer 4 and forms a Schottky contact with the drift layer 4. The first electrode 5 is a Pt / Au double layer structure; and a second electrode 6, which is disposed on the area of ​​the conductive layer 2 not covered by the diffusion barrier layer 3 and forms an ohmic contact with the conductive layer 2. The second electrode 6 is a Ti / Au double layer structure.

[0034] Example 3 This embodiment provides a gallium oxide Schottky diode, with the structure as follows: Figure 4 As shown, the structure includes a functional layer and an electrode layer. The functional layer includes: a substrate layer 1, made of (30-30) oriented single-crystal sapphire with a thickness of 200 μm; and a conductive layer 2, disposed on the substrate layer 1, made of heavily doped α-Ga₂O₃ thin film with Sn as the dopant element and a carrier concentration of 1 × 10⁻⁶. 20 cm -3 The conductive layer 2 has a thickness of 50 nm; the diffusion barrier layer 3, disposed on a portion of the conductive layer 2, has a thickness of 10 nm and is composed of a 5 nm Al2O3 film 31, a 3 nm Si3N4 film 33, and a 2 nm SiO2 film 32; the drift layer 4, disposed on the diffusion barrier layer 3, is a lightly doped α-Ga2O3 film with Sn as the dopant element and a carrier concentration of 1 × 10⁻⁶. 17 cm -3The thickness is 0.5 μm. The electrode layer structure includes: a first electrode 5, disposed on the drift layer 4, forming a Schottky contact with the drift layer 4, the first electrode 5 being a PtO2 / Pt / Au multilayer structure; and a second electrode 6, disposed on the area of ​​the conductive layer 2 not covered by the diffusion barrier layer 3, forming an ohmic contact with the conductive layer 2, the second electrode 6 being a Ti / Al / Ni / Au multilayer structure.

[0035] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the scope of protection of this invention.

Claims

1. A gallium oxide Schottky diode with a diffusion barrier structure, characterized in that, The device includes a substrate layer, a conductive layer, a diffusion barrier layer, a drift layer, a first electrode, and a second electrode. The conductive layer is disposed on the substrate layer and is composed of a heavily doped α-Ga2O3 thin film. The diffusion barrier layer covers a portion of the conductive layer and is composed of one or more stacked layers of Al2O3 thin film, SiO2 thin film, and Si3N4 thin film. The drift layer is disposed on the diffusion barrier layer and is composed of a lightly doped α-Ga2O3 thin film. The first electrode forms a Schottky contact with the drift layer. The second electrode is disposed on a region of the conductive layer not covered by the diffusion barrier layer and forms an ohmic contact with the conductive layer.

2. The gallium oxide Schottky diode with a diffusion barrier structure according to claim 1, characterized in that, The diffusion barrier layer is composed of stacked Al2O3 film, SiO2 film and Si3N4 film.

3. The gallium oxide Schottky diode with a diffusion barrier structure according to claim 1 or 2, characterized in that, The thickness of the diffusion barrier layer is 3~10nm.

4. The gallium oxide Schottky diode with a diffusion barrier structure according to claim 1, characterized in that, The carrier concentration of the conductive layer is 10. 18 ~10 20 cm -3 The carrier concentration of the drift layer is 10. 15 ~10 17 cm -3 .

5. The gallium oxide Schottky diode with a diffusion barrier structure according to claim 4, characterized in that, The doping elements of the conductive layer and the drift layer are selected from one or more of Sn, Si, Ge, Zr, Ir, and Hf.

6. The gallium oxide Schottky diode with a diffusion barrier structure according to claim 4, characterized in that, The thickness of the conductive layer is 20~2000nm, and the thickness of the drift layer is 0.3~50μm.

7. The gallium oxide Schottky diode with a diffusion barrier structure according to claim 1, characterized in that, The substrate layer is made of sapphire or diamond.

8. The gallium oxide Schottky diode with a diffusion barrier structure according to claim 7, characterized in that, The thickness of the substrate layer is 50~1000μm.

9. The gallium oxide Schottky diode with a diffusion barrier structure according to claim 1, characterized in that, The material of the first electrode is selected from one or more of Au, Pt, Ni, Cu, W, Zr, and PtO2.

10. The gallium oxide Schottky diode with a diffusion barrier structure according to claim 1, characterized in that, The material of the second electrode is selected from one or more of Au, Ti, Al, Ni, In, and ITO.

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