GaN-based bidirectional switching device

Abstract

The disclosure provides a GaN-based bidirectional switch device, which comprises, from bottom to top, a substrate, a buffer layer, a channel layer, a barrier layer and a voltage-withstanding enhancement layer; wherein the voltage-withstanding enhancement layer is made of p-type doped GaN material, and comprises an extended inclined first auxiliary voltage-withstanding structure and a second auxiliary voltage-withstanding structure, and the first auxiliary voltage-withstanding structure and the second auxiliary voltage-withstanding structure are oppositely arranged on the upper surface of the barrier layer.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor power device technology, and specifically to a GaN-based bidirectional switching device. Background Technology

[0002] Gallium nitride (GaN), as a third-generation semiconductor material, possesses characteristics such as a wide bandgap, high breakdown field strength, and high electron mobility compared to first-generation semiconductor materials like silicon and second-generation semiconductor materials like gallium arsenide. This has made it an ideal material for manufacturing high-frequency, high-voltage, and high-power semiconductor devices. With the rapid development of 5G communications, new energy vehicles, and smart grids, the demand for high-efficiency power devices is increasing, and bidirectional switching applications with bidirectional current conduction and voltage blocking characteristics are becoming increasingly widespread.

[0003] Traditional bidirectional switches consist of two insulated-gate transistors (IGBTs) connected in reverse series and a diode connected in antiparallel, resulting in a large chip area and high conduction losses. Therefore, researchers have developed a gallium nitride dual-gate bidirectional switch as a single device, which reduces the chip area and exhibits completely symmetrical forward and reverse conduction and blocking characteristics. However, its breakdown voltage and on-resistance performance still require further optimization. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In view of the above problems, this disclosure provides a GaN-based bidirectional switching device to at least partially solve the technical problems of low breakdown voltage and high on-resistance of traditional GaN bidirectional switching devices.

[0006] (II) Technical Solution

[0007] This disclosure provides a GaN-based bidirectional switching device, comprising, from bottom to top: a substrate, a buffer layer, a channel layer, a barrier layer, and a voltage withstand enhancement layer; wherein, the voltage withstand enhancement layer is made of p-type doped GaN material and includes an extended and inclined first auxiliary voltage withstand structure and a second auxiliary voltage withstand structure, the first auxiliary voltage withstand structure and the second auxiliary voltage withstand structure being disposed opposite to each other on the upper surface of the barrier layer.

[0008] According to embodiments of this disclosure, it further includes: a first gate electrode, a second gate electrode, a source electrode, and a drain electrode; the first gate electrode is disposed on the upper surface of the first auxiliary withstand voltage structure, and the second gate electrode is disposed on the upper surface of the second auxiliary withstand voltage structure; the source electrode and the drain electrode are symmetrically disposed at the edge of the upper surface of the barrier layer and located on both sides of the withstand voltage enhancement layer.

[0009] According to embodiments of this disclosure, the source electrode and the drain electrode respectively employ Schottky contact metal systems with different work functions, and the Schottky barrier of the drain electrode is higher than that of the source electrode.

[0010] According to embodiments of this disclosure, when the switching direction of the GaN-based bidirectional switching device is reversed, the current transport functions of the source electrode and the drain electrode are interchanged.

[0011] According to embodiments of this disclosure, the vertical height gradient of the first auxiliary withstand voltage structure decreases along the direction from the source electrode to the drain electrode; the vertical height gradient of the second auxiliary withstand voltage structure decreases along the direction from the drain electrode to the source electrode.

[0012] According to an embodiment of this disclosure, the distance between the withstand voltage enhancement layer and the drain electrode is less than the distance between the withstand voltage enhancement layer and the source electrode.

[0013] According to an embodiment of this disclosure, the first gate electrode is located in the maximum thickness region of the first auxiliary withstand voltage structure, the second gate electrode is located in the maximum thickness region of the second auxiliary withstand voltage structure, and the thickness gradient change rate of the maximum thickness region along the inclined direction is a preset value.

[0014] According to embodiments of this disclosure, the tilt angle of the first auxiliary pressure-resistant structure and the second auxiliary pressure-resistant structure of the pressure-resistant reinforcement layer is 5°-15°.

[0015] According to embodiments of this disclosure, the materials of the buffer layer and the channel layer are GaN.

[0016] According to embodiments of this disclosure, the barrier layer is made of AlGaN.

[0017] (III) Beneficial Effects

[0018] This disclosure overcomes the shortcomings of existing technologies by providing a GaN-based bidirectional switching device. By extending a voltage-enhancing layer with tilted first and second auxiliary voltage-enhancing structures, the electric field distribution is optimized, resulting in a more uniform electric field between the gate and drain, thus improving the device's voltage withstand performance. Simultaneously, the asymmetric Schottky barriers of the source and drain electrodes differentiate the bidirectional conduction characteristics, making it more adaptable to applications with varying bidirectional voltage levels. Furthermore, the two gates (the first and second gate electrodes) are independently controlled, enabling bidirectional switching on and off. Therefore, the GaN-based bidirectional switching device provided by this disclosure has optimized voltage withstand performance and on-resistance, making it suitable for high-frequency and low-to-medium voltage applications, such as 5G communications, new energy vehicles, and renewable energy. Attached Figure Description

[0019] To gain a more complete understanding of this disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0020] Figure 1 The schematic diagram illustrates the structure of the GaN-based bidirectional switching device provided in the embodiments of this disclosure.

[0021] Explanation of reference numerals in the attached figures:

[0022] 1-Substrate;

[0023] 2-Buffer layer;

[0024] 3-Channel layer;

[0025] 4-Barrier layer;

[0026] 5-First auxiliary pressure-resistant structure;

[0027] 6-Second auxiliary pressure-resistant structure;

[0028] 7 - First gate electrode;

[0029] 8 - Second gate electrode;

[0030] 9 - Source electrode;

[0031] 10 - Drain electrode. Detailed Implementation

[0032] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0034] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0035] Figure 1The schematic diagram illustrates the structure of the GaN-based bidirectional switching device provided in the embodiments of this disclosure.

[0036] like Figure 1 As shown, the bidirectional switching device can be sequentially comprised from bottom to top as follows: substrate 1, buffer layer 2, channel layer 3, barrier layer 4, withstand voltage enhancement layer (including first auxiliary withstand voltage structure 5 and second auxiliary withstand voltage structure 6), first gate electrode 7, second gate electrode 8, source electrode 9 and drain electrode 10.

[0037] Specifically, substrate 1 can be a Si substrate to reduce costs and ensure good thermal conductivity.

[0038] The material of buffer layer 2 can be GaN, which is used to alleviate the lattice mismatch problem between Si substrate and GaN.

[0039] The channel layer 3 can be made of GaN, providing a two-dimensional electron gas transport channel.

[0040] The material of barrier layer 4 can be AlGaN, which induces the formation of a two-dimensional electron gas through polarization effect.

[0041] The voltage withstand enhancement layer can be made of p-type doped GaN material. The tilt direction and placement of the voltage withstand enhancement layer should be close to the drain end, that is, the distance between the voltage withstand enhancement layer and the drain electrode is smaller than the distance between the voltage withstand enhancement layer and the source electrode.

[0042] The voltage withstand enhancement layer may include a first auxiliary voltage withstand structure 5 and a second auxiliary voltage withstand structure 6 with extended tilting (i.e., the voltage withstand enhancement layer has a non-perpendicular geometric configuration in three-dimensional space, such as a trapezoid or inclined plane) and the first auxiliary voltage withstand structure 5 and the second auxiliary voltage withstand structure 6 are disposed opposite to each other on the upper surface of the barrier layer 4 and located between the source electrode 9 and the drain electrode 10. At the same time, the voltage withstand enhancement layer with extended tilting electric field (the distribution of the extended tilting electric field is not parallel to the device surface, and the electric field lines have an inclined spatial distribution) adopts a tilting structure with decreasing height along the direction from the source electrode 9 to the drain electrode 10. That is, along the direction from the source electrode 9 to the drain electrode 10, the vertical height gradient of the first auxiliary voltage withstand structure 5 decreases; along the direction from the drain electrode 10 to the source electrode 9, the vertical height gradient of the second auxiliary voltage withstand structure 6 decreases.

[0043] In the embodiments of this disclosure, the tilt angle of the first auxiliary pressure-resistant structure 5 and the second auxiliary pressure-resistant structure 6 of the pressure-resistant reinforcement layer is 5°-15°.

[0044] Understandably, the first auxiliary withstand voltage structure 5 and the second auxiliary withstand voltage structure 6 adopt an inclined structure, which can disperse the electric field, avoid local peaks, and improve the reverse breakdown voltage of the bidirectional switching device.

[0045] Based on the above embodiments, in this embodiment, the gate electrodes (first gate electrode 7 and second gate electrode 8) form an ohmic contact with the voltage withstand enhancement layer. Specifically, the first gate electrode 7 is disposed on the upper surface of the first auxiliary voltage withstand structure 5 and located in the region of maximum thickness of the first auxiliary voltage withstand structure 5; the second gate electrode 8 is disposed on the upper surface of the second auxiliary voltage withstand structure 6 and located in the region of maximum thickness of the second auxiliary voltage withstand structure 6. Furthermore, the thickness gradient change rate of this maximum thickness region along the inclined direction is a preset value (preferably 0), i.e., located at the point where the voltage withstand enhancement layer has the maximum flatness.

[0046] The source electrode 9 and the drain electrode 10 are symmetrically disposed at the edge of the upper surface of the barrier layer 4 and on both sides of the voltage-resistant enhancement layer, and are symmetrically distributed about the vertical centerline of the GaN-based bidirectional switching device.

[0047] Furthermore, the source electrode 9 and drain electrode 10 employ Schottky contact metal systems with different work functions, i.e., they employ asymmetric Schottky contact metals. The source electrode 9 can be a low-barrier metal, and the drain electrode 10 can be a high-barrier metal. For example, a low-work-function metal (such as Ti) is deposited on the source electrode 9, and a high-work-function metal (such as Pt) is deposited on the drain electrode 10. The Schottky barrier of the drain electrode 10 is higher than that of the source electrode 9, thus forming a differentiated Schottky barrier height.

[0048] Understandably, source-drain designs using metals with different work functions can optimize conduction and blocking performance by adjusting the barrier height. Asymmetric Schottky not only decouples bidirectional characteristics, significantly reduces on-resistance, and optimizes conduction characteristics, but also differentiates bidirectional conduction characteristics through the asymmetric Schottky barrier, enhancing control flexibility to adapt to various application scenarios.

[0049] In some exemplary embodiments, when the switching direction of the GaN-based bidirectional switching device is reversed, the current transport functions of the source electrode 9 and the drain electrode 10 are interchanged. Specifically, the source electrode 9, which serves as an electron injection terminal when forward biased, can switch to an electron collection function when reverse biased, and correspondingly, the original drain electrode 10 can switch to an electron injection function.

[0050] It should be noted that the positions of the withstand voltage enhancement layer and the first gate electrode 7 and the second gate electrode 8 thereon can be adjusted and changed in the source electrode 9 and the drain electrode 10 according to the breakdown voltage requirements.

[0051] For example, regarding the dual-gate GaN bidirectional switching device with an extended tilted electric field, a voltage-reinforcing layer, and an asymmetric Schottky source-drain contact structure, the operating principle of this disclosure embodiment is as follows: 2DEG conduction is formed through polarization effect. In the forward conduction state, 2DEG is formed in the channel below the gate, thereby forming an electron flow path from the source electrode 9 to the drain electrode 10, and the device is turned on. In the off state, the 2DEG in the GaN channel layer 3 below the gate is depleted, and the device cannot conduct, remaining in a blocked state. The thickness of the voltage-reinforcing layer decreases with increasing distance from the gate. The voltage-reinforcing layer assists in depleting the 2DEG at the channel, making the electric field on the device surface more uniform, thereby improving the breakdown voltage.

[0052] The drain electrode 10 has a high Schottky barrier, while the source electrode 9 has a relatively low Schottky barrier. At low voltages, the current is primarily blocked by the potential barrier formed by the Schottky contact of the source electrode 9 or the drain electrode 10. When only one gate voltage is applied, this bidirectional switching device can only conduct current in one direction, exhibiting a certain blocking capability in the other. As the voltage at the drain electrode 10 increases, the gate controls the current flow by controlling the two-dimensional electron gas channel. The high Schottky barrier of the drain electrode 10 helps to increase the breakdown voltage.

[0053] In some exemplary embodiments, the tilting of the first auxiliary withstand voltage structure 5 and the second auxiliary withstand voltage structure 6 can be achieved by combining electron beam or laser direct-write grayscale exposure with reactive ion etching (RIE) and ALE processes. First, a high-contrast chemically amplified photoresist (such as AR-N 7520) can be coated, and grayscale exposure can be performed using electron beam or laser direct-write technology. A continuous slope profile can be formed on the photoresist using dose gradient control, and the tilt angle can be defined as 5°-15°. Subsequently, inductively coupled reactive ion etching (ICP-RIE) is used to transfer the slope morphology of the photoresist to the withstand voltage enhancement layer. Then, a Cl2 / BCl3 / Ar mixed gas (ratio 50:20:30) can be used for etching under ICP power of 800 W and bias power of 50 W to initially form the tilted structure. To repair surface defects and reduce roughness, atomic layer etching (ALE) can be further used for refinement. After 20-30 cycles, the surface roughness is reduced, and the damage caused by etching is repaired.

[0054] The overall fabrication of GaN-based bidirectional switching devices can be completed using a gate-first process and conventional mass production methods.

[0055] The GaN-based bidirectional switching device provided in this disclosure employs an extended, tilted electric field modulation structure, which enables a more uniform electric field distribution between the gate and drain, alleviating the problem of electric field concentration at the gate edge and near the drain, thereby improving the device's breakdown voltage. Simultaneously, based on the different application scenarios of bidirectional conduction, source and drain Schottky contact metal systems with different barrier heights are specifically adopted to optimize device characteristics. Therefore, the introduction of the above structure not only optimizes the electric field distribution but also significantly improves the bidirectional conduction characteristics, effectively reducing on-resistance while enhancing the device's breakdown voltage performance, making it particularly suitable for application scenarios with different bidirectional operating voltages.

[0056] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0057] Although this disclosure has been shown and described with reference to specific exemplary embodiments thereof, those skilled in the art will understand that various changes in form and detail may be made to this disclosure without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. Therefore, the scope of this disclosure should not be limited to the above embodiments, but should be defined not only by the appended claims, but also by their equivalents.

Claims

1. A GaN-based bidirectional switching device, characterized in that, From bottom to top, they include: Substrate, buffer layer, channel layer, barrier layer, and voltage withstand enhancement layer; among which, The withstand voltage enhancement layer is made of p-type doped GaN material and includes an extended and inclined first auxiliary withstand voltage structure and a second auxiliary withstand voltage structure, which are disposed opposite to each other on the upper surface of the barrier layer.

2. The GaN-based bidirectional switching device according to claim 1, characterized in that, Also includes: First gate electrode, second gate electrode, source electrode, and drain electrode; The first gate electrode is disposed on the upper surface of the first auxiliary withstand voltage structure, and the second gate electrode is disposed on the upper surface of the second auxiliary withstand voltage structure; The source electrode and the drain electrode are symmetrically disposed at the edge of the upper surface of the barrier layer and on both sides of the withstand voltage enhancement layer.

3. The GaN-based bidirectional switching device according to claim 2, characterized in that, The source electrode and the drain electrode each employ Schottky contact metal systems with different work functions, and the Schottky barrier of the drain electrode is higher than that of the source electrode.

4. The GaN-based bidirectional switching device according to claim 2 or 3, characterized in that, When the switching direction of the GaN-based bidirectional switching device is reversed, the current transfer functions of the source electrode and the drain electrode are interchanged.

5. The GaN-based bidirectional switching device according to claim 2, characterized in that, Along the direction from the source electrode to the drain electrode, the vertical height gradient of the first auxiliary withstand voltage structure decreases; along the direction from the drain electrode to the source electrode, the vertical height gradient of the second auxiliary withstand voltage structure decreases.

6. The GaN-based bidirectional switching device according to claim 2, characterized in that, The distance between the withstand voltage enhancement layer and the drain electrode is less than the distance between the withstand voltage enhancement layer and the source electrode.

7. The GaN-based bidirectional switching device according to claim 2, characterized in that, The first gate electrode is located in the maximum thickness region of the first auxiliary withstand voltage structure, and the second gate electrode is located in the maximum thickness region of the second auxiliary withstand voltage structure. The thickness gradient change rate of the maximum thickness region along the inclined direction is a preset value.

8. The GaN-based bidirectional switching device according to claim 1, characterized in that, The tilt angle of the first auxiliary pressure-resistant structure and the second auxiliary pressure-resistant structure of the pressure-resistant reinforcement layer is 5°-15°.

9. The GaN-based bidirectional switching device according to claim 1, characterized in that, The materials of the buffer layer and the channel layer are GaN.

10. The GaN-based bidirectional switching device according to claim 1, characterized in that, The barrier layer is made of AlGaN.

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