A GaN bidirectional blocking vertical power device based on a composite drain

Abstract

The application discloses a GaN bidirectional blocking vertical power device based on a composite drain, which comprises a Schottky drain, a plurality of ohmic drains, a substrate, a drift layer, a channel layer, a conductive layer, a gate dielectric, a source and a gate, wherein the Schottky drain, the substrate, the drift layer, the channel layer, the conductive layer and the gate dielectric are sequentially arranged from bottom to top, the plurality of ohmic drains are uniformly embedded in the Schottky drain, and the upper surfaces of the plurality of ohmic drains and the Schottky drain are in contact with the lower surface of the substrate; the Schottky drain adopts Schottky contact with the substrate, and the plurality of ohmic drains adopt ohmic contact with the substrate; the source is arranged on both sides of the gate dielectric, and the lower surface of the source extends downward to the channel layer; the gate is arranged in the middle of the gate dielectric, and the gate extends downward to the drift layer and is spaced apart from the drift layer, the channel layer and the conductive layer through the gate dielectric. The application can effectively reduce the on-voltage, maintain the rectification characteristic of the Schottky contact, and still have the bidirectional blocking capability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductors, and particularly relates to a GaN bidirectional blocking vertical power device based on a composite drain. BACKGROUND

[0002] Compared with lateral devices, vertical devices have wider current channels, are easier to realize large current, large power and low power consumption, have better voltage resistance, and can effectively avoid a series of problems caused by functional degradation of the device due to surface electric field concentration. Since the body conduction is realized, current collapse can be effectively suppressed, the unit device area utilization rate is higher, the device area can be effectively reduced, and the cost can be reduced. The vertical power device has high static input impedance, a simple driving circuit, small required driving power, fast switching speed, small switching loss, high working frequency and good dynamic characteristics.

[0003] The bidirectional blocking device is an important device in an AC-AC (alternating current-alternating current) conversion circuit. In a traditional mode, a conventional transistor and a diode capable of withstanding high voltage are connected in series to realize the function of bidirectional blocking. However, the series-connected diode causes an increase in on-state voltage drop, thereby increasing the loss. The bidirectional blocking device has a reverse voltage resistance capability, and the diode can be removed. Compared with the traditional series diode mode, the bidirectional blocking device reduces the number of devices and also reduces the on-state voltage drop and loss. The bidirectional blocking vertical power device based on the third-generation wide-bandgap semiconductor GaN has a reduced device area and parasitic capacitance, and has good switching characteristics.

[0004] In the existing vertical power device based on a Schottky drain, the gold-semiconductor contact between the Schottky drain and the substrate is a Schottky contact. When the metal and the semiconductor material are in contact, the energy band of the semiconductor is bent at the interface, a Schottky barrier is formed, and good rectification characteristics are achieved, so that the bidirectional blocking characteristics can be realized. However, the existence of the barrier leads to a large interface resistance, so that the forward characteristic has a large on-voltage of about 1V. SUMMARY

[0005] In order to solve the above problems in the prior art, the application provides a GaN bidirectional blocking vertical power device based on a composite drain. The technical problems to be solved by the application are solved by the following technical scheme.

[0006] The application provides a GaN bidirectional blocking vertical power device based on a composite drain, which comprises a Schottky drain, a plurality of ohmic drains, a substrate, a drift layer, a channel layer, a conductive layer, a gate dielectric, a source and a gate, wherein

[0007] The Schottky drain, the substrate, the drift layer, the channel layer, the conductive layer and the gate dielectric are sequentially arranged from bottom to top, the plurality of ohmic drains are uniformly embedded in the Schottky drain, and the upper surfaces of the plurality of ohmic drains and the Schottky drain are in contact with the lower surface of the substrate.

[0008] The Schottky drain and the substrate adopt Schottky contact, and the plurality of ohmic drains and the substrate adopt ohmic contact.

[0009] The source is arranged on both sides of the gate dielectric, and the lower surface of the source extends downward to the channel layer; the gate is arranged in the middle of the gate dielectric, and the gate extends downward to the drift layer and is spaced apart from the drift layer, the channel layer and the conductive layer by the gate dielectric.

[0010] Further, the thickness of the ohmic drain is less than the thickness of the Schottky drain.

[0011] Further, the ohmic drain grows into a strip-shaped structure, and a plurality of the ohmic drains are arranged in parallel inside the Schottky drain and extend from one side of the Schottky drain to the opposite side.

[0012] Further, the source forms ohmic contact with the channel layer, and the gate forms Schottky contact with the gate dielectric.

[0013] Further, the GaN bidirectional blocking vertical power device based on the composite drain further comprises a current blocking layer arranged on the left and right sides of the upper surface of the drift layer, and the upper surface of the current blocking layer is in contact with the lower surface of the conductive layer.

[0014] Further, the drift layer is an n-GaN drift layer with a doping concentration of 1×10 15 ~ 5×10 18 cm -3 ; the channel layer is a p + GaN channel layer with a doping concentration of 1×10 17 cm -3 ~ 5×10 20 cm -3 ; the conductive layer is an n + GaN conductive layer with a doping concentration of 1×10 18 cm -3 ~ 1×10 20 cm -3 .

[0015] Further, a T-shaped groove extending to the upper surface of the channel layer is formed in the middle of the gate dielectric, and a 0.002-0.2 μm gate dielectric is arranged in the T-shaped groove, and a T-shaped gate is formed on the gate dielectric of the T-shaped groove.

[0016] Further, the thickness of the drift layer is 0.02-30 μm, the thickness of the channel layer is 10-1000 nm, and the thickness of the conductive layer is 10-1000 nm.

[0017] Compared with the prior art, the present application has the following advantages:

[0018] 1. When the metal-semiconductor contact of the Schottky drain is a Schottky contact, the band bending at the interface of the semiconductor forms a high potential energy area, i.e. a Schottky barrier. The present application is based on a GaN bidirectional blocking vertical power device with a composite drain. When a reverse voltage is applied to the drain, the electron must be higher than the energy of the barrier to cross the barrier, thereby playing a role in reverse blocking.

[0019] 2. The ohmic contact does not produce obvious additional impedance. The present application is based on a GaN bidirectional blocking vertical power device with a composite drain, and proposes a composite drain form. The addition of an ohmic square electrode can effectively reduce the on-voltage and still maintain the rectifying property of the Schottky contact, but still has the bidirectional blocking capability.

[0020] 3. The composite of the Schottky electrode and the ohmic electrode reduces the on-resistance of the device, thereby reducing the power consumption.

[0021] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Fig. 1 is a structure schematic diagram of a GaN bidirectional blocking vertical power device based on a composite drain provided by an embodiment of the present application;

[0023] Figure 2 Fig. 2 is a structure schematic diagram of a composite drain provided by an embodiment of the present application;

[0024] Figure 3 Fig. 3 is a structure schematic diagram of another composite drain provided by an embodiment of the present application;

[0025] Figure 4 Fig. 4 is a comparison diagram of the forward output characteristic curves of a vertical power device based on a Schottky drain and a vertical power device based on a composite drain provided by an embodiment of the present application;

[0026] Figure 5 Fig. 5 is a structure schematic diagram of another GaN bidirectional blocking vertical power device based on a composite drain provided by an embodiment of the present application.

[0027] Reference Signs List:

[0028] 1 - Schottky drain; 2 - Ohmic drain; 3 - Substrate; 4 - Drift layer; 5 - Channel layer; 6 - Conductive layer; 7 - Gate dielectric; 8 - Source; 9 - Gate; 10 - Current blocking layer; 11 - Barrier layer. DETAILED DESCRIPTION

[0029] In order to further clarify the technical means and effects taken by the present application to achieve the predetermined object, a GaN bidirectional blocking vertical power device based on a composite drain according to the present application is described in detail below in combination with the drawings and specific embodiments.

[0030] The foregoing and other technical contents, features and effects of the present application can be clearly presented in the detailed description of the specific embodiments below in combination with the drawings. Through the description of the specific embodiments, the technical means and effects taken by the present application to achieve the predetermined object can be more deeply and specifically understood, however, the attached drawings are provided for reference and illustration only, and are not intended to limit the technical solutions of the present application.

[0031] It should be noted that in this document, relational terms such as first and second and the like can only be used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant are intended to cover non-exclusive inclusion, so that a product or device including a list of elements does not exclude other elements not explicitly listed. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the product or device including the element.

[0032] Embodiment One

[0033] The present embodiment provides a GaN bidirectional blocking vertical power device based on a composite drain, please refer to Figure 2 and Figure 3 The vertical power device includes a Schottky drain 1, a plurality of ohmic drains 2, a substrate 3, a drift layer 4, a channel layer 5, a conductive layer 6, a gate dielectric 7, a source 8 and a gate 9. The Schottky drain 1, the substrate 3, the drift layer 4, the channel layer 5, the conductive layer 6 and the gate dielectric 7 are arranged in order from bottom to top, the plurality of ohmic drains 2 are uniformly embedded inside the Schottky drain 1, and the upper surfaces of the plurality of ohmic drains 2 and the Schottky drain 1 are in contact with the lower surface of the substrate 3. The Schottky drain 1 adopts Schottky contact with the substrate 3; the plurality of ohmic drains 2 adopt ohmic contact with the substrate 3.

[0034] The source electrode 8 is arranged on both sides of the gate dielectric 7, and the upper surface of the source electrode 8 is flush with the upper surface of the gate dielectric 7 and extends downward to the inside of the channel layer 5. The middle part of the gate dielectric 7 is provided with a gate electrode 9, which extends downward to the upper surface of the drift layer 4 and is spaced apart from the drift layer 4, the channel layer 5 and the conductive layer 6 by the gate dielectric 7.

[0035] In the embodiment, as shown in Figure 2 , the ohmic drain electrode 2 has a long strip structure, and a plurality of the ohmic drain electrodes 2 are arranged in parallel inside the Schottky drain electrode 1 and extend from one side of the Schottky drain electrode 1 to the opposite side. The thickness of the plurality of ohmic drain electrodes 2 is less than the thickness of the Schottky drain electrode 1. In other embodiments, the ohmic drain electrode 2 can also have other suitable shapes, such as a cylindrical shape (as shown in Figure 3 ), a hexagonal shape, etc. It should be noted that it is necessary to maintain the Schottky drain electrode to ensure the depletion of carriers when a reverse voltage is applied.

[0036] Further, the substrate 3 of the embodiment is selected from one of sapphire, SiC, Si and GaN. The Schottky drain electrode 1 adopts a metal that can form a Schottky contact with the substrate 3, such as any one of the multilayer metals of Ni / Au, Ni / Au / Ni, Pt / Au, Ni / Pt / Au and W / Ti / Pt; and the ohmic drain electrode 2 adopts one of the multilayer metals of Ti / Al / Ni / Au, Ti / Al / Ti / Au, Ti / Al / Mo / Au or Ti / Al / Ti / TiN.

[0037] Preferably, the drift layer 4 is an n-GaN drift layer, the thickness is 0.02-30 μm, and the doping concentration is 1×10 15 ~1×10 18 cm -3 ; the channel layer 5 is a p + GaN channel layer, the doping concentration is 1×10 17 cm -3 ~5×10 20 cm -3 , and the thickness is 10-1000 nm; and the conductive layer 6 is an n + GaN conductive layer, the thickness is 10-1000 nm, and the doping concentration is 1×10 18 cm -3 ~1×10 20 cm -3 .

[0038] The available materials of the gate dielectric 7 include SiO2, SiN xHfO2, Al2O3 or TiO2, and the thickness is 0.002-0.2 μm. Further, the middle part of the gate dielectric 7 is formed with a T-shaped groove extending to the upper surface of the channel layer 5, and a layer of 0.002-0.2 μm of gate dielectric is arranged in the T-shaped groove, and a T-shaped gate 9 is formed on the gate dielectric in the T-shaped groove.

[0039] In the specific manufacturing process, first, a layer of 0.002-0.2 μm of gate dielectric 7 is grown on the conductive layer 6, and a T-shaped gate groove is etched in the middle part of the gate dielectric 7, which extends downward to the upper surface or inside of the drift layer 4, then, a layer of 0.002-0.02 μm of gate dielectric 7 is deposited in the gate groove, and finally, a T-shaped gate 9 is grown in the gate groove.

[0040] In this embodiment, the source 8 forms an ohmic contact with the channel layer 5, and the gate 9 forms a Schottky contact with the gate dielectric 7.

[0041] Specifically, the source 8 uses a multi-layer metal of Ti / Al / Ni / Au or Ti / Al / Pt / Au to form an ohmic contact with the channel layer 5, and the gate 9 uses a metal that can form a Schottky contact with the gate dielectric 7, such as a multi-layer metal of Ni / Au / Ni or Ni / Au or W / Au or Mo / Au.

[0042] In actual use, when the metal-semiconductor contact of the Schottky drain 1 is a Schottky contact, the energy band bends at the interface of the semiconductor to form a high potential region, i.e. a Schottky barrier. This embodiment is based on a vertical power device with a composite drain, and when a reverse voltage is applied to the drain, electrons must have energy higher than the barrier to overcome the barrier, which plays a role in reverse blocking. However, due to the existence of the barrier, the Schottky contact has a large interface resistance, and cannot be directly turned on in forward conduction, which has a turn-on voltage. In contrast, the ohmic contact has a small contact resistance, and therefore, the composite drain combining the Schottky drain and the ohmic drain can reduce the forward turn-on voltage.

[0043] See Figure 4 , Figure 4 The figure shows a comparison of the forward output characteristic curves of the vertical power device based on the Schottky drain and the vertical power device based on the composite drain of this embodiment, where the dashed line is the vertical power device based on the Schottky drain, and the solid line is the vertical power device based on the composite drain of this embodiment. From bottom to top, the gate voltages V G = 5, 6, 7, 8 V, it can be seen that the vertical power device based on the Schottky drain can be turned on at about 1 V, while the vertical power device based on the composite drain of this embodiment reduces the turn-on voltage to almost zero.

[0044] Further, as Figure 4As shown, when the gate voltage V G At 6V, the solid line represents the vertical power device based on the composite drain in this embodiment of the invention, and the on-resistance in the linear region can be estimated as R. on =4.5×10 4 Ω, the dashed line represents a vertical power device based on a Schottky drain, and the on-resistance in the linear region can be estimated as R. on =3.4×10 5 As can be seen from Ω, the composite drain structure in this embodiment of the invention effectively reduces the on-resistance, thereby reducing power consumption.

[0045] When the metal-semiconductor contact of a Schottky drain is a Schottky contact, band bending occurs at the semiconductor interface, forming a high-potential region, i.e., the Schottky barrier. This invention is based on a GaN bidirectional blocking vertical power device with a composite drain. When a reverse voltage is applied to the drain, electrons must have energy higher than the barrier to overcome it, thus achieving reverse blocking. This embodiment proposes a composite drain design for the GaN bidirectional blocking vertical power device, incorporating an ohmic square electrode. This effectively reduces the turn-on voltage while maintaining the rectification characteristics of the Schottky contact, while still possessing bidirectional blocking capability.

[0046] Example 2

[0047] Based on Example 1, this example provides another GaN bidirectional blocking vertical power device based on a composite drain, such as... Figure 5 As shown, the vertical power device includes a Schottky drain 1, multiple ohmic drains 2, a substrate 3, a drift layer 4, a channel layer 5, a barrier layer 11, a gate dielectric 7, a source 8, and a gate 9. The Schottky drain 1, substrate 3, drift layer 4, channel layer 5, barrier layer 11, and gate dielectric 7 are arranged sequentially from bottom to top. The multiple ohmic drains 2 are uniformly embedded inside the Schottky drain 1, and the upper surfaces of both the multiple ohmic drains 2 and the Schottky drain 1 are in contact with the lower surface of the substrate 3. The Schottky drain 1 and substrate 3 use a Schottky contact; the multiple ohmic drains 2 and substrate 3 all use ohmic contacts. The thickness of each of the multiple ohmic drains 2 is less than the thickness of the Schottky drain 1. The source 8 is disposed on both sides of the gate dielectric 7, and the upper surface of the source 8 is flush with the upper surface of the gate dielectric 7 and extends downward into the interior of the channel layer 5. A gate 9 is disposed in the middle of the gate dielectric 7. The gate 9 extends downward to the upper surface of the drift layer 4 and is separated from the drift layer 4, the channel layer 5 and the barrier layer 11 by the gate dielectric 7.

[0048] Furthermore, the device also includes a current blocking layer 10, thereby forming a current aperture vertical electron transistor (CAVET) structure. The current blocking layer 10 is disposed on the left and right sides of the upper surface of the drift layer 4, and the upper surface of the current blocking layer 10 is in contact with the lower surface of the conductive layer 6.

[0049] Preferably, the drift layer 4 is an n-GaN drift layer with a thickness of 0.02–30 μm and a doping concentration of 1 × 10⁻⁶. 15 ~1×10 18 cm -3 ; Channel layer 5 is p + GaN channel layer, doped at a concentration of 1×10⁻⁶ 17 cm -3 ~5×10 20 cm -3 The thickness of the barrier layer 11 is 10–1000 nm. The barrier layer 11 is made of AlGaN material with an Al content of 0.05–0.8% and a thickness of 10–200 nm. The barrier layer 11 and the channel layer 5 form an AlGaN / GaN structure, forming a two-dimensional electron gas for conductivity.

[0050] The function of the current blocking layer 10 is to suppress carrier transport in the non-gate covered region, causing current to accumulate in the aperture region. Preferably, the thickness of the current blocking layer 10 is 0.2 to 1 μm, symmetrically distributed on the left and right sides of the upper surface of the drift layer 4, and the material is p-type GaN.

[0051] In this embodiment, as Figure 2 As shown, the ohmic drain 2 has an elongated strip structure, and multiple ohmic drains 2 are arranged in parallel inside the Schottky drain 1 and extend from one side of the Schottky drain 1 to the opposite side. The thickness of each of the multiple ohmic drains 2 is less than the thickness of the Schottky drain 1. In other embodiments, the ohmic drain 2 can also be other suitable shapes, such as cylindrical, hexagonal, etc.

[0052] In the several embodiments provided by this invention, it should be understood that the apparatus and methods disclosed in this invention can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For example, the division of modules is merely a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed.

[0053] In addition, each function module in each embodiment of the present application can be integrated in one processing module, or each module can exist physically alone, or two or more modules can be integrated in one module. The integrated module can be realized in the form of hardware or in the form of hardware plus software function module.

[0054] The above is a further detailed description of the present application in combination with specific preferred embodiments, and the specific implementation of the present application should not be limited to these descriptions. For ordinary skilled persons in the technical field of the present application, some simple deductions or substitutions can be made without departing from the concept of the present application, and all of them should be regarded as falling within the protection scope of the present application.

Claims

1. A GaN bidirectional blocking vertical power device based on a composite drain, characterized in that, It includes a Schottky drain (1), multiple ohmic drains (2), a substrate (3), a drift layer (4), a channel layer (5), a conductive layer (6), a gate dielectric (7), a source (8), and a gate (9), wherein, The Schottky drain (1), the substrate (3), the drift layer (4), the channel layer (5), the conductive layer (6), and the gate dielectric (7) are arranged sequentially from bottom to top. The plurality of ohmic drains (2) are uniformly embedded inside the Schottky drain (1), and the upper surfaces of the plurality of ohmic drains (2) and the Schottky drain (1) are in contact with the lower surface of the substrate (3). The Schottky drain (1) and the substrate (3) are connected by a Schottky contact, and the plurality of ohmic drains (2) and the substrate (3) are connected by ohmic contacts. The source electrode (8) is disposed on both sides of the gate dielectric (7), and the lower surface of the source electrode (8) extends downward to the channel layer (5); the gate electrode (9) is disposed in the middle of the gate dielectric (7), and the gate electrode (9) extends downward to the drift layer (4) and is spaced apart from the drift layer (4), the channel layer (5) and the conductive layer (6) through the gate dielectric (7); The ohmic drain (2) has a long strip structure, and multiple ohmic drains (2) are arranged in parallel inside the Schottky drain (1) and extend from one side of the Schottky drain (1) to the opposite side; The GaN bidirectional blocking vertical power device further includes a current blocking layer (10), which is disposed on the left and right sides of the upper surface of the drift layer (4), and the upper surface of the current blocking layer (10) is in contact with the lower surface of the channel layer (5).

2. The GaN bidirectional blocking vertical power device based on a composite drain according to claim 1, characterized in that, The thickness of the ohmic drain (2) is less than the thickness of the Schottky drain (1).

3. The GaN bidirectional blocking vertical power device based on a composite drain according to claim 1, characterized in that, The source electrode (8) forms an ohmic contact with the channel layer (5).

4. The GaN bidirectional blocking vertical power device based on a composite drain according to claim 1, characterized in that, The drift layer (4) is n - GaN drift layer, with a doping concentration of 1×10⁻⁶ 15 ~5×10 18 cm -3 The channel layer (5) is p + GaN channel layer, doping concentration of 1×10 17 cm -3 ~5×10 20 cm -3 The conductive layer (6) is n + GaN conductive layer, with a doping concentration of 1×10⁻⁶ 18 cm -3 ~1×10 20 cm -3 .

5. The GaN bidirectional blocking vertical power device based on a composite drain according to claim 1, characterized in that, A T-shaped groove extending to the upper surface of the channel layer (5) is formed in the middle of the gate dielectric (7). A gate dielectric layer of 0.002 to 0.2 μm is disposed in the T-shaped groove, and a T-shaped gate (9) is formed on the gate dielectric of the T-shaped groove.

6. The GaN bidirectional blocking vertical power device based on a composite drain according to any one of claims 1 to 5, characterized in that, The thickness of the drift layer (4) is 0.02 to 30 μm, the thickness of the channel layer (5) is 10 to 1000 nm, and the thickness of the conductive layer (6) is 10 to 1000 nm.

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