GaN HEMT vertical devices with integrated diodes having reverse freewheeling capability

Abstract

The application belongs to the technical field of power semiconductors, and relates to a GaN HEMT longitudinal device with an integrated diode having reverse freewheeling capability. The high-concentration two-dimensional electron gas concentration between the current sinking layer, the heavily doped GaN or AlGaN barrier layer and the GaN channel layer changes the traditional lateral withstand voltage mechanism by the distance between the gate and the drain, and simultaneously integrates the current sinking layer and the N + The freewheeling diode composed of the GaN layer provides a current flow path when the GaN device is reversed. The structure can reduce the cell width, improve the integration, effectively solve the current generated by the excessive di / dt and dv / dt when the GaN device is applied to the high-frequency case, provide a discharge channel for the GaN device, and increase the anti-di / dt and dv / dt capability of the GaN device.

Description

Technical Field

[0001] This invention belongs to the field of power semiconductor technology, and specifically relates to a GaN HEMT vertical device with an integrated diode having reverse freewheeling capability. Background Technology

[0002] Gallium nitride (GaN) is a wide-bandgap semiconductor material with a bandgap of 3.4 eV. Compared with traditional semiconductor materials such as silicon (Si) and gallium arsenide (GaAs), it possesses higher critical electric field, electron saturation drift velocity, and good chemical stability. AlGaN / GaN heterojunction high electron mobility transistor (HEMT) structures based on GaN material exhibit electron mobilities exceeding 1800 cm⁻¹. 2 / vs and the surface density of two-dimensional electron gas (2-DEG) is 10 13 cm -2 This gives GaN-based devices significant advantages in both radio frequency and power electronics fields.

[0003] Traditional GaN HEMT devices consistently face the challenge that the breakdown voltage (BV) is proportional to the gate-to-drain spacing, necessitating a larger lateral area to increase the voltage and leading to decreased integration density. Furthermore, lateral devices are severely affected by surface transverse well states and high electric fields, causing reliability issues such as current collapse. Since GaN itself lacks a body diode, a diode must be connected in parallel in the application circuit, increasing losses and reducing efficiency. Moreover, the high-frequency application characteristics of GaN devices mean that overshoot currents due to excessively fast switching speeds can only be stored in the gate inductor, increasing the risk of oscillation. Integrating a freewheeling diode provides GaN devices with a current discharge path, resulting in higher resistance to di / dt and dv / dt. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a GaN HEMT device with an integrated diode having reverse freewheeling capability. By using a current sink layer (Sinker layer), a high concentration of electrons from the two-dimensional electron gas region is introduced into the bulk region, optimizing the surface electric field distribution. Simultaneously, a reverse freewheeling diode is integrated, reducing system power consumption and manufacturing costs.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A GaN HEMT vertical device with an integrated diode having reverse freewheeling capability includes an AlN nucleation layer 1, a heavily doped AlGaN or GaN buffer layer 2 on the nucleation layer 1, a lightly doped GaN channel layer 3 on the heavily doped AlGaN or GaN buffer layer 2, and an AlGaN barrier layer 4 on the lightly doped GaN channel layer 3.

[0007] It also includes a GaN current deposition layer 8 located on the sides of the AlN nucleation layer 1, the heavily doped AlGaN or GaN buffer layer 2, the lightly doped GaN channel layer 3, and the AlGaN barrier layer 4, and an N-type current deposition layer 8 located above the GaN current deposition layer 8. + A heavily doped GaN layer 12, a P-type doped Si substrate 10 located below the GaN current sink layer 8, and a metallized source 11 located below the P-type doped Si substrate 10.

[0008] It also includes a Mg-doped P-GaN capping layer 6 on the AlGaN barrier layer 4; a Schottky contact gate 5 on the Mg-doped P-GaN capping layer 6; a metallized drain 7 to the right of the Schottky contact gate 5; a Si3N4 passivation layer 9 between the Schottky contact gate 5 and the metallized drain 7 and above the AlGaN barrier layer 4; and an N-type passivation layer above the Si3N4 passivation layer 9. + A doped GaN layer 12; the metallized drain 7 and the lightly doped GaN channel layer 3 form an ohmic contact;

[0009] When the gate-source voltage exceeds the threshold voltage, the two-dimensional electron gas in the channel is turned on. When the drain-source voltage exceeds 0, the metallized drain 7, the lightly doped GaN channel layer 3, the GaN current deposition layer 8, and the metallized source 11 can achieve forward conduction of the semiconductor device. + The doped GaN layer 12 can form a PN junction that can achieve reverse freewheeling when the current is reversed. This is achieved by integrating a freewheeling diode into the PN junction composed of the GaN current sink layer 8 between the metallized source 11 and the metallized drain 7 and the N+ doped GaN layer 12.

[0010] The present invention also provides a second GaN HEMT vertical device with an integrated diode having reverse freewheeling capability, comprising an AlN nucleation layer 1, a heavily doped AlGaN or GaN buffer layer 2 on the nucleation layer 1, a lightly doped GaN channel layer 3 on the heavily doped AlGaN or GaN buffer layer 2, and an AlGaN barrier layer 4 on the lightly doped GaN channel layer 3.

[0011] It also includes a GaN current deposition layer 8 located on the sides of the AlN nucleation layer 1, the heavily doped AlGaN or GaN buffer layer 2, and the lightly doped GaN channel layer 3, and N on the GaN current deposition layer 8. + A doped GaN layer 12, a P-type doped Si substrate 10 located under the AlN nucleation layer 1, and a metallized source 11 located under the P-type doped Si substrate 10.

[0012] It also includes two Mg-doped P-GaN capping layers 6 located on the AlGaN barrier layer 4; a Schottky contact gate 5 located on the Mg-doped P-GaN capping layer 6; a metallized drain 7 located to the right of the Schottky contact gate 5; a Si3N4 passivation layer 9 located between the Schottky contact gate 5 and the metallized drain 7 and above the AlGaN barrier layer 4; the metallized drain 7 extends to the right side of the device, covering the Si3N4 passivation layer 9, and is connected to the N + The doped GaN layer 12 forms an ohmic contact; the metallized drain 7 and the lightly doped GaN channel layer 3 form an ohmic contact;

[0013] The metallized drain 7, lightly doped GaN channel layer 3, GaN current sink layer 8, and metallized source 11 enable forward conduction of the semiconductor device. This is achieved by integrating a freewheeling diode into a PN junction formed by the GaN current sink layer 8 and the N+ doped GaN layer 12 between the metallized source 11 and the metallized drain 7.

[0014] As a preferred method, the light doping concentration is 10. 15 -10 16 cm -3 The two-dimensional electron gas concentration region is on the order of magnitude of 4 nm-5 nm in the GaN channel layer, and the heavy doping concentration is on the order of 10 nm. 18 -10 19 cm -3 .

[0015] As a preferred embodiment, the p-type doped Si substrate 10 can be replaced with a SiC substrate, a GaN substrate, or a sapphire substrate.

[0016] As a preferred embodiment, the semiconductor is GaN.

[0017] The beneficial effects of this invention are: the GaN current deposition layer 8,N of this invention + The doped GaN layer 12, barrier layer 4, and lightly doped GaN channel layer 3 utilize a high concentration of two-dimensional electron gas to convert the current into a vertical direction through the current sinking layer (Sinker layer), optimizing the surface electric field distribution. Simultaneously, it integrates the GaN current sinking layer (Sinker layer) 8 and N... +The freewheeling diode, composed of a doped GaN layer 12, provides a current flow path for the GaN device in reverse. This structure reduces system area and cost, effectively addressing the problem of excessive current generated by excessive di / dt and dv / dt in GaN devices used at high frequencies. The freewheeling diode provides a discharge path, increasing the GaN device's resistance to di / dt and dv / dt. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the cross-sectional structure of an existing GaN HEMT device.

[0019] Figure 2 This is a schematic diagram of the GaN HEMT vertical device structure with reverse freewheeling capability of an integrated diode according to Embodiment 1 of the present invention.

[0020] Figure 3 This is a schematic diagram of the GaN HEMT device circuit structure provided in Embodiment 1 of the present invention;

[0021] Figures 4-12 This is a schematic diagram of the process implemented in Embodiment 1 of the present invention;

[0022] Figure 13 This is a schematic diagram of the GaN HEMT vertical device structure with reverse freewheeling capability of the integrated diode in Embodiment 2 of the present invention.

[0023] The attached diagram lists the components represented by each number as follows:

[0024] Wherein, 1 is the AlN nucleation layer, 2 is the heavily doped AlGaN or GaN buffer layer, 3 is the lightly doped GaN channel layer, 4 is the AlGaN barrier layer, 5 is the Schottky contact gate, 6 is the Mg-doped P-GaN capping layer, 7 is the metallized drain, 8 is the GaN current deposition layer, 9 is the Si3N4 passivation layer, 10 is the P-type doped Si substrate, 11 is the metallized source, and 12 is the N-type passivation layer. + Doped GaN layer. Detailed Implementation

[0025] To make the content and principles of the present invention clearer, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] like Figure 2 As shown, this embodiment provides a GaN HEMT vertical device with an integrated diode having reverse freewheeling capability, including an AlN nucleation layer 1, a heavily doped AlGaN or GaN buffer layer 2 on the nucleation layer 1, a lightly doped GaN channel layer 3 on the heavily doped AlGaN or GaN buffer layer 2, and an AlGaN barrier layer 4 on the lightly doped GaN channel layer 3.

[0029] It also includes a GaN current deposition layer 8 located on the sides of the AlN nucleation layer 1, the heavily doped AlGaN or GaN buffer layer 2, the lightly doped GaN channel layer 3, and the AlGaN barrier layer 4, and an N-type current deposition layer 8 located above the GaN current deposition layer 8. + A heavily doped GaN layer 12, a P-type doped Si substrate 10 located below the GaN current sink layer 8, and a metallized source 11 located below the P-type doped Si substrate 10.

[0030] It also includes a Mg-doped P-GaN capping layer 6 on the AlGaN barrier layer 4; a Schottky contact gate 5 on the Mg-doped P-GaN capping layer 6; a metallized drain 7 to the right of the Schottky contact gate 5; a Si3N4 passivation layer 9 between the Schottky contact gate 5 and the metallized drain 7 and above the AlGaN barrier layer 4; and an N-type passivation layer above the Si3N4 passivation layer 9. + A doped GaN layer 12; the metallized drain 7 and the lightly doped GaN channel layer 3 form an ohmic contact;

[0031] When the gate-source voltage exceeds the threshold voltage, the two-dimensional electron gas in the channel is turned on. When the drain-source voltage exceeds 0, the metallized drain 7, the lightly doped GaN channel layer 3, the GaN current deposition layer 8, and the metallized source 11 can achieve forward conduction of the semiconductor device. + The doped GaN layer 12 can form a PN junction, which can achieve reverse freewheeling when the direction of the current is reversed.

[0032] Lightly doped with a doping concentration of 10 15 -10 16 cm -3 The electron gas concentration is on the order of magnitude, with a two-dimensional electron gas concentration region of 4 nm-5 nm in the GaN channel layer. Heavily doped concentrations are in the range of 10⁻⁶. 18 -10 19 cm

[0033] The p-type doped Si substrate 10 is replaced with a SiC substrate, or a GaN substrate, or a sapphire substrate.

[0034] This embodiment also provides a method for fabricating a GaN HEMT vertical device with an integrated diode having reverse freewheeling capability, see [link to documentation]. Figures 4-12 :

[0035] Step 1: Grow a GaN HEMT heterojunction structure on the substrate, from bottom to top: substrate, nucleation layer, buffer layer, channel layer, and barrier layer.

[0036] Specifically, the growth methods used in the above steps include MOCVD, MBE, and HVPE.

[0037] Step 2: As Figure 5 As shown, the above structure is etched to form a GaN current deposition layer (Sinker layer).

[0038] Step 3: As Figure 6 As shown, etching is performed on the above-mentioned material to form a shape as shown. Figure 6 structure.

[0039] Specifically, the etching methods used in the above steps include ICP (inductively coupled plasma etching) and PEC (photochemical etching).

[0040] Step 4: Deposit the above structure, and then etch away the excess portion to form a structure like... Figure 8 The structure shown.

[0041] Step 5: Etch the above structure, etching the left and right sides respectively, to form the P-type GaN layer and metal deposition as shown. Figures 9-10 The structure shown.

[0042] Step 6: Grow a GaN layer on top of the above structure. For example... Figure 11 As shown

[0043] Step 7: Perform back metal deposition to form the metal source. For example... Figure 12 As shown

[0044] by Figure 2 Taking the GaN HEMT device with vertically integrated freewheeling diode as an example, the working principle of the present invention is explained as follows:

[0045] When the device is forward-biased, a positive voltage is applied to the gate, along with a forward voltage greater than the threshold voltage, causing a two-dimensional electron gas to form in the channel. The current flows from the metallized drain 7, through the region of the two-dimensional electron gas formed by the lightly doped GaN channel layer 3 and the AlGaN barrier layer 4, through the GaN current sink layer (Sinker layer) 8, and towards the metallized source 11. This process transforms the traditional lateral structure of the GaN HEMT device into a vertical structure, optimizing the surface electric field distribution.

[0046] When the device is reverse-following current, the gate is turned off, and the barrier layer below the p-GaN capping layer rises, making the conduction band higher than the Fermi level. The two-dimensional electron gas is turned off, and at this time, the GaN current sink layer (Sinker layer) and N... + The freewheeling diode composed of a doped GaN layer 12 provides a discharge path for the high di / dt and dv / dt generated during the energy release process from parasitic capacitance and inductance in high-frequency applications. Simultaneously, it eliminates the need for an additional parallel reverse-biased freewheeling diode in dual-pulse circuits, improving system efficiency and reducing losses.

[0047] When the device withstands reverse voltage, the main difference from the conventional GaN HEMT device's withstand voltage mechanism lies in the introduction of an additional leakage channel in this invention. This bypasses the two-dimensional electron gas region, significantly reducing leakage current and improving withstand voltage. MOCVD growth is performed on the Si substrate using a (1 1 1) crystal plane, while paying attention to the doping of the buffer layer. The withstand voltage is then related to the Si substrate, the thickness of the AlN nucleation layer 1, and the thickness of the heavily doped AlGaN or GaN buffer layer 2, i.e., the distance between the metallized drain 7 and the metallized source 11.

[0048] Example 2

[0049] like Figure 13 As shown, this embodiment provides a GaN HEMT vertical device with an integrated diode having reverse freewheeling capability, including an AlN nucleation layer 1, a heavily doped AlGaN or GaN buffer layer 2 on the nucleation layer 1, a lightly doped GaN channel layer 3 on the heavily doped AlGaN or GaN buffer layer 2, and an AlGaN barrier layer 4 on the lightly doped GaN channel layer 3.

[0050] It also includes a GaN current deposition layer 8 located on the sides of the AlN nucleation layer 1, the heavily doped AlGaN or GaN buffer layer 2, and the lightly doped GaN channel layer 3, and N on the GaN current deposition layer 8. + A doped GaN layer 12, a P-type doped Si substrate 10 located under the AlN nucleation layer 1, and a metallized source 11 located under the P-type doped Si substrate 10.

[0051] It also includes two Mg-doped P-GaN capping layers 6 located on the AlGaN barrier layer 4; a Schottky contact gate 5 located on the Mg-doped P-GaN capping layer 6; a metallized drain 7 located to the right of the Schottky contact gate 5; a Si3N4 passivation layer 9 located between the Schottky contact gate 5 and the metallized drain 7 and above the AlGaN barrier layer 4; the metallized drain 7 extends to the right side of the device, covering the Si3N4 passivation layer 9, and is connected to the N + The doped GaN layer 12 forms an ohmic contact; the metallized drain 7 and the lightly doped GaN channel layer 3 form an ohmic contact;

[0052] The metallized drain 7, lightly doped GaN channel layer 3, GaN current deposition layer 8, and metallized source 11 enable forward conduction of the semiconductor device.

[0053] Lightly doped with a doping concentration of 10 15 -10 16 cm -3 The two-dimensional electron gas concentration region is on the order of magnitude, with a concentration of 4 nm-5 nm in the GaN channel layer, and the heavy doping concentration is on the order of 10 nm. 18 -10 19 cm -3 .

[0054] The p-type doped Si substrate 10 is replaced with a SiC substrate, or a GaN substrate, or a sapphire substrate.

[0055] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A GaN HEMT vertical device with an integrated diode having reverse freewheeling capability, comprising an AlN nucleation layer (1), a heavily doped AlGaN or GaN buffer layer (2) on the nucleation layer (1), a lightly doped GaN channel layer (3) on the heavily doped AlGaN or GaN buffer layer (2), and an AlGaN barrier layer (4) on the lightly doped GaN channel layer (3); It also includes a GaN current deposition layer (8) located on the sides of the AlN nucleation layer (1), the heavily doped AlGaN or GaN buffer layer (2), the lightly doped GaN channel layer (3), and the AlGaN barrier layer (4), and an N-type current deposition layer (8) located above the GaN current deposition layer (8). + A heavily doped GaN layer (12), a P-type doped Si substrate (10) located below the current sink layer (8) of the GaN, and a metallized source (11) located below the P-type doped Si substrate (10). It also includes a Mg-doped P-GaN capping layer (6) on the AlGaN barrier layer (4); a Schottky contact gate (5) on the Mg-doped P-GaN capping layer (6); a metallized drain (7) to the right of the Schottky contact gate (5); a Si3N4 passivation layer (9) between the Schottky contact gate (5) and the metallized drain (7) and above the AlGaN barrier layer (4); and an N-type passivation layer (9) above the Si3N4 passivation layer (9). + A doped GaN layer (12); the metallized drain (7) and the lightly doped GaN channel layer (3) form an ohmic contact; Its features are: When the gate-source voltage is greater than the threshold voltage, the two-dimensional electron gas in the channel is turned on. When the drain-source voltage is greater than 0, the metallized drain (7), the lightly doped GaN channel layer (3), the GaN current sink layer (8), and the metallized source (11) can realize the forward conduction of the semiconductor device. The GaN current sink layer (8) between the metallized source (11) and the metallized drain (7) and the N+ doped GaN layer (12) form a PN junction, thereby realizing a freewheeling diode.

2. A GaN HEMT vertical device with an integrated diode having reverse freewheeling capability, comprising an AlN nucleation layer (1), a heavily doped AlGaN or GaN buffer layer (2) on the nucleation layer (1), a lightly doped GaN channel layer (3) on the heavily doped AlGaN or GaN buffer layer (2), and an AlGaN barrier layer (4) on the lightly doped GaN channel layer (3); It also includes a GaN current deposition layer (8) located on the side of the AlN nucleation layer (1), the heavily doped AlGaN or GaN buffer layer (2), and the lightly doped GaN channel layer (3), and N on the GaN current deposition layer (8). + A doped GaN layer (12), a P-type doped Si substrate (10) located under the AlN nucleation layer (1), and a metallized source (11) located under the P-type doped Si substrate (10). It also includes two Mg-doped P-GaN capping layers (6) on the AlGaN barrier layer (4); a Schottky contact gate (5) on the Mg-doped P-GaN capping layer (6); a metallized drain (7) to the right of the Schottky contact gate (5); a Si3N4 passivation layer (9) between the Schottky contact gate (5) and the metallized drain (7) and above the AlGaN barrier layer (4); the metallized drain (7) extends over the Si3N4 passivation layer (9) to the right side of the device and is connected to the N + The doped GaN layer (12) forms an ohmic contact; the metallized drain (7) and the lightly doped GaN channel layer (3) form an ohmic contact; Its features are: The metallized drain (7), lightly doped GaN channel layer (3), GaN current sink layer (8), and metallized source (11) enable forward conduction of the semiconductor device. The GaN current sink layer (8) between the metallized source (11) and the metallized drain (7) and the N+ doped GaN layer (12) form a PN junction, thereby realizing a freewheeling diode.

3. A GaN HEMT vertical device with an integrated diode having reverse freewheeling capability according to claim 1 or 2, characterized in that: Lightly doped with a doping concentration of 10 15 -10 16 cm -3 The two-dimensional electron gas concentration region is on the order of magnitude, with a concentration of 4 nm-5 nm in the GaN channel layer, and the heavy doping concentration is on the order of 10 nm. 18 -10 19 cm -3 .

4. A GaN HEMT vertical device with an integrated diode having reverse freewheeling capability according to claim 1 or 2, characterized in that: The P-type doped Si substrate (10) is replaced with a SiC substrate, or a GaN substrate, or a sapphire substrate.

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