An RC-GaN HEMT device with integrated Schottky barrier diode

Abstract

The application belongs to the technical field of semiconductors, and particularly relates to an RC-GaN HEMT device integrated with a Schottky barrier diode. The application integrates a Schottky barrier diode on the basis of a conventional GaN HEMT. When the absolute value of a negative voltage applied to a drain increases to a value capable of overcoming the barrier of a Schottky metal of a source, the device starts to be reversely conducted. At this time, the current is continued to flow through the Schottky barrier diode below the AlGaN / GaN heterojunction channel, and the current is from an anode to a cathode through an AlGaN layer with an Al component change. The reverse conduction voltage of the device is not affected by the threshold voltage of a gate. When the absolute value of the negative voltage applied to the drain further increases to a certain degree, the 2DEG channel below the gate of the HEMT structure above the device is turned on, and the reverse conduction current of the device is further increased. When the device is forward blocked, the gate is zero-biased, and the P-GaN makes the 2DEG channel below the gate be depleted, so that the device is enhanced. The application enables the GaN HEMT device to have the function of reverse current continuation, and meanwhile, avoids the decline of the performance of the device caused by a parasitic effect.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, and in particular relates to an RC-GaNHEMT device with an integrated Schottky barrier diode. Background Technology

[0002] Gallium nitride (GaN) materials have attracted widespread attention due to their physical properties, such as high critical breakdown electric field, high electron mobility, high saturation velocity, and high two-dimensional electron gas (2DEG) concentration. Currently, GaN HEMTs are being applied in important fields such as fast charging, data centers, electric vehicles, and power transportation.

[0003] In power switching systems, switching devices often need to be used in conjunction with diodes to provide a freewheeling path for the circuit and reduce device losses. Si-based power MOSFETs are naturally reverse-conducting devices due to their parasitic body diode; however, GaN HEMTs lack a freewheeling body diode. Typically, a freewheeling diode is connected in parallel across the GaN switch to prevent breakdown or burnout of the switch due to induced electromotive force in the circuit. However, discrete freewheeling diodes not only increase system size and cost but also increase parasitic capacitance and inductance, leading to increased switching losses. To address these issues, the current mainstream improvement method is to integrate a Schottky diode in the gate-drain junction region of a traditional GaN HEMT device to achieve reverse conduction. However, the introduced Schottky metal electrode depletes the GaN HEMT channel, affecting the device's operating characteristics. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes an RC-GaN HEMT device integrating a Schottky barrier diode.

[0005] The technical solution of this invention is as follows:

[0006] An RC-GaN HEMT device integrating a Schottky barrier diode includes a substrate 01, a first buffer layer 02, an AlGaN layer 03, a second buffer layer 04, a GaN Channel layer 05, and an AlGaN Barrier layer 06 stacked sequentially from bottom to top along the vertical direction of the device; the GaN Channel layer 05 and the AlGaN Barrier layer 06 form a heterojunction, and a 2DEG is formed at the heterojunction interface; the device surface has a source structure, a gate structure, and a drain structure sequentially from left to right along the lateral direction;

[0007] The source structure is located at one end of the upper surface of the device, including a Schottky source structure and an Ohmic source structure formed by source Schottky metal 08 and source Ohmic metal 07, respectively. That is, source Schottky metal 08 and source Ohmic metal 07 jointly lead out the source. The source Schottky metal 08 is located at one end of the upper surface of the device, with its bottom contacting the top of the first buffer layer 02 and its side contacting the AlGaN layer 03. The source Ohmic metal 07 is located on the upper surface of the AlGaN Barrier layer 06, and is adjacent to but not in contact with the source Schottky metal 08 in the lateral direction of the device. The drain structure is located at the other end of the upper surface of the device, formed by drain Ohmic metal 09. The side of drain Ohmic metal 09 away from the source structure extends downwards along the vertical direction of the device to contact the top of the AlGaN layer 03, and the other side of drain Ohmic metal 09 is located on the upper surface of the AlGaN barrier layer 06. The upper surface of the barrier layer 06; the gate structure is located on the upper surface of the AlGaN barrier layer 06 between the source structure and the drain structure, and the gate structure includes a P-type GaN layer 10 and a gate metal 11 located on the upper surface of the P-type GaN layer 10;

[0008] The Al composition in the AlGaN layer O3 is varied to modulate the polarization effect and generate a high concentration of electrons.

[0009] Furthermore, the Al composition in the AlGaN layer 03 changes in such a way that the Al composition gradually increases from bottom to top along the vertical direction of the device (linear change or step change).

[0010] Furthermore, the substrate 01 is made of one of the following materials: Si, sapphire, SiC, and GaN.

[0011] Furthermore, the source ohmic metal 07 and drain ohmic metal 09 are made of any one of Ti / Al, Ni / Au / Ni, or Ti / Al / Ni / Au.

[0012] Furthermore, the contact between the gate metal 11 and the P-type GaN layer 10 is a Schottky contact or an ohmic contact, and the material used for the gate metal 11 is any one of Pt / Au, W / Au, and Ni / Au.

[0013] The GaN HEMT devices described above include, but are not limited to, p-GaN gate enhancement GaN HEMT devices and trench gate enhancement GaN HEMT devices.

[0014] The beneficial effects of this invention are as follows: by integrating a Schottky barrier diode (SBD) with an Al composition variation layer, the GaN HEMT device has the function of reverse freewheeling, while avoiding the degradation of device performance caused by parasitic effects. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the epitaxial structure of the device proposed in this invention.

[0016] Figure 2 This is a schematic diagram of the structure of the device proposed in this invention after etching out the P-GaN gate, Schottky source, Ohmic source and drain.

[0017] Figure 3 This is a schematic diagram of the GaN RC-HEMT device structure with Al composition variation SBD proposed in this invention.

[0018] Figure 4 The figure shown is an example of Al composition variation in an AlGaN layer with Al composition variation in this invention. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings.

[0020] This invention proposes a reverse-conducting GaN HEMT device integrating a Schottky barrier diode, such as... Figure 3 As shown, the device includes a substrate 01 stacked vertically from bottom to top, a buffer layer 102 above the substrate 01, an AlGaN layer 03 with Al composition variation above the buffer layer 102, a buffer layer 204 above the AlGaN layer 03 with Al composition variation, a GaN Channel layer 05 above the buffer layer 204, and an AlGaN Barrier layer 06 above the GaN Channel layer 05. The GaN Channel layer 05 and the AlGaN Barrier layer 06 form a heterojunction, and a 2DEG is formed at the heterojunction interface. The device surface is arranged horizontally from left to right as a Schottky source structure, an ohmic source structure, a gate structure, and a trench drain structure.

[0021] The gate structure includes a P-type GaN layer 10 above the AlGaN barrier layer 06 and a gate metal 11 above the P-type GaN layer 10; the trench drain structure includes a drain ohmic metal 09 above the AlGaN layer 03 with Al composition variation and extending above the AlGaN barrier layer 06, the side of the drain ohmic metal 09 being in contact with the buffer layer 204 and the GaNChannel layer 05; the ohmic source structure is composed of a source ohmic metal 07 above the AlGaN barrier layer 06; the Schottky source structure is composed of a source Schottky metal 08 above the buffer layer 102, and the side of the source Schottky metal 08 being in contact with the AlGaN layer 03 with Al composition variation.

[0022] The working principle of the reverse-conducting GaN HEMT with integrated Schottky barrier diode proposed in this invention is as follows:

[0023] In traditional GaN HEMT devices, with zero gate bias and a negative drain voltage, as Vgd increases beyond the positive V... GS(th) A two-dimensional electron gas channel is formed under the gate, and the device conducts in reverse. However, the reverse conduction voltage drop is large at this time, which will result in a large dead zone power consumption. Figure 3 This is a schematic diagram of the structure of the present invention. This structure integrates a Schottky barrier diode on the basis of a traditional GaN HEMT. A negative voltage is applied to the drain. When the absolute value of the negative voltage applied to the drain increases to overcome the Schottky metal barrier at the source, the device begins reverse conduction. At this time, current flows through the Schottky barrier diode below the AlGaN / GaN heterojunction channel, and the current flows from the anode through the AlGaN layer with Al composition variation to the cathode. The reverse conduction voltage of the device is not affected by the gate threshold voltage. When the absolute value of the negative voltage applied to the drain further increases to a certain extent, the 2DEG channel under the gate of the HEMT structure above the device opens, further increasing the reverse conduction current of the device. During forward blocking, the gate is zero biased, and the P-GaN depletes the 2DEG channel below the gate, achieving enhancement mode. During forward conduction, a forward voltage is applied to the gate and drain, and the integrated Schottky barrier diode is in a reverse blocking state. Current flows from the drain through the 2DEG channel at the AlGaN / GaN heterojunction to the ohmic source.

[0024] In this invention, AlGaN layer 03 is an AlGaN material with varying Al composition, wherein the Al composition increases from bottom to top, and the variation range of Al composition includes, but is not limited to, 0-1. Figure 4 The variations shown can be in various ranges. The Al composition of the AlGaN layer can vary in forms including, but not limited to, linear variations and step variations.

Claims

1. An RC-GaN HEMT device integrating a Schottky barrier diode, comprising a substrate (01), a first buffer layer (02), an AlGaN layer (03), a second buffer layer (04), a GaN Channel layer (05), and an AlGaN Barrier layer (06) stacked sequentially from bottom to top along the vertical direction of the device; the GaN Channel layer (05) and the AlGaN Barrier layer (06) form a heterojunction, and a 2DEG is formed at the heterojunction interface; the device surface has a source structure, a gate structure, and a drain structure sequentially from left to right along the lateral direction; Its features are, The source structure is located at one end of the upper surface of the device, including a Schottky source structure and an Ohm source structure formed by source Schottky metal (08) and source Ohm metal (07), respectively. The source Schottky metal (08) is located at one end of the upper surface of the device, with its bottom contacting the top of the first buffer layer (02) and its side contacting the AlGaN layer (03). The source Ohm metal (07) is located on the upper surface of the AlGaN Barrier layer (06), and the source Ohm metal (07) and source Schottky metal (08) are adjacent to but not in contact with each other in the lateral direction of the device. The drain structure is located at the other end of the upper surface of the device and is formed by drain Ohm metal (09). The side of the drain Ohm metal (09) away from the source structure extends downward along the vertical direction of the device to contact the top of the AlGaN layer (03), and the other side of the drain Ohm metal (09) is located on the upper surface of the AlGaN Barrier layer (06). The upper surface of the barrier layer (06); the gate structure is located on the upper surface of the AlGaN barrier layer (06) between the source structure and the drain structure, and the gate structure includes a P-type GaN layer (10) and a gate metal (11) located on the upper surface of the P-type GaN layer (10). The Al composition in the AlGaN layer (03) is varied to adjust the polarization effect and generate a high concentration of electrons. The Al composition in the AlGaN layer (03) varies in that the Al composition gradually increases from bottom to top along the vertical direction of the device.

2. The RC-GaN HEMT device with integrated Schottky barrier diode according to claim 1, characterized in that, The substrate (01) is made of one of the following materials: Si, sapphire, SiC, and GaN.

3. The RC-GaN HEMT device with integrated Schottky barrier diode according to claim 1, characterized in that, The source ohmic metal (07) and drain ohmic metal (09) are made of any one of Ti / Al, Ni / Au / Ni, or Ti / Al / Ni / Au.

4. The RC-GaN HEMT device with integrated Schottky barrier diode according to claim 1, characterized in that, The contact between the gate metal (11) and the P-type GaN layer (10) is a Schottky contact or an ohmic contact, and the material used for the gate metal (11) is any one of Pt / Au, W / Au, or Ni / Au.

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