A source field plate connected p-n junction junction field plate gan power device

Abstract

This invention relates to a P-N junction field plate GaN power device with a source field plate connection, belonging to the field of semiconductor device technology. From bottom to top, it includes a substrate, an AlN nucleation layer, a GaN buffer layer, a GaN channel layer, an AlN intercalation layer, and an AlGaN barrier layer. Source and drain electrodes are respectively disposed on both sides of the AlGaN barrier layer. A gate electrode is disposed above the AlGaN barrier layer. An N-type doped GaN cap layer is disposed between the gate and drain electrodes. A P-N junction field plate is disposed above the N-type doped GaN cap layer, with the source electrode extending beyond the source field plate. Under high drain voltage bias, the resulting gradient potential difference improves the channel electric field. The source field plate connects the source electrode and the P-N junction, creating a potential difference across the P-N junction. Optimizing the electric field distribution at the device channel can improve the device's breakdown voltage and significantly enhance the breakdown characteristics of HEMT devices.

Description

Technical Field

[0001] This invention relates to a GaN HEMT with a PN junction field plate for source field plate connection, belonging to the field of semiconductor device technology. Background Technology

[0002] GaN, as a third-generation semiconductor material, has the advantages of a large bandgap, high critical breakdown field strength, high electron saturation velocity, and high electron mobility. GaN-based power semiconductor devices are more likely to meet the requirements of power electronic systems for high efficiency and high frequency.

[0003] Currently, GaN devices are mainly lateral structures, with the most common form being the GaN high electron mobility transistor (HEMT). While GaN material itself has a theoretically high breakdown field strength, in practical applications, GaN HEMT devices in the off-state experience a high concentration of electric field near the gate edge (especially on the drain side) during high-voltage operation due to the gate edge electric field concentration effect. This leads to localized avalanche breakdown, severely limiting the device's breakdown voltage. Therefore, achieving high breakdown voltage in traditional GaN HEMT devices still faces many challenges.

[0004] To address this issue, researchers have proposed numerous techniques in recent years to further improve the breakdown voltage of devices. Among these, field plate technology is a commonly used technique to suppress the electric field concentration effect at the gate edge and improve the breakdown voltage of semiconductor devices. Typically, a metal field plate is used to modulate the electric field of the channel layer, such as a gate field plate or a source field plate. Although the metal field plate can effectively optimize the electric field peak at the gate edge, it also generates a new electric field at the edge of the field plate. Therefore, the breakdown voltage of GaN HEMT has not yet reached the theoretical limit of the material. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a GaN HEMT with a PN junction field plate connected to a source field plate. By employing a PN junction field plate, a gradient potential difference is formed under high drain voltage bias, thereby improving the channel electric field. Furthermore, the source field plate connects the source and the PN junction, creating a potential difference across the PN junction. Optimizing the electric field distribution at the device channel can improve the device's breakdown voltage and significantly enhance the breakdown characteristics of the HEMT device.

[0006] The technical solution of the present invention is as follows:

[0007] A GaN power device with a PN junction field plate connected to a source field plate includes, from bottom to top, a substrate, an AlN nucleation layer, a GaN buffer layer, a GaN channel layer, an AlN intercalation layer, and an AlGaN barrier layer. A source electrode and a drain electrode are respectively disposed on both sides of the AlGaN barrier layer above the GaN channel layer. A gate electrode is disposed above the AlGaN barrier layer near the source electrode. An N-type doped GaN cap layer is disposed above the AlGaN barrier layer between the gate electrode and the drain electrode. A PN junction field plate is disposed above the N-type doped GaN cap layer. The PN junction field plate is formed by horizontally arranged P-type doped AlGaN and N-type doped AlGaN on the same horizontal plane. A SiN passivation layer is disposed above the PN junction field plate, the AlGaN barrier layer, and the gate electrode. A source field plate extending from the source electrode is disposed above the passivation layer. The source field plate is connected to the upper left side of the P-type doped AlGaN, and the source field plate does not contact the drain electrode.

[0008] This invention features a lateral PN junction field plate composed of P-type AlGaN and N-type AlGaN above the device, and a source field plate connected to the PN junction to form a potential difference. The electric field is optimized by forming a field plate with a gradually varying potential through the lateral PN junction field plate.

[0009] The introduction of the lateral PN junction field plate weakens the peak electric field at the gate. As the drain voltage increases, the depletion region of two-dimensional electrons in the channel below the gate extends towards the drain, eventually reaching the drain electrode and causing breakdown. The P-type AlGaN above the barrier layer consumes the two-dimensional electron gas in the channel of the device's drift region (between the gate and drain), causing the depletion region to reach the drain prematurely. This invention forms a vertical PN junction structure by placing an N-type GaN cap layer below the lateral PN junction field plate composed of P-type AlGaN and N-type AlGaN. This suppresses the depletion effect of the P-type AlGaN's vertical electric field on the two-dimensional electron gas in the channel of the device's drift region (between the gate and drain), allowing the depletion region to withstand more lateral voltage when the drift region expands, thus improving the device's lateral breakdown voltage.

[0010] A vertical PN junction structure is formed between the N-type doped GaN cap layer and the P-type doped AlGaN. Thanks to the polarization effect between GaN and AlGaN, a potential well is formed, which enhances the ability to confine electrons and avoids the diffusion of the barrier layer of the N-type doped GaN cap layer.

[0011] Preferably, the substrate material is one of Si, SiC, and Al2O3; more preferably, it is a SiC substrate layer.

[0012] Preferably, the thickness of the AlN nucleation layer is 1~1000 nm.

[0013] Preferably, the thickness of the GaN buffer layer is 0.1~50μm.

[0014] Preferably, the thickness of the GaN channel layer is 1~1000nm.

[0015] Preferably, the thickness of the AlN intercalation layer is 0.2~10 nm.

[0016] Preferably, the Al mass percentage of the AlGaN barrier layer is 5% to 40%.

[0017] Preferably, the thickness of the AlGaN barrier layer is 5~50nm.

[0018] Preferably, the thickness of the N-type doped GaN cap layer is 0.1~1000nm.

[0019] Preferably, the thickness of the P-type doped AlGaN is 1~500 nm, the thickness of the N-type doped AlGaN is 1~500 nm, and the thickness of the P-type doped AlGaN is consistent with the thickness of the N-type doped AlGaN.

[0020] More preferably, the thicknesses of both the P-type doped AlGaN and the N-type doped AlGaN should be less than or equal to the thickness of the gate electrode.

[0021] Preferably, the sum of the lengths of the P-type doped AlGaN and the N-type doped AlGaN is consistent with the length of the N-type doped GaN cap layer.

[0022] Preferably, the length of the P-type doped AlGaN is 1~100 μm, and the length of the N-type doped AlGaN is 0.1~100 μm. The sum of the lengths of the P-type doped AlGaN and the N-type doped AlGaN is less than the distance between the gate electrode and the drain electrode. To avoid the gate electrode and the drain electrode being connected through the junction field plate, the distance between the gate electrode and the drain electrode in the device used in this invention is 13 μm, and the sum of the lengths of the P-type doped AlGaN and the N-type doped AlGaN should be less than 13 μm.

[0023] Preferably, the Al mass percentage of the P-type doped AlGaN and N-type doped AlGaN is 5% to 40%.

[0024] Preferably, the N-type doped GaN cap layer is made of Si doped with a concentration of 1×10⁻⁶. 16 ~5×10 18 cm -3 .

[0025] Preferably, the p-type doped AlGaN is Mg doped with a concentration of 1×10⁻⁶. 15 ~1×1018 cm -3 .

[0026] Preferably, the N-type doped AlGaN is Si-doped with a concentration of 1×10⁻⁶. 19 ~1×10 20 cm -3 .

[0027] Preferably, the passivation layer thickness is 0.1~10μm; this thickness is the thickness from the upper surface of the N-type doped GaN cap layer to the lower surface of the source field plate, and the passivation layer thickness is greater than the gate electrode thickness.

[0028] Preferably, the passivation layer material is SiO2 or Si3N4.

[0029] Preferably, the distance between the source electrode and the drain electrode is 20 μm, the distance from the source electrode to the gate electrode is 5 μm, the gate electrode length is 2 μm, the distance from the gate electrode to the drain electrode is 13 μm, and the length of the source field plate is 8~19 μm. For the source field plate to function effectively, it should be no less than 7 μm and no more than 20 μm.

[0030] Compared with the prior art, the present invention provides a GaNHEMT that uses a PN junction field plate connected by a source field plate to achieve a high breakdown voltage.

[0031] The beneficial effects of this invention are as follows:

[0032] 1. More uniform electric field distribution

[0033] Conventional source and gate field plates, while able to reduce the electric field peak at the gate edge, also create a new peak at the edge of the field plate.

[0034] This invention utilizes P-type AlGaN and N-type AlGaN to form a junction field plate on the surface of the device. When the device operates under high voltage, the junction field plate is in a reverse bias state, resulting in a uniformly distributed potential in the P-type AlGaN. Because the potential in the junction field plate is uniformly distributed from low to high, the formation of new electric field peaks in the drift region is avoided, and the electric field distribution in the channel layer is made more uniform.

[0035] This invention uses a source field plate to connect the source electrode to the PN junction field plate, forming a potential difference across the two ends of the junction field plate, while also optimizing the electric field in the channel region between the junction field plate and the gate electrode.

[0036] 2. Higher breakdown voltage

[0037] Compared to conventional GaN HEMT devices, this invention utilizes a PN junction field plate and a source field plate to optimize the lateral electric field distribution of the channel, preventing premature breakdown due to excessively high gate edge electric field peaks. Simultaneously, because a P-type AlGaN is grown vertically on the N-type GaN cap layer, a vertically oriented PN diode is formed between the AlGaN and GaN layers. This not only enhances the vertical breakdown voltage capability between the gate and drain but also suppresses the depletion of the two-dimensional electron gas in the channel (between the gate and drain) by the vertical electric field of the P-type AlGaN. This allows the depletion region to withstand more lateral voltage as the drift region expands. This improves the device's breakdown voltage and achieves a higher breakdown voltage.

[0038] 3. Higher reliability

[0039] This invention reduces local Joule heating during device operation by lowering the peak value of the local electric field, thus preventing the formation of hot spots. Furthermore, a uniform electric field distribution can delay lattice damage caused by localized high temperatures, improving the long-term reliability of the device. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the InGaN / GaN superlattice back barrier layer structure in an example of the present invention;

[0041] Figure 2 This is a schematic diagram illustrating the breakdown of a conventional GaNHEMT device and a source field plate connected to a junction field plate GaNHEMT device in an example of this invention.

[0042] Figure 3 This is a schematic diagram of the lateral electric field intensity distribution in the channel region at the breakdown moment of a conventional GaNHEMT device and a source field plate connected to a junction field plate GaNHEMT device in an example of the present invention.

[0043] Figure labels: 101, Substrate; 102, AlN nucleation layer; 103, GaN buffer layer; 104, GaN channel layer; 105, AlN intercalation layer; 106, AlGaN barrier layer; 107, N-type doped GaN cap layer; 108, Source electrode; 109, Drain electrode; 110, Gate electrode; 111, P-type doped AlGaN; 112, N-type doped AlGaN; 113, Passivation layer; 114, Source field plate. Detailed Implementation

[0044] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0045] Example 1

[0046] A GaN power device with a PN junction and a junction field plate connected to a source field plate, such as Figure 1As shown, from bottom to top, the structure includes a substrate (101), an AlN nucleation layer (102), a GaN buffer layer (103), a GaN channel layer (104), an AlN intercalation layer (105), and an AlGaN barrier layer (106). A source electrode (108) and a drain electrode (109) are respectively disposed on both sides of the AlGaN barrier layer above the GaN channel layer. A gate electrode (110) is disposed above the AlGaN barrier layer near the source electrode. An N-type doped GaN cap layer is disposed above the AlGaN barrier layer between the gate electrode and the drain electrode. 107) A PN junction field plate is provided above the N-type doped GaN cap layer. The PN junction field plate is formed by P-type doped AlGaN (111) and N-type doped AlGaN (112) arranged horizontally side by side on the same horizontal plane. A SiN passivation layer (113) is provided above the PN junction field plate, the AlGaN barrier layer and the gate electrode. A source field plate (114) extending from the source electrode is provided above the passivation layer. The source field plate is connected to the upper left of the P-type doped AlGaN (111). The source field plate does not contact the drain electrode.

[0047] This invention features a lateral PN junction field plate composed of P-type AlGaN and N-type AlGaN on top of the device, connected to the PN junction by a source field plate to form a potential difference. The introduction of the lateral PN junction field plate weakens the peak electric field at the gate, causing the depletion region of two-dimensional electrons in the channel below the gate to extend towards the drain as the drain voltage increases, eventually reaching the drain electrode and causing breakdown. The P-type AlGaN above the barrier layer consumes the two-dimensional electron gas in the channel of the device's drift region (between the gate and drain), causing the depletion region to reach the drain prematurely. This invention, by placing an N-type GaN cap layer below the lateral PN junction field plate composed of P-type and N-type AlGaN, forms a vertical PN junction structure. This suppresses the depletion effect of the P-type AlGaN's vertical electric field on the two-dimensional electron gas in the channel of the device's drift region (between the gate and drain), allowing the depletion region to withstand more lateral voltage as the drift region expands, thus improving the device's breakdown voltage.

[0048] A vertical PN junction structure is formed between the N-type doped GaN cap layer and the P-type doped AlGaN. Thanks to the polarization effect between GaN and AlGaN, a potential well is formed, which enhances the ability to confine electrons and avoids the diffusion of the barrier layer of the N-type doped GaN cap layer.

[0049] The substrate (101) is a SiC substrate layer. The AlN nucleation layer (102) has a thickness of 200 nm, the GaN buffer layer (103) has a thickness of 1 μm, the GaN channel layer (104) has a thickness of 200 nm, the AlN intercalation layer (105) has a thickness of 1 nm, the AlGaN barrier layer (106) has a thickness of 20 nm, the N-type doped GaN cap layer (107) has a thickness of 2 nm, the P-type doped AlGaN (111) has a thickness of 50 nm, and the N-type doped AlGaN (112) has a thickness of 50 nm. The thickness of both the P-type doped AlGaN and the N-type doped AlGaN should be less than the thickness of the gate electrode. The passivation layer (113) is made of SiO2 and has a thickness of 200 nm. This thickness is the distance from the upper surface of the N-type doped GaN cap layer (107) to the lower surface of the source field plate. The thickness of the passivation layer is greater than the thickness of the gate electrode.

[0050] The Al mass percentage of the Al in the AlGaN barrier layer (106) is 20%, and the Al mass percentage of the P-type doped AlGaN (111) and N-type doped AlGaN (112) is also 20%.

[0051] The N-type doped GaN cap layer (107) is made of Si doped at a concentration of 1×10⁻⁶. 18 cm -3 P-type doped AlGaN(111) is Mg doped at a concentration of 1×10⁻⁶. 16 cm -3 N-type doped AlGaN(112) is doped with Si at a concentration of 1×10⁻⁶. 19 cm -3 ,

[0052] The sum of the lengths of the P-type doped AlGaN (111) and the N-type doped AlGaN (112) is consistent with the length of the N-type doped GaN cap layer (107).

[0053] In this embodiment, the distance between the source and drain electrodes is 20 μm, the distance from the source electrode to the gate electrode is 5 μm, the gate electrode length is 2 μm, the distance from the gate electrode to the drain electrode is 13 μm, and the length of the source field plate is 8~19 μm. For the source field plate to function effectively, it should be no less than 7 μm but no more than 20 μm. The sum of the lengths of the P-type doped AlGaN (111) and the N-type doped AlGaN (112) should be less than 13 μm to avoid the gate electrode and drain electrode being connected through the junction field plate.

[0054] Example 2

[0055] A GaN power device with a PN junction and a junction field plate connected to a source field plate has the structure shown in Example 1, except that the substrate (101) material is Si; the AlN nucleation layer (102) has a thickness of 1. nm; the thickness of the GaN buffer layer (103) is 0.1 μm; the thickness of the GaN channel layer (104) is 1 nm; the thickness of the AlN intercalation layer (105) is 0.2 nm; the Al mass percentage of the AlGaN barrier layer (106) is 5%; the thickness of the AlGaN barrier layer (106) is 50 nm; the thickness of the N-type doped GaN cap layer (107) is 0.1 nm; the thickness of the P-type doped AlGaN (111) is 1 nm, and the thickness of the N-type doped AlGaN (112) is 1 nm; the Al mass percentage of the P-type doped AlGaN (111) and the N-type doped AlGaN (112) is 5%; the N-type doped GaN cap layer (107) is Si doped with a concentration of 5 × 10⁻⁶. 18 cm -3 P-type doped AlGaN(111) is Mg doped at a concentration of 1×10⁻⁶. 18 cm -3 N-type doped AlGaN(112) is made by Si doping at a concentration of 1×10⁻⁶. 20 cm -3 The passivation layer (113) is made of Si3N4 and has a thickness of 0.1 μm.

[0056] Example 3

[0057] A GaN power device with a PN junction and a junction field plate connected to a source field plate has the structure shown in Example 1, except that the substrate (101) material is Al2O3; the AlN nucleation layer (102) has a thickness of 1000 mm. nm; the thickness of the GaN buffer layer (103) is 50 μm; the thickness of the GaN channel layer (104) is 1000 nm; the thickness of the AlN intercalation layer (105) is 10 nm; the Al mass percentage of the AlGaN barrier layer (106) is 40%; the thickness of the AlGaN barrier layer (106) is 5 nm; the thickness of the N-type doped GaN cap layer (107) is 1000 nm; the thickness of the P-type doped AlGaN (111) is 500 nm, and the thickness of the N-type doped AlGaN (112) is 500 nm; the Al mass percentage of the P-type doped AlGaN (111) and the N-type doped AlGaN (112) is 40%; the N-type doped GaN cap layer (107) is Si doped with a concentration of 1×10⁻⁶. 16 cm -3 P-type doped AlGaN(111) is Mg doped at a concentration of 1×10⁻⁶. 15 cm -3N-type doped AlGaN(112) is made by Si doping at a concentration of 1×10⁻⁶. 19 cm -3 The passivation layer (113) has a thickness of 10 μm.

Claims

1. A GaN power device with a PN junction and a junction field plate connected to a source field plate, characterized in that, From bottom to top, the structure includes a substrate, an AlN nucleation layer, a GaN buffer layer, a GaN channel layer, an AlN intercalation layer, and an AlGaN barrier layer. A source electrode and a drain electrode are respectively disposed on both sides of the AlGaN barrier layer above the GaN channel layer. A gate electrode is disposed above the AlGaN barrier layer near the source electrode. An N-type doped GaN cap layer is disposed above the AlGaN barrier layer between the gate electrode and the drain electrode. A PN junction field plate is disposed above the N-type doped GaN cap layer. The PN junction field plate is formed by horizontally arranged P-type doped AlGaN and N-type doped AlGaN on the same horizontal plane. A passivation layer is disposed above the PN junction field plate, the AlGaN barrier layer, and the gate electrode. A source field plate extending from the source electrode is disposed above the passivation layer. The source field plate is connected to the upper leftmost side of the P-type doped AlGaN, and the source field plate does not contact the drain electrode.

2. The GaN power device with a PN junction and a junction field plate connected according to claim 1, characterized in that, The GaN power device with a PN junction connected to the source field plate includes one or more of the following schemes: I. The substrate material is one of Si, SiC, or Al2O3; II. The thickness of the AlN nucleation layer is 1~1000 nm; III. The thickness of the GaN buffer layer is 0.1~50μm; IV. The thickness of the GaN channel layer is 1~1000nm; V. The thickness of the AlN intercalation layer is 0.2~10 nm; VI. The thickness of the AlGaN barrier layer is 5~50nm; VII. The Al mass percentage of the AlGaN barrier layer is 5%~40%; VIII. The thickness of the N-type doped GaN cap layer is 0.1~1000nm; IX. The N-type doped GaN cap layer is made of Si doped at a concentration of 1×10⁻⁶. 16 ~5×10 18 cm -3 ; X. The passivation layer thickness is 0.1~10μm; this thickness is the distance from the upper surface of the N-type doped GaN cap layer to the lower surface of the source field plate, and the passivation layer thickness is greater than the gate electrode thickness. XI. The passivation layer material is SiO2 or Si3N4.

3. The GaN power device with a PN junction and junction field plate connected according to claim 2, characterized in that, The substrate is a SiC substrate layer.

4. The GaN power device with a PN junction and a junction field plate connected according to claim 1, characterized in that, The thickness of the P-type doped AlGaN is 1~500nm, the thickness of the N-type doped AlGaN is 1~500nm, and the thickness of the P-type doped AlGaN is consistent with the thickness of the N-type doped AlGaN.

5. The GaN power device with a PN junction and junction field plate connected according to claim 4, characterized in that, The thickness of both P-type doped AlGaN and N-type doped AlGaN is less than or equal to the thickness of the gate electrode.

6. The GaN power device with a PN junction and junction field plate connected according to claim 1, characterized in that, The sum of the lengths of P-type doped AlGaN and N-type doped AlGaN is consistent with the length of the cap layer of N-type doped GaN.

7. The GaN power device with a PN junction and a junction field plate connected according to claim 1, characterized in that, The length of the P-type doped AlGaN is 1~100μm, and the length of the N-type doped AlGaN is 0.1~100μm. The sum of the lengths of the P-type doped AlGaN and the N-type doped AlGaN is less than the distance between the gate electrode and the drain electrode.

8. The GaN power device with a PN junction and a junction field plate connected according to claim 1, characterized in that, The Al mass percentage of the P-type doped AlGaN and N-type doped AlGaN is 5% to 40%.

9. The GaN power device with a PN junction and a junction field plate connected according to claim 1, characterized in that, The p-type doped AlGaN is Mg doped at a concentration of 1×10⁻⁶. 15 ~1×10 18 cm -3 .

10. The GaN power device with a PN junction and junction field plate connected according to claim 1, characterized in that, The N-type doped AlGaN is Si-doped at a concentration of 1×10⁻⁶. 19 ~1×10 20 cm -3 .

Images