P-N junction field plate GaN power device connected with source field plate

Abstract

The invention relates to a source field plate connected P-N junction field plate GaN power device, and belongs to the technical field of semiconductor devices, the source field plate connected P-N junction field plate GaN power device comprises a substrate, an AlN nucleating layer, a GaN buffer layer, a GaN channel layer, an AlN intercalation layer and an AlGaN barrier layer in sequence from bottom to top, two sides of the AlGaN barrier layer are respectively provided with a source electrode and a drain electrode, a gate electrode is arranged above the AlGaN barrier layer, and the source field plate connected P-N junction field plate GaN power device is arranged above the AlGaN barrier layer. An N-type doped GaN cap layer is arranged between the gate electrode and the drain electrode, a P-N junction field plate is arranged above the N-type doped GaN cap layer, the source electrode extends out of the source field plate, a gradient potential difference is formed when high drain electrode voltage is biased, so that a channel electric field is improved, the source electrode is connected with a P-N junction by means of source field plate connection, and the P-N junction field plate is connected with the source electrode. And a potential difference is formed at two ends of the P-N junction. The electric field distribution at the channel of the device is optimized, the breakdown voltage of the device can be improved, and the breakdown characteristic of the HEMT device is powerfully improved.

Description

Technical Field

[0001] The invention relates to a PN junction field plate GaN HEMT connected with a source field plate, belonging to the technical field of semiconductor devices. Background Art

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

[0003] Currently, GaN devices primarily utilize lateral structures, most commonly in the form of GaN high electron mobility transistors (HEMTs). While the theoretical breakdown field strength of GaN material itself is very high, in practical applications, when operating at high voltage in the off state, the electric field concentration effect at the gate edge causes the electric field to become highly concentrated near the gate edge (especially on the drain side), leading to localized avalanche breakdown and severely limiting the device's withstand voltage. Consequently, achieving high breakdown voltages in conventional GaN HEMTs remains challenging.

[0004] To address this issue, researchers have proposed numerous technologies in recent years to further improve device breakdown voltage. Field plate technology is a commonly used technique for suppressing the electric field concentration effect at the gate edge and increasing the breakdown voltage of semiconductor devices. Metal field plates, such as gate and source field plates, are typically used to modulate the channel layer electric field. While metal field plates can effectively optimize the electric field peak at the gate edge, they also generate a new electric field at the edge of the field plate. As a result, the breakdown voltage of GaN HEMTs has not yet reached the theoretical limit of the material. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention provides a GaN HEMT with a source field plate connected to a PN junction field plate. The PN junction field plate, when biased with a high drain voltage, creates a gradient potential difference that improves the channel electric field. Furthermore, the source field plate connects the source electrode to the PN junction, creating a potential difference across the PN junction. This optimizes the electric field distribution in the device channel, increasing the device's breakdown voltage and significantly improving the HEMT's breakdown characteristics.

[0006] The technical solutions of the present invention are as follows: A PN junction field plate GaN power device connected with a source field plate comprises, 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 arranged on both sides of the AlGaN barrier layer above the GaN channel layer; a gate electrode is arranged above the AlGaN barrier layer close to the source electrode; an N-type doped GaN cap layer is arranged above the AlGaN barrier layer between the gate electrode and the drain electrode; a PN junction field plate is arranged above the N-type doped GaN cap layer; the PN junction field plate is formed by P-type doped AlGaN and N-type doped AlGaN arranged side by side laterally in the same horizontal plane; a SiN passivation layer is arranged above the PN junction field plate, the AlGaN barrier layer and the gate electrode; a source field plate extending from the source electrode is arranged above the passivation layer; the source field plate is connected to the upper leftmost portion of the P-type doped AlGaN layer, and the source field plate does not contact the drain electrode.

[0007] The present invention sets a lateral PN junction field plate composed of P-type AlGaN and N-type AlGaN above the device, and uses a source field plate connected to the PN junction to form a potential difference. The lateral PN junction field plate forms a field plate with a gradient potential to optimize the electric field.

[0008] Due to the introduction of the lateral PN junction field plate, the peak gate electric field is weakened. The depletion region of two-dimensional electrons in the channel below the gate expands toward the drain as the drain voltage increases, eventually reaching the drain electrode and causing breakdown at the drain. The P-type AlGaN above the barrier layer consumes the two-dimensional electron gas in the device's drift region (between the gate and drain), causing the depletion region to reach the drain prematurely. The present invention forms a vertical PN junction structure by placing an N-type GaN cap layer beneath the lateral PN junction field plate composed of P-type AlGaN and N-type AlGaN. This suppresses the vertical electric field of the P-type AlGaN from depleting the two-dimensional electron gas in the device's drift region (between the gate and drain). This allows the depletion region to withstand more lateral voltage as the drift region expands, thereby improving the device's lateral withstand voltage capability.

[0009] 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.

[0010] Preferably, the substrate material is one of Si, SiC, and Al2O3; more preferably, it is a SiC substrate layer.

[0011] Preferably, the thickness of the AlN nucleation layer is 1-1000 nm.

[0012] Preferably, the thickness of the GaN buffer layer is 0.1-50 μm.

[0013] Preferably, the thickness of the GaN channel layer is 1-1000 nm.

[0014] Preferably, the thickness of the AlN intercalation layer is 0.2-10 nm.

[0015] Preferably, the Al mass percentage of the AlGaN barrier layer is 5% to 40%.

[0016] Preferably, the thickness of the AlGaN barrier layer is 5-50 nm.

[0017] Preferably, the thickness of the N-type doped GaN cap layer is 0.1 to 1000 nm.

[0018] Preferably, the thickness of the P-type doped AlGaN is 1-500 nm, and 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.

[0019] Further preferably, the thickness 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.

[0020] 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.

[0021] Preferably, the length of the P-type doped AlGaN is 1 to 100 μm, the length of the N-type doped AlGaN is 0.1 to 100 μm, and 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 and drain electrodes. To avoid connection between the gate and drain electrodes via the junction field plate, the distance between the gate and drain electrodes of the device used in the present 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.

[0022] Preferably, the mass percentage of Al in the P-type doped AlGaN and the N-type doped AlGaN is 5% to 40%.

[0023] Preferably, the N-type doped GaN cap layer is doped with Si at a concentration of 1×10 16 ~5×10 18 cm -3 .

[0024] Preferably, the P-type doped AlGaN is doped with Mg at a concentration of 1×10 15 ~1×1018 cm -3 .

[0025] Preferably, the N-type doped AlGaN is doped with Si at a concentration of 1×10 19 ~1×10 20 cm -3 .

[0026] Preferably, the passivation layer has a thickness of 0.1-10 μm; the 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 thickness of the passivation layer is greater than the thickness of the gate electrode.

[0027] Preferably, the passivation layer material is SiO2 or Si3N4.

[0028] Preferably, the spacing 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 source field plate length is 8-19 μm. To be effective, the source field plate should be no less than 7 μm but no more than 20 μm.

[0029] Compared with the prior art, the present invention provides a GaN HEMT that uses a PN junction field plate connected to a source field plate to achieve a high breakdown voltage.

[0030] The beneficial effects of the present invention are: 1. More uniform electric field distribution Conventional technologies such as source field plates and gate field plates can weaken the electric field peak at the gate edge, but they will also form a new peak at the edge of the field plate.

[0031] The present invention uses P-type AlGaN and N-type AlGaN to form a junction field plate on the device surface. When the device is operating at high voltage, the junction field plate is in a reverse bias state, resulting in a uniformly distributed electric potential in the P-type AlGaN. Because the potential in the junction field plate is evenly 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 more uniform.

[0032] The present invention uses a source field plate to connect the source electrode to the PN junction field plate, forming a potential difference at both ends of the junction field plate, and can optimize the electric field in the channel region between the junction field plate and the gate electrode.

[0033] 2. Higher breakdown voltage Compared to conventional GaN HEMT devices, this invention utilizes a PN junction field plate and a source field plate, optimizing the lateral electric field distribution in the channel and preventing premature breakdown caused by excessively high electric field peaks at the gate edge. Furthermore, due to the vertical growth of P-type AlGaN on the N-type GaN cap layer, a vertical PN diode is formed between the AlGaN and GaN. This not only enhances the device's vertical voltage withstand capability between the gate and drain, but also suppresses the depletion of the two-dimensional electron gas in the device's drift region (between the gate and drain) by the vertical electric field caused by the P-type AlGaN. This allows the depletion region to withstand greater lateral voltage as the drift region expands. This improves the device's voltage withstand capability and achieves a higher breakdown voltage.

[0034] 3. Higher reliability The present invention reduces local Joule heating during device operation by lowering the local electric field peak, thus avoiding the formation of hot spots. Furthermore, the uniform electric field distribution can delay lattice damage to the material caused by local high temperatures, thereby improving the long-term reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the InGaN / GaN superlattice back barrier layer structure in an example of the present invention; Figure 2 Schematic diagram of the breakdown of a conventional GaN HEMT device and a source field plate connected to a junction field plate GaN HEMT device in an example of the present invention; Figure 3 Schematic diagram of the electric field intensity distribution in the lateral direction of the channel region at the breakdown moment of the conventional GaN HEMT device and the source field plate connected to the junction field plate GaN HEMT device in an example of the present invention; Figure symbols: 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 DESCRIPTION

[0036] The present invention will be further described below with reference to embodiments and accompanying drawings, but is not limited thereto.

[0037] Example 1

[0038] A PN junction field plate GaN power device with a source field plate connection, such as Figure 1As shown, it includes, from bottom to top, 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), wherein a source electrode (108) and a drain electrode (109) are respectively provided on both sides of the AlGaN barrier layer above the GaN channel layer, a gate electrode (110) is provided above the AlGaN barrier layer close to the source electrode, and an N-type doped GaN cap layer ( 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 side by side in 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 leftmost side of the P-type doped AlGaN (111), and the source field plate is not in contact with the drain electrode.

[0039] The present invention places a lateral PN junction field plate composed of P-type AlGaN and N-type AlGaN above the device, and uses a source field plate connected to the PN junction to create a potential difference. The introduction of the lateral PN junction field plate weakens the peak gate electric field, allowing the depletion region of two-dimensional electrons in the channel below the gate to expand toward the drain as the drain voltage increases, eventually reaching the drain electrode and causing breakdown at the drain. The P-type AlGaN above the barrier layer depletes the two-dimensional electron gas (2DEG) in the device's drift region (between the gate and drain), causing the depletion region to reach the drain prematurely. The present 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 vertical electric field of the P-type AlGaN from depleting the 2DEG in the device's drift region (between the gate and drain). This allows the depletion region to withstand more lateral voltage as the drift region expands, improving the device's withstand voltage capability.

[0040] 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.

[0041] 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, which is the thickness 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.

[0042] The AlGaN barrier layer (106) has an Al mass percentage of 20%, the P-type doped AlGaN (111) and the N-type doped AlGaN (112) have an Al mass percentage of 20%, The N-type doped GaN cap layer (107) is doped with Si at a concentration of 1×10 18 cm -3 , P-type doped AlGaN (111) is doped with Mg at a concentration of 1×10 16 cm -3 , N-type doped AlGaN (112) is doped with Si at a concentration of 1×10 19 cm -3 , 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).

[0043] In this embodiment, the spacing 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 source field plate length is 8 to 19 μm. To be effective, the source field plate 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 prevent the gate electrode and the drain electrode from being connected through the junction field plate.

[0044] Example 2

[0045] A PN junction field plate GaN power device connected to a source field plate has a structure as shown in Example 1, except that the substrate (101) is made of Si; the thickness of the AlN nucleation layer (102) is 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 doped with Si at a concentration of 5×10 18 cm -3 ; P-type doped AlGaN (111) is doped with Mg at a concentration of 1×10 18 cm -3 ; N-type doped AlGaN (112) is doped with Si at a concentration of 1×10 20 cm -3 The material of the passivation layer (113) is Si3N4; the thickness of the passivation layer (113) is 0.1 μm.

[0046] Example 3

[0047] A PN junction field plate GaN power device connected to a source field plate has a structure as shown in Example 1, except that the substrate (101) is made of Al2O3; the thickness of the AlN nucleation layer (102) is 1000 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 doped with Si at a concentration of 1×10 16 cm -3 ; P-type doped AlGaN (111) is doped with Mg at a concentration of 1×10 15 cm -3; N-type doped AlGaN (112) is doped with Si at a concentration of 1×10 19 cm -3 ; The thickness of the passivation layer (113) is 10 μm.

Claims

1. A PN junction field plate GaN power device connected to a source field plate, characterized in that: 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. A source electrode and a drain electrode are respectively arranged on both sides of the AlGaN barrier layer above the GaN channel layer. A gate electrode is arranged above the AlGaN barrier layer close to the source electrode. An N-type doped GaN cap layer is arranged above the AlGaN barrier layer between the gate electrode and the drain electrode. A PN junction field plate is arranged above the N-type doped GaN cap layer. The PN junction field plate is formed by P-type doped AlGaN and N-type doped AlGaN arranged side by side in the same horizontal plane. A passivation layer is arranged above the PN junction field plate, the AlGaN barrier layer and the gate electrode. A source field plate extending from the source electrode is arranged above the passivation layer. The source field plate is connected to the upper leftmost part of the P-type doped AlGaN, and the source field plate does not contact the drain electrode.

2. The PN junction field plate GaN power device with source field plate connection according to claim 1, characterized in that: The PN junction field plate GaN power device connected to the source field plate includes one or more of the following solutions: Ⅰ. The substrate material is one of Si, SiC, and 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% to 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 doped with Si at a concentration of 1×10 16 ~5×10 18 cm -3 ; X. The passivation layer has a thickness of 0.1 to 10 μm; 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 thickness of the passivation layer is greater than the thickness of the gate electrode; Ⅺ. The passivation layer material is SiO2 or Si3N4.

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

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

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

6. The PN junction field plate GaN power device with source field plate connection according to claim 1, characterized in that: 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.

7. The PN junction field plate GaN power device with source field plate connection according to claim 1, characterized in that: The length of the P-type doped AlGaN is 1-100 μm, the length of the N-type doped AlGaN is 0.1-100 μm, and 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 PN junction field plate GaN power device with source field plate connection according to claim 1, characterized in that: The Al mass percentage of the P-type doped AlGaN and the N-type doped AlGaN is 5% to 40%.

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

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

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