An Enhancement-Type Multi-Barrier GaN HEMT Device Based on Electric Field Control of p-AlGaN Buried Layer

Abstract

This invention relates to an enhancement-mode multi-barrier GaN HEMT device based on electric field modulation of a p-AlGaN buried layer, belonging to the field of semiconductor power device technology. This device aims to solve the problems of current collapse effect and low breakdown voltage caused by uneven electric field distribution in the blocking state, which are inherent in traditional GaN HEMTs. The technical solution involves embedding a p-AlGaN buried layer below the source in the buffer layer to form a PN junction with the buffer layer to modulate the electric field. Simultaneously, the traditional uniform barrier layer is replaced with a multi-barrier layer structure with a stepped Al composition. This invention can effectively suppress current collapse, make the electric field distribution more uniform, thereby significantly improving the breakdown voltage, while maintaining good normally-off characteristics and output capability.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor power device technology and relates to an enhancement-mode multi-barrier GaN HEMT device based on the electric field modulation of p-AlGaN buried layer. Background Technology

[0002] Enhancement-mode gallium nitride (GaN) high electron mobility transistors (HEMTs), as power devices with normally-off characteristics, have shown great application potential in the field of power electronics. Compared with traditional depletion-mode devices, HEMTs are in a closed state when there is no gate voltage, which can significantly improve system safety and simplify circuit design. These devices operate using a two-dimensional electron gas (2DEG) formed by an aluminum gallium nitride / gallium nitride heterojunction, which has the advantages of high charge density and high mobility.

[0003] However, traditional gallium nitride (GaN) HEMT devices still face many challenges in practical applications. The first is the current collapse effect, primarily stemming from the high-density surface states generated by polarization discontinuities at the interface between the aluminum gallium nitride (AlGaN) barrier layer and gallium nitride (GaN). Under high-speed switching or high-voltage operating conditions, these surface states trap electrons, depleting the two-dimensional electron gas and causing a sharp increase in the device's on-resistance, thus affecting its stability and efficiency.

[0004] Secondly, uneven electric field distribution is also a key factor limiting device performance. In the blocking state, the electric field tends to concentrate at the gate edge, easily generating excessively high electric field peaks. This localized strong electric field not only induces leakage current but also causes the device to break down prematurely, limiting the improvement of the device's breakdown voltage.

[0005] To overcome these shortcomings, existing research attempts to improve electric field distribution and suppress trapping effects by optimizing the epitaxial layer structure. Therefore, developing a novel enhancement-mode gallium nitride device structure that can effectively reduce current collapse and improve breakdown voltage is of great significance for promoting the development of high-frequency, high-power-density power adapters and automotive electronics. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide an enhanced multi-barrier GaN HEMT device based on the electric field modulation of p-AlGaN buried layer.

[0007] To achieve the above objectives, the present invention provides the following technical solution: An enhancement-mode multi-barrier GaN HEMT device based on electric field modulation of a p-AlGaN buried layer includes: Substrate layer 11; Buffer layer 10 is located on the upper surface of the substrate layer 11; The p-AlGaN buried layer 9 is embedded in the buffer layer 10, and the p-AlGaN buried layer 9 is in contact with the lower surface of the source electrode 6; GaN channel layer 8 is located on the upper surface of buffer layer 10; A gradient multi-barrier layer 5 is located on the upper surface of the GaN channel layer 8. The gradient multi-barrier layer 5 adopts a three-layer AlGaN structure with a stepped gradient of Al composition. p-GaN cap layer 4 is located on the upper surface of the gradient multi-barrier layer 5; Gate 1 is located on the upper surface of the p-GaN cap layer 4; The source electrode 6 is located on the left side of the device and is in contact with the GaN channel layer 8 and the gradient multi-barrier layer 5. Drain 7 is located on the right side of the device and is in contact with the GaN channel layer 8 and the gradient multi-barrier layer 5. The first passivation layer 2 and the second passivation layer 3 are located on the upper surface of the gradient multi-barrier layer 5 on both sides of the gate 1, respectively.

[0008] Furthermore, the gradient multi-barrier layer 5 is divided into a first barrier layer, a second barrier layer, and a third barrier layer from top to bottom, and the thickness of the first barrier layer, the second barrier layer, and the third barrier layer is 0.005 mm. .

[0009] Furthermore, the Al composition in the first barrier layer is 0.35, the Al composition in the second barrier layer is 0.25, and the Al composition in the third barrier layer is 0.15.

[0010] Furthermore, the first, second, and third barrier layers are all doped with n-type arsenic impurities, and their doping concentrations are all 1.0 × 10⁻⁶. 18 cm -3 .

[0011] Furthermore, the p-GaN cap layer 4 is doped with p-type boron (B) impurity at a concentration of 3.0 × 10⁻⁶. 17 cm -3 .

[0012] Furthermore, the length of the p-AlGaN buried layer 9 is 10. Its material is AlGaN, in which the molar composition of Al is 0.05.

[0013] Furthermore, the p-AlGaN buried layer 9 is doped with p-type impurity Mg, and the doping concentration is 1.0 × 10⁻⁶. 19 cm -3 .

[0014] Furthermore, the buffer layer 10 is made of AlGaN, wherein the molar composition of Al is 0.05, and the buffer layer 10 is doped with n-type impurity arsenic As, with a doping concentration of 1.0 × 10⁻⁶. 14 cm -3 .

[0015] Furthermore, the GaN channel layer 8 is doped with n-type arsenic (As) impurity at a concentration of 1.0 × 10⁻⁶. 15 cm -3 .

[0016] Furthermore, the p-AlGaN buried layer 9 and the buffer layer 10 form a PN junction, which is used to adjust the electric field distribution of the buffer layer 10 and the GaN channel layer 8 when the device is in a blocking state.

[0017] The beneficial effects of this invention are as follows: (1) This invention replaces the traditional uniform barrier layer with a three-layer barrier layer with a graded Al composition. In a uniform barrier layer, the polarization discontinuity at the heterojunction interface leads to high-density surface states trapping electrons, causing current collapse. By designing the graded Al composition, the polarization charge is continuously distributed rather than concentrated and abruptly distributed, reducing the peak polarization charge density at the interface and lowering the surface trap concentration. At the same time, the multi-barrier structure generates new quantum potential wells due to the band discontinuity, which additionally increases the conduction channel and improves the carrier concentration, effectively suppressing current collapse.

[0018] (2) A PN junction is formed by introducing a p-AlGaN buried layer below the source and an n-type AlGaN buffer layer. When the device is in a blocking state (high voltage bias), this structure can effectively regulate the electric field distribution in the buffer layer and the channel. It reduces the original electric field peak at the gate edge and introduces a new electric field spike at the interface between the p-type buried layer and the buffer layer, making the overall electric field distribution more uniform. Simulation results show that this structure increases the breakdown voltage of the device from 500V in the traditional structure to 720V, an increase of approximately 44%.

[0019] (3) While achieving a high breakdown voltage, the device maintains a turn-on voltage of about 1.1V and a stable saturation output current (about 0.3 A / mm), ensuring the normally-off characteristics and driving capability of the enhanced device.

[0020] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the structure of the p-AlGaN buried layer enhancement-type multi-barrier GaN HEMT device proposed in this invention; Figure 2 The output characteristic curves of the p-AlGaN buried layer enhancement-type multi-barrier GaN HEMT device are shown as Id-Vd curves. Figure 3 The transfer characteristic curves, Id-Vg curves, of the p-AlGaN buried layer enhancement-type multi-barrier GaN HEMT device are shown. Figure 4 The transconductance characteristic curves, Gm curves, of p-AlGaN buried layer enhanced multi-barrier GaN HEMT devices; Figure 5 The breakdown characteristic curves, BV curves, of a p-AlGaN buried layer enhancement-type multi-barrier GaN HEMT device; Figure 6 The electron concentration distribution of a p-AlGaN buried layer enhancement-type multi-barrier GaN HEMT device under different drain-source voltages is shown. Figure 7 This is a graph showing the electron concentration distribution of a p-AlGaN buried layer enhancement-type multi-barrier GaN HEMT device under different gate voltages.

[0022] Figure reference numerals: 1: Gate, 2: First passivation layer, 3: Second passivation layer, 4: p-GaN cap layer, 5: Gradient multi-barrier layer, 6: Source, 7: Drain, 8: GaN channel layer, 9: p-AlGaN buried layer, 10: Buffer layer, 11: Substrate layer. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0024] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0025] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0026] Example 1 This embodiment details the specific structure and parameter configuration of an enhancement-mode multi-barrier GaN HEMT device based on p-AlGaN buried layer electric field modulation. (Refer to...) Figure 1 The device is built on substrate 11.

[0027] A buffer layer 10 is grown on the upper surface of the substrate layer 11. The buffer layer 10 is made of AlGaN with an Al composition molar fraction of 0.05 and is doped with n-type arsenic impurity, with the doping concentration controlled at 1.0 × 10⁻⁶. 14 cm -3 A p-AlGaN buried layer 9 is embedded in the buffer layer 10, located directly below the source 6 and in direct contact with its lower surface. The length of the p-AlGaN buried layer 9 is set to 10. The material is also AlGaN with an Al molar fraction of 0.05, but it is doped with p-type magnesium impurity at a concentration of 1.0 × 10¹¹. 19 cm -3 This design allows the p-AlGaN buried layer 9 and the n-type buffer layer 10 to form a PN junction structure below the source.

[0028] A GaN channel layer 8 is provided above the buffer layer 10, which is doped with n-type arsenic impurity at a concentration of 1.0 × 10⁻⁶. 15 cm -3 The upper surface of the GaN channel layer 8 is in contact with the graded multi-barrier layer 5. The graded multi-barrier layer 5 consists of three AlGaN layers with different Al compositions, each with a thickness of 0.005 μm. From top to bottom, the Al compositions of these three barrier layers are 0.35, 0.25, and 0.15, respectively, and all are doped with a concentration of 1.0 × 10⁻⁶. 18 cm -3 n-type impurity arsenic.

[0029] The gate region of the device is located in the middle and consists of a bottom p-GaN cap layer 4 and a top gate layer 1. The p-GaN cap layer 4 is formed by doping with a concentration of 3.0 × 10⁻⁶. 17 cm -3 The p-type boron impurity depletes the electrons in the lower channel, ensuring the device is in the off state at zero gate voltage. A first passivation layer 2 and a second passivation layer 3 are respectively provided on both sides of the gate 1 to protect the surface of the barrier layer. A source 6 is located on the left side of the device, and a drain 7 is located on the right side. Both the source 6 and drain 7 are in lateral contact with the GaN channel layer 8 and the graded multi-barrier layer 5.

[0030] Example 2 This embodiment illustrates the working process and physical characteristics of the above-mentioned device in the on-state, with a focus on referring to... Figure 2 , Figure 3 , Figure 4 and Figure 6 .

[0031] When the device needs to switch from the off state to the on state, a forward bias voltage is applied to gate 1. According to... Figure 3 The transfer characteristic curve shows that when the gate-source voltage exceeds the turn-on voltage of about 1.1V, the depletion effect of the p-GaN cap layer 4 on the channel is overcome, and electrons begin to accumulate in the GaN channel layer 8.

[0032] Once in the conduction state, the graded multi-barrier layer 5 begins to play a crucial role. Due to the three-layer graded composition design within the barrier layer, the band discontinuity between different Al compositions creates additional quantum potential wells, thus adding two extra conduction paths beyond the conventional channel. Combined with... Figure 6 The electron concentration distribution diagram shows that when the gate voltage Vg is equal to 5V and the drain voltage Vd is equal to 20V, the electron concentration below gate 1 is significantly increased, forming a high-density two-dimensional electron gas.

[0033] During current transport, the gradient multi-barrier layer 5 ensures a continuous spatial distribution of polarization charges rather than abrupt changes at a single interface, effectively reducing the probability of electron capture by surface states. (Refer to...) Figure 2 The output characteristic curves show that the saturated output current of the device reaches about 0.3 A / mm, and the Id-Vd curves exhibit good stability, proving the structure's ability to suppress current collapse effect. Figure 4 The transconductance characteristic curves shown further confirm that the device has good charge control capability and linearity during the conduction phase.

[0034] Example 3 This embodiment illustrates the electric field control process of the device in the off-state, with a focus on... Figure 5 .

[0035] When the gate voltage is lower than the turn-on voltage and a high voltage is applied to the drain 7, the device enters the blocking state. At this time, the PN junction formed by the p-AlGaN buried layer 9 embedded in the buffer layer 10 and the buffer layer begins to intervene in electric field modulation.

[0036] In conventional structures, high voltage can lead to severe electric field concentration at the edge of gate 1, easily inducing premature breakdown. However, in the structure of this invention, the presence of the p-AlGaN buried layer 9 alters the potential distribution. As the drain-source voltage increases, the depletion region extends towards the depth of the buffer layer and the drain direction. The p-AlGaN buried layer 9 introduces a new electric field spike at its interface with the buffer layer 10. This spike, along with the existing gate edge electric field peak, shares the voltage drop, resulting in a more uniform overall electric field distribution.

[0037] Reference Figure 5 The breakdown characteristic curve shows that, thanks to this electric field modulation mechanism, the breakdown voltage of the device is significantly increased from 500V in the traditional structure to 720V, an improvement of approximately 44%. This process confirms that introducing a p-type buried layer to modulate the electric field distribution of the buffer layer and channel is an effective way to improve the breakdown voltage capability of gallium nitride power devices.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An enhancement-mode multi-barrier GaN HEMT device based on electric field modulation of a p-AlGaN buried layer, characterized in that: include: Substrate (11); A buffer layer (10) is located on the upper surface of the substrate layer (11); The p-AlGaN buried layer (9) is embedded in the buffer layer (10), and the p-AlGaN buried layer (9) is in contact with the lower surface of the source (6); GaN channel layer (8) is located on the upper surface of the buffer layer (10); A gradient multi-barrier layer (5) is located on the upper surface of the GaN channel layer (8). The gradient multi-barrier layer (5) adopts a three-layer AlGaN structure with a stepped gradient of Al composition. p-GaN cap layer (4) is located on the upper surface of the gradient multi-barrier layer (5); The gate (1) is located on the upper surface of the p-GaN cap layer (4); The source electrode (6) is located on the left side of the device and is in contact with the GaN channel layer (8) and the gradient multi-barrier layer (5); The drain (7) is located on the right side of the device and is in contact with the GaN channel layer (8) and the gradient multi-barrier layer (5); The first passivation layer (2) and the second passivation layer (3) are located on the upper surface of the gradient multi-barrier layer (5) on both sides of the gate (1).

2. The enhancement-mode multi-barrier GaN HEMT device based on p-AlGaN buried layer electric field modulation according to claim 1, characterized in that: The gradient multi-barrier layer (5) is divided into a first barrier layer, a second barrier layer, and a third barrier layer from top to bottom, and the thickness of the first barrier layer, the second barrier layer, and the third barrier layer is 0.005 mm. .

3. The enhancement-mode multi-barrier GaN HEMT device based on p-AlGaN buried layer electric field modulation according to claim 2, characterized in that: The Al composition in the first barrier layer is 0.35, the Al composition in the second barrier layer is 0.25, and the Al composition in the third barrier layer is 0.

15.

4. The enhancement-mode multi-barrier GaN HEMT device based on p-AlGaN buried layer electric field modulation according to claim 2, characterized in that: The first, second, and third barrier layers are all doped with n-type arsenic impurities, and their doping concentrations are all 1.0 × 10⁻⁶. 18 cm -3 .

5. The enhancement-mode multi-barrier GaN HEMT device based on p-AlGaN buried layer electric field modulation according to claim 1, characterized in that: The p-GaN cap layer (4) is doped with p-type boron (B) impurity, with a doping concentration of 3.0 × 10⁻⁶. 17 cm -3 .

6. The enhancement-mode multi-barrier GaN HEMT device based on p-AlGaN buried layer electric field modulation according to claim 1, characterized in that: The length of the p-AlGaN buried layer (9) is 10. Its material is AlGaN, in which the molar composition of Al is 0.

05.

7. The enhancement-mode multi-barrier GaN HEMT device based on p-AlGaN buried layer electric field modulation according to claim 6, characterized in that: The p-AlGaN buried layer (9) is doped with p-type impurity Mg, and the doping concentration is 1.0 × 10⁻⁶. 19 cm -3 .

8. The enhancement-mode multi-barrier GaN HEMT device based on p-AlGaN buried layer electric field modulation according to claim 1, characterized in that: The buffer layer (10) is made of AlGaN, with an Al molar composition of 0.05, and is doped with n-type arsenic impurity As at a concentration of 1.0 × 10⁻⁶. 14 cm -3 .

9. The enhancement-mode multi-barrier GaN HEMT device based on p-AlGaN buried layer electric field modulation according to claim 1, characterized in that: The GaN channel layer (8) is doped with n-type arsenic (As) impurity at a concentration of 1.0 × 10⁻⁶. 15 cm -3 .

10. The enhancement-mode multi-barrier GaN HEMT device based on p-AlGaN buried layer electric field modulation according to claim 1, characterized in that: The p-AlGaN buried layer (9) and the buffer layer (10) form a PN junction, which is used to adjust the electric field distribution of the buffer layer (10) and the GaN channel layer (8) when the device is in a blocking state.

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