GaN-based power device with patterned island p-type buried layer electric field modulation structure

Abstract

The application belongs to the technical field of semiconductors, and provides a GaN-based power device with a patterned island-shaped p-type buried layer electric field regulating structure, to solve the problems of uneven electric field distribution and obvious local electric field peak in the off state of the existing GaN-based power device. The application introduces an electric field regulating structure composed of a GaN epitaxial layer and a p-type buried layer into the buffer layer, and patterns the p-type buried layer into a p-type island-shaped structure distributed at intervals, so that the p-type buried layer is discretely distributed in the buffer layer. On the one hand, the p-type island-shaped structure can provide a three-dimensional nucleation and lateral combination morphology basis for subsequent epitaxy, which helps to release epitaxial stress and regulate dislocation propagation path, thereby reducing the defect density in the subsequent epitaxial layer and improving the device consistency and reliability. On the other hand, the p-type island-shaped structure and the GaN epitaxial layer form a PN junction diode, which realizes effective regulation of the internal electric field distribution of the buffer layer in the off state of the device and improves the withstand voltage capability and working reliability of the device.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology and relates to GaN-based power devices, specifically providing a GaN-based power device with a patterned island-shaped p-type buried layer electric field modulation structure. Background Technology

[0002] Currently, gallium nitride (GaN)-based power devices are widely used in power electronics, communication power supplies, and new energy vehicles due to their high critical breakdown electric field, high electron mobility, and high-frequency characteristics, especially power devices based on GaN heterostructures. However, as GaN-based power devices develop towards higher voltage ratings and higher power densities, the electric field distribution in the off-state has gradually become one of the key factors limiting performance improvement and reliability enhancement. Specifically, existing GaN-based power devices typically experience high electric field stress at the buffer layer, gate edge, and drain edge, and the electric field tends to concentrate in local areas, forming electric field spikes. This non-uniform electric field distribution not only reduces the device's breakdown voltage but may also lead to increased leakage current and device reliability degradation.

[0003] To address the aforementioned issues, existing technologies typically employ methods such as buffer layer doping control or buffer layer thickening to adjust the electric field. However, both thickened and doped buffer layer structures introduce stress concentration and lattice mismatch issues during subsequent epitaxial growth, adversely affecting the crystal quality of the upper epitaxial material, increasing dislocation and defect density, and causing premature device breakdown due to additional buffer layer defects. This also impacts device consistency and reliability. Therefore, achieving electric field control while maintaining epitaxial layer growth quality and reducing internal device defects is crucial for improving the breakdown characteristics and reliability of gallium nitride (GaN)-based power devices. Summary of the Invention

[0004] The purpose of this invention is to provide a GaN-based power device with a patterned island-shaped p-type buried layer electric field control structure, in order to solve the problems of uneven electric field distribution and obvious local electric field spikes in the off state of existing GaN-based power devices.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] First, a GaN-based power device with a patterned island-shaped p-type buried layer electric field control structure, comprising: a substrate layer 3, a buffer layer 4 disposed on the substrate layer, a channel layer 5 disposed on the buffer layer, a barrier layer 6 disposed on the channel layer, a p-type cap layer 7 disposed on the barrier layer, and a drain 8, a source 9, and a gate 10.

[0007] The drain and source are disposed on the channel layer and are located on both sides of the barrier layer, respectively. The source forms an ohmic contact with the channel layer, and the drain forms a Schottky contact with the channel layer; the gate is disposed on the p-type cap layer.

[0008] The buffer layer is embedded with a patterned island-shaped p-type buried layer electric field control structure, which includes a GaN epitaxial layer 1 and a p-type buried layer 2. The p-type buried layer is patterned to form multiple p-type island structures that are spaced apart from each other, and the GaN epitaxial layer is filled between the p-type island structures.

[0009] Second, a GaN-based power device with a patterned island-shaped p-type buried layer electric field control structure includes: a substrate layer 3, a buffer layer 4 disposed on the substrate layer, a channel layer 5 disposed on the buffer layer, a barrier layer 6 disposed on the channel layer, a p-type cap layer 7 disposed on the barrier layer, and a source 9 and a gate 10.

[0010] Two p-type cap layers are symmetrically disposed on the barrier layer, and two gates are respectively disposed on the two p-type cap layers; two sources are disposed on the channel layer and are respectively located on both sides of the barrier layer, and the sources and the channel layer form an ohmic contact;

[0011] The buffer layer is embedded with a patterned island-shaped p-type buried layer electric field control structure, which includes a GaN epitaxial layer 1 and a p-type buried layer 2. The p-type buried layer is patterned to form multiple p-type island structures that are spaced apart from each other, and the GaN epitaxial layer is filled between the p-type island structures.

[0012] Furthermore, in the two GaN-based power devices mentioned above, the p-type island structure is elongated, and multiple p-type island structures that are spaced apart from each other are arranged side by side in the horizontal or vertical direction.

[0013] Furthermore, in the two GaN-based power devices mentioned above, the p-type island structure is conical, and multiple p-type island structures spaced apart from each other are arranged in a matrix.

[0014] Furthermore, in the two GaN-based power devices mentioned above, the GaN epitaxial layer is either an intrinsic GaN layer or an n-type GaN layer, and the doping concentration of the n-type GaN layer is 1×10⁻⁶. 13 cm -3 Up to 1×10 17 cm -3 .

[0015] Furthermore, in the two GaN-based power devices mentioned above, the p-type buried layer is a p-type GaN layer, which is formed by Mg doping with a doping concentration of 1×10⁻⁶. 13 cm -3Up to 1×10 17 cm -3 .

[0016] Furthermore, in the two GaN-based power devices mentioned above, the thickness of the patterned island-shaped p-type buried electric field control structure is 0.3 μm to 1 μm. It should be noted that the thickness of the patterned island-shaped p-type buried electric field control structure in this invention is the same as the height of the p-type island structure. Moreover, since the GaN epitaxial layer is filled between the p-type island structures, the thickness of the GaN epitaxial layer is also the same as the height of the p-type island structure.

[0017] Furthermore, in the two GaN-based power devices mentioned above, the spacing between the p-type island structures is 0.2 μm to 5 μm.

[0018] Based on the above technical solution, the beneficial effect of the present invention is that it provides a GaN-based power device with a patterned island-shaped p-type buried layer electric field modulation structure, which has the following advantages:

[0019] 1) This invention introduces an electric field modulation structure composed of GaN epitaxial layer and p-type buried layer in buffer layer, and patterns the p-type buried layer into p-type island structure that is distributed at intervals, so that the p-type buried layer is discretely distributed in buffer layer. The p-type island structure can provide a morphological basis for three-dimensional nucleation and lateral merging for subsequent epitaxy, which helps to release epitaxial stress and control dislocation propagation path, thereby reducing the defect density in subsequent epitaxial layer to a certain extent, and thus improving the crystal quality, device consistency and reliability of upper semiconductor region;

[0020] 2) The p-type island structure and the GaN epitaxial layer above it form a PN junction diode in the interface region. During the device switching process, part of the PN junction is reverse biased. The expansion of the depletion region inside the PN junction in the reverse bias state reduces the number of free carriers inside the buffer layer, effectively blocking the carrier transport in the buffer layer, thereby reducing the leakage current in the switching state and reducing the device switching loss. In the device withstand voltage state, as the drain-source voltage continues to rise and reaches a certain voltage value, the depletion region inside the PN junction further expands until it is completely depleted, achieving complete punch-through. This allows the free carriers swept into the buffer layer of the GaN epitaxial layer to be quickly swept out by the built-in electric field in the depletion region, forming a stable and uniformly distributed leakage current, achieving a smooth linear distribution of potential, thereby reducing the local electric field peak and suppressing electric field spikes, improving the device withstand voltage and operational reliability.

[0021] 3) The p-type island structure and the GaN epitaxial layers filled on both sides form PN junction diodes respectively, and the anodes of the two PN junction diodes are connected, so that the bias direction of the two PN junction diodes connected by the anodes can be reversed when the device is in forward or reverse breakdown voltage. Based on its structural symmetry, electric field modulation under reverse breakdown voltage can also be achieved, thereby improving the reverse breakdown voltage capability of the device. Attached Figure Description

[0022] Figure 1 This is a schematic cross-sectional view of the reverse-resistance GaNHEMT device with a patterned island-shaped p-type buried layer electric field control structure in Embodiment 1 of the present invention.

[0023] Figure 2 This is a three-dimensional structural schematic diagram of the graphical island-shaped p-type buried layer electric field control structure in Embodiment 1 of the present invention.

[0024] Figure 3 This is the equivalent circuit diagram of the graphical island-shaped p-type buried layer electric field control structure in Embodiment 1 of the present invention.

[0025] Figure 4 This is a surface potential distribution diagram of the patterned island-shaped p-type buried layer electric field control structure in Embodiment 1 of the present invention under low drain-source voltage conditions.

[0026] Figure 5 This is a surface potential distribution diagram of the patterned island-shaped p-type buried layer electric field control structure in Embodiment 1 of the present invention under high drain-source voltage conditions.

[0027] Figure 6 This is a three-dimensional structural schematic diagram of the graphical island-shaped p-type buried layer electric field control structure in Embodiment 2 of the present invention.

[0028] Figure 7 This is a schematic cross-sectional view of the dual-gate GaN HEMT device with a patterned island-shaped p-type buried layer electric field modulation structure in Embodiment 3 of the present invention.

[0029] In the above figures, 1 is the GaN epitaxial layer, 2 is the p-type buried layer, 3 is the substrate layer, 4 is the buffer layer, 5 is the channel layer, 6 is the barrier layer, 7 is the p-type cap layer, 8 is the drain, 9 is the source, and 10 is the gate. Detailed Implementation

[0030] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0031] Example 1: This example provides a reverse-resistance GaNHEMT device with a patterned island-shaped p-type buried layer electric field modulation structure, the structure of which is as follows. Figure 1As shown, it specifically includes: a substrate layer 3, a buffer layer 4 disposed on the substrate layer, a channel layer 5 disposed on the buffer layer, a barrier layer 6 disposed on the channel layer, a p-type cap layer 7 disposed on the barrier layer, and a drain 8, a source 9, and a gate 10; the drain and source are disposed on the channel layer and are located on opposite sides of the barrier layer, the source forms an ohmic contact with the channel layer, and the drain forms a Schottky contact with the channel layer; the gate is disposed on the p-type cap layer;

[0032] The buffer layer is embedded with a patterned island-shaped p-type buried layer electric field control structure, which includes a GaN epitaxial layer 1 and a p-type buried layer 2, such as... Figure 2 As shown, the p-type buried layer is patterned to form multiple p-type island structures that are spaced apart from each other. The p-type island structures are elongated and arranged side by side in the horizontal or vertical direction. The GaN epitaxial layer is filled between the p-type island structures.

[0033] In terms of working principle, such as Figure 3 The figure shows the equivalent circuit diagram of the patterned island-shaped p-type buried layer electric field control structure. As can be seen from the figure, the GaN epitaxial layer is in an intrinsic state (unintentionally doped) and behaves as an n-type semiconductor. Based on this, the p-type island structure and the GaN epitaxial layers filled on both sides form a PN junction inlay structure, and the junction surface of the PN junction is the interface between the two. The two sides of a single p-type island structure form PN junction diodes with the adjacent GaN epitaxial layers, and the anodes of the two PN junction diodes are connected. When a bias voltage is applied between the drain and source, the two PN junction diodes are in the forward bias state and the reverse bias state, respectively.

[0034] like Figure 4 The figure shows the surface potential distribution of the graphical island-shaped p-type buried layer electric field control structure under low drain-source voltage conditions. As can be seen from the figure, when a lower forward bias voltage is applied between the drain and source, the depletion region inside the reverse biased PN junction expands compared to zero bias, and the area of ​​the depletion region in the PN junction in-layer structure increases, thereby reducing the number of free-moving charge carriers in the PN junction in-layer structure, and ultimately reducing the leakage current of the buffer layer.

[0035] like Figure 5The figure shows the surface potential distribution of the graphical island-shaped p-type buried layer electric field control structure under high drain-source voltage conditions. As can be seen from the figure, when a high forward bias voltage is applied between the drain and source, the depletion region inside the reverse-biased PN junction further expands, causing the PN junction intercalation structure to be completely depleted. According to the Poisson equation in semiconductors, the charge distribution in a semiconductor is proportional to the second derivative of the potential distribution. When the PN junction intercalation structure is completely depleted, the doping concentration of the N-region and P-region inside the PN junction is fixed and completely ionized. The potential distribution in the N-region of the PN junction intercalation structure is a parabola with a gradually increasing slope (absolute value) and opens downward (from high potential to low potential). The potential distribution in the P-region is a parabola with a gradually decreasing slope (absolute value) and opens upward (from high potential to low potential). The slope is related to the doping concentration. Therefore, by reducing the doping concentration of the N-region and P-region, the rate of change of the slope of the internal potential distribution curve of the PN junction intercalation structure can be reduced, making the potential close to a smooth slope distribution.

[0036] In summary, this embodiment achieves effective control of the electric field distribution inside the buffer layer during device turn-off by using the graphical island-shaped p-type buried layer electric field control structure. During device switching, the expansion of the depletion region inside the reverse-biased PN junction reduces the number of freely moving charge carriers inside the buffer layer, effectively blocking the transport of charge carriers in the buffer layer, thereby reducing leakage current and device switching losses during switching. When the device is in a withstand voltage state, as the drain-source voltage continues to rise and reaches a certain voltage value, the depletion region inside the PN junction further expands until it is completely depleted, achieving complete punch-through and forming a stable and uniformly distributed leakage current. This results in a smooth and linear distribution of potential, thereby reducing local electric field peaks and suppressing electric field spikes, improving the device's withstand voltage capability and operational reliability.

[0037] On the other hand, by introducing p-type island structures, a lateral epitaxial growth and stress release interface can be constructed in the buffer layer, effectively suppressing the upward extension of dislocations, thereby reducing the leakage current of the buffer layer caused by crystal defects.

[0038] Example 2: This example provides a reverse-resistance GaNHEMT device with a patterned island-shaped p-type buried layer electric field modulation structure. The difference between this device and Example 1 is that: Figure 6 As shown, the p-type island structure is conical and arranged in a matrix. It should be noted that in this embodiment, the p-type buried layer is composed of several conical p-type island structures arranged in a matrix, which can achieve the same electric field distribution modulation effect inside the buffer layer as in Embodiment 1. Furthermore, it can simultaneously form electric field distribution modulation in both the transverse and longitudinal directions, further improving the modulation effect.

[0039] Example 3: This example provides a dual-gate GaNHEMT device with a patterned island-shaped p-type buried layer electric field modulation structure, such as... Figure 7 As shown, it specifically includes: a substrate layer 3, a buffer layer 4 disposed on the substrate layer, a channel layer 5 disposed on the buffer layer, a barrier layer 6 disposed on the channel layer, a p-type cap layer 7 disposed on the barrier layer, and a source 9 and a gate 10; two p-type cap layers are symmetrically disposed on the barrier layer, and two gates are respectively disposed on the two p-type cap layers; two sources are disposed on the channel layer and are respectively located on both sides of the barrier layer, and both sources form ohmic contacts with the channel layer;

[0040] The buffer layer is embedded with a patterned island-shaped p-type buried layer electric field control structure, which includes a GaN epitaxial layer 1 and a p-type buried layer 2. The p-type buried layer is patterned to form multiple p-type island structures that are spaced apart from each other. The p-type island structures are elongated and arranged side by side in the horizontal or vertical direction. The GaN epitaxial layer is filled between the p-type island structures.

[0041] In addition, the p-type island structure can also be conical, and several conical p-type island structures arranged in a matrix together constitute a p-type buried layer.

[0042] It should be noted that, since the dual-gate GaN HEMT itself has bidirectional blocking capability, thanks to the geometric symmetry of the patterned island-shaped p-type buried layer electric field control structure proposed in this invention, as mentioned above, in the bidirectional blocking state, the patterned island-shaped p-type buried layer electric field control structure of the dual-gate GaN HEMT device can achieve a smooth and linear distribution of internal potential, thereby reducing the local electric field peak and suppressing electric field spikes, ultimately improving the bidirectional withstand voltage capability and operational reliability of the device.

[0043] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A GaN-based power device with a patterned island-shaped p-type buried layer electric field modulation structure, characterized in that, include: Substrate layer (3), buffer layer (4) disposed on the substrate layer, channel layer (5) disposed on the buffer layer, barrier layer (6) disposed on the channel layer, p-type cap layer (7) disposed on the barrier layer, drain (8), source (9), and gate (10). The drain and source are disposed on the channel layer and are located on opposite sides of the barrier layer, respectively. The source forms an ohmic contact with the channel layer, and the drain forms a Schottky contact with the channel layer; the gate is disposed on the p-type cap layer. The buffer layer is embedded with a patterned island-shaped p-type buried layer electric field control structure, which includes a GaN epitaxial layer (1) and a p-type buried layer (2). The p-type buried layer is patterned to form multiple p-type island structures that are spaced apart from each other. The GaN epitaxial layer is filled between the p-type island structures. The p-shaped island structure is elongated, with multiple p-shaped island structures spaced apart from each other arranged side by side in the horizontal or vertical direction, and the corresponding horizontal or vertical cross-section is conical; or, the p-shaped island structure is conical, with multiple p-shaped island structures spaced apart from each other arranged in a matrix. The height of the p-type island structure is the same as the thickness of the GaN epitaxial layer, and the same as the thickness of the patterned island p-type buried layer electric field control structure. The thickness of the patterned island p-type buried layer electric field control structure is 0.3um~1um. The GaN epitaxial layer is either an intrinsic GaN layer or an n-type GaN layer, wherein the doping concentration of the n-type GaN layer is 1×10⁻⁶. 13 cm -3 Up to 1×10 17 cm -3 ; The p-type buried layer is a p-type GaN layer, which is formed by Mg doping with a doping concentration of 1×10⁻⁶. 13 cm -3 Up to 1×10 17 cm -3 .

2. A GaN-based power device with a patterned island-shaped p-type buried layer electric field modulation structure, characterized in that, include: The substrate layer (3), the buffer layer (4) disposed on the substrate layer, the channel layer (5) disposed on the buffer layer, the barrier layer (6) disposed on the channel layer, the p-type cap layer (7) disposed on the barrier layer, and the source (9) and the gate (10). Two p-type cap layers are symmetrically disposed on the barrier layer, and two gates are respectively disposed on the two p-type cap layers; two sources are disposed on the channel layer and are respectively located on both sides of the barrier layer, and the sources and the channel layer form an ohmic contact; The buffer layer is embedded with a patterned island-shaped p-type buried layer electric field control structure, which includes a GaN epitaxial layer (1) and a p-type buried layer (2). The p-type buried layer is patterned to form multiple p-type island structures that are spaced apart from each other. The GaN epitaxial layer is filled between the p-type island structures. The p-shaped island structure is elongated, with multiple p-shaped island structures spaced apart from each other arranged side by side in the horizontal or vertical direction, and the corresponding horizontal or vertical cross-section is conical; or, the p-shaped island structure is conical, with multiple p-shaped island structures spaced apart from each other arranged in a matrix. The height of the p-type island structure is the same as the thickness of the GaN epitaxial layer, and the same as the thickness of the patterned island p-type buried layer electric field control structure. The thickness of the patterned island p-type buried layer electric field control structure is 0.3um~1um. The GaN epitaxial layer is either an intrinsic GaN layer or an n-type GaN layer, wherein the doping concentration of the n-type GaN layer is 1×10⁻⁶. 13 cm -3 Up to 1×10 17 cm -3 ; The p-type buried layer is a p-type GaN layer, which is formed by Mg doping with a doping concentration of 1×10⁻⁶. 13 cm -3 Up to 1×10 17 cm -3 .

3. The GaN-based power device with a patterned island-shaped p-type buried layer electric field modulation structure according to claim 1 or 2, characterized in that, The spacing between the p-type island structures is 0.2 μm to 5 μm.

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