GaN power diode

Abstract

The application discloses a GaN power diode, which comprises a cathode metal, an N-type heavily doped GaN substrate, an N-type lightly doped GaN epitaxial layer, a composite P region, a P-type heavily doped GaN contact layer and an anode metal. The N-type heavily doped GaN substrate forms an ohmic contact with the cathode metal; the N-type lightly doped GaN epitaxial layer is formed on the N-type heavily doped GaN substrate; the composite P region is formed on the N-type lightly doped GaN epitaxial layer, and the composite P region comprises a first P region, a second P region and a third P region arranged in sequence from left to right, wherein the doping concentration of the first P region and the third P region is lower than that of the second P region; the P-type heavily doped GaN contact layer is formed on the composite P region; and the anode metal forms an ohmic contact with the P-type heavily doped GaN contact layer. The application can improve the breakdown voltage of the PN junction edge region.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and specifically to a GaN power diode. Background Technology

[0002] Gallium nitride (GaN), as a representative of third-generation wide-bandgap semiconductor materials, has become an ideal material for fabricating high-voltage, high-efficiency, and high-frequency power devices due to its high critical breakdown electric field, high electron saturation drift velocity, and excellent thermal conductivity. Compared with traditional silicon (Si)-based power devices, GaN power devices can achieve higher power density and lower switching losses in a smaller volume, and are widely used in cutting-edge fields such as new energy vehicles, industrial motor drives, and communication power supplies.

[0003] In terms of device structure, vertically oriented PN or PIN junction diodes are core components in power electronic systems, undertaking key functions such as rectification, freewheeling, and clamping. To fully leverage the performance advantages of GaN materials, the industry is focusing on developing vertical GaN power diodes. These devices typically form a heavily doped P-type region on a lightly doped N-type drift region (I-region) grown epitaxially, constituting the core structure of the PIN diode.

[0004] However, current vertical GaN PIN diodes face a significant challenge in achieving high breakdown voltages: under reverse bias, the peak electric field concentrates at the edge of the PN junction formed by the P-region and the N-type drift region. This electric field concentration effect easily leads to premature avalanche breakdown in this region, severely limiting the realization of the device's theoretical breakdown voltage and becoming a bottleneck restricting further performance improvements. Utility Model Content

[0005] This application provides a GaN power diode that can improve the breakdown voltage of the PN junction edge region.

[0006] This application provides a GaN power diode, comprising: Cathode metal; An N-type heavily doped GaN substrate forms an ohmic contact with the cathode metal; An N-type lightly doped GaN epitaxial layer is formed on the N-type heavily doped GaN substrate; A composite P-region is formed on the N-type lightly doped GaN epitaxial layer. The composite P-region includes a first P-region, a second P-region, and a third P-region arranged from left to right, wherein the doping concentration of the first P-region and the third P-region is lower than the doping concentration of the second P-region. A p-type heavily doped GaN contact layer is formed on the composite p-region; The anode metal forms an ohmic contact with the p-type heavily doped GaN contact layer.

[0007] In the GaN power diode provided in the embodiments of this application, the size and doping concentration of the first P region and the third P region are exactly the same.

[0008] In the GaN power diode provided in this application embodiment, the lateral width of the second P region is greater than the lateral width of the first P region and the third P region, constituting the main conductive region of the composite P region.

[0009] In the GaN power diode provided in this application embodiment, the doping concentrations of the first P region, the second P region, and the third P region are all higher than the doping concentration of the lightly doped N-type GaN epitaxial layer, and all are lower than the doping concentration of the heavily doped P-type GaN contact layer.

[0010] The GaN power diode provided in this application embodiment also includes a junction termination extension structure, which includes a first junction termination ion implantation region and a second junction termination ion implantation region located on both sides of the anode metal.

[0011] In the GaN power diode provided in this application embodiment, the implanted ions in the first junction terminal ion implantation region and the second junction terminal ion implantation region are nitrogen ions.

[0012] In the GaN power diode provided in the embodiments of this application, the maximum implantation depth of the first junction-terminated ion implantation region and the second junction-terminated ion implantation region extends to the interface between the lightly doped N-type GaN epitaxial layer and the composite P-region.

[0013] The GaN power diode provided in this application embodiment also includes a device isolation structure, which includes a first ion implantation isolation region located on the side of the first junction terminal ion implantation region away from the anode metal, and a second ion implantation isolation region located on the side of the second junction terminal ion implantation region away from the anode metal.

[0014] In the GaN power diode provided in the embodiments of this application, the implanted ions in the first ion implantation isolation region and the second ion implantation isolation region are nitrogen ions.

[0015] In the GaN power diode provided in the embodiments of this application, the P-type heavily doped GaN contact layer and the P-type doping in the composite P region are Mg doped; the N-type lightly doped GaN epitaxial layer and the N-type heavily doped GaN substrate are Si doped.

[0016] In summary, the GaN power diode provided in this application includes a cathode metal, an N-type heavily doped GaN substrate, an N-type lightly doped GaN epitaxial layer, a composite P-region, a P-type heavily doped GaN contact layer, and an anode metal. The N-type heavily doped GaN substrate forms an ohmic contact with the cathode metal; the N-type lightly doped GaN epitaxial layer is formed on the N-type heavily doped GaN substrate; the composite P-region is formed on the N-type lightly doped GaN epitaxial layer, and the composite P-region includes a first P-region, a second P-region, and a third P-region arranged sequentially from left to right, wherein the doping concentration of the first P-region and the third P-region is lower than the doping concentration of the second P-region; the P-type heavily doped GaN contact layer is formed on the composite P-region; and the anode metal forms an ohmic contact with the P-type heavily doped GaN contact layer. This application embodiment employs a composite P-region composed of a highly doped second P-region and a low-doped first P-region and a third P-region. This effectively optimizes the electric field distribution in the PN junction edge region under reverse bias without sacrificing the device's on-resistance, avoiding premature breakdown caused by electric field concentration, thereby significantly improving the breakdown voltage of the PN junction edge region. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the GaN power diode provided in this application. Detailed Implementation

[0019] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0020] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, components, features, and elements with the same names in different embodiments of this application may have the same meaning or different meanings, the specific meaning of which must be determined by its interpretation in that specific embodiment or further in conjunction with the context of that specific embodiment.

[0021] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0022] In the following description, the use of suffixes such as "module," "part," or "unit" to denote elements is solely for the purpose of illustrative purposes and has no specific meaning in itself. Therefore, "module," "part," or "unit" may be used interchangeably.

[0023] The following describes in detail the embodiments involved in this application. It should be noted that the order of description of the embodiments in this application is not intended to limit the priority of the embodiments.

[0024] The technical solutions shown in this application will be described in detail below through specific embodiments. It should be noted that the order of description of the following embodiments is not intended to limit the priority of the embodiments.

[0025] Current vertical GaN PIN diodes face a significant challenge in achieving high breakdown voltages: under reverse bias, the peak electric field concentrates at the edge of the PN junction formed by the P-region and the N-type drift region. This electric field concentration effect easily leads to premature avalanche breakdown in this region, severely limiting the realization of the device's theoretical breakdown voltage and becoming a bottleneck restricting further performance improvements.

[0026] Based on this, this application provides a GaN power diode, such as... Figure 1 As shown, Figure 1 This is a schematic diagram of the GaN power diode provided in this application. The GaN power diode has a fully vertical PIN structure, which includes, from bottom to top: cathode metal 1, N-type heavily doped GaN substrate 2, N-type lightly doped GaN epitaxial layer 3, composite P region, P-type heavily doped GaN contact layer 5, and anode metal 6.

[0027] In this device, cathode metal 1 is formed on the back side of N-type heavily doped GaN substrate 2 and forms an ohmic contact with the N-type heavily doped GaN substrate, serving as the cathode of the device.

[0028] The lightly doped N-type GaN epitaxial layer 3 is formed on the heavily doped N-type GaN substrate 2. It serves as the intrinsic region (I region) of the PIN diode and is used to withstand the main reverse voltage.

[0029] The composite P-region is formed on top of the lightly doped N-type GaN epitaxial layer 3. From left to right, it consists of a first P-region 4-1, a second P-region 4-2, and a third P-region 4-3. The first P-region 4-1 and the third P-region 4-3 have the same doping concentration, but the doping concentration is lower than that of the second P-region 4-2. The first and third P-regions have identical dimensions. Laterally, the width of the second P-region 4-2 is greater than that of the first P-region 4-1 and the third P-region 4-3, constituting the main conductive region of the composite P-region. Furthermore, the doping concentrations of the first P-region 4-1, the second P-region 4-2, and the third P-region 4-3 are all higher than those of the underlying lightly doped N-type GaN epitaxial layer 3, but lower than those of the above-top heavily doped P-type GaN contact layer 5.

[0030] The P-type heavily doped GaN contact layer 5 is formed on the composite P region to improve the contact characteristics with the anode metal.

[0031] The anode metal 6 is formed on the P-type heavily doped GaN contact layer 5 and forms an ohmic contact with it, serving as the anode of the device.

[0032] In some embodiments, to further optimize the reverse breakdown voltage capability of the device and achieve device isolation, the GaN power diode may further include a junction termination extension structure, which includes a first junction termination ion implantation region 7-1 and a second junction termination ion implantation region 7-2 located on both sides of the anode metal 6. The implanted ions in the first junction termination ion implantation region 7-1 and the second junction termination ion implantation region 7-2 are nitrogen ions. The maximum implantation depth of the first junction termination ion implantation region 7-1 and the second junction termination ion implantation region 7-2 extends to the interface between the N-type lightly doped GaN epitaxial layer 3 and the composite P-region (specifically the first P-region 4-1 and the second P-region 4-3) to effectively modulate the surface electric field.

[0033] In this embodiment, the GaN power diode may further include a device isolation structure, comprising a first ion implantation isolation region 8-1 located on the side of the first junction terminal ion implantation region 7-1 away from the anode metal 6, and a second ion implantation isolation region 8-2 located on the side of the second junction terminal ion implantation region 7-2 away from the anode metal 6. The implanted ions in the first ion implantation isolation region 8-1 and the second ion implantation isolation region 8-2 are nitrogen ions. The maximum ion implantation depth of the first ion implantation isolation region 8-1 and the second ion implantation isolation region 8-2 can penetrate deep into the interior of the lightly doped N-type GaN epitaxial layer 3 (e.g., approximately 150 nm from its surface) to achieve effective electrical isolation.

[0034] Regarding the doping type, in this embodiment, the P-type doping in the heavily P-type doped GaN contact layer 5 and the composite P region is preferably Mg (magnesium) doping; while the N-type doping in the heavily N-type doped GaN substrate 2 and the lightly N-type doped GaN epitaxial layer 3 is preferably Si (silicon) doping.

[0035] In practical applications, the fabrication method of this GaN power diode may include the following steps: Step 101: Provide an N-type heavily doped GaN substrate 2, and sequentially grow an N-type lightly doped GaN epitaxial layer 3, a P-type GaN layer (with a doping concentration corresponding to the final second P-region 4-2) as a precursor of the second P-region, and a P-type heavily doped GaN contact layer 5 on it.

[0036] Step 102 involves photolithography and ion implantation to implant N-type ions (such as Si ions) into the edge region of the P-type GaN layer, which serves as the precursor to the second P-region. By precisely controlling the implantation dose, the P-type doping in the edge region is partially compensated, thereby forming the first P-region 4-1 and the third P-region 4-3 with lower doping concentrations, while the uncompensated middle region becomes the highly doped second P-region 4-2.

[0037] Step 103: By depositing and patterning a metal layer, an anode metal 6 is formed on the P-type heavily doped GaN contact layer 5, followed by rapid thermal annealing to make the anode metal 6 form a good ohmic contact with the underlying P-type heavily doped GaN contact layer 5.

[0038] Step 104: Through ion implantation process, the first junction terminal ion implantation region 7-1, the second junction terminal ion implantation region 7-2, the first ion implantation isolation region 8-1, and the second ion implantation isolation region 8-2 are formed sequentially.

[0039] Step 105: Prepare cathode metal 1 on the back side of the heavily doped N-type GaN substrate 2 and complete alloying to form an ohmic contact. In summary, the GaN power diode provided in this application includes a cathode metal 1, an N-type heavily doped GaN substrate 2, an N-type lightly doped GaN epitaxial layer 3, a composite P-region, a P-type heavily doped GaN contact layer 5, and an anode metal 6. The N-type heavily doped GaN substrate 2 forms an ohmic contact with the cathode metal 1; the N-type lightly doped GaN epitaxial layer 3 is formed on the N-type heavily doped GaN substrate 2; the composite P-region is formed on the N-type lightly doped GaN epitaxial layer 3, and the composite P-region includes a first P-region 4-1, a second P-region 4-2, and a third P-region 4-3 arranged sequentially from left to right, wherein the doping concentration of the first P-region 4-1 and the third P-region 4-3 is lower than the doping concentration of the second P-region 4-2; the P-type heavily doped GaN contact layer 5 is formed on the composite P-region; and the anode metal 6 forms an ohmic contact with the P-type heavily doped GaN contact layer 5. This embodiment employs a composite P-region composed of a highly doped second P-region 4-2 and a lightly doped first P-region 4-1 and a third P-region 4-3. During forward conduction, the current primarily flows through the low-resistance second P-region 4-2, thus maintaining a low on-resistance. During reverse breakdown, the lightly doped first P-region 4-1 and third P-region 4-3 effectively reduce the electric field strength at the edge of the PN junction formed with the lightly doped N-type GaN epitaxial layer 3. This effectively optimizes the electric field distribution at the PN junction edge region under reverse bias without sacrificing the device's on-resistance, preventing premature breakdown caused by electric field concentration and significantly improving the breakdown voltage at the PN junction edge region.

[0040] The GaN power diode provided in this application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of this application. At the same time, those skilled in the art will have changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A GaN power diode, characterized in that, include: Cathode metal; An N-type heavily doped GaN substrate forms an ohmic contact with the cathode metal; An N-type lightly doped GaN epitaxial layer is formed on the N-type heavily doped GaN substrate; A composite P-region is formed on the N-type lightly doped GaN epitaxial layer. The composite P-region includes a first P-region, a second P-region, and a third P-region arranged from left to right, wherein the doping concentration of the first P-region and the third P-region is lower than the doping concentration of the second P-region. A p-type heavily doped GaN contact layer is formed on the composite p-region; The anode metal forms an ohmic contact with the p-type heavily doped GaN contact layer.

2. The GaN power diode as described in claim 1, characterized in that, The size and doping concentration of the first and third P regions are exactly the same.

3. The GaN power diode as described in claim 1, characterized in that, The lateral width of the second P region is greater than that of the first P region and the third P region, forming the main conductive region of the composite P region.

4. The GaN power diode as described in claim 1, characterized in that, The doping concentrations of the first P-region, the second P-region, and the third P-region are all higher than the doping concentration of the lightly doped N-type GaN epitaxial layer, and all are lower than the doping concentration of the heavily doped P-type GaN contact layer.

5. The GaN power diode as described in claim 1, characterized in that, It also includes a junction terminal extension structure, which includes a first junction terminal ion implantation region and a second junction terminal ion implantation region located on both sides of the anode metal.

6. The GaN power diode as described in claim 5, characterized in that, The implanted ions in the first junction terminal ion implantation region and the second junction terminal ion implantation region are nitrogen ions.

7. The GaN power diode as described in claim 5, characterized in that, The maximum implantation depth of the first junction-terminated ion implantation region and the second junction-terminated ion implantation region extends to the interface between the lightly doped N-type GaN epitaxial layer and the composite P-region.

8. The GaN power diode as described in claim 5, characterized in that, It also includes a device isolation structure, which includes a first ion implantation isolation region located on the side of the first junction terminal ion implantation region away from the anode metal, and a second ion implantation isolation region located on the side of the second junction terminal ion implantation region away from the anode metal.

9. The GaN power diode as described in claim 8, characterized in that, The implanted ions in the first ion implantation isolation region and the second ion implantation isolation region are nitrogen ions.

10. The GaN power diode as claimed in claim 1, characterized in that, The P-type heavily doped GaN contact layer and the P-type doping in the composite P region are Mg doped; the N-type lightly doped GaN epitaxial layer and the N-type heavily doped GaN substrate are Si doped.

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