A pn junction diode with good p-type ohmic contact and a preparation method thereof

Abstract

This application relates to the field of semiconductor device technology, and particularly to a pn junction diode with good p-type ohmic contact and its fabrication method, comprising: a substrate, an n-type doped alloy nitride layer, a p-type doped alloy nitride layer, and a p-type doped nitride layer; the p-type doped nitride layer is located at the end of the surface of the p-type doped alloy nitride layer, and a two-dimensional hole gas channel is formed between the p-type doped nitride layer and the p-type doped alloy nitride layer; a two-dimensional hole gas can be formed between the p-type doped nitride layer and the two-dimensional hole gas is located within the two-dimensional hole gas channel; an anode is provided above the p-type doped nitride layer, and a cathode is also provided on the n-type doped alloy nitride layer. This application can solve the problem that the large potential barrier between the p-type AlGaN material and the metal in existing p-type ohmic contact diodes makes it difficult to form a good ohmic contact.

Description

Technical Field

[0001] This application relates to the field of semiconductor device technology, and in particular to a pn junction diode with good p-type ohmic contact and its fabrication method. Background Technology

[0002] Gallium nitride (GaN), as a representative of third-generation semiconductor materials, has many excellent characteristics compared to silicon or gallium arsenide, such as wide bandgap, superior radiation noise immunity, high avalanche breakdown electric field, good thermal conductivity, and high electron drift velocity under strong field. Therefore, GaN power diodes have received increasing attention in terms of high power and high efficiency.

[0003] An ohmic contact is defined as a contact between a metal and a semiconductor where no significant additional impedance is generated and the equilibrium carrier concentration within the semiconductor does not change significantly. A good ohmic contact is crucial for device performance. Materials such as GaN and AlGaN have relatively high potential barriers between themselves and the contact metal, and p-type ohmic contacts require a high work function of the metal. For pn junction diodes, fabricating a good p-type ohmic contact is extremely difficult. Summary of the Invention

[0004] This application provides a pn junction diode with good p-type ohmic contact and a method for fabricating the same, which is used to reduce the ohmic contact resistance of the pn junction diode to form a good p-type ohmic contact.

[0005] To address the aforementioned technical problems, in a first aspect, embodiments of this application provide a pn junction diode with good p-type ohmic contact, comprising: a substrate and an n-type doped alloy nitride layer disposed on the substrate; a p-type doped alloy nitride layer and a p-type doped nitride layer are sequentially stacked on the n-type doped alloy nitride layer; one end of the p-type doped alloy nitride layer is flush with the end of the n-type doped alloy nitride layer, and the other end of the p-type doped alloy nitride layer is located on the surface of the n-type doped alloy nitride layer; the p-type doped nitride layer comprises a plurality of p-type doped nitride layers, each p-type doped nitride layer being located at the end of the surface of the p-type doped alloy nitride layer. A two-dimensional hole gas channel is formed between the p-type doped nitride layer and the p-type doped alloy nitride layer; a two-dimensional hole gas can be formed between the p-type doped nitride layer and the p-type doped alloy nitride layer, and the two-dimensional hole gas is located in the two-dimensional hole gas channel; an anode is provided above the p-type doped nitride layer, the anode covers the surface of the p-type doped nitride layer and part of the surface of the p-type doped alloy nitride layer, and the anode and the p-type doped alloy nitride layer form a p-type ohmic contact; a cathode is also provided on the n-type doped alloy nitride layer, there is a gap between the cathode and the p-type doped alloy nitride layer, and the cathode and the n-type doped alloy nitride layer form an ohmic contact.

[0006] In some exemplary embodiments, the material of the p-type doped alloy nitride layer is AlGaN, and / or the material of the n-type doped alloy nitride layer is AlGaN.

[0007] In some exemplary embodiments, the material of the p-type doped nitride layer includes GaN or AlN.

[0008] In some exemplary embodiments, the p-type doped nitride layer includes two layers, which are located at opposite ends of the surface of the p-type doped alloy nitride layer, and there is a gap between the two p-type doped nitride layers.

[0009] Secondly, embodiments of this application also provide another pn junction diode with good p-type ohmic contact, comprising: a substrate and an n-type doped alloy nitride layer disposed on the substrate; a p-type doped alloy nitride layer and a p-type doped nitride layer are sequentially stacked on the n-type doped alloy nitride layer; the two ends of the p-type doped alloy nitride layer are flush with the two ends of the n-type doped alloy nitride layer; the p-type doped nitride layer comprises a plurality of p-type doped nitride layers, the p-type doped nitride layers being located at the ends of the surface of the p-type doped alloy nitride layers, and each p-type doped alloy nitride layer having a certain degree of contact. A two-dimensional hole gas channel is formed between the nitride layer and the p-type doped alloy nitride layer; a two-dimensional hole gas can be formed between the p-type doped nitride layer and the p-type doped alloy nitride layer, and the two-dimensional hole gas is located in the two-dimensional hole gas channel; an anode is provided above the p-type doped nitride layer, the anode covers the surface of the p-type doped nitride layer and part of the surface of the p-type doped alloy nitride layer, and the anode and the p-type doped alloy nitride layer form a p-type ohmic contact; a cathode is also provided below the substrate, and the cathode forms an ohmic contact with the n-type doped alloy nitride layer.

[0010] In some exemplary embodiments, the material of the p-type doped alloy nitride layer is AlGaN, and / or the material of the n-type doped alloy nitride layer is AlGaN.

[0011] In some exemplary embodiments, the material of the p-type doped nitride layer includes GaN or AlN.

[0012] In some exemplary embodiments, the p-type doped nitride layer includes two layers, which are located at opposite ends of the surface of the p-type doped alloy nitride layer, and there is a gap between the two p-type doped nitride layers; the ends of the two p-type doped nitride layers are flush with the ends of the p-type doped alloy nitride layer and the ends of the n-type doped alloy nitride layer, respectively.

[0013] Thirdly, embodiments of this application also provide a method for fabricating a pn junction diode with good p-type ohmic contact, comprising the following steps: forming an n-type doped alloy nitride layer, a p-type doped alloy nitride material layer, and a p-type doped nitride material layer stacked sequentially on a substrate; etching the p-type doped alloy nitride material layer and the p-type doped nitride material layer to expose a portion of the surface of the n-type doped alloy nitride layer, forming a p-type doped alloy nitride layer; exposing a portion of the surface of the p-type doped alloy nitride layer, forming a p-type doped nitride layer; forming a two-dimensional hole channel between the p-type doped nitride layers; forming an anode above the p-type doped nitride layer, the anode covering the surface of the p-type doped nitride layer and a portion of the surface of the p-type doped alloy nitride layer; forming a cathode on the n-type doped alloy nitride layer, with a gap between the cathode and the p-type doped alloy nitride layer.

[0014] In some exemplary embodiments, etching a p-type doped nitride material layer to expose a portion of the surface of a p-type doped alloy nitride layer to form a p-type doped nitride layer includes: etching a p-type doped nitride material layer located in the middle of the p-type doped alloy nitride layer to expose the surface of the middle of the p-type doped alloy nitride layer, and retaining p-type doped nitride material layers located at both ends of the surface of the p-type doped alloy nitride layer to form two p-type doped nitride layers.

[0015] The technical solution provided in this application has at least the following advantages:

[0016] This application addresses the problem in existing diodes where the large potential barrier between the p-type AlGaN material and the metal makes it difficult to form a good ohmic contact. This application provides a pn junction diode with good p-type ohmic contact and its fabrication method. The pn junction diode includes a substrate and an n-type doped alloy nitride layer disposed on the substrate. A p-type doped alloy nitride layer and another p-type doped nitride layer are sequentially stacked on the n-type doped alloy nitride layer. One end of the p-type doped alloy nitride layer is flush with the end of the n-type doped alloy nitride layer, and the other end of the p-type doped alloy nitride layer is located on the surface of the n-type doped alloy nitride layer. Multiple p-type doped nitride layers are included. The nitride layer is located at the end of the surface of the p-type doped alloy nitride layer, and a two-dimensional hole gas channel is formed between each p-type doped alloy nitride layer; a two-dimensional hole gas can be formed between the p-type doped alloy nitride layers, and the two-dimensional hole gas is located in the two-dimensional hole gas channel; an anode is provided above the p-type doped nitride layer, the anode covers the surface of the p-type doped nitride layer and part of the surface of the p-type doped alloy nitride layer, and the anode and the p-type doped alloy nitride layer form a p-type ohmic contact; a cathode is also provided on the n-type doped alloy nitride layer, there is a gap between the cathode and the p-type doped alloy nitride layer, and the cathode and the n-type doped alloy nitride layer form an ohmic contact. This application utilizes a heterojunction of a p-type doped nitride layer (e.g., p-type GaN) and a p-type doped alloy nitride layer (e.g., p-type AlGaN) to generate two-dimensional holes, thereby reducing the ohmic contact resistance and forming a good p-type ohmic contact. This improves the device's operating life and reliability, and has good application prospects. Attached Figure Description

[0017] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments, and unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0018] Figure 1 A schematic diagram of a pn junction diode with good p-type ohmic contact is provided for one embodiment of this application;

[0019] Figure 2 A schematic diagram of a pn junction diode with good p-type ohmic contact is provided for another embodiment of this application;

[0020] Figure 3 A schematic flowchart illustrating a method for fabricating a pn junction diode with good p-type ohmic contact according to an embodiment of this application;

[0021] Figure 4This is a schematic flowchart illustrating a method for fabricating a pn junction diode with good p-type ohmic contact, provided for another embodiment of this application. Detailed Implementation

[0022] As is known from the background art, currently, it is very difficult to fabricate pn junction diodes with good p-type ohmic contacts because the potential barrier between GaN and AlGaN materials and the contact metal is relatively high, and the p-type ohmic contact requires a relatively high work function of the metal.

[0023] With the continuous development of aerospace technologies such as space satellites and space exploration, the demand for power systems that are resistant to high temperatures, high power, miniaturized, and adaptable to extreme radiation environments is becoming increasingly apparent. GaN and AlGaN-based diodes offer advantages such as high power density and high reliability, and have broad application prospects in the field of power electronics. Gallium nitride (GaN) power diodes are receiving increasing attention for their high power and high efficiency.

[0024] Compared to ordinary silicon (Si), AlGaN offers advantages such as a large bandgap, high breakdown field strength, high electron mobility, radiation resistance, and high temperature resistance. Because wide-bandgap semiconductors generate relatively high potential barriers when in contact with most metals, and AlGaN has a significant barrier between itself and the contact metal, and because p-type ohmic contacts require a relatively high work function from the metal, fabricating high-quality p-type ohmic contact pn junction diodes is quite challenging.

[0025] To address this technical problem, this application proposes a pn junction diode with good p-type ohmic contact, comprising: a substrate and an n-type doped alloy nitride layer disposed on the substrate; a p-type doped alloy nitride layer and a p-type doped nitride layer are sequentially stacked on the n-type doped alloy nitride layer; one end of the p-type doped alloy nitride layer is flush with the end of the n-type doped alloy nitride layer, and the other end of the p-type doped alloy nitride layer is located on the surface of the n-type doped alloy nitride layer; multiple p-type doped nitride layers are included, with each p-type doped nitride layer located at the end of its surface, and each p-type doped alloy nitride layer having a p-type ohmic contact. A two-dimensional hole gas channel is formed between the doped nitride layer and the p-type doped alloy nitride layer; a two-dimensional hole gas can be formed between the p-type doped nitride layer and the p-type doped alloy nitride layer, and the two-dimensional hole gas is located in the two-dimensional hole gas channel; an anode is provided above the p-type doped nitride layer, the anode covers the surface of the p-type doped nitride layer and part of the surface of the p-type doped alloy nitride layer, and the anode and the p-type doped alloy nitride layer form a p-type ohmic contact; a cathode is also provided on the n-type doped alloy nitride layer, there is a gap between the cathode and the p-type doped alloy nitride layer, and the cathode and the n-type doped alloy nitride layer form an ohmic contact. This application embodiment reduces the ohmic contact resistance by utilizing the two-dimensional hole gas between a p-type doped nitride layer (e.g., p-GaN) and a p-type doped alloy nitride layer (e.g., p-AlGaN), forming a good p-type ohmic contact, reducing the fabrication difficulty of pn junction diodes, and making the practical application scenarios of AlGaN-based pn junction diodes more extensive.

[0026] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0027] See Figure 1This application provides a pn junction diode with good p-type ohmic contact, comprising: a substrate 100 and an n-type doped alloy nitride layer 102 disposed on the substrate 100; a p-type doped alloy nitride layer 103 and a p-type doped nitride layer 104 are sequentially stacked on the n-type doped alloy nitride layer 102; one end of the p-type doped alloy nitride layer 103 is flush with the end of the n-type doped alloy nitride layer 102, and the other end of the p-type doped alloy nitride layer 103 is located on the surface of the n-type doped alloy nitride layer 102; a plurality of p-type doped nitride layers 104 are included, each p-type doped nitride layer 104 is located at the end of the surface of the p-type doped alloy nitride layer 103, and each p-type doped nitride layer 104 is connected to the p-type doped alloy nitride layer 102. Two-dimensional hole gas channels are formed between the gold nitride layers 103; two-dimensional hole gas (2DHG) can be formed between the p-type doped nitride layer 104 and the p-type doped alloy nitride layer 103, and the two-dimensional hole gas (2DHG) is located in the two-dimensional hole gas channels; an anode 106 is provided above the p-type doped nitride layer 104, and the anode 106 covers the surface of the p-type doped nitride layer 104 and part of the surface of the p-type doped alloy nitride layer 103, and the anode 106 and the p-type doped alloy nitride layer 103 form a p-type ohmic contact; a cathode 101 is also provided on the n-type doped alloy nitride layer 102, and there is a gap between the cathode 101 and the p-type doped alloy nitride layer 103, and the cathode 101 and the n-type doped alloy nitride layer 102 form an ohmic contact.

[0028] It should be noted that the substrate 100 can be an epitaxial substrate of the n-type doped alloy nitride layer 102, or a self-supporting substrate of the n-type doped alloy nitride layer 102. The substrate 100 is located below the n-type doped alloy nitride layer 102, and the two ends of the substrate 100 are flush with the two ends of the n-type doped alloy nitride layer 102. The material of the substrate 100 may include one of sapphire, silicon carbide (SiC), silicon (Si), and gallium nitride.

[0029] like Figure 1 As shown, along the direction from left to right, that is, from the p-type doped alloy nitride layer 103 to the cathode 101, the length of the p-type doped alloy nitride layer 103 is less than the length of the n-type doped alloy nitride layer 102. One end of the p-type doped alloy nitride layer 103 is flush with one end of the n-type doped alloy nitride layer 102, and the other end of the p-type doped alloy nitride layer 103 is located on the surface of the n-type doped alloy nitride layer 102.

[0030] In some embodiments, the material of the p-type doped alloy nitride layer 103 is AlGaN, and / or the material of the n-type doped alloy nitride layer 102 is AlGaN.

[0031] In some embodiments, the material of the p-type doped nitride layer 104 includes GaN or AlN.

[0032] Specifically, when the materials of the p-type doped alloy nitride layer 103 and the n-type doped alloy nitride layer 102 are both AlGaN, and the material of the p-type doped nitride layer 104 is p-type gallium nitride (p-GaN), a two-dimensional hole gas (2DHG) will be generated at the interface between the p-GaN and p-AlGaN heterojunctions due to the polarization effect. In this embodiment, 2DHG is used to improve the ohmic contact characteristics between the anode 106 and p-AlGaN, as shown in the specific structure below. Figure 1 As shown, it consists of a cathode 101, an n-type doped alloy nitride layer 102 (n-type doped AlGaN layer), a p-type doped alloy nitride layer 103 (p-type doped AlGaN layer), a p-type doped nitride layer 104 (p-type doped GaN layer), and an anode 106. The dashed line between the p-type doped nitride layer 104 and the p-type doped alloy nitride layer 103 represents a two-dimensional hole channel.

[0033] The pn junction diode with good p-type ohmic contact in this embodiment uses AlGaN material for the p-type doped alloy nitride layer 103 and GaN material for the p-type doped nitride layer 104. There are two-dimensional holes in the p-GaN and p-AlGaN heterojunction. The two-dimensional holes between the p-type doped nitride layer 104 and the p-type doped alloy nitride layer 103 reduce the p-type ohmic contact resistance to form a good ohmic contact.

[0034] In practical applications, good p-type ohmic contact performance is very important for device performance. This application proposes to use two-dimensional cavitation gas to reduce the ohmic contact resistance of pn junction diodes, thereby forming good p-type ohmic contacts and making the practical application scenarios of this AlGaN-based pn junction diode more extensive.

[0035] It should be noted that, due to the relatively thin thickness of the p-type doped nitride layer 104, Figure 1 The diagram shown illustrates the structure of a pn junction diode based on a quasi-vertical pn junction diode made of AlGaN material. This type of pn junction diode possesses the superior properties of AlGaN material, as well as excellent ohmic contact characteristics. Figure 1 As shown, one end of the n-type doped alloy nitride layer 102 is flush with one end of the p-type doped alloy nitride layer 103, and the other end extends out of the side end of the p-type doped alloy nitride layer 103; the cathode 101 is located on the surface of the n-type doped alloy nitride layer 102 exposed on the surface of the p-type doped alloy nitride layer 103, and there is a gap between the cathode 101 and the p-type doped alloy nitride layer 103.

[0036] Please continue reading. Figure 1 In some embodiments, the p-type doped nitride layer 104 includes two layers, which are located at opposite ends of the surface of the p-type doped alloy nitride layer 103, and there is a gap between the two p-type doped nitride layers 104.

[0037] In some embodiments, the two-dimensional hole channel is directly opposite the p-type doped nitride layer 104, and there is a one-to-one correspondence between the two-dimensional hole channel and the p-type doped nitride layer 104.

[0038] See Figure 2 This application also provides another pn junction diode with good p-type ohmic contact, comprising: a substrate 100 and an n-type doped alloy nitride layer 102 disposed on the substrate 100; a p-type doped alloy nitride layer 103 and a p-type doped nitride layer 104 are sequentially stacked on the n-type doped alloy nitride layer 102; the two ends of the p-type doped alloy nitride layer 103 are flush with the two ends of the n-type doped alloy nitride layer 102; a plurality of p-type doped nitride layers 104 are included, and the p-type doped nitride layers 104 are located at the ends of the surface of the p-type doped alloy nitride layers 103, and each p-type doped nitride layer 104 is connected to the n-type doped alloy nitride layer 102. Two-dimensional hole gas channels are formed between the p-type doped alloy nitride layers 103; two-dimensional hole gas can be formed between the p-type doped alloy nitride layers 104 and 103, and the two-dimensional hole gas is located in the two-dimensional hole gas channels; an anode 106 is provided above the p-type doped nitride layer 104, the anode 106 covers the surface of the p-type doped nitride layer 104 and part of the surface of the p-type doped alloy nitride layer 103, and the anode 106 and the p-type doped alloy nitride layer 103 form a p-type ohmic contact; a cathode 101 is also provided below the substrate 100, and the cathode 101 forms an ohmic contact with the n-type doped alloy nitride layer 102.

[0039] It should be noted that the substrate 100 can be a self-supporting substrate of an n-type doped alloy nitride layer 102. Figure 2 In the structure of the pn diode shown, the cathode 101 is disposed below the n-type doped alloy nitride layer 102. The cathode 101 is located below the self-supporting substrate, and both ends of the cathode 101 are flush with the substrate 100 and the two ends of the n-type doped alloy nitride layer 102. The substrate 100 can be made of one of sapphire, silicon carbide (SiC), silicon (Si), or gallium nitride.

[0040] The cathode 101 is configured as follows: Figure 2 The structure of the pn diode shown is similar to Figure 1Unlike the quasi-vertical structure, the cathode 101 and anode 106 are located on the same side of the n-type doped alloy nitride layer 102. Additionally, Figure 1 The illustrated pn junction diode structure shows that the length of the p-type doped alloy nitride layer 103 is shorter than the length of the n-type doped alloy nitride layer 102. Here, the length direction refers to... Figure 1 The direction from left to right is from the p-type doped alloy nitride layer 103 to the cathode 101; one end of the p-type doped alloy nitride layer 103 is flush with one end of the n-type doped alloy nitride layer 102, and the other end is located on the surface of the n-type doped alloy nitride layer 102.

[0041] In some embodiments, the material of the p-type doped alloy nitride layer 103 is AlGaN, and / or the material of the n-type doped alloy nitride layer 102 is AlGaN.

[0042] In some embodiments, the material of the p-type doped nitride layer 104 includes GaN or AlN.

[0043] like Figure 2 As shown, in some embodiments, the p-type doped nitride layer 104 includes two layers, which are located at opposite ends of the surface of the p-type doped alloy nitride layer 103, and there is a gap between the two p-type doped nitride layers 104; the ends of the two p-type doped nitride layers 104 are flush with the ends of the p-type doped alloy nitride layer 103 and the n-type doped alloy nitride layer 102, respectively.

[0044] AlGaN pn junction diodes offer advantages such as high power density and resistance to high temperatures and voltages. AlGaN has a wider bandgap, resulting in higher breakdown voltages and better high-temperature characteristics. To address the challenge of forming good ohmic contacts due to the large potential barrier between p-AlGaN and the metal, this application provides... Figure 1 and Figure 2 Two structures of a pn junction diode with good p-type ohmic contact are shown. By utilizing the heterojunction at the end of a p-type doped nitride layer 104 (e.g., p-type GaN) and a p-type doped alloy nitride layer 103 (e.g., p-type AlGaN) to generate a two-dimensional hole gas, the ohmic contact resistance is reduced, thus forming a good p-type ohmic contact, thereby improving the device's operating life and reliability, and showing good application prospects.

[0045] The following examples illustrate the method for fabricating a pn junction diode with good p-type ohmic contact provided in this application.

[0046] like Figure 3As shown in the embodiments of this application, a method for fabricating a pn junction diode with good p-type ohmic contact is also provided, including the following steps:

[0047] Step S1: Form an n-type doped alloy nitride layer 102, a p-type doped alloy nitride material layer and a p-type doped nitride material layer stacked sequentially on a substrate 100.

[0048] Step S2: Etch the p-type doped alloy nitride material layer and the p-type doped nitride material layer to expose a portion of the surface of the n-type doped alloy nitride layer 102, forming a p-type doped alloy nitride layer 103; and expose a portion of the surface of the p-type doped alloy nitride layer 103 to form a p-type doped nitride layer 104; a two-dimensional cavitation channel is formed between the p-type doped nitride layer 104 and the p-type doped alloy nitride layer 103.

[0049] Step S3: An anode 106 is formed above the p-type doped nitride layer 104, and the anode 106 covers the surface of the p-type doped nitride layer 104 and part of the surface of the p-type doped alloy nitride layer 103.

[0050] Step S4: A cathode 101 is formed on the n-type doped alloy nitride layer 102, and there is a gap between the cathode 101 and the p-type doped alloy nitride layer 103.

[0051] In some embodiments, the etching of the p-type doped nitride material layer in step S2 to expose a portion of the surface of the p-type doped alloy nitride layer 103 and form a p-type doped nitride layer 104 includes: etching the p-type doped nitride material layer located in the middle of the p-type doped alloy nitride layer 103 to expose the surface of the middle of the p-type doped alloy nitride layer 103, and retaining the p-type doped nitride material layers located at both ends of the surface of the p-type doped alloy nitride layer 103 to form two p-type doped nitride layers 104.

[0052] The above preparation method is provided in the embodiments of this application. Figure 1 The method shown illustrates the fabrication of a pn junction diode, through which the following is obtained: Figure 1 The quasi-vertical structure shown.

[0053] In step S1, the substrate 100 can be an epitaxial substrate or a self-supporting substrate of an n-type doped alloy nitride layer 102. The material of the substrate 100 includes one of sapphire, silicon carbide (SiC), silicon (Si), and gallium nitride. Before forming the sequentially stacked n-type doped alloy nitride layers 102 on the substrate 100, the substrate 100 is first pretreated and heat-treated. Specifically, the pretreatment and heat treatment steps are as follows: the substrate 100 is ultrasonically cleaned with acetone, anhydrous ethanol solution, and deionized water, and then heat-treated at 1050°C for 10 minutes in a hydrogen atmosphere.

[0054] When using an epitaxial substrate, an n-type doped alloy nitride layer 102 is deposited on the substrate 100 using a metal-organic chemical vapor deposition (MOCVD) process. After forming the n-type doped alloy nitride layer 102 on the substrate 100, a p-type doped alloy nitride layer 103 and a p-type doped nitride layer 104 are deposited on the n-type doped alloy nitride layer 102 using an MOCVD process. Preferably, the materials of the n-type doped alloy nitride layer 102 and the p-type doped alloy nitride layer 103 are Al. x Ga (1-x) N, where the value of x is between 0.1 and 0.2. In the embodiments of this application, the thickness of the substrate 100 is 30 nm to 200 nm; the thickness of the n-type doped alloy nitride layer 102 is 10 nm to 30 nm, and the thickness of the p-type doped alloy nitride layer 103 is 10 nm to 30 nm.

[0055] Specifically, a p-type doped nitride layer 104 with a thickness of 60 nm-90 nm is deposited using MOCVD. For example, the material of the p-type doped nitride layer 104 is p-type gallium nitride (GaN) or p-type aluminum nitride (AlN). The thickness of the p-type doped nitride layer 104 can be 50 nm to 110 nm. During the deposition of the p-type doped nitride layer 104, the reaction chamber pressure in the MOCVD process is 10 Torr to 100 Torr, the Ga source flow rate is 50 μmol / min to 100 μmol / min, the ammonia flow rate is 3000 sccm to -6000 sccm, the hydrogen flow rate is 1000 sccm to 2000 sccm, and the temperature is 900 °C.

[0056] In step S2, the p-type doped alloy nitride material layer is etched to expose the surface of one end of the n-type doped alloy nitride layer 102, for subsequent formation of the cathode 101 on this surface. Then, the p-type doped nitride material layer is etched to expose a portion of the surface of the p-type doped alloy nitride layer 103, forming a p-type doped nitride layer 104; a two-dimensional hole channel is formed between the p-type doped nitride layer 104 and the p-type doped alloy nitride layer 103. Specifically, the p-type doped nitride material layer is etched, retaining the p-type doped nitride material layers at both ends of the surface of the p-type doped alloy nitride layer 103, exposing the surface of the middle portion of the p-type doped alloy nitride layer 103 to form the p-type doped nitride layer 104. When the material of the p-type doped nitride layer 104 is p-type GaN, and the materials of the p-type doped alloy nitride layer 103 and the n-type doped alloy nitride layer 102 are all AlGaN, two-dimensional cavitation gas (2DHG) will be generated at the interface between the p-GaN and p-AlGaN heterojunctions due to the polarization effect. In this embodiment, the two-dimensional cavitation gas 2DHG is used to improve the ohmic contact characteristics between the anode 106 and p-AlGaN.

[0057] In step S3, an anode 106 is formed above the p-type doped nitride layer 104, and the anode 106 covers the surface of the p-type doped nitride layer 104 and part of the surface of the p-type doped alloy nitride layer 103.

[0058] In step S4, a cathode 101 is formed on the n-type doped alloy nitride layer 102, and there is a gap between the cathode 101 and the p-type doped alloy nitride layer 103.

[0059] Prepared according to the above preparation method Figure 1 The quasi-vertical pn junction diode shown has a lower defect density (such as dislocations) and better crystal quality in the homoepitaxial GaN layer, thus the quasi-vertical GaN structure is advantageous for obtaining better device characteristics. The substrate 100 mainly uses materials such as silicon, sapphire, and silicon carbide, and from bottom to top consists of an n-type doped alloy nitride layer 102, a p-type doped alloy nitride layer 103, a two-dimensional hole gas channel, and a p-type doped nitride layer 104. The anode 106 and cathode 101 are deposited on the same side of the substrate 100. Charge carriers flow vertically from the anode 106 through the p-type doped nitride layer 104, and then laterally through the n-type doped alloy nitride layer 102 to the cathode 101. Based on the advantages of low cost, large size, and Si-based compatibility of heteroepitaxial technology, the quasi-vertical structure can pursue higher device characteristics while minimizing costs, thus possessing enormous development prospects and application potential.

[0060] like Figure 4As shown in the embodiments of this application, a method for fabricating a pn junction diode with good p-type ohmic contact is also provided, for fabricating such a diode. Figure 2 The p-type ohmic contact pn junction diode includes the following steps:

[0061] Step S1: Form an n-type doped alloy nitride layer 102, a p-type doped alloy nitride layer 103, and a p-type doped nitride material layer stacked sequentially on a substrate 100.

[0062] Step S2: Etch the p-type doped nitride material layer to expose part of the surface of the p-type doped alloy nitride layer 103, forming a p-type doped nitride layer 104; a two-dimensional cavitation channel is formed between the p-type doped nitride layer 104 and the p-type doped alloy nitride layer 103.

[0063] Step S3: An anode 106 is formed above the p-type doped nitride layer 104, and the anode 106 covers the surface of the p-type doped nitride layer 104 and part of the surface of the p-type doped alloy nitride layer 103.

[0064] Step S4: A cathode is formed below the n-type doped alloy nitride layer, and the cathode forms an ohmic contact with the n-type doped alloy nitride layer.

[0065] When preparing such Figure 2 In the pn junction diode, in step S1, the substrate 100 is selected as a self-supporting substrate of an n-type doped alloy nitride layer 102, and a p-type doped alloy nitride layer 103 and a p-type doped nitride layer 104 are sequentially formed on the n-type doped alloy nitride layer 102.

[0066] and Figure 1 The quasi-vertical structure shown is different, Figure 2 The length of the p-type doped alloy nitride layer 103 in the pn junction diode shown is equal to the length of the n-type doped alloy nitride layer 102. Here, the length direction refers to... Figure 2 The direction from left to right is that the p-type doped nitride layer 104 located at the left end of the p-type doped alloy nitride layer 103 points to the p-type doped nitride layer 104 located at the right end of the p-type doped alloy nitride layer 103.

[0067] When forming a p-type doped nitride layer 104 on a p-type doped alloy nitride layer 103, firstly, a p-type doped nitride material layer (epitaxial layer) is formed on the side of the p-type doped alloy nitride layer 103 away from the n-type doped alloy nitride layer 102. Then, step S2 is performed to etch the p-type doped nitride material layer to form the p-type doped nitride layer 104. A two-dimensional hole channel is formed between the p-type doped nitride layer 104 and the p-type doped alloy nitride layer 103.

[0068] Next, step S3 is performed to form an anode 106 above the p-type doped nitride layer 104. Finally, step S4 is performed to form a cathode 101 below the n-type doped alloy nitride layer 102. The cathode 101 forms an ohmic contact with the n-type doped alloy nitride layer 102, that is, the cathode 101 is formed below the self-supporting substrate of the n-type doped alloy nitride layer 102. Thus, a cathode 106 is fabricated as shown in the image. Figure 2 The pn junction diode shown has good pn ohmic contact because the heterojunction of the p-type doped nitride layer 104 and the p-type doped alloy nitride layer 103 can generate two-dimensional holes to reduce the ohmic contact resistance and form a good p-type ohmic contact. Therefore, the pn junction diode with this structure has a good p-type ohmic contact and the device has a high operating life and reliability.

[0069] Based on the above technical solutions, this application addresses the problem in existing diodes where the large potential barrier between the p-type AlGaN material and the metal makes it difficult to form a good ohmic contact. This application provides a pn junction diode with good p-type ohmic contact and its fabrication method. The pn junction diode includes a substrate 100 and an n-type doped alloy nitride layer 102 disposed on the substrate 100. A p-type doped alloy nitride layer 103 and a p-type doped nitride layer 104 are sequentially stacked on the n-type doped alloy nitride layer 102. One end of the p-type doped alloy nitride layer 103 is flush with the end of the n-type doped alloy nitride layer 102, and the other end of the p-type doped alloy nitride layer 103 is located on the surface of the n-type doped alloy nitride layer 102. Multiple p-type doped nitride layers 104 are included, and the p-type doped nitride layers 104 are positioned... At the end of the surface of the p-type doped alloy nitride layer 103, a two-dimensional hole gas channel is formed between each p-type doped alloy nitride layer 104 and the p-type doped alloy nitride layer 103; a two-dimensional hole gas can be formed between the p-type doped alloy nitride layer 104 and the p-type doped alloy nitride layer 103, and the two-dimensional hole gas is located in the two-dimensional hole gas channel; an anode 106 is provided above the p-type doped nitride layer 104, the anode 106 covers the surface of the p-type doped nitride layer 104 and part of the surface of the p-type doped alloy nitride layer 103, and the anode 106 and the p-type doped alloy nitride layer 103 form a p-type ohmic contact; a cathode 101 is also provided on the n-type doped alloy nitride layer 102, there is a gap between the cathode 101 and the p-type doped alloy nitride layer 103, and the cathode 101 and the n-type doped alloy nitride layer 102 form an ohmic contact. This application utilizes a heterojunction of a p-type doped nitride layer 104 (e.g., p-type GaN) and a p-type doped alloy nitride layer 103 (e.g., p-type AlGaN) to generate two-dimensional holes to reduce the ohmic contact resistance, thereby forming a good p-type ohmic contact, which improves the device's operating life and reliability, and has good application prospects.

[0070] Those skilled in the art will understand that the above-described embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of this application. Any person skilled in the art can make their own modifications and alterations without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A pn ​​junction diode with good p-type ohmic contact, characterized in that, include: A substrate and an n-type doped alloy nitride layer disposed on the substrate; The n-type doped alloy nitride layer is sequentially stacked with a p-type doped alloy nitride layer and at least two discrete p-type doped nitride layers; one end of the p-type doped alloy nitride layer is flush with the end of the n-type doped alloy nitride layer, and the other end of the p-type doped alloy nitride layer is located on the surface of the n-type doped alloy nitride layer. The at least two p-type doped nitride layers are respectively located at both ends of the upper surface of the p-type doped alloy nitride layer. The thickness of the p-type doped nitride layer is 60 nm to 90 nm. There is a spacing between adjacent p-type doped nitride layers, and a two-dimensional hole gas channel is formed between each p-type doped nitride layer and the p-type doped alloy nitride layer. Two-dimensional holes can be formed between the p-type doped nitride layers and the p-type doped alloy nitride layers, and the two-dimensional holes are located within the two-dimensional hole gas channel. An anode is provided above the p-type doped nitride layer. The anode simultaneously covers the upper surfaces of the at least two p-type doped nitride layers and a portion of the upper surface of the p-type doped alloy nitride layer located between them, and the anode forms a p-type ohmic contact with the p-type doped alloy nitride layer. A cathode is also provided on the n-type doped alloy nitride layer, and there is a gap between the cathode and the p-type doped alloy nitride layer, and the cathode and the n-type doped alloy nitride layer form an ohmic contact. The two-dimensional hole channel is directly opposite the p-type doped nitride layer, and there is a one-to-one correspondence between the two-dimensional hole channel and the p-type doped nitride layer.

2. The pn junction diode with good p-type ohmic contact according to claim 1, characterized in that, The material of the p-type doped alloy nitride layer is AlGaN, and / or the material of the n-type doped alloy nitride layer is AlGaN.

3. The pn junction diode with good p-type ohmic contact according to claim 1, characterized in that, The material of the p-type doped nitride layer includes GaN or AlN.

4. A pn ​​junction diode with good p-type ohmic contact, characterized in that, include: A substrate and an n-type doped alloy nitride layer disposed on the substrate; A p-type doped alloy nitride layer and at least two discrete p-type doped nitride layers are sequentially stacked on the n-type doped alloy nitride layer; the two ends of the p-type doped alloy nitride layer are flush with the two ends of the n-type doped alloy nitride layer. The at least two p-type doped nitride layers are respectively located at both ends of the upper surface of the p-type doped alloy nitride layer. The thickness of the p-type doped nitride layer is 60 nm to 90 nm. There is a spacing between adjacent p-type doped nitride layers, and a two-dimensional hole gas channel is formed between each p-type doped nitride layer and the p-type doped alloy nitride layer. Two-dimensional holes can be formed between the p-type doped nitride layers and the p-type doped alloy nitride layers, and the two-dimensional holes are located within the two-dimensional hole gas channel. An anode is provided above the p-type doped nitride layer. The anode simultaneously covers the upper surfaces of the at least two p-type doped nitride layers and a portion of the upper surface of the p-type doped alloy nitride layer located between them, and the anode forms a p-type ohmic contact with the p-type doped alloy nitride layer. A cathode is also provided below the substrate, and the cathode forms an ohmic contact with the n-type doped alloy nitride layer; The two-dimensional hole channel is directly opposite the p-type doped nitride layer, and there is a one-to-one correspondence between the two-dimensional hole channel and the p-type doped nitride layer.

5. The pn junction diode with good p-type ohmic contact according to claim 4, characterized in that, The material of the p-type doped alloy nitride layer is AlGaN, and / or the material of the n-type doped alloy nitride layer is AlGaN.

6. The pn junction diode with good p-type ohmic contact according to claim 4, characterized in that, The material of the p-type doped nitride layer includes GaN or AlN.

7. The pn junction diode with good p-type ohmic contact according to claim 4, characterized in that, The p-type doped nitride layer comprises two layers, which are located at opposite ends of the surface of the p-type doped alloy nitride layer, and there is a gap between the two p-type doped nitride layers. The ends of the two p-type doped nitride layers are respectively flush with the ends of the p-type doped alloy nitride layer and the n-type doped alloy nitride layer.

8. A method for fabricating a pn junction diode with good p-type ohmic contact, the method being used to fabricate a pn junction diode with good p-type ohmic contact as described in claim 1 or 4, characterized in that, Includes the following steps: An n-type doped alloy nitride layer, a p-type doped alloy nitride material layer, and a p-type doped nitride material layer are formed sequentially on a substrate. The p-type doped alloy nitride material layer and the P-type doped nitride material layer are etched to expose part of the surface of the n-type doped alloy nitride layer, thereby forming a p-type doped alloy nitride layer. And expose part of the surface of the p-type doped alloy nitride layer to form a p-type doped nitride layer; a two-dimensional cavitation channel is formed between the p-type doped nitride layer and the p-type doped alloy nitride layer; An anode is formed above the p-type doped nitride layer, the anode covering the surface of the p-type doped nitride layer and a portion of the surface of the p-type doped alloy nitride layer; A cathode is formed on the n-type doped alloy nitride layer, and there is a gap between the cathode and the p-type doped alloy nitride layer.

9. The method for fabricating a pn junction diode with good p-type ohmic contact according to claim 8, characterized in that, The etching of the p-type doped nitride material layer to expose a portion of the surface of the p-type doped alloy nitride layer, forming a p-type doped nitride layer, includes: The p-type doped nitride material layer located in the middle of the p-type doped alloy nitride layer is etched to expose the surface of the middle part of the p-type doped alloy nitride layer, while the p-type doped nitride material layers located at both ends of the surface of the p-type doped alloy nitride layer are retained, forming two p-type doped nitride layers.

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