Hydrogen terminated diamond / gallium oxide hetero lateral diode and method of fabrication

Abstract

The present application relates to a kind of hydrogen terminal diamond / gallium oxide hetero lateral diode and preparation method, lateral diode includes: diamond substrate layer, n type Ga2O3 layer, hydrogen terminal diamond surface layer, cathode and anode, wherein, the n type Ga2O3 layer is located on one side of the diamond substrate layer, the hydrogen terminal diamond surface layer is located on the other side of the diamond substrate layer, the cathode is located on the n type Ga2O3 layer, the anode is located on the hydrogen terminal diamond surface layer.This lateral diode is combined together by the method of hetero integration p type electrically conductive diamond and n type electrically conductive Ga2O3, preparation ultra-wide bandgap semiconductor hetero integrated quasi-vertical diode device, effectively solve the problem that diamond is difficult to realize n type doping, gallium oxide is difficult to realize p type doping, improve the breakdown voltage of diode, realize ultra-wide bandgap semiconductor complementary conduction device.

Description

Technical Field

[0001] The present invention belongs to the field of diode power electronic devices, and in particular relates to a hydrogen-terminated diamond / gallium oxide heterogeneous lateral diode and a preparation method thereof. Background Art

[0002] With the increasing application of power electronic devices, demanding operating conditions such as high temperature, high voltage, high electric field, and low power consumption have placed higher demands on the devices themselves. Power devices, represented by diodes, have garnered widespread attention. Simultaneously, the primary semiconductor materials used to manufacture these devices have also evolved, from first-generation semiconductor materials such as silicon (Si) and germanium (Ge) to the currently widely used third-generation semiconductor materials such as gallium nitride (GaN) and silicon carbide (SiC). In recent years, ultra-wide bandgap semiconductor materials, such as diamond and gallium oxide (Ga2O3), have gradually come into the spotlight.

[0003] Compared with previous generations of semiconductor materials, gallium oxide (Ga2O3) has a larger bandgap (4.6-4.9 eV) and a higher breakdown field strength (8 MV / cm). At the same time, its Baliga figure of merit is as high as 3000, which is 4 times that of gallium nitride (GaN) and 10 times that of silicon carbide (SiC). In addition, other physical and chemical properties of gallium oxide (Ga2O3) are also relatively stable, including electrical properties and luminescence properties. In terms of material growth and preparation, Ga2O3 materials can be grown over large areas while ensuring low dislocations, which highlights its huge low-cost advantage. These many factors combined determine that Ga2O3 is the only choice among ultra-wide bandgap semiconductor materials for use in power devices. However, there are still some problems that need to be solved in the application of gallium oxide materials. On the one hand, taking the widely used β-Ga2O3 as an example, there are many donor defects in it, such as oxygen vacancies, gallium vacancies, interstitial oxygen and interstitial gallium, which makes it naturally have a certain n-type conductivity, making it easier to achieve high-quality n-type doping. At the same time, it becomes very difficult to achieve high-quality p-type doping of β-Ga2O3. Therefore, the reverse breakdown voltage of Ga2O3 will be affected when it is used in diode devices. On the other hand, power diode devices generate a lot of heat during operation. Due to the low thermal conductivity of Ga2O3 materials, the thermal effect of the device becomes very obvious, and the reverse leakage current of the diode will also increase accordingly. The influence of various unfavorable factors also poses a great challenge to the reliability of the device.

[0004] In summary, the current Ga2O3 diodes have problems such as low reverse breakdown voltage, low thermal conductivity, and large reverse leakage current. Summary of the Invention

[0005] To address the above-mentioned problems in the prior art, the present invention provides a hydrogen-terminated diamond / gallium oxide heterojunction lateral diode and a method for fabricating the same. The technical problems to be solved by the present invention are achieved through the following technical solutions:

[0006] The embodiment of the present invention provides a hydrogen-terminated diamond / gallium oxide heterojunction lateral diode, comprising: a diamond substrate layer, an n-type Ga2O3 layer, a hydrogen-terminated diamond surface layer, a cathode and an anode, wherein:

[0007] The n-type Ga2O3 layer is located on one side of the diamond substrate layer, the hydrogen-terminated diamond surface layer is located on the other side of the diamond substrate layer, the cathode is located on the n-type Ga2O3 layer, and the anode is located on the hydrogen-terminated diamond surface layer.

[0008] In one embodiment of the present invention, the material of the diamond substrate layer includes single crystal diamond and has a thickness of 300-500 μm.

[0009] In one embodiment of the present invention, the thickness of the n-type Ga2O3 layer is 8-15 μm.

[0010] In one embodiment of the present invention, the thickness of the hydrogen-terminated diamond surface layer is 3-5 nm.

[0011] In one embodiment of the present invention, the cathode material includes one or more of Ti and Au, and has a thickness of 180-220 nm.

[0012] In one embodiment of the present invention, the material of the anode includes Au, and the thickness is 80-120 nm.

[0013] Another embodiment of the present invention provides a method for preparing a hydrogen-terminated diamond / gallium oxide heterojunction lateral diode, comprising the steps of:

[0014] S1, preparing a hydrogen-terminated diamond surface layer on a diamond substrate layer, and depositing a first protective layer and a second protective layer on the hydrogen-terminated surface layer;

[0015] S2, etching away a portion of the first protective layer and the second protective layer until a portion of the hydrogen-terminated diamond surface layer is exposed, and the exposed hydrogen-terminated diamond surface layer is degraded to expose a portion of the diamond substrate layer;

[0016] S3, transferring the n-type Ga2O3 layer onto the exposed diamond substrate layer;

[0017] S4, preparing a cathode on the n-type Ga2O3 layer;

[0018] S5, etching away the remaining first protective layer and the second protective layer to expose the remaining hydrogen-terminated diamond surface layer;

[0019] S6. Preparing an anode on the exposed hydrogen-terminated diamond surface layer.

[0020] In one embodiment of the present invention, step S1 includes:

[0021] Performing hydrogen plasma treatment on the surface of the diamond substrate layer using MPCVD equipment to form the hydrogen-terminated diamond surface layer;

[0022] Depositing SiO2 on the hydrogen-terminated diamond surface layer to form a first protective layer;

[0023] Au is deposited on the first protective layer to form a second protective layer.

[0024] In one embodiment of the present invention, the thickness of the first protective layer is 180-220 nm, and the thickness of the second protective layer is 80-120 nm.

[0025] In one embodiment of the present invention, etching away a portion of the first protective layer and the second protective layer in step S2 until a portion of the hydrogen-terminated diamond surface layer is exposed comprises:

[0026] The Au material of the second protective layer is etched away using a KI I2 solution, and the SiO2 material of the first protective layer is etched away using an acid solution until the hydrogen-terminated diamond surface layer is exposed.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The lateral diode of the present invention combines p-type conductive diamond and n-type conductive Ga2O3 together through a heterogeneous integration method to prepare an ultra-wide bandgap semiconductor heterogeneous integrated quasi-vertical diode device, which effectively solves the problem that it is difficult to achieve n-type doping of diamond and p-type doping of gallium oxide, improves the breakdown voltage of the diode, and realizes an ultra-wide bandgap semiconductor complementary conductive device.

[0029] 2. The lateral diode of the present invention adopts a diamond substrate layer. Diamond, as an ultra-wide bandgap semiconductor material with high breakdown field strength and high thermal conductivity, can effectively solve the problem of extremely low thermal conductivity of gallium oxide, alleviate the defects of obvious thermal effect and large reverse leakage current of the device, and realize a high-performance ultra-wide bandgap semiconductor diode suitable for applications in ultra-high temperature, high pressure and strong electric field environments.

[0030] 3. The lateral diode of the present invention uses hydrogen-terminated diamond as the p-type region of the gallium oxide diode. Compared with p-type doped diamond, the process is simpler and the cost is lower. The surface hole concentration and mobility levels are more impressive, thereby improving device performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic structural diagram of a hydrogen-terminated diamond / gallium oxide heterojunction lateral diode provided by an embodiment of the present invention;

[0032] Figure 2a-2f A schematic diagram of a process for preparing a hydrogen-terminated diamond / gallium oxide heterojunction lateral diode provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0034] Example 1

[0035] See Figure 1 , Figure 1 A schematic structural diagram of a hydrogen-terminated diamond / gallium oxide heterojunction lateral diode provided in an embodiment of the present invention.

[0036] The lateral diode includes a diamond substrate layer 1, an n-type Ga2O3 layer 2, a hydrogen-terminated diamond surface layer 3, a cathode 4, and an anode 5. The n-type Ga2O3 layer 2 is located on one side of the diamond substrate layer 1, the hydrogen-terminated diamond surface layer 3 is located on the other side of the diamond substrate layer 1, the cathode 4 is located on the n-type Ga2O3 layer 2, and the anode 5 is located on the hydrogen-terminated diamond surface layer 3.

[0037] Specifically, the n-type Ga2O3 layer 2 and the hydrogen-terminated diamond surface layer 3 are both located on the upper surface of the diamond substrate layer 1. The n-type Ga2O3 layer 2 and the hydrogen-terminated diamond surface layer 3 are separated by a certain distance and do not contact each other. The cathode 4 is located directly above the n-type Ga2O3 layer 2, and the anode 5 is located directly above the p-type hydrogen-terminated diamond surface layer 3.

[0038] In one specific embodiment, the material of the diamond substrate layer 1 includes, but is not limited to, single crystal diamond, and has a thickness of 300-500 μm. The thickness of the n-type Ga2O3 layer 2 is 8-15 μm. The thickness of the hydrogen-terminated diamond surface layer 3 is 3-5 nm. The material of the cathode 4 includes one or more of Ti and Au, and has a thickness of 180-220 nm. For example, the material of the cathode 4 is Ti / Au, and has a thickness of 50 / 150 nm. The material of the anode 5 includes Au, and has a thickness of 80-120 nm. For example, the thickness of the anode 5 is 100 nm.

[0039] Diamond is the material with the best p-type conductivity among the known wide bandgap and ultra-wide bandgap semiconductor materials. When hydrogen-terminated diamond treated with hydrogen plasma is exposed to air for a period of time, a layer of two-dimensional hole gas 2DHG will form on its surface, showing p-type conductivity. The hole concentration is generally around 10 12 -10 14 cm -2 , the hole mobility is generally around 300 cm 2 / V·s, but achieving n-type doping in diamond remains a global physical challenge. Therefore, the lateral diode of this embodiment combines p-type conductive diamond and n-type conductive Ga2O3 through a heterogeneous integration method to produce an ultra-wide bandgap semiconductor heterogeneous integrated quasi-vertical diode device. This effectively addresses the difficulties of achieving n-type doping in diamond and p-type doping in gallium oxide, improves the breakdown voltage of the diode, and realizes an ultra-wide bandgap semiconductor complementary conductive device. The lateral diode of this embodiment utilizes a diamond substrate layer. Diamond, as an ultra-wide bandgap semiconductor material with high breakdown field strength and high thermal conductivity, effectively addresses the extremely low thermal conductivity of gallium oxide, alleviating the device's significant thermal effects and high reverse leakage current, thereby achieving a high-performance ultra-wide bandgap semiconductor diode suitable for applications in ultra-high temperature, high voltage, and strong electric field environments. The lateral diode of this embodiment utilizes hydrogen-terminated diamond as the p-type region of the gallium oxide diode. Compared to p-type doped diamond, this method offers simpler processing and lower costs, while also achieving impressive surface hole concentration and mobility levels, thereby improving device performance. The lateral diode of this embodiment is of great significance to the development of ultra-wide bandgap semiconductors and integrated circuits.

[0040] Example 2

[0041] Based on Example 1, see Figure 2a-2f , Figure 2a-2f A schematic diagram of a method for preparing a hydrogen-terminated diamond / gallium oxide heterojunction lateral diode according to an embodiment of the present invention. The method comprises the following steps:

[0042] S1. Prepare a hydrogen-terminated diamond surface layer 3 on the diamond substrate layer 1, and deposit a first protective layer 31 and a second protective layer 32 on the hydrogen-terminated surface layer 3. Figure 2a .

[0043] First, a single crystal diamond material with a thickness of 300-500 μm is selected, and the surface of the diamond substrate layer 1 is treated with hydrogen plasma using an MPCVD device to form a hydrogen-terminated diamond surface layer 3 .

[0044] Then, SiO2 is deposited on the hydrogen-terminated diamond surface layer 3 to form a first protective layer 31. Optionally, the thickness of SiO2 is 200 nm.

[0045] Finally, Au is deposited on the first protective layer 31 to form the second protective layer 32. Optionally, the thickness of Au is 100 nm.

[0046] In this embodiment, since the stability of the hydrogen-terminated diamond surface layer is relatively poor, two protective layers are prepared to protect the hydrogen-terminated surface layer 20 to ensure the performance of the hydrogen-terminated surface layer 20 .

[0047] S2, etching away a portion of the first protective layer 31 and the second protective layer 32 until a portion of the hydrogen-terminated diamond surface layer 3 is exposed, and the exposed hydrogen-terminated diamond surface layer 3 degenerates to expose a portion of the diamond substrate layer 1, see Figure 2b .

[0048] Specifically, first, half of the Au material is etched away using a KI / I2 solution, and then half of the SiO2 material is etched away using an acid solution until half of the hydrogen-terminated diamond surface layer 3 is exposed. Finally, the exposed hydrogen-terminated diamond surface layer 3 is allowed to naturally degenerate until half of the diamond substrate layer 1 is exposed.

[0049] S3, transfer the n-type Ga2O3 layer 2 onto the exposed diamond substrate layer 1, see Figure 2c .

[0050] Specifically, the pre-prepared n-type Ga2O3 layer 2 is transferred onto the exposed diamond substrate layer 1 so as to be at a certain distance from the hydrogen-terminated diamond surface layer 3.

[0051] S4. Prepare cathode 4 on n-type Ga2O3 layer 2, see Figure 2d .

[0052] Specifically, first, a layer of Ti / Au with a thickness of 200nm (50 / 150nm) was deposited on the n-type Ga2O3 layer 2 to form the cathode 4 electrode. Then, the device was annealed at 470°C in an N2 atmosphere for 60s to form a good ohmic contact.

[0053] S5, etch away the remaining first protective layer 31 and the second protective layer 32 to expose the remaining hydrogen-terminated diamond surface layer 3, see Figure 2e .

[0054] Specifically, first, a photoresist is coated on the surface of the Ga2O3 device as a protective layer, and the other half of the Au material is etched away using a KI I2 solution, and the other half of the SiO2 material is etched away using an acid solution until the other half of the hydrogen-terminated diamond surface layer 3 is exposed.

[0055] S6. Prepare an anode 5 on the exposed hydrogen-terminated diamond surface layer 3, see Figure 2f .

[0056] Specifically, a layer of Au with a thickness of 100 nm is deposited on the exposed hydrogen-terminated diamond surface layer 3 to form the anode 5, thereby obtaining a hydrogen-terminated diamond / gallium oxide heterojunction lateral diode.

[0057] This embodiment combines p-type conductive diamond and n-type conductive Ga2O3 through a heterogeneous integration method to prepare an ultra-wide bandgap semiconductor heterogeneous integrated quasi-vertical diode device, effectively solving the key problems of difficulty in achieving n-type doping in diamond and p-type doping in gallium oxide. It also effectively solves the physical problem of extremely low thermal conductivity of gallium oxide, and realizes a high-performance ultra-wide bandgap semiconductor diode suitable for applications in ultra-high temperature, high voltage, and strong electric field environments. It reduces device preparation costs and improves device performance, which is of great significance to the development of ultra-wide bandgap semiconductors and integrated circuits.

[0058] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a hydrogen-terminated diamond / gallium oxide heterojunction lateral diode, characterized in that: Including steps: S1, preparing a hydrogen-terminated diamond surface layer (3) on a diamond substrate layer (1), and depositing a first protective layer (31) and a second protective layer (32) on the hydrogen-terminated surface layer (3); S2, etching away a portion of the first protective layer (31) and the second protective layer (32) until a portion of the hydrogen-terminated diamond surface layer (3) is exposed, and the exposed hydrogen-terminated diamond surface layer (3) is degraded to expose a portion of the diamond substrate layer (1); S3, transferring the n-type Ga2O3 layer (2) onto the exposed diamond substrate layer (1); S4, preparing a cathode (4) on the n-type Ga2O3 layer (2); S5, etching away the remaining first protective layer (31) and the second protective layer (32) to expose the remaining hydrogen-terminated diamond surface layer (3); S6. Preparing an anode (5) on the exposed hydrogen-terminated diamond surface layer (3).

2. The method for preparing a hydrogen-terminated diamond / gallium oxide heterojunction lateral diode according to claim 1, characterized in that: Step S1 includes: Performing hydrogen plasma treatment on the surface of the diamond substrate layer (1) using MPCVD equipment to form the hydrogen-terminated diamond surface layer (3); Depositing SiO2 on the hydrogen-terminated diamond surface layer (3) to form a first protective layer (31); Au is deposited on the first protective layer (31) to form a second protective layer (32).

3. The method for preparing a hydrogen-terminated diamond / gallium oxide heterojunction lateral diode according to claim 2, characterized in that: The thickness of the first protective layer (31) is 180-220 nm, and the thickness of the second protective layer (32) is 80-120 nm.

4. The method for preparing a hydrogen-terminated diamond / gallium oxide heterojunction lateral diode according to claim 1, wherein: In step S2, a portion of the first protective layer (31) and the second protective layer (32) is etched away until a portion of the hydrogen-terminated diamond surface layer (3) is exposed, comprising: The Au material of the second protective layer (32) is etched away using a KI / I2 etching solution, and the SiO2 material of the first protective layer (31) is etched away using an acid solution until the hydrogen-terminated diamond surface layer (3) is exposed.

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