Boron-nitrogen co-doped room-temperature high-conductivity n-type diamond and epitaxial preparation method thereof

Abstract

A boron-nitrogen co-doped room-temperature high-conductivity n-type diamond and its epitaxial preparation method are disclosed. The boron-nitrogen co-doped room-temperature high-conductivity n-type diamond comprises, from bottom to top: an undoped single-crystal diamond substrate, an undoped diamond pre-growth buffer layer, and a boron-nitrogen co-doped diamond epitaxial layer; the boron doping concentration in the boron-nitrogen co-doped diamond epitaxial layer is 1×10⁻⁶. 15 ~1×10 20 at / cm 3 The nitrogen doping concentration is 1×10 16 ~1×10 21 at / cm 3 This invention also discloses an epitaxial preparation method for boron-nitrogen co-doped room-temperature high-conductivity n-type diamond. The boron-nitrogen co-doped room-temperature high-conductivity n-type diamond epitaxial layer of this invention exhibits a high N-doping concentration, resulting in a negative Hall coefficient, high carrier concentration, and low resistivity at room temperature. The method of this invention has no residual boron source in the reaction chamber, high nitrogen doping efficiency and concentration, stable doping state at the epitaxial interface, good batch repeatability, and is highly efficient, stable, and controllable.

Description

Technical Field

[0001] This invention relates to the field of diamond semiconductor material preparation technology, specifically to a boron-nitrogen co-doped room temperature high conductivity n-type diamond and its epitaxial preparation method. Background Technology

[0002] Diamond, with its wide bandgap, high breakdown field strength, high thermal conductivity, high carrier mobility, low dielectric constant, and excellent chemical stability, is an ultrawide bandgap semiconductor material with great application potential. It holds broad application prospects in high-power electronic devices, high-frequency devices, deep-ultraviolet detectors, radiation detectors, and quantum devices. Diamond has a bandgap of approximately 5.5 eV, a thermal conductivity of up to about 2200 W / m·K, and excellent breakdown field strength and carrier transport properties, giving it significant advantages in high-temperature, high-power, and high-radiation environments.

[0003] However, intrinsic diamond typically exhibits high insulation due to its large bandgap. To realize the application of diamond in semiconductor devices, effective p-type and n-type doping is required. Currently, boron-doped diamond can stably achieve room-temperature p-type conductivity, while the preparation of room-temperature n-type conductive diamond still faces significant challenges. Although nitrogen atoms can serve as donor impurities in diamond, their deep donor energy levels and high activation energies result in low effective ionized carrier concentrations at room temperature, making it difficult to obtain room-temperature high-conductivity n-type diamond that meets the requirements of device applications. Therefore, improving the effective doping concentration of nitrogen atoms in the diamond epitaxial layer, mitigating the ionization behavior of nitrogen-related donors, and achieving high carrier concentration and low resistivity at room temperature are key technical challenges in the current preparation of n-type diamond materials.

[0004] CN120797187A discloses a boron-nitrogen co-doped N-type diamond and its preparation method based on MPCVD technology. The method mainly involves epitaxially forming a boron-nitrogen co-doped N-type diamond layer by introducing boron, nitrogen, and carbon sources and growth gases onto the surface of an intrinsic diamond layer. Hydrogen etching can be used to remove amorphous carbon from the surface after the boron-nitrogen co-doped layer is grown. The key aspects of this method are conventional boron-nitrogen co-doping and post-growth surface treatment. Further improvements are needed in increasing the nitrogen atom doping concentration, achieving low resistivity at room temperature with higher N-doping concentrations, and improving the room-temperature n-type conductivity repeatability of different batches of samples. In particular, while existing related technologies have reported n-type conductive or highly conductive diamonds, their Hall effect testing conditions are not explicitly limited to room temperature, and the reported resistivity remains relatively high.

[0005] CN121496566A discloses a method for epitaxially growing highly conductive N-type diamond based on boron-phosphorus-nitrogen co-doping technology. The method uses borane, phosphine, and ammonia as a mixed boron-phosphorus-nitrogen source gas. Boron, phosphorus, and nitrogen co-doping reduces the activation energy of phosphorus atoms, and n-type conductivity is achieved relying on phosphorus-related donors and BP complexes. The core of this technique lies in improving the doping efficiency of phosphorus and the effect of phosphorus-related donors, rather than increasing the effective doping concentration of nitrogen atoms in diamond under phosphorus-free conditions. Furthermore, the SIMS test results show a nitrogen atom concentration of 3.1 × 10⁻⁶. 16 cm -3 This indicates that the nitrogen doping concentration is still relatively limited. Furthermore, the resistivity reported in this technical solution embodiment is 2.66 × 10⁻⁶. -1 Ω·cm and 3.83×10 -1 A resistivity of Ω·cm is not conducive to reducing carrier transport losses within the material, nor to reducing device on-resistance and improving current transport capability, which may limit its application in high-power, high-current-density electronic devices.

[0006] Therefore, although existing technologies have proposed methods for preparing n-type diamond by boron-nitrogen co-doping or boron-phosphorus-nitrogen co-doping, how to significantly increase the N doping concentration in the diamond epitaxial layer through MPCVD without introducing phosphorus, and how to stably activate the N-provided carriers at room temperature to exhibit a negative Hall coefficient, high carrier concentration and low resistivity, remains a key technical problem that urgently needs to be solved in the preparation of n-type diamond materials. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a boron-nitrogen co-doped room temperature high conductivity n-type diamond with high N doping concentration in the diamond epitaxial layer without the introduction of phosphorus, exhibiting negative Hall coefficient, high carrier concentration and low resistivity at room temperature.

[0008] The further technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide an epitaxial preparation method for boron-nitrogen co-doped room temperature high conductivity n-type diamond with no residual boron source in the reaction chamber, which will not interfere with the subsequent nitrogen source doping, high nitrogen doping efficiency and concentration, stable doping state at the epitaxial interface, good batch repeatability, and high efficiency, stability and controllability.

[0009] The technical solution adopted by this invention to solve its technical problem is as follows: A boron-nitrogen co-doped room temperature high conductivity n-type diamond, comprising, from bottom to top: an undoped single-crystal diamond substrate, an undoped diamond pre-growth buffer layer, and a boron-nitrogen co-doped diamond epitaxial layer; the boron doping concentration in the boron-nitrogen co-doped diamond epitaxial layer is 1×10⁻⁶. 15 ~1×10 20at / cm 3 (More preferably 1×10) 17 ~1×10 19 at / cm 3 The nitrogen doping concentration is 1×10 16 ~1×10 21 at / cm 3 (More preferably 1×10) 18 ~1×10 20 at / cm 3 First-principles calculations show that boron-nitrogen co-doping can form boron-nitrogen composite defect structures such as BN, BN2, BN3, and BN4 in the diamond lattice. With increasing nitrogen content, the local electronic structure is modulated, and the material's conductivity gradually shifts from boron-dominated p-type characteristics to nitrogen-related composite defect-dominated n-type characteristics. These calculations provide a theoretical basis for the p-type to n-type conductivity transition in boron-nitrogen co-doped diamond. Compared to existing techniques that primarily focus on regulating the conductivity type of boron-nitrogen co-doping or rely on phosphorus-related donors, this invention further achieves a higher concentration of boron and nitrogen synergistically introduced into the diamond epitaxial layer, resulting in an epitaxial layer exhibiting highly conductive n-type characteristics at room temperature.

[0010] The undoped single-crystal diamond substrate is used to provide a lattice-matched single-crystal epitaxial growth substrate. The undoped diamond pre-growth buffer layer is used to improve the substrate surface condition, isolate substrate surface defects, etching damage, and residual active species generated during nitrogen-assisted etching, reduce the influence of reaction chamber memory effect on the subsequent boron-nitrogen co-doped epitaxial growth process, and provide a stable homogeneous epitaxial interface for the boron-nitrogen co-doped diamond epitaxial layer. The boron-nitrogen co-doped diamond epitaxial layer serves as a functional layer for achieving room-temperature n-type conductivity. Through the synergistic incorporation of boron and nitrogen elements and the formation of boron-nitrogen composite defects, the local electronic structure of diamond is regulated, thereby increasing the room-temperature electron concentration and reducing the resistivity.

[0011] The limitation of the boron and nitrogen doping concentration range is mainly based on the effective incorporation capacity of elements and the room-temperature carrier activation requirements during boron-nitrogen co-doping. Due to the significant size difference between nitrogen and carbon atoms, nitrogen atoms need to overcome a high lattice formation energy to enter the diamond lattice. Simultaneously, the nitrogen-related donor energy levels are deep, resulting in low effective incorporation concentration and low room-temperature electron activation efficiency when using single nitrogen doping. Therefore, achieving high concentrations of nitrogen doping in diamond is quite challenging. This invention regulates the surface activity state during growth through nitrogen-assisted etching and combines it with boron and nitrogen co-doping, enabling boron and nitrogen atoms to participate in lattice construction during growth. This promotes the formation of boron-nitrogen composite defects such as BN, BN2, and BN3, thereby improving the effective incorporation capacity of nitrogen in the diamond lattice. Boron can regulate the local lattice environment and stabilize the boron-nitrogen composite structure, while nitrogen is the main source of electron carriers. Higher concentrations of boron and nitrogen co-doping can increase the number of nitrogen-related donors and boron-nitrogen composite defects, increase room-temperature electron concentration, and reduce material resistivity, thus obtaining an n-type diamond epitaxial layer with high conductivity.

[0012] Preferably, the thickness of the undoped diamond pre-growth buffer layer is 1–5 μm. This thickness range can effectively cover substrate surface defects and improve epitaxial interface quality, while avoiding excessive thickness that would increase growth time and process costs.

[0013] Preferably, the thickness of the boron-nitrogen co-doped diamond epitaxial layer is 1–5 μm. This thickness range ensures that the doped layer has a sufficient effective current-carrying area and reduces the influence of the substrate and interface on electrical performance testing, while avoiding stress accumulation and increased defects caused by excessive thickness.

[0014] Preferably, the boron-nitrogen co-doped diamond epitaxial layer exhibits n-type conductivity characteristics at 10–500℃ (more preferably 10–300℃, even more preferably 10–200℃), with a negative Hall coefficient and a carrier concentration of -1×10⁻⁶. 15 ~-1×10 22 cm -3 (More preferably -1×10) 18 ~-1×10 22 cm -3 Its resistivity is 0.01–10 Ω·cm (more preferably 0.01–1.00 Ω·cm). (Ω·cm), where it still exhibits n-type conductivity characteristics under room temperature conditions of 10–40℃, with a negative Hall coefficient and a carrier concentration of -1×10. 15 ~-1×10 20 cm -3 (More preferably -1×10) 18 ~-1×10 20 cm -3Its resistivity is 0.01–10 Ω·cm (more preferably 0.01–1.00 Ω·cm). Unlike existing technologies that do not explicitly define room temperature Hall test conditions or mainly rely on high-temperature electrical responses to prove n-type conductivity, this invention directly confirms that the obtained epitaxial layer has a negative Hall coefficient through room temperature Hall effect testing and obtains a room temperature resistivity as low as 0.08 Ω·cm, indicating that the boron-nitrogen co-doped diamond epitaxial layer can generate effective n-type carrier contributions under room temperature conditions.

[0015] The technical solution adopted by the present invention to further solve its technical problem is as follows: A method for epitaxial preparation of boron-nitrogen co-doped room temperature high conductivity n-type diamond, comprising the following steps: (1) The cleaned undoped single crystal diamond substrate is placed in the reaction chamber of a microwave plasma chemical vapor deposition equipment. After evacuation, a mixture of hydrogen and nitrogen is introduced to etch the inner wall of the reaction chamber, the reaction environment and the surface of the undoped single crystal diamond substrate. (2) In the reaction chamber after etching, hydrogen and methane are introduced to perform undoped diamond pre-growth on the surface of the undoped single crystal diamond substrate to form an undoped diamond pre-growth buffer layer. (3) Hydrogen source gas, boron source gas, nitrogen source gas and carbon source gas are introduced into the surface of the undoped diamond pre-growth buffer layer formed in step (2) to perform boron-nitrogen co-doped diamond epitaxial growth, forming a boron-nitrogen co-doped diamond epitaxial layer, and then cooled to room temperature under a reducing atmosphere to obtain boron-nitrogen co-doped room temperature high conductivity n-type diamond.

[0016] The inventive concept of this invention is as follows: This method does not introduce phosphorus. It achieves synergistic regulation of chamber residue control, substrate surface condition, epitaxial interface quality, and boron-nitrogen doping behavior by sequentially performing nitrogen mixed gas etching, methane gas pre-growth of undoped diamond, and boron-nitrogen co-doped diamond epitaxial growth on a single-crystal diamond substrate. Specifically, nitrogen mixed gas etching cleans or reduces the influence of residual boron sources in the MPCVD chamber walls and reaction environment, weakens the boron source memory effect generated by the preceding boron-containing growth process, and activates the surface of the single-crystal diamond substrate. This ensures that subsequent batches of nitrogen source gas can participate more stably and effectively in diamond epitaxial growth and be incorporated into the crystal lattice, serving as a crucial pretreatment step to promote subsequent high-concentration nitrogen doping. The introduction of methane gas for undoped diamond pre-growth consumes or isolates residual active species that may form after the reaction between the nitrogen source and residual boron source in the chamber, and constructs a stable pure diamond epitaxial buffer layer between the substrate and the boron-nitrogen co-doped layer, thereby reducing chamber residue. The effects of residual memory effect, interface contamination, substrate surface defects, and etching damage on subsequent boron / nitrogen co-doping stages are investigated. Improving the effective incorporation of nitrogen during boron-nitrogen co-doping by regulating the epitaxial interface state is a key step in enhancing the doping stability, repeatability, process reproducibility, and batch consistency of subsequent boron-nitrogen co-doped epitaxial growth. Furthermore, by simultaneously introducing boron and nitrogen source gases for boron-nitrogen synergistic co-doping epitaxial growth, the local electronic structure of nitrogen-related defects is controlled. This results in a stable negative Hall coefficient in room temperature Hall effect testing, increasing the effective n-type carrier concentration at room temperature and reducing room temperature resistivity.

[0017] Preferably, in step (1), the size of the undoped single-crystal diamond substrate is 3-20 mm × 3-20 mm (more preferably 5-10 mm × 5-10 mm), and the growth surface is polished.

[0018] Preferably, in step (1), before use, the undoped single-crystal diamond substrate is ultrasonically cleaned sequentially using acetone, isopropanol, ethanol, and deionized water as cleaning solutions. After cleaning, the substrate surface is dried with nitrogen gas. Ultrasonic cleaning removes organic contaminants and particulate impurities from the substrate surface.

[0019] Preferably, the washing time for each washing solution is 10 to 60 minutes.

[0020] Preferably, in step (1), the vacuuming to the base pressure ≤ 1×10 -7 Torr.

[0021] Preferably, in step (1), the flow rate of hydrogen is 100-500 sccm (more preferably 200-400 sccm), and the flow rate of nitrogen is 0.5-5.0 sccm (more preferably 1-4 sccm).

[0022] Preferably, in step (1), the input power of the microwave source during the etching process is 2 kW to 5 kW (more preferably 2.5 kW to 4.0 kW), the gas pressure in the reaction chamber is 100 to 250 Torr (more preferably 125 to 200 Torr), and the etching time is 10 to 60 min (more preferably 15 to 45 min). Under these conditions, the active species in the hydrogen-nitrogen mixed plasma can etch and desorb non-diamond carbon and weakly bound boron-containing residues on the inner wall of the chamber and the substrate surface, and renew the active sites through surface hydrogen extraction and re-termination processes, thereby reducing the influence of the background boron source, weakening the boron source memory effect, and activating the substrate surface. The above parameter range can ensure plasma stability and sufficient etching process, while avoiding excessive etching that leads to substrate surface roughening and increased defects.

[0023] Preferably, in step (2), the flow rate of hydrogen is 100–500 sccm (more preferably 200–400 sccm), and the flow rate of methane is 5–20 sccm (more preferably 8–18 sccm). This flow rate range maintains a stable hydrocarbon plasma and provides a suitable carbon source concentration, ensuring continuous epitaxial growth of the undoped diamond buffer layer. Simultaneously, it avoids insufficient methane leading to a low growth rate or excessive methane causing non-diamond carbon deposition and increased surface defects.

[0024] Preferably, in step (2), during the pre-growth, the input power of the microwave source is 2 kW to 5 kW (more preferably 3.0 kW to 4.5 kW), the gas pressure in the reaction chamber is 100 to 250 Torr (more preferably 125 to 200 Torr), and the pre-growth time is 20 to 60 min (more preferably 20 to 40 min). Under these conditions, hydrocarbon plasma can promote the continued reaction and desorption of residual active species, while forming a continuous undoped diamond buffer layer to isolate the substrate and residual species, so that the plasma and the growth surface reach a stable state before co-doping, thereby improving the batch repeatability of subsequent boron-nitrogen doping and electrical properties, and avoiding insufficient buffering due to insufficient parameters or excessive parameters leading to non-diamond carbon generation, increased defects, and prolonged process time.

[0025] Preferably, in step (3), the hydrogen source gas includes hydrogen gas, etc.

[0026] Preferably, in step (3), the boron source gas includes a hydrogen mixture containing diborane or the like. The hydrogen is a carrier gas of diborane or the like in the boron source gas, and the volume fraction of diborane or the like is ≥0.01% (more preferably 0.01-10%).

[0027] Preferably, in step (3), the nitrogen source gas includes nitrogen gas, etc.

[0028] Preferably, in step (3), the carbon source gas includes methane, etc.

[0029] Preferably, in step (3), the atomic ratio of hydrogen atoms in the hydrogen source gas, boron atoms in the boron source gas, nitrogen atoms in the nitrogen source gas, and carbon atoms in the carbon source gas is 1250–7500:0.01–0.80:20–80:100 (more preferably 3000–7000:0.10–0.70:30–70:100). The hydrogen source gas can maintain a stable microwave plasma, promote the dissociation of the boron, nitrogen, and carbon source gases, and selectively etch non-diamond carbon, thereby ensuring the stable growth of the boron-nitrogen co-doped diamond epitaxial layer. The boron and nitrogen source gases are simultaneously introduced during microwave plasma chemical vapor deposition, enabling boron and nitrogen atoms to form a synergistic doping growth structure in the diamond lattice. This modulates the local electronic structure of the diamond, reduces the activation energy of nitrogen-related donor levels, and thus obtains highly conductive n-type diamond. Secondary ion mass spectrometry (D-SIMS) and Hall effect measurements verify that as the nitrogen content relative to boron in the boron-nitrogen co-doped epitaxial layer increases, the Hall coefficient of the epitaxial layer changes from positive to negative, thereby controlling the transition from p-type to n-type conductivity. When the nitrogen proportion in the boron-nitrogen co-doping is low, the sample exhibits boron-dominated p-type conductivity. When the nitrogen proportion further increases to a certain range, the Hall coefficient of the sample turns negative, exhibiting n-type conductivity characteristics. This demonstrates that by controlling the B / C and N / C atomic ratios, the concentrations of B and N doping, conductivity type, and carrier concentration in the boron-nitrogen co-doped diamond epitaxial layer can be effectively adjusted.

[0030] Preferably, in step (3), during the epitaxial growth, the input power of the microwave source is 2 kW to 5 kW (more preferably 3.0 kW to 4.5 kW), the gas pressure in the reaction chamber is 100 to 250 Torr (more preferably 125 to 200 Torr), and the pre-growth time is 10 to 120 min (more preferably 20 to 80 min).

[0031] Preferably, in step (3), the reducing atmosphere includes a hydrogen atmosphere or the like.

[0032] The nitrogen, hydrogen, and methane gases used in this invention are all high-purity gases with a purity of ≥99.999%.

[0033] The beneficial effects of this invention are as follows: (1) This invention differs from the traditional method of preparing single nitrogen-doped n-type diamond: In traditional nitrogen-doped diamond, nitrogen atoms usually form deep donor levels with high activation energies, resulting in low effective ionized carrier concentration at room temperature and high material resistivity, which makes it difficult to meet the application requirements of room temperature high conductivity n-type diamond in semiconductor devices; The method of this invention introduces boron source gas and nitrogen source gas simultaneously during the diamond epitaxial growth process. Through the synergistic co-doping effect of boron and nitrogen elements, the local structure and electronic state distribution in the diamond lattice are regulated, the ionization behavior of nitrogen-related donors is improved, thereby increasing the n-type carrier concentration, reducing the resistivity of the diamond epitaxial layer, and obtaining highly conductive n-type boron-nitrogen co-doped diamond; Unlike the existing boron-nitrogen co-doped n-type diamond which mainly focuses on conductivity type conversion and high-temperature electrical response verification, this invention further realizes room temperature n-type conductivity at higher boron and nitrogen doping concentrations, and the resulting epitaxial layer has a negative Hall coefficient, higher electron concentration and lower resistivity; (2) The method of the present invention adopts a continuous process route of "nitrogen mixed gas etching - undoped diamond pre-growth buffer layer - boron-nitrogen co-doping epitaxial growth", which connects the substrate surface treatment, epitaxial buffer layer construction and boron-nitrogen co-doping growth process, avoiding surface contamination and process fluctuations that may be introduced by multiple transfers or repeated treatments. After multiple batches of repeated experiments and room temperature Hall effect tests, the boron-nitrogen co-doped diamond epitaxial layers obtained under the same or similar process parameter windows can all exhibit negative Hall coefficients and n-type conductivity characteristics, indicating that the method can stably prepare room temperature n-type conductive diamond, and has good experimental repeatability, process stability and batch reproducibility. Moreover, the process is efficient, stable and controllable, with a clear process flow and a clear parameter control range. It is compatible with existing MPCVD diamond epitaxial growth equipment and can provide a reliable material preparation route for the stable preparation of high conductivity n-type diamond materials and their application in high-power electronic devices, deep ultraviolet detectors, radiation detectors and other fields. Attached Figure Description

[0034] Figure 1 (a) to (c) are the Raman spectra of boron-nitrogen co-doped room-temperature high-conductivity n-type diamond examples 1 to 3 of this invention (test range: 800 cm⁻¹). -1 ~1800 cm -1 ); Figure 2 These are PL test images of boron-nitrogen co-doped room temperature high conductivity n-type diamonds obtained in Examples 1, 2, and Comparative Example 2, and boron-nitrogen co-doped n-type diamonds obtained in Comparative Example 4, according to the present invention. Figure 3 This is a Tauc fitting graph of the ultraviolet absorption test of boron-nitrogen co-doped room temperature high conductivity n-type diamond Example 1 of the present invention; Figure 4(a) and (b) are D-SIMS test images of boron-nitrogen co-doped room temperature high conductivity n-type diamond Examples 1 and 2 of the present invention, respectively; Figure 5 These are microscope images of Example 2 of boron-nitrogen co-doped room-temperature high-conductivity n-type diamond of the present invention (the upper left is a full-size image of the sample under the microscope). Figure 6 This is the D-SIMS test pattern of boron-nitrogen co-doped room temperature high conductivity n-type diamond Example 3 of the present invention; Figure 7 (a) to (c) are Raman spectra of boron-nitrogen co-doped p-type diamonds obtained in Comparative Examples 1 to 3 of this invention (test range: 800 cm⁻¹). -1 ~1800 cm -1 ); Figure 8 This is a D-SIMS test pattern of boron-nitrogen co-doped p-type diamond obtained in Comparative Example 1 of this invention; Figure 9 This is a D-SIMS test image of the boron-nitrogen co-doped p-type diamond obtained in Comparative Example 2 of this invention; Figure 10 This is the Raman spectrum of the boron-nitrogen co-doped n-type diamond obtained in Comparative Example 4 of this invention (test range: 800 cm⁻¹). -1 ~1800 cm -1 ); Figure 11 These are microscope images of the boron-nitrogen co-doped n-type diamond obtained in Comparative Example 4 of this invention (the upper left is a full-size image of the sample under the microscope). Figure 12 (a) to (d) are schematic diagrams of first-principles calculation models of different boron-nitrogen composite defect structures, where (a) is a BN structure, (b) is a BN2 structure, (c) is a BN3 structure, and (d) is a BN4 structure. Detailed Implementation

[0035] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0036] The undoped single-crystal diamond substrates used in the embodiments and comparative examples of this invention are 5 mm × 5 mm in size, and the growth surface is polished. Before use, the undoped single-crystal diamond substrates are ultrasonically cleaned for 35 min in sequence with acetone, isopropanol, ethanol and deionized water as cleaning solutions. After cleaning, the substrate surface is dried with nitrogen gas. The nitrogen, hydrogen and methane gases used in this invention are all high-purity gases with a purity of ≥99.999%. Unless otherwise specified, the raw materials or chemical reagents used in the embodiments and comparative examples of this invention are obtained through conventional commercial channels.

[0037] Example 1 of a boron-nitrogen co-doped room temperature high conductivity n-type diamond The boron-nitrogen co-doped room-temperature high-conductivity n-type diamond comprises, from bottom to top: an undoped single-crystal diamond substrate, an undoped diamond pre-growth buffer layer, and a boron-nitrogen co-doped diamond epitaxial layer; the boron doping concentration in the boron-nitrogen co-doped diamond epitaxial layer is 9.95 × 10⁻⁶. 18 at / cm 3 The nitrogen doping concentration is 9.98 × 10⁻⁶. 19 at / cm 3 The thickness of the undoped diamond pre-grown buffer layer is 3 μm; the thickness of the boron-nitrogen co-doped diamond epitaxial layer is 3 μm; the boron-nitrogen co-doped diamond epitaxial layer exhibits n-type conductivity characteristics at room temperature (25°C), with a negative Hall coefficient and a carrier concentration of -2.23 × 10⁻⁶. 19 cm -3 Its resistivity is 0.08 Ω·cm; at 130 ℃, it exhibits n-type conductivity, with a negative Hall coefficient and a carrier concentration of -3.61 × 10⁻⁶. 21 cm -3 Its resistivity is 0.05 Ω·cm.

[0038] Example 1: Epitaxial Preparation Method of Boron-Nitrogen Co-doped Room Temperature High Conductivity n-type Diamond (1) Place the cleaned undoped single-crystal diamond substrate in the reaction chamber of the microwave plasma chemical vapor deposition equipment, and evacuate to a background pressure ≤1×10 -7 After Torr, a mixture of hydrogen (flow rate of 200 sccm) and nitrogen (flow rate of 1 sccm) was introduced. Under the conditions of microwave source input power of 3 kW and gas pressure of 125 Torr, the inner wall of the reaction chamber, the reaction environment and the surface of the undoped single crystal diamond substrate were etched for 30 min. (2) In the etched reaction chamber, hydrogen (flow rate of 200 sccm) and methane (flow rate of 12 sccm) are introduced. Under the conditions of microwave source input power of 3.5 kW and gas pressure of 125 Torr, undoped diamond pre-growth is performed on the surface of the undoped single crystal diamond substrate for 30 min to form an undoped diamond pre-growth buffer layer. (3) Hydrogen (flow rate of 400 sccm), a hydrogen mixture containing diborane (flow rate of 5 sccm, volume fraction of diborane of 1%), nitrogen (flow rate of 5 sccm), and methane (flow rate of 16 sccm) are introduced into the surface of the undoped diamond pre-growth buffer layer formed in step (2). The atomic ratio of H in hydrogen (excluding hydrogen used as a carrier gas for diborane), B in diborane, N in nitrogen, and C in methane is 5000:0.625:62.5:100. Under the conditions of microwave source input power of 3.5 kW and gas pressure of 125 Torr, boron-nitrogen co-doped diamond epitaxial growth is performed for 30 min to form a boron-nitrogen co-doped diamond epitaxial layer. The layer is then cooled to room temperature under a hydrogen atmosphere to obtain boron-nitrogen co-doped room temperature high conductivity n-type diamond.

[0039] like Figure 1 As shown in (a), at approximately 1333.86 cm -1 A characteristic peak of diamond appears near the point where the peak corresponds to sp in the diamond lattice. 3 The vibrational modes of the hybrid carbon atoms indicate that the prepared sample has a typical diamond crystal structure.

[0040] like Figure 2 As shown, the area around 575 nm can be attributed to NV. 0 The zero-phonon line of the color center exhibits NV at approximately 637 nm. - The zero phonon line of the color center, along with its corresponding phonon band, shows that the NV color center correlated luminescence of the sample in this embodiment is significantly stronger than that of the comparative example, indicating that its nitrogen-related defects are formed more fully. This can help prove that the process in this embodiment is beneficial to improving the effective incorporation and doping stability of N element.

[0041] like Figure 3 As shown, the optical bandgap of the sample in this embodiment of the invention is approximately 4.38 eV, indicating that the diamond epitaxial layer still maintains wide bandgap semiconductor characteristics after boron-nitrogen co-doping.

[0042] like Figure 4 As shown in (a), D-SIMS testing revealed a depth of 3 μm. Based on the results, the boron concentration in this boron-nitrogen co-doped room-temperature high-conductivity n-type diamond is 9.95 × 10⁻⁶. 18 at / cm 3 The nitrogen atom concentration is 9.98 × 10⁻⁶. 19 at / cm 3 .

[0043] Example 2 of a boron-nitrogen co-doped room temperature high conductivity n-type diamond The only difference between this embodiment and Embodiment 1 is that the boron doping concentration in the boron-nitrogen co-doped diamond epitaxial layer is 9.20 × 10⁻⁶.18 at / cm 3 The nitrogen doping concentration is 6.95 × 10⁻⁶. 19 at / cm 3 The boron-nitrogen co-doped diamond epitaxial layer exhibits n-type conductivity at room temperature (25°C), with a negative Hall coefficient and a carrier concentration of -1.61 × 10⁻⁶. 18 cm -3 Its resistivity is 0.22 Ω·cm.

[0044] Example 2: Epitaxial fabrication method of boron-nitrogen co-doped room temperature high conductivity n-type diamond The difference between this embodiment and Method Embodiment 1 is only that in step (3), hydrogen (flow rate of 400 sccm), a hydrogen mixture containing diborane (flow rate of 1.5 sccm, volume fraction of diborane of 1%), nitrogen (flow rate of 4 sccm), and methane (flow rate of 16 sccm) are introduced into the surface of the undoped diamond pre-grown buffer layer formed in step (2), so that the atomic ratio of H in hydrogen (excluding hydrogen used as a carrier gas for diborane), B in diborane, N in nitrogen, and C in methane is 5000:0.1875:50:100. The rest is the same as in Method Embodiment 1.

[0045] like Figure 1 As shown in (b), at approximately 1333.99 cm -1 A characteristic peak of diamond appears near the point where the peak corresponds to sp in the diamond lattice. 3 The vibrational modes of the hybrid carbon atoms indicate that the prepared sample has a typical diamond crystal structure.

[0046] like Figure 2 As shown, the area around 575 nm can be attributed to NV. 0 The zero-phonon line of the color center exhibits NV at approximately 637 nm. - The zero phonon line of the color center, along with its corresponding phonon band, shows that the NV color center correlated luminescence of the sample in this embodiment is significantly stronger than that of the comparative example, indicating that its nitrogen-related defects are formed more fully. This can help prove that the process in this embodiment is beneficial to improving the effective incorporation and doping stability of N element.

[0047] like Figure 4 As shown in (b), D-SIMS testing revealed a depth of 3 μm. Based on the results, the boron concentration in this boron-nitrogen co-doped room-temperature high-conductivity n-type diamond is 9.20 × 10⁻⁶. 18 at / cm 3 The nitrogen atom concentration is 6.95 × 10⁻⁶. 19 at / cm 3 .

[0048] like Figure 5 As shown, the boron-nitrogen co-doped room-temperature high-conductivity n-type diamond surface obtained in this embodiment of the invention has a single-crystal diamond morphology.

[0049] Example 3 of a boron-nitrogen co-doped room temperature high conductivity n-type diamond The only difference between this embodiment and Embodiment 1 is that the boron doping concentration in the boron-nitrogen co-doped diamond epitaxial layer is 3.54 × 10⁻⁶. 18 at / cm 3 The nitrogen doping concentration is 7.89 × 10⁻⁶. 18 at / cm 3 The boron-nitrogen co-doped diamond epitaxial layer exhibits n-type conductivity at room temperature (25°C), with a negative Hall coefficient and a carrier concentration of -1.45 × 10⁻⁶. 18 cm -3 Its resistivity is 0.62 Ω·cm.

[0050] Example 3: Epitaxial Preparation Method of Boron-Nitrogen Co-doped Room Temperature High Conductivity n-type Diamond The difference between this embodiment and Method Embodiment 1 is only that in step (3), hydrogen (flow rate of 400 sccm), a hydrogen mixture containing diborane (flow rate of 1.0 sccm, volume fraction of diborane of 1%), nitrogen (flow rate of 4 sccm), and methane (flow rate of 16 sccm) are introduced onto the surface of the undoped diamond pre-grown buffer layer formed in step (2), such that the atomic ratio of H in the hydrogen (excluding hydrogen used as a carrier gas for diborane), B in diborane, N in nitrogen, and C in methane is 5000:0.125:50:100. The rest is the same as in Method Embodiment 1.

[0051] like Figure 1 As shown in (c), at approximately 1334.01 cm -1 A characteristic peak of diamond appears near the point where the peak corresponds to sp in the diamond lattice. 3 The vibrational modes of the hybrid carbon atoms indicate that the prepared sample has a typical diamond crystal structure.

[0052] like Figure 6 As shown, D-SIMS testing revealed a depth of 3 μm. Based on the results, the boron concentration in this boron-nitrogen co-doped room-temperature high-conductivity n-type diamond is 3.54 × 10⁻⁶. 18 at / cm 3 The nitrogen atom concentration is 7.89 × 10⁻⁶. 18 at / cm 3 .

[0053] Comparative Example 1 The only difference between this comparative example and Method Example 1 is that in step (3), hydrogen (flow rate 400 sccm), a hydrogen mixture containing diborane (flow rate 5 sccm, diborane volume fraction 1%), nitrogen (flow rate 1 sccm), and methane (flow rate 16 sccm) are introduced onto the surface of the undoped diamond pre-growth buffer layer formed in step (2), so that the atomic ratio of H in the hydrogen (excluding the hydrogen used as a carrier gas), B in diborane, N in nitrogen, and C in methane is 5000:0.625:12.5:100; finally, p-type diamond epitaxially grown using boron-nitrogen co-doping technology is obtained. The rest is the same as in Method Example 1.

[0054] like Figure 7 As shown in (a), at approximately 1334.30 cm -1 The presence of diamond characteristic peaks near the location indicates that changing the ratio of boron and nitrogen source gases did not destroy the basic crystal structure of the diamond epitaxial layer.

[0055] like Figure 8 As shown, D-SIMS testing revealed a depth of 3 μm. Based on the results, the boron concentration in the p-type diamond epitaxially grown using this boron-nitrogen co-doping technique is 3.45 × 10⁻⁶. 18 at / cm 3 The nitrogen atom concentration is 4.34 × 10⁻⁶. 17 at / cm 3 This indicates that both boron and nitrogen have been incorporated into the epitaxial layer, with the boron concentration being approximately eight times that of nitrogen. Combined with Hall effect measurements, it is evident that due to insufficient effective nitrogen incorporation, nitrogen-related donors and nitrogen-enriched boron-nitrogen recombination defects cannot generate sufficient electronic contributions. Boron acceptor activity dominates, resulting in a p-type conductive epitaxial layer with a carrier concentration of only 2.63 × 10⁻⁶. 16 cm -3 With a resistivity as high as 42.1 Ω·cm, it is impossible to obtain the high electron concentration, low resistivity, room temperature n-type conductivity required by this invention.

[0056] Comparative Example 2 The only difference between this comparative example and method example 1 is that in step (1), no etching process is performed; that is, the cleaned undoped single-crystal diamond substrate is placed in the reaction chamber of a microwave plasma chemical vapor deposition equipment and evacuated to a base pressure ≤ 1×10⁻⁶. -7 After Torr, step (2) is performed for the pre-growth of undoped diamond; finally, p-type diamond epitaxially grown using boron-nitrogen co-doping technology is obtained. The rest of the method is the same as in Example 1.

[0057] like Figure 2 As shown, compared with Method Example 1, the NV in this comparative sample is... 0 and NV- The color center-related luminescence intensity was significantly reduced, indicating that the formation of nitrogen-related defects was suppressed when hydrogen-nitrogen mixed plasma etching was not performed. This further illustrates that the etching process is beneficial for the effective incorporation of nitrogen and the stable formation of nitrogen-related defects.

[0058] like Figure 7 As shown in (b), at approximately 1333.58 cm -1 The presence of diamond characteristic peaks near the epitaxial layer indicates that the resulting epitaxial layer still maintains the diamond crystal structure. This result also shows that whether or not etching is performed will not change the basic diamond phase of the epitaxial layer, but will affect the subsequent doping effect and electrical properties.

[0059] like Figure 9 As shown, D-SIMS testing revealed a depth of 3 μm. Based on the results, the boron concentration in the p-type diamond epitaxially grown using this boron-nitrogen co-doping technique is 2.25 × 10⁻⁶. 18 at / cm 3 The nitrogen atom concentration is 2.14 × 10⁻⁶. 17 at / cm 3 This indicates that although the epitaxial layer obtained in this comparative example still contains both boron and nitrogen, the lack of nitrogen etching significantly affected the introduction of nitrogen, resulting in a marked reduction in nitrogen content.

[0060] Comparative Example 3 The only difference between this comparative example and Comparative Example 2 is that in step (3), hydrogen (flow rate of 400 sccm), a hydrogen mixture containing diborane (flow rate of 0.3 sccm, volume fraction of diborane of 1%), nitrogen (flow rate of 1 sccm), and methane (flow rate of 16 sccm) are introduced onto the surface of the undoped diamond pre-growth buffer layer formed in step (2), so that the atomic ratio of H in hydrogen (excluding hydrogen as a carrier gas), B in diborane, N in nitrogen, and C in methane is 5000:0.0375:12.5:100; finally, p-type diamond epitaxially grown by boron-nitrogen co-doping technology is obtained. The rest is the same as Comparative Example 2.

[0061] like Figure 7 As shown in (c), at approximately 1334.09 cm -1 The presence of diamond characteristic peaks near the location indicates that changing the ratio of boron and nitrogen source gases did not destroy the basic crystal structure of the diamond epitaxial layer.

[0062] Comparative Example 4 The only difference between this comparative example and Method Example 1 is that step (2) is omitted, and the undoped diamond pre-growth operation is not performed. That is, after the etching process is completed in step (1), the boron-nitrogen co-doped diamond epitaxial growth operation is performed in step (3); finally, n-type diamond epitaxially grown by boron-nitrogen co-doping technology is obtained. The rest is the same as in Method Example 1.

[0063] like Figure 2 As shown, compared with Method Example 1, the NV in this comparative sample is... 0 and NV - The weak color center-related luminescence intensity indicates that the effective formation of nitrogen-related defects is affected when undoped diamond pre-growth is not performed. This suggests that the pre-growth buffer layer is beneficial for stabilizing the subsequent boron-nitrogen co-doping interface and promoting the effective incorporation of nitrogen and the formation of nitrogen-related defects.

[0064] like Figure 10 As shown, at approximately 1333.70 cm -1 The presence of diamond characteristic peaks near the location indicates that the epitaxial layer obtained without a pre-growth buffer layer still maintains the diamond crystal structure.

[0065] like Figure 11 As shown, the boron-nitrogen co-doped n-type diamond surface obtained in the comparative example of this invention has a single-crystal diamond morphology.

[0066] To compare the effects of different preparation processes on the conductivity type and electrical properties of boron-nitrogen co-doped diamond, Hall effect tests were performed on the boron-nitrogen co-doped p-type or n-type diamond epitaxial layers obtained in Examples 1-3 and Comparative Examples 1-4 of this invention at room temperature or 130°C using ohmic contact electrodes. The Hall coefficient, carrier type, carrier concentration, resistivity, and mobility were obtained respectively, and the test results are shown in Table 1.

[0067] Table 1. Comparison of Hall effect measurements of boron-nitrogen co-doped p-type or n-type diamonds obtained in Examples 1-3 and Comparative Examples 1-4 of this invention.

[0068] Note: In the table, Example 1 (130°C) means that Example 1 was tested at 130°C, while the others were tested at room temperature.

[0069] As shown in Table 1, the Hall coefficients of the boron-nitrogen co-doped n-type diamonds obtained in Examples 1-3 of this invention are all negative, indicating that they exhibit n-type conductivity at both room temperature and 130°C; at room temperature, their carrier concentration is -1.45 × 10⁻⁶. 18 ~-2.23×10 19 cm -3The resistivity ranges from 0.08 to 0.62 Ω·cm, indicating that the method of this invention can obtain room-temperature n-type diamond with high electron concentration and low resistivity. Furthermore, as the nitrogen content relative to boron increases, the likelihood of forming nitrogen-enriched boron-nitrogen composite defects increases, making the material more prone to exhibiting n-type conductivity. Even when the test temperature increases, the Hall coefficient remains negative, indicating that electrons are still the dominant charge carriers, and the boron-nitrogen co-doped diamond epitaxial layer maintains n-type conductivity after heating. Compared to room temperature, the increased charge carrier concentration and decreased resistivity suggest that heating may promote the thermal activation of electrons in nitrogen-related donors and boron-nitrogen composite defects, increasing the number of electrons participating in conduction.

[0070] As shown in Table 1, the boron-nitrogen co-doped diamond epitaxial layer obtained in Comparative Example 1 exhibits p-type conductivity characteristics. Compared with Example 1 of the present invention, its majority carriers are converted from electrons to holes, and the carrier concentration is reduced from -2.23 × 10⁻⁶. 19 cm -3 It becomes 2.63×10 16 cm -3 The resistivity increased from 0.08 Ω·cm to 42.1 Ω·cm. This is because, after reducing the ratio of nitrogen source to boron source, the effective incorporation of nitrogen atoms and the formation of nitrogen-enriched boron-nitrogen composite donor defects were suppressed, while the effects of substitutional boron and boron-related acceptor defects were relatively enhanced. This caused the donor-acceptor compensation balance to change from donor dominance to acceptor dominance. Since the net carrier concentration in the material depends on the difference between the effective concentrations of donor defects and acceptor defects, when the boron-nitrogen ratio crosses the compensation balance point, even if the feed ratio changes only slightly, it will cause a reversal of the conductivity type and an order-of-magnitude change in carrier concentration and resistivity. This indicates that by adjusting the flow ratio of boron source gas and nitrogen source gas, the electrical properties of boron-nitrogen co-doped diamond epitaxial layers can be controlled. Although the p-type diamond epitaxially grown by boron-nitrogen co-doping technology obtained in Comparative Example 2 exhibits a positive Hall coefficient, its resistivity is significantly increased and its electron concentration is significantly reduced. This indicates that when nitrogen mixed gas etching is lacking, the influence of residual boron source in the chamber and the boron source memory effect are difficult to effectively weaken, and the stability of subsequent effective nitrogen source doping is reduced, resulting in increased resistivity, i.e., the room temperature p-type conductivity is significantly reduced. The p-type diamond epitaxially grown by boron-nitrogen co-doping technology obtained in Comparative Example 3 has a positive Hall coefficient, indicating p-type conductivity. This suggests that in the absence of nitrogen mixed gas etching and insufficient N / C atomic ratio, boron acceptor is more likely to dominate the conductivity behavior, making it difficult to stably obtain room temperature n-type conductive diamond. The resistivity of the boron-nitrogen co-doped diamond epitaxial layer obtained in Comparative Example 4 increased, the electron concentration decreased, and the electrical performance fluctuations between different batches of samples increased. This indicates that the methane gas undoped diamond pre-growth treatment can consume or isolate residual active species in the reaction environment after nitrogen gas etching and form a stable pure diamond epitaxial buffer layer, thereby improving the doping stability and batch repeatability of subsequent boron-nitrogen co-doped epitaxial growth.

[0071] To analyze the impact of different local boron-nitrogen complex defect structures on carrier activation and transport properties, i.e., electronic structure and conductivity, in boron-nitrogen co-doped diamond at the atomic scale, first-principles calculations based on density functional theory were used to establish four typical local boron-nitrogen complex defect models: BN, BN2, BN3, and BN4. Their structures and electronic properties were calculated, and the donor ionization energy and effective electron mass of different defect models were obtained to provide a theoretical explanation for the experimentally observed changes in conductivity type and electrical properties. The results are shown in Table 2 and... Figure 12 As shown.

[0072] Table 2. Comparison of ionization energy and effective electron mass results for boron-nitrogen co-doped p-type or n-type diamonds obtained in Examples 1-3 and Comparative Examples 1-4 of this invention.

[0073] Note: In the table, "-" indicates that B and N in the BN structure undergo charge compensation, and there are no corresponding free electrons for calculating ionization energy.

[0074] As shown in Table 2 and Figure 12 As shown, different localized boron-nitrogen complex defect structures exhibit different electronic activation and transport characteristics, i.e., different formation stability and electronic structure features. Specifically, the donor ionization energy of the BN2 structure is 0.68 eV, indicating that electrons are difficult to fully activate at room temperature; the donor ionization energy of the BN3 structure is 0.25 eV, and the effective electron mass is 0.34 m. 0 In the calculated nitrogen-containing complex defect model, it exhibits both a lower donor ionization energy and a smaller effective electron mass, indicating that it is more conducive to room-temperature electron activation and transport; the donor ionization energy of the BN4 structure is 0.38 eV, but its effective electron mass increases to 0.62 m. 0This indicates that further increasing the number of local nitrogen coordination sites does not necessarily lead to a sustained improvement in electron transport performance. The calculation results above show that the electrical properties of boron-nitrogen co-doped diamond depend not only on the total boron and nitrogen content but also on the local coordination structures formed in the crystal lattice. Among these, BN3-type nitrogen-enriched recombination defects exhibit lower donor ionization energy and smaller effective electron mass, suggesting that they are more conducive to electron generation and transport at room temperature. The nitrogen-enriched boron-nitrogen recombination defects formed during boron-nitrogen co-doping may be an important structural source for achieving room-temperature n-type conductivity, thus being more conducive to achieving room-temperature n-type conductivity.

Claims

1. A boron-nitrogen co-doped room-temperature high-conductivity n-type diamond, characterized in that: From bottom to top, it comprises: an undoped single-crystal diamond substrate, an undoped diamond pre-growth buffer layer, and a boron-nitrogen co-doped diamond epitaxial layer; the boron doping concentration in the boron-nitrogen co-doped diamond epitaxial layer is 1×10⁻⁶. 15 ~1×10 20 at / cm 3 The nitrogen doping concentration is 1×10 16 ~1×10 21 at / cm 3 .

2. The boron-nitrogen co-doped room-temperature high-conductivity n-type diamond according to claim 1, characterized in that: The thickness of the undoped diamond pre-grown buffer layer is 1–5 μm; the thickness of the boron-nitrogen co-doped diamond epitaxial layer is 1–5 μm; the boron-nitrogen co-doped diamond epitaxial layer exhibits n-type conductivity characteristics at 10–500 °C, with a negative Hall coefficient and a carrier concentration of -1 × 10⁻⁶. 15 ~-1×10 22 cm -3 Its resistivity is 0.01–10 Ω·cm. It exhibits n-type conductivity even at room temperature (10–40 °C), with a negative Hall coefficient and a carrier concentration of -1 × 10⁻⁶. 15 ~-1×10 20 cm -3 Its resistivity is 0.01–10 Ω·cm.

3. A method for epitaxial preparation of boron-nitrogen co-doped room-temperature high-conductivity n-type diamond as described in claim 1 or 2, characterized in that, Includes the following steps: (1) The cleaned undoped single crystal diamond substrate is placed in the reaction chamber of a microwave plasma chemical vapor deposition equipment. After evacuation, a mixture of hydrogen and nitrogen is introduced to etch the inner wall of the reaction chamber, the reaction environment and the surface of the undoped single crystal diamond substrate. (2) In the reaction chamber after etching, hydrogen and methane are introduced to perform undoped diamond pre-growth on the surface of the undoped single crystal diamond substrate to form an undoped diamond pre-growth buffer layer. (3) Hydrogen source gas, boron source gas, nitrogen source gas and carbon source gas are introduced into the surface of the undoped diamond pre-growth buffer layer formed in step (2) to perform boron-nitrogen co-doped diamond epitaxial growth, forming a boron-nitrogen co-doped diamond epitaxial layer, and then cooled to room temperature under a reducing atmosphere to obtain boron-nitrogen co-doped room temperature high conductivity n-type diamond.

4. The epitaxial preparation method of boron-nitrogen co-doped room-temperature high-conductivity n-type diamond according to claim 3, characterized in that: In step (1), the undoped single-crystal diamond substrate has a size of 3–20 mm × 3–20 mm, and the growth surface is polished. Before use, the undoped single-crystal diamond substrate is ultrasonically cleaned sequentially with acetone, isopropanol, ethanol, and deionized water as cleaning solutions. After cleaning, the substrate surface is dried with nitrogen gas. The cleaning time for each cleaning solution is 10–60 min. The vacuuming process is performed until the base pressure is ≤1 × 10⁻⁶. -7 Torr; the flow rate of hydrogen is 100-500 sccm, and the flow rate of nitrogen is 0.5-5.0 sccm; in the etching process, the input power of the microwave source is 2 kW-5 kW, the gas pressure in the reaction chamber is 100-250 Torr, and the etching time is 10-60 min.

5. The epitaxial preparation method of boron-nitrogen co-doped room-temperature high-conductivity n-type diamond according to claim 3 or 4, characterized in that: In step (2), the flow rate of hydrogen is 100-500 sccm and the flow rate of methane is 5-20 sccm; in the pre-growth, the input power of the microwave source is 2 kW-5 kW, the gas pressure in the reaction chamber is 100-250 Torr, and the pre-growth time is 20-60 min.

6. The epitaxial preparation method of boron-nitrogen co-doped room-temperature high-conductivity n-type diamond according to any one of claims 3 to 5, characterized in that: In step (3), the hydrogen source gas includes hydrogen; the boron source gas includes a hydrogen mixture containing diborane; the nitrogen source gas includes nitrogen; the carbon source gas includes methane; the atomic ratio of hydrogen atoms in the hydrogen source gas, boron atoms in the boron source gas, nitrogen atoms in the nitrogen source gas, and carbon atoms in the carbon source gas is 1250–7500:0.01–0.80:20–80:100; in the epitaxial growth, the input power of the microwave source is 2 kW–5 kW, the gas pressure in the reaction chamber is 100–250 Torr, and the pre-growth time is 10–120 min; the reducing atmosphere includes a hydrogen atmosphere.

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