A method for preparing n-type semiconductor diamond material

Abstract

The preparation method of the n-type semiconductor diamond material of the present invention includes the following process steps: (1) pretreatment of single crystal diamond to remove impurities on the surface of single crystal diamond; (2) preparation of doped blank, wherein the pretreated single crystal diamond is placed in n-type doped elemental powder or compound powder and molded, or the n-type doped elemental powder or compound powder is placed in a foil or inorganic non-metallic material container and then the pretreated single crystal diamond is placed in n-type doped elemental powder or compound powder and molded; (3) the doped blank is placed in a static high pressure device and thermal diffusion doping is carried out under a determined doping pressure and doping temperature. After the thermal diffusion doping is completed, the encapsulating material and impurities on the surface of the doped diamond are cleaned and dried to obtain an n-type semiconductor diamond material with complete crystal lattice, high doping concentration and excellent performance.

Description

Technical Field

[0001] The invention belongs to the technical field of n-type semiconductor diamond materials, and particularly relates to a method for preparing n-type semiconductor diamond materials. Background Art

[0002] Compared with other semiconductor materials, semiconductor diamond materials have greater advantages in electrical and thermal properties and are very ideal semiconductor materials. Therefore, they have extremely broad application prospects in the field of semiconductor devices.

[0003] For semiconductor diamond materials, the most disclosed in the prior art is p-type semiconductor diamond based on boron (B) doping and its preparation method. This is because the atomic radius of boron (B) is close to the atomic radius of diamond carbon (C), which makes the doping efficiency of boron (B) doped diamond higher and the preparation difficulty lower. In terms of its electrical properties, the acceptor energy level of boron (B) doped diamond is located at about 0.37eV on the valence band, the energy level is shallow, and the conductivity is good. However, the doping atoms used to prepare n-type semiconductor diamond are usually phosphorus (P), sulfur (S) or arsenic (As), and their atomic radius is much larger than the atomic radius of diamond carbon (C) atoms. At normal pressure, the percentage of the difference between the atomic radius of phosphorus (P) and the atomic radius of carbon (C) to the atomic radius of carbon is 37.7%, the percentage of the difference between the atomic radius of sulfur (S) and the atomic radius of carbon (C) to the atomic radius of carbon is 32.5%, and the percentage of the difference between the atomic radius of arsenic (As) and the atomic radius of carbon (C) to the atomic radius of carbon is 55.8%. Therefore, the doping atomic radius roughly increases the difficulty of preparing n-type semiconductor diamond; furthermore, the distance between carbon atoms in diamond is small and the CC bond energy is large, making it difficult for doped atoms to replace carbon atoms to form effective solid solution doping.

[0004] The existing methods for preparing n-type semiconductor diamond mainly include ion implantation, epitaxial growth doping and high temperature and high pressure growth process doping. The ion implantation method is a method in which the doping material is first ionized into ions, focused into an ion beam, and then injected into the diamond crystal after electric field acceleration. The ion implantation method for diamond n-type doping has the following disadvantages: (1) The high-energy, large-volume n-type doping material ion beam will cause serious damage to the diamond lattice, reduce the quality of the substrate, and further affect its electrical properties; (2) In order to repair the damaged lattice and activate the n-type doping material, this method requires high-temperature annealing (1450°C) in a high vacuum environment after implantation, but during the annealing process, graphitization will inevitably occur on the diamond surface. The epitaxial growth doping method is to add a certain proportion of gas containing doping elements to the growth atmosphere of the diamond, and use the gas phase growth method to allow the impurity elements to enter the diamond. Diamond epitaxial growth doping method has the following disadvantages: (1) high concentration of n-type doping will affect the uniformity of diamond film growth and the quality of crystals (n-type doping material has a large atomic radius), making it difficult to obtain high-quality and high-doping efficiency n-type diamond; (2) some n-type doping gases are highly toxic (phosphine H3P used for phosphorus doping and hydrogen sulfide H2S used for sulfur doping are both highly toxic); (3) doping gases will pollute the expensive growth chamber, so that the growth chamber can only grow diamonds with the same doping material. The carbon source selected by the doping method in the high temperature and high pressure growth process is high-purity graphite, and the single substance powder of the doping material or its compound powder is added to the synthesis system in a certain proportion. Under the conditions of high temperature and high pressure (usually less than 6GPa), the doping material atoms are incorporated into the diamond crystal as the diamond grows. The n-type doping of diamond by the doping method during high temperature and high pressure growth has the following disadvantages: (1) the growth environment for synthesizing n-type diamond is relatively complex (for example, there is a catalyst), and other impurities are easily introduced during the growth process; (2) although this method requires a high-pressure growth environment, its pressure is relatively low (usually less than 6 GPa). Since the n-type dopant with a larger atomic radius has a poor match with the carbon atom, it is difficult for the n-type dopant to enter the diamond lattice, and it is difficult to obtain a high-concentration n-type semiconductor diamond. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a new method for preparing n-type semiconductor diamond material to solve the problems of large atomic volume of n-type doping material, mismatch with diamond carbon atom lattice and difficulty in doping, so as to obtain n-type semiconductor diamond with complete lattice and improve doping concentration.

[0006] The method for preparing the n-type semiconductor diamond material of the present invention is to form the n-type semiconductor diamond material by doping the n-type dopant into the single crystal diamond by thermal diffusion under high pressure conditions, and the process steps are as follows:

[0007] (1) Pretreatment of single crystal diamond

[0008] Soaking the single crystal diamond with at least one of concentrated nitric acid, concentrated hydrochloric acid and concentrated sulfuric acid to dissolve impurities on the surface of the single crystal diamond, then ultrasonically washing the soaked single crystal diamond with anhydrous ethanol and deionized water in turn to remove impurities on the surface of the single crystal diamond, and then drying the ultrasonically washed single crystal diamond;

[0009] (2) Preparation of doped green body

[0010] The single crystal diamond pretreated in step (1) is placed in a single substance powder or compound powder of an n-type doping substance for compression molding to obtain a doped body, wherein the doped body is composed of a single crystal diamond and an n-type doping substance encapsulating the single crystal diamond; this preparation method is only applicable to single substance powder or compound powder of an n-type doping substance with good moldability;

[0011] Alternatively, a single substance powder or compound powder of an n-type doping substance is placed in a foil or inorganic non-metallic material container, and then the single crystal diamond pretreated in step (1) is placed in the single substance powder or compound powder of the n-type doping substance for compression molding to obtain a doped blank, wherein the doped blank is composed of single crystal diamond, n-type doping substance wrapped around the single crystal diamond, and foil or inorganic non-metallic material wrapped around the n-type doping substance. This preparation method is applicable to single substance powder or compound powder of n-type doping substance with various formability, but is particularly applicable to single substance powder or compound powder of n-type doping substance with poor formability.

[0012] (3) High-pressure thermal diffusion doping and cleaning of diamond after doping

[0013] The doped body prepared in step (2) is placed in a static high-pressure device, firstly pressurized to the doping pressure, then heated to the doping temperature and kept at the temperature for thermal diffusion doping. After the heat preservation and pressure holding time is reached, the body is first cooled to room temperature and then reduced to normal pressure. The encapsulating material and impurities on the surface of the doped diamond are then cleaned and removed, and the body is dried to obtain an n-type semiconductor diamond material.

[0014] In the above-mentioned method for preparing n-type semiconductor diamond material, in step (1), the temperature of soaking the single crystal diamond in at least one of concentrated nitric acid, concentrated hydrochloric acid and concentrated sulfuric acid is from room temperature to the boiling point of the acid used, the soaking time is determined according to whether the impurities on the surface of the single crystal diamond are completely dissolved, the ultrasonic washing time is determined according to whether the impurities on the surface of the single crystal diamond are completely removed, and the drying temperature is 60-100°C.

[0015] In the above-mentioned method for preparing n-type semiconductor diamond material, in step (2), the mass purity of the elemental powder or compound powder of the n-type doping substance is ≥98%; the n-type doping substance is phosphorus (P), sulfur (S) or arsenic (As).

[0016] In the above-mentioned method for preparing n-type semiconductor diamond material, in step (2), the molding pressure of the doped blank is 50-1000 MPa, and the holding time is 0.1-2 min; the foil is tantalum foil, rhenium foil or platinum foil; and the inorganic non-metallic material container is made of boron nitride, graphite, magnesium oxide or aluminum oxide.

[0017] In the above-mentioned method for preparing n-type semiconductor diamond material, in step (3), the pressure increasing rate for increasing the pressure from normal pressure to the doping pressure and the pressure decreasing rate for decreasing the pressure from the doping pressure to normal pressure are determined according to the safe pressure increasing and decreasing rate range of the static high-pressure equipment used, and the temperature increasing rate for increasing the temperature from room temperature to the doping temperature and the temperature decreasing rate for decreasing the temperature from the doping temperature to room temperature are 50 to 400°C / min.

[0018] The doping mechanism of the method described in the present invention is as follows: the atomic distance of carbon atoms in diamond is reduced to a small extent under high pressure conditions (large bulk modulus and extremely high incompressibility), while the atomic distance of n-type doping substances (such as phosphorus, sulfur, arsenic, etc.) is reduced to a relatively large extent under pressure conditions (relatively small bulk modulus and high compressibility), so the matching degree between carbon atoms and n-type doping substance atoms can be increased under high pressure, making it easier for n-type doping substance atoms to enter the diamond lattice. Under high pressure conditions, the thermal activation energy of n-type doping substance atoms can be increased by high temperature, which can increase the diffusion driving force of n-type doping substance atoms and increase the rate at which they diffuse into the diamond lattice, thereby increasing the doping concentration and obtaining n-type semiconductor diamond with excellent performance.

[0019] According to the above doping mechanism, the higher the doping pressure and doping temperature, the better. However, due to the limitation of static high-pressure equipment, when using the method described in the present invention, the doping pressure and doping temperature should be determined according to the pressure and temperature allowed by the static high-pressure equipment available. In view of the types of existing static high-pressure equipment, in the above method for preparing n-type semiconductor diamond material, the doping pressure in step (3) can be controlled at 5 to 30 GPa, the doping temperature can be controlled at 500 to 3000°C, and the heat preservation and pressure holding time is 10 to 10000s.

[0020] In the above-mentioned method for preparing n-type semiconductor diamond material, in step (3), the cleaning of the doped sample is preferably firstly immersed in concentrated nitric acid and aqua regia in sequence to remove the encapsulating material, and then ultrasonically washed with anhydrous ethanol and deionized water in sequence to remove impurities on the surface of the doped diamond; the drying temperature is 60 to 100°C.

[0021] The present invention has the following beneficial effects:

[0022] (1) Compared with the existing ion implantation method, epitaxial growth doping method and high temperature and high pressure growth process doping method, the method of the present invention effectively solves the problems of large atomic radius of n-type doping material, mismatch with diamond carbon atom lattice and doping difficulty, making it easier for n-type doping material atoms to enter the diamond lattice, thereby obtaining n-type semiconductor diamond with complete lattice, high doping concentration and excellent performance.

[0023] (2) The method of the present invention is simple in process and uses conventional equipment, so it is easy to master and promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the assembly of the doped blank in Example 1 into a static high-pressure device; in the figure, 1 is a steel plug; 2 is a molybdenum sheet; 3 is a graphite sheet; 4 is a graphite column; 5 is a zirconium dioxide tube; 6 is a graphite heating tube; 7 is a boron nitride tube; 8 is pyrophyllite; 9 is a square single crystal diamond sheet; 10 is red phosphorus (n-type doping substance).

[0025] Figure 2 This is a schematic diagram of the assembly of the doped blanks in Example 2, Example 3, Example 4, and Example 5 placed in a static high-pressure device; in the figure, 11 is a zirconium dioxide column; 12 is a zirconium dioxide tube; 13 is magnesium oxide; 14 is an aluminum oxide tube; 15 is a tantalum heating element; 16 is a round single crystal diamond sheet; 17 is red phosphorus (n-type doping substance); and 18 is a tantalum sheet.

[0026] Figure 3 Graphs showing the Raman spectra of the single crystal diamond sheet before doping and the prepared phosphorus-doped n-type semiconductor diamond sheet in Example 1.

[0027] Figure 4 These are X-ray photoelectron spectroscopy analysis test spectra of the phosphorus-doped n-type semiconductor diamond sheet prepared in Example 1, wherein (a) is the spectrum of carbon element, and (b) is the spectrum of phosphorus element.

[0028] Figure 5 Graphs showing the Raman spectra of the single crystal diamond sheet before doping and the prepared phosphorus-doped n-type semiconductor diamond sheet in Example 2.

[0029] Figure 6 These are X-ray photoelectron spectroscopy analysis test spectra of the phosphorus-doped n-type semiconductor diamond sheet prepared in Example 2, wherein (a) is the spectrum of carbon element, and (b) is the spectrum of phosphorus element.

[0030] Figure 7 Graphs showing the Raman spectra of the single crystal diamond sheet before doping and the prepared phosphorus-doped n-type semiconductor diamond sheet in Example 3.

[0031] Figure 8 These are X-ray photoelectron spectroscopy analysis test spectra of the phosphorus-doped n-type semiconductor diamond sheet prepared in Example 3, wherein (a) is the spectrum of carbon element, and (b) is the spectrum of phosphorus element.

[0032] Fig. 9 Graphs showing the Raman spectra of the single crystal diamond sheet before doping and the prepared phosphorus-doped n-type semiconductor diamond sheet in Example 4.

[0033] Fig.10 These are X-ray photoelectron spectroscopy analysis test spectra of the phosphorus-doped n-type semiconductor diamond sheet prepared in Example 4, wherein (a) is the spectrum of carbon element, and (b) is the spectrum of phosphorus element. DETAILED DESCRIPTION

[0034] The preparation method of the n-type semiconductor diamond material of the present invention is further described below by way of examples and in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0035] In the following embodiments, the static high-pressure equipment used in Example 1 is a 1400t domestic six-sided top press, model: 420 cylinder diameter six-sided top press, produced by Guilin Guiye Machinery Co., Ltd.; the static high-pressure equipment used in Examples 2, 3, 4 and 5 is a two-stage six-eight type large-cavity static high-pressure device based on an 800t domestic hinged six-sided top press, model: DS6X800A, produced by Zhangjiakou Prospecting Machinery Factory.

[0036] In the following examples, the mass purity of the doped red phosphorus powder is 98.5%; the doped red phosphorus powder, single crystal diamond sheet and other raw materials used are all purchased from the market.

[0037] Example 1

[0038] In this embodiment, a square single crystal diamond sheet with a size of about 3 mm×3 mm×1 mm and red phosphorus powder are used to prepare n-type semiconductor diamond material. The process steps are as follows:

[0039] (1) Pretreatment of single crystal diamond wafers

[0040] The square single crystal diamond sheet was soaked in aqua regia at room temperature (25°C) for 24 hours, and then the soaked square single crystal diamond sheet was ultrasonically washed with anhydrous ethanol and deionized water for 30 minutes each, and then the square single crystal diamond sheet after ultrasonic washing was dried in an oven at 80°C;

[0041] (2) Preparation of doped green body

[0042] The square single crystal diamond sheet pretreated in step (1) is placed in red phosphorus powder for compression molding at a compression pressure of 50 MPa and maintained at the pressure for 1 minute to obtain a doped green body consisting of the square single crystal diamond sheet and red phosphorus wrapping the square single crystal diamond sheet;

[0043] (3) High-pressure thermal diffusion doping and cleaning of diamond after doping

[0044] The doped green body prepared in step (2) is placed in a 1400t domestic six-sided top press and assembled as follows: Figure 1 As shown; then the pressure is increased to a doping pressure of 5 GPa at a pressure increase rate of 0.2 GPa / min, and then the temperature is increased to a doping temperature of 1300°C at a heating rate of 100°C / min, and the temperature is maintained for 900 seconds for thermal diffusion doping. After the thermal diffusion doping time is reached, the temperature is first cooled to room temperature at a cooling rate of 100°C / min, and then the pressure is reduced to normal pressure at a pressure reduction rate of 0.2 GPa / min; the sample is subsequently taken out and placed in concentrated nitric acid and aqua regia at room temperature (25°C) for 24 hours each, and then ultrasonically washed with anhydrous ethanol and deionized water for 30 minutes each, and dried in an oven at 80°C after washing to obtain a phosphorus-doped n-type semiconductor diamond sheet.

[0045] The n-type semiconductor diamond sheet prepared in this example was tested by Raman spectroscopy, and the spectrum is shown in Figure 3 , Figure 3 The results show that the n-type semiconductor diamond sheet after phosphorus doping only has diamond phase. The n-type semiconductor diamond sheet prepared in this example was tested with a multimeter and found to have weak conductivity. The n-type semiconductor diamond sheet prepared in this example was analyzed with X-ray photoelectron spectroscopy, and the spectrum is shown in FIG. Figure 4 ,from Figure 4 Obvious carbon-phosphorus bond and phosphorus-carbon bond signals can be observed, indicating that n-type impurity phosphorus atoms have entered the diamond lattice.

[0046] Example 2

[0047] In this embodiment, a circular single crystal diamond sheet with a diameter of about 2 mm and a height of about 1 mm and red phosphorus powder are used to prepare an n-type semiconductor diamond material. The process steps are as follows:

[0048] (1) Pretreatment of single crystal diamond wafers

[0049] The circular single crystal diamond sheet was soaked in aqua regia at room temperature (25°C) for 24 hours, and then the soaked circular single crystal diamond sheet was ultrasonically washed with anhydrous ethanol and deionized water for 30 minutes each, and then the ultrasonically washed circular single crystal diamond sheet was dried in an oven at 80°C;

[0050] (2) Preparation of doped green body

[0051] The circular single crystal diamond sheet pretreated in step (1) is placed in red phosphorus powder for compression molding at a compression pressure of 400 MPa and maintained at the pressure for 1 minute to obtain a doped green body consisting of the circular single crystal diamond sheet and the red phosphorus wrapping the circular single crystal diamond sheet;

[0052] (3) High-pressure thermal diffusion doping and cleaning of diamond after doping

[0053] The doped body prepared in step (2) is placed in a two-stage six-eight-type large-cavity static high-pressure device, and the assembly method is as follows: Figure 2 As shown; then the pressure is increased to a doping pressure of 10 GPa at a pressure increase rate of 3.4 GPa / h, and then the temperature is increased to a doping temperature of 1500°C at a heating rate of 100°C / min, and the temperature is maintained for 120s for thermal diffusion doping. After the thermal diffusion doping time is reached, the temperature is first cooled to room temperature at a cooling rate of 100°C / min, and then the pressure is reduced to normal pressure at a pressure reduction rate of 3.4 GPa / h; then the sample is taken out and placed in concentrated nitric acid and aqua regia at room temperature (25°C) for 24 hours respectively, and then ultrasonically washed with anhydrous ethanol and deionized water for 30 minutes each. After washing, it is dried in an oven at 80°C to obtain a phosphorus-doped n-type semiconductor diamond sheet.

[0054] The n-type semiconductor diamond sheet prepared in this example was tested by Raman spectroscopy, and the spectrum is shown in Figure 5 , Figure 5 It shows that the n-type semiconductor diamond sheet after phosphorus doping only has diamond phase. The n-type semiconductor diamond sheet prepared in this example is analyzed by X-ray photoelectron spectroscopy, and the spectrum is shown in Figure 6 ,from Figure 6 Obvious carbon-phosphorus bond and phosphorus-carbon bond signals can be observed, indicating that n-type impurity phosphorus atoms have entered the diamond lattice.

[0055] Example 3

[0056] In this embodiment, a circular single crystal diamond sheet with a diameter of about 2 mm and a height of about 1 mm and red phosphorus powder are used to prepare an n-type semiconductor diamond material. The process steps are as follows:

[0057] (1) Pretreatment of single crystal diamond wafers

[0058] The circular single crystal diamond sheet was soaked in aqua regia at room temperature (25°C) for 24 hours, and then the soaked circular single crystal diamond sheet was ultrasonically washed with anhydrous ethanol and deionized water for 30 minutes each, and then the ultrasonically washed circular single crystal diamond sheet was dried in an oven at 80°C;

[0059] (2) Preparation of doped green body

[0060] The circular single crystal diamond sheet pretreated in step (1) is placed in red phosphorus powder for compression molding at a compression pressure of 900 MPa and maintained at the pressure for 1 minute to obtain a doped green body consisting of the circular single crystal diamond sheet and the red phosphorus wrapping the circular single crystal diamond sheet;

[0061] (3) High-pressure thermal diffusion doping and cleaning of diamond after doping

[0062] The doped body prepared in step (2) is placed in a two-stage six-eight-type large-cavity static high-pressure device, and the assembly method is as follows: Figure 2 As shown; then the pressure is increased to a doping pressure of 15 GPa at a pressure increase rate of 3.4 GPa / h, and then the temperature is increased to a doping temperature of 500°C at a heating rate of 100°C / min, and the temperature and pressure are maintained for 2400s for thermal diffusion doping. After the thermal diffusion doping time is reached, the temperature is first cooled to room temperature at a cooling rate of 100°C / min, and then the pressure is reduced to normal pressure at a pressure reduction rate of 3.4 GPa / h; then the sample is taken out and placed in concentrated nitric acid and aqua regia in turn at room temperature (25°C) for 24 hours each, and then ultrasonically washed with anhydrous ethanol and deionized water for 30 minutes each, and after washing, it is dried in an oven at 80°C to obtain a phosphorus-doped n-type semiconductor diamond sheet.

[0063] The n-type semiconductor diamond sheet prepared in this example was tested by Raman spectroscopy, and the spectrum is shown in Figure 7 , Figure 7 It shows that the n-type semiconductor diamond sheet after phosphorus doping only has diamond phase. The n-type semiconductor diamond sheet prepared in this example is analyzed by X-ray photoelectron spectroscopy, and the spectrum is shown in Figure 8 ,from Figure 8 Obvious carbon-phosphorus bond and phosphorus-carbon bond signals can be observed, indicating that n-type impurity phosphorus atoms have entered the diamond lattice.

[0064] Example 4

[0065] In this embodiment, a circular single crystal diamond sheet with a diameter of about 2 mm and a height of about 1 mm and red phosphorus powder are used to prepare an n-type semiconductor diamond material. The process steps are as follows:

[0066] (1) Pretreatment of single crystal diamond wafers

[0067] The circular single crystal diamond sheet was soaked in aqua regia at room temperature (25°C) for 24 hours, and then the soaked circular single crystal diamond sheet was ultrasonically washed with anhydrous ethanol and deionized water for 30 minutes each, and then the ultrasonically washed circular single crystal diamond sheet was dried in an oven at 80°C;

[0068] (2) Preparation of doped green body

[0069] The circular single crystal diamond sheet pretreated in step (1) is placed in red phosphorus powder for compression molding at a compression pressure of 900 MPa and maintained at the pressure for 1 minute to obtain a doped green body consisting of the circular single crystal diamond sheet and the red phosphorus wrapping the circular single crystal diamond sheet;

[0070] (3) High-pressure thermal diffusion doping and cleaning of diamond after doping

[0071] The doped body prepared in step (2) is placed in a two-stage six-eight-type large-cavity static high-pressure device, and the assembly method is as follows: Figure 2 As shown; then the pressure is increased to a doping pressure of 15 GPa at a pressure increase rate of 3.4 GPa / h, and then the temperature is increased to a doping temperature of 1600°C at a heating rate of 100°C / min, and the temperature is maintained for 10 seconds for thermal diffusion doping. After the thermal diffusion doping time is reached, the temperature is first cooled to room temperature at a cooling rate of 100°C / min, and then the pressure is reduced to normal pressure at a pressure reduction rate of 3.4 GPa / h; then the sample is taken out and placed in concentrated nitric acid and aqua regia at room temperature (25°C) for 24 hours respectively, and then ultrasonically washed with anhydrous ethanol and deionized water for 30 minutes each. After washing, it is dried in an oven at 80°C to obtain a phosphorus-doped n-type semiconductor diamond sheet.

[0072] The n-type semiconductor diamond sheet prepared in this example was tested by Raman spectroscopy, and the spectrum is shown in Fig. 9 , Fig. 9 It shows that the n-type semiconductor diamond sheet after phosphorus doping only has diamond phase. The n-type semiconductor diamond sheet prepared in this example is analyzed by X-ray photoelectron spectroscopy, and the spectrum is shown in Fig.10 ,from Fig.10 Strong carbon-phosphorus bond and phosphorus-carbon bond signals can be observed, indicating that more n-type impurity phosphorus atoms have entered the diamond lattice. The n-type semiconductor diamond sheet prepared in this embodiment was tested with a multimeter and found to have good conductivity. The n-type semiconductor diamond sheet prepared in this embodiment was subjected to a Hall effect test, and the test data are shown in Table 1 below.

[0073] Table 1 Hall effect test data

[0074]

[0075] The data in Table 1 show that the method of the present invention can obtain n-type semiconductor diamond material with high doping concentration and excellent electrical properties.

[0076] Example 5

[0077] In this embodiment, a circular single crystal diamond sheet with a diameter of about 2 mm and a height of about 1 mm and red phosphorus powder are used to prepare an n-type semiconductor diamond material. The process steps are as follows:

[0078] (1) Pretreatment of single crystal diamond wafers

[0079] The circular single crystal diamond sheet was soaked in aqua regia at room temperature (25°C) for 24 hours, and then the soaked circular single crystal diamond sheet was ultrasonically washed with anhydrous ethanol and deionized water for 30 minutes each, and then the ultrasonically washed circular single crystal diamond sheet was dried in an oven at 80°C;

[0080] (2) Preparation of doped green body

[0081] The single crystal diamond pretreated in step (1) is placed in red phosphorus powder for compression molding at a compression pressure of 900 MPa and maintained at the pressure for 1 minute to obtain a doped green body consisting of a circular single crystal diamond sheet and red phosphorus wrapping the circular single crystal diamond sheet;

[0082] (3) High-pressure thermal diffusion doping and cleaning of diamond after doping

[0083] The doped body prepared in step (2) is placed in a two-stage six-eight-type large-cavity static high-pressure device, and the assembly method is as follows: Figure 2 As shown; then the pressure is increased to a doping pressure of 15 GPa at a pressure increase rate of 3.4 GPa / h, and then the temperature is increased to a doping temperature of 1500°C at a heating rate of 100°C / min, and the temperature is maintained for 300 seconds for thermal diffusion doping. After the thermal diffusion doping time is reached, the temperature is first cooled to room temperature at a cooling rate of 100°C / min, and then the pressure is reduced to normal pressure at a pressure reduction rate of 3.4 GPa / h; then the sample is taken out and placed in concentrated nitric acid and aqua regia in turn at room temperature (25°C) for 24 hours each, and then ultrasonically washed with anhydrous ethanol and deionized water for 30 minutes each, and after washing, it is dried in an oven at 80°C to obtain a phosphorus-doped n-type semiconductor diamond sheet.

[0084] The n-type semiconductor diamond sheet prepared in this example was subjected to a Hall effect test, and the test data are shown in Table 2 below.

[0085] Table 2 Hall effect test data

[0086]

[0087] It can be seen from the above-mentioned Examples 3, 4 and 5 that, using the same single crystal diamond and n-type doping material, applying the same molding pressure and holding time to prepare the doped green body, using the same static high pressure equipment, setting the same pressure increase and heating rate and temperature decrease and pressure reduction rate, under the same doping pressure, as the doping temperature increases, the obtained n-type semiconductor diamond has a higher doping concentration and better electrical properties.

Claims

1. A method for preparing an n-type semiconductor diamond material, characterized in that Under high pressure conditions, n-type dopants are doped into single crystal diamond by thermal diffusion to form n-type semiconductor diamond material. The process steps are as follows: (1) Pretreatment of single crystal diamond Soaking the single crystal diamond with at least one of concentrated nitric acid, concentrated hydrochloric acid and concentrated sulfuric acid to dissolve impurities on the surface of the single crystal diamond, then ultrasonically washing the soaked single crystal diamond with anhydrous ethanol and deionized water in turn to remove impurities on the surface of the single crystal diamond, and then drying the ultrasonically washed single crystal diamond; (2) Preparation of doped green body The single crystal diamond pretreated in step (1) is placed in a single substance powder or compound powder of an n-type doping substance for compression molding to obtain a doped body, wherein the doped body is composed of the single crystal diamond and the n-type doping substance encapsulating the single crystal diamond; Alternatively, a single substance powder or compound powder of an n-type doping substance is placed in an inorganic non-metallic material container, and then the single crystal diamond pretreated in step (1) is placed in the single substance powder or compound powder of the n-type doping substance for compression molding to obtain a doped blank, wherein the doped blank is composed of the single crystal diamond, the n-type doping substance encapsulating the single crystal diamond, and the inorganic non-metallic material encapsulating the n-type doping substance; (3) High-pressure thermal diffusion doping and cleaning of diamond after doping The doped body prepared in step (2) is placed in a static high-pressure device, firstly pressurized to the doping pressure, then heated to the doping temperature and kept at the temperature for thermal diffusion doping, and after the heat preservation and pressure holding time is reached, firstly cooled to room temperature, then reduced to normal pressure, and then cleaned to remove the wrapping material and impurities on the surface of the doped diamond and dried to obtain an n-type semiconductor diamond material; The doping pressure is 10 to 30 GPa, the doping temperature is 500 to 3000° C., and the heat and pressure holding time is 10 to 10000 s.

2. The method for preparing n-type semiconductor diamond material according to claim 1, characterized in that In step (1), the temperature for soaking the single crystal diamond in at least one of concentrated nitric acid, concentrated hydrochloric acid and concentrated sulfuric acid is from room temperature to the boiling point of the acid used; in step (2), the mass purity of the elemental powder or compound powder of the n-type doping material is ≥98%.

3. The method for preparing the n-type semiconductor diamond material according to claim 1 or 2, characterized in that In step (2), the compression molding pressure of the doped blank is 50-1000 MPa, and the holding time is 0.1-2 min; the inorganic non-metallic material container is made of boron nitride, graphite, magnesium oxide or aluminum oxide.

4. The method for preparing the n-type semiconductor diamond material according to claim 1 or 2, characterized in that In step (3), the pressure increasing rate from normal pressure to doping pressure and the pressure decreasing rate from doping pressure to normal pressure are determined according to the safe pressure increasing and decreasing rate range of the static high-pressure equipment used, and the temperature increasing rate from room temperature to doping temperature and the temperature decreasing rate from doping temperature to room temperature are 50 to 400°C / min.

5. The method for preparing n-type semiconductor diamond material according to claim 3, characterized in that In step (3), the pressure increasing rate from normal pressure to doping pressure and the pressure decreasing rate from doping pressure to normal pressure are determined according to the safe pressure increasing and decreasing rate range of the static high-pressure equipment used, and the temperature increasing rate from room temperature to doping temperature and the temperature decreasing rate from doping temperature to room temperature are 50 to 400°C / min.

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