CN113278947B - Crystal diamond nitrogen-doped semiconductor composite material and preparation method thereof - Google Patents

Abstract

The invention discloses a nitrogen-doped crystal form diamond semiconductor material, and belongs to the field of diamond semiconductors. Wherein the nitrogen-doped crystal form diamond semiconductor composite material comprises IIa type diamond crystals prepared by a high-temperature high-pressure method as a substrate material and CH₄Ar and NH₃And as a gas source, growing the nitrogen-doped crystal diamond on the substrate material. The invention further discloses a method for preparing the nitrogen-doped crystal diamond semiconductor material. The nitrogen-doped crystal form diamond semiconductor material prepared by the invention has better electrical property and semiconductor property, can promote the development of diamond semiconductor devices, and is also beneficial to the industrialized development of diamond-based semiconductor devices.

Description

Crystal diamond nitrogen-doped semiconductor composite material and preparation method thereof

Technical Field

The invention belongs to the field of diamond semiconductors, and particularly relates to a crystal type diamond nitrogen-doped semiconductor composite material and a preparation method thereof.

Background

Diamond, as a material with the highest natural hardness, has many excellent properties such as large forbidden bandwidth (5.5eV), extremely high thermal conductivity, corrosion resistance, good light transmittance, high longitudinal wave velocity, dielectric breakdown field strength, and the like, and is considered to be the most promising semiconductor material at present. At present, a P-type semiconductor is obtained by doping boron element in diamond, and the technical development is relatively mature. Significant challenges remain in obtaining high performance N-type semiconductor diamonds. At present, the doped N-type diamond film has deep impurity level, so that the concentration of a current carrier is low, the Hall mobility is low, the resistivity is high, and the N-type diamond film material cannot meet the manufacturing requirement of an electronic device, so that the N-type diamond film material is difficult to apply. The reason is that: the solid solubility of N-type impurity atoms in diamond crystals is low, the energy level of N-type donor impurities is deep to increase the atom ionization activation amount, and the crystal defects of the diamond can generate a charge compensation effect to reduce the carrier concentration. Therefore, finding out proper doping elements and doping methods has important significance for successfully preparing the N-type semiconductor diamond.

In the prior art, N-type diamond is generally prepared by a method of doping group V elements (N, P) and group VI elements (O, S) as electron donors, and a semiconductor material with good performance is attempted to be obtained; among them, nitrogen has received much attention from scientists as an impurity having the largest content in natural and synthetic diamonds; however, since nitrogen atoms have strong electronegativity, when nitrogen is substitutionally doped into diamond to form 4C-N configuration with four surrounding carbon atoms, unpaired electrons are bound near the nitrogen atoms, thus resulting in a defect level of 1.7eV (EC-1.7eV) deep in conduction band when nitrogen is used as a donor element; this seriously affects the conductivity at room temperature, resulting in failure as a semiconductor material with good performance.

Disclosure of Invention

In order to solve at least one of the above technical problems, the technical solution adopted by the present invention is as follows:

the invention provides a nitrogen-doped crystal form diamond semiconductor material, which comprises IIa type diamond crystals prepared by a high-temperature high-pressure method as a substrate material, and CH4, Ar and NH3 as gas sources to grow nitrogen-doped crystal form diamond on the substrate material.

In some embodiments of the invention, the high temperature high pressure process is a temperature gradient process. The temperature gradient method is that under the condition of high temperature and high pressure, the graphite at the upper part in the growth cavity is converted into diamond and dissolved in a catalyst, and due to the difference of temperature, the diamond is diffused from a high concentration area at a high temperature to a low concentration area at a low temperature and is crystallized and separated out on seed crystals at the low temperature. The method has the advantages that the catalyst is placed on the seed crystal at the lower part of the method to provide a space, and the existence of the seed crystal controls the nucleation quantity, so that the diamond crystal can grow for a long time and is suitable for the growth of large-size diamond crystals. The method can regulate and control the entering mode and the entering amount of the doping elements by regulating the process conditions, internal devices, catalyst components and the like. The large-size functional diamond single crystal synthesized after doping is more beneficial to expanding the application range of the diamond single crystal.

The diamond single crystal obtained by the high-temperature high-pressure static pressure catalyst method is in a six-octahedral shape and consists of more developed {100} and {111 }. In some preferred embodiments of the invention, the nitrogen-doped crystal diamond is grown by taking the {111} plane of the diamond crystal as a growth plane.

The microwave field is a high-frequency electromagnetic field, and electrons are violently oscillated under the action of the microwave field, so that collision with other atoms, ions, groups and molecules is promoted, the ionization degree of reaction gas is increased, and high-density plasma is generated. In the process of preparing the diamond film by microwave plasma CVD, the deposition gas is excited into a plasma state under the action of microwave energy, the ionization degree of the gas can reach more than 10 percent, and the supersaturation condition is met to ensure that CH is used₄Supersaturated hydrogen atoms, carbon-containing groups and the like are filled in the reaction atmosphere, so that the deposition rate is improved, and the deposition quality of the diamond film is greatly improved.

A second aspect of the present invention provides a method for preparing a nitrogen-doped crystalline diamond semiconductor composite material according to the first aspect of the present invention, comprising the steps of:

s1, IIa type diamond crystal prepared by high temperature and high pressure method;

and S2, growing the nitrogen-doped crystal diamond on the substrate material by taking the IIa type diamond crystal obtained in the step S1 as the substrate material and CH4, Ar and NH3 as gas sources.

In some embodiments of the invention, in step S1, the high temperature and high pressure process is referred to as a temperature gradient process.

In some embodiments of the present invention, the step S1 specifically includes:

s11, selecting the size of 0.5 multiplied by 0.5mm²The graphite as seed crystal, the mass ratio is 61: 39 FeNi is used as a catalyst, and a temperature gradient method is used for diamond growth;

s12, utilizing a mass ratio of 1: 0.063 Ti/Cu as denitrifier to remove nitrogen, IIa type diamond monocrystal is prepared.

In some embodiments of the invention, the growing in step S2 is performed using chemical vapor deposition. In some preferred embodiments of the present invention, the vapor deposition is microwave plasma chemical vapor deposition.

In some embodiments of the present invention, the step S2 specifically includes:

s21, grinding the diamond single crystal prepared in the step S1 on 1.5-micron diamond powder to enable the surface of the diamond single crystal to generate fine and uniform scratches, then putting the diamond single crystal into ethanol suspension of the diamond powder for ultrasonic treatment for 30min, and finally taking out the diamond single crystal, cleaning and drying the diamond single crystal to be used as a substrate material;

s22, placing the substrate material on a diamond-coated quartz plate at the center of the quartz tube reactor for contacting a plasma ball generated by microwave discharge;

and S23, growing the nitrogen-doped crystal form diamond film on the {111} plane of the substrate material by using CH4 and Ar as gas sources and NH3 as an N doping source. .

In some embodiments of the invention, in step S23, the ratio of the dopant source to the gas source is 16: 84.

the invention has the advantages of

Compared with the prior art, the invention has the following beneficial effects:

the invention uses IIa type diamond crystal prepared by high temperature and high pressure method as substrate material, and CH₄Ar and NH₃The nitrogen-doped crystal diamond grown on the substrate material as a gas source has two significant advantages:

(1) the IIa type diamond crystal prepared by the high-temperature high-pressure method is used as a substrate material, which is beneficial to the growth of the nitrogen-doped crystal type diamond, and compared with a diamond film prepared by the diamond crystal obtained by the CVD method, the IIa type diamond crystal has better semiconductor performance and obtains unexpected technical effects.

(2) The invention uses pure CH₄As a gas source, hydrogen is not needed, so that the reaction is easier to control and the cost is lower.

In addition, the invention uses microwave plasma CVD method to prepare the nitrogen-doped diamond film, and the advantages are mainly reflected in the following aspects: (1) the method has the advantages of high diamond film preparation speed and high quality; (2) the microwave can generate high-density plasma, so that the concentration of active groups is greatly improved, and the deposition of a film is facilitated; (3) the method has wider operating pressure range and can form stable plasma under higher reaction pressure; (4) the method can realize the deposition of the diamond film by adopting various mixed gases; (5) the method generates plasma without electrodes and does not introduce electrode impurities, so that the prepared diamond film has good quality and high purity. In addition, the microwave plasma CVD method can realize the low-temperature deposition of the diamond film, and the crystallinity and the crystal quality of the generated film are good.

Drawings

Fig. 1 shows an electron scanning electron microscope picture of a diamond single crystal produced in example 1 of the present invention.

Fig. 2 shows an electron scanning electron microscope picture of the nitrogen-doped crystalline diamond prepared in example 2 of the present invention.

Detailed Description

Unless otherwise indicated, implied from the context, or customary in the art, all parts and percentages herein are by weight and the testing and characterization methods used are synchronized with the filing date of the present application. Where applicable, the contents of any patent, patent application, or publication referred to in this application are incorporated herein by reference in their entirety and their equivalent family patents are also incorporated by reference, especially as they disclose definitions relating to synthetic techniques, products and process designs, polymers, comonomers, initiators or catalysts, and the like, in the art. To the extent that a definition of a particular term disclosed in the prior art is inconsistent with any definitions provided herein, the definition of the term provided herein controls.

The numerical ranges in this application are approximations, and thus may include values outside of the ranges unless otherwise specified. A numerical range includes all numbers from the lower value to the upper value, in increments of 1 unit, provided that there is a separation of at least 2 units between any lower value and any higher value. For example, if a compositional, physical, or other property (e.g., molecular weight, melt index, etc.) is recited as 100 to 1000, it is intended that all individual values, e.g., 100, 101, 102, etc., and all subranges, e.g., 100 to 166, 155 to 170, 198 to 200, etc., are explicitly recited. For ranges containing a numerical value less than 1 or containing a fraction greater than 1 (e.g., 1.1, 1.5, etc.), then 1 unit is considered appropriate to be 0.0001, 0.001, 0.01, or 0.1. For ranges containing single digit numbers less than 10 (e.g., 1 to 5), 1 unit is typically considered 0.1. These are merely specific examples of what is intended to be expressed and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application.

When used with respect to chemical compounds, the singular includes all isomeric forms and vice versa (e.g., "hexane" includes all isomers of hexane, individually or collectively) unless expressly specified otherwise. In addition, unless explicitly stated otherwise, the use of the terms "a", "an" or "the" are intended to include the plural forms thereof.

The terms "comprising," "including," "having," and derivatives thereof do not exclude the presence of any other component, step or procedure, and are not intended to exclude the presence of other elements, steps or procedures not expressly disclosed herein. To the extent that any doubt is eliminated, all compositions herein containing, including, or having the term "comprise" may contain any additional additive, adjuvant, or compound, unless expressly stated otherwise. Rather, the term "consisting essentially of … …" excludes any other components, steps or processes from the scope of any of the terms hereinafter recited, insofar as such terms are necessary for performance. The term "consisting of … …" does not include any components, steps or processes not specifically described or listed. Unless explicitly stated otherwise, the term "or" refers to the listed individual members or any combination thereof.

In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more apparent, the present invention is further described in detail below with reference to the following embodiments.

Examples

The following examples are used herein to demonstrate preferred embodiments of the invention. It will be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventor to function in the invention, and thus can be considered to constitute preferred modes for its practice. Those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit or scope of the invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs and the disclosures and references cited herein and the materials to which they refer are incorporated by reference.

Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.

The experimental methods not specifically described in the following examples are conventional methods unless otherwise specified. The instruments used in the following examples are, unless otherwise specified, laboratory-standard instruments; the test materials used in the following examples were purchased from a conventional biochemical reagent store unless otherwise specified.

Example 1 preparation of type IIa diamond single crystals

This example produced type IIa diamond single crystal by a temperature gradient method of a high temperature and high pressure method.

The high-temperature high-pressure equipment adopts an SDP 6X 1200 cubic press, and a carbon source is artificial high-purity graphite (purity is 99.9%) which is arranged at the high-temperature end of the cavity; the size of the seed crystal is 0.5 multiplied by 0.5mm²The {100} plane or the {111} plane of the seed crystal is used for crystal growth, and FeNi (64:36 wt%) is placed as a catalyst between a carbon source and the seed crystal. During synthesis, the pressure is set to be 5.6GPa, the temperature is 1436K, the synthesis speed is 1.0mg/h, Ti/Cu (1: 0.063) is used as a nitrogen removing agent for removing nitrogen, and the high-quality IIa type diamond single crystal is prepared.

As a result, as shown in FIG. 1, the {100} plane of the diamond single crystal produced in this example developed more sufficiently. The {100} surface of the crystal grown by the {100} surface has obvious growth protrusions, while the {111} surface of the crystal grown by the {111} surface has no obvious protrusions and is relatively flat and smooth.

Example 2 preparation of a crystalline form diamond nitrogen-doped semiconductor composite

The invention adopts Microwave Plasma Chemical Vapor Deposition (MPCVD) to prepare the crystal form diamond nitrogen-doped semiconductor composite material.

The diamond single crystal prepared in example 1 was used as a substrate material, and the substrate material was first pretreated to generate defects on the surface of the substrate material for facilitating diamond growth, which have high potential energy and promote diamond nucleation, thereby increasing nucleation density, and the diamond particles remaining on the surface can also be used as seed crystals to promote nucleation.

The specific operation of the substrate material pretreatment is as follows: the diamond single crystal prepared in the example 1 is ground on diamond powder with the diameter of 1.5 μm to enable the surface of the diamond single crystal to generate fine and uniform scratches, then the diamond single crystal is placed into ethanol suspension of the diamond powder for ultrasonic treatment for 30min, and finally the diamond single crystal is taken out, washed clean and dried for later use.

The substrate material was placed on a diamond coated quartz plate in the center of a quartz tube reactor for contacting a plasma ball generated by microwave discharge. The plasma reactor tube may be evacuated to 1X 10 by a turbomolecular pump^-5Pa。

Using CH₄And Ar as a gas source, NH₃As a doping source for N. The flow of each gas is controlled by a mass flow controller. And growing on the {111} plane of the substrate material to obtain the nitrogen-doped crystal diamond film.

The inventors have verified through a number of experiments that the volume ratio of the doping source to the gas source is 16: at 84, the doping effect was the best, and at other ratios, no effective doping was achieved, with the results shown in table 1:

TABLE 1 influence of doping source and gas source on average nitrogen doping amount

CH4:Ar:NH3	Amount of nitrogen (x 10)18cm-3)
		2：82：11	0.3
2：82：13	0.6
		2：82：15	0.8
2：82：16	1.9
		2：82：17	1.4
2：82：19	1.1

The growth conditions are shown in table 2:

TABLE 2 growth conditions for nitrogen-doped diamond of crystal form

In order to understand the microstructure and the compactness and uniformity of the crystal structure of the nitrogen-doped crystal diamond film prepared in the embodiment, the inventors observed the morphology of the prepared nitrogen-doped crystal diamond film by using an Ultra55 type field emission Scanning Electron Microscope (SEM) of Zeiss, germany.

The results are shown in fig. 2, from which it is clear that the film surface shows distinct graphite flakes growing in the form of graphite walls perpendicular to the substrate surface, and this morphology of needle-like structure is typical of high nitrogen content.

In order to obtain the electrochemical properties of the nitrogen-doped crystal form diamond film, the inventors tested the electrochemical activity of the nitrogen-doped crystal form diamond film by cyclic voltammetry, and the electrolyte solution was 5mM [ Fe (CN)₆]^3-/4-And 0.1M KCl solution, the scanning potential range is +0.65V to-0.25V, and the scanning speed range is 1mV/s to 30 mV/s; the double-layer capacitance of the nitrogen-doped crystal form diamond film is tested by cyclic voltammetry, and the electrolyte solution is 0.1M H₂SO₄The scanning potential range is 0V- +0.9V, and the scanning speed range is 5 mV/s-100 mV/s.

The electrochemical activity parameters of the nitrogen-doped crystal diamond film measured by cyclic voltammetry are specifically shown in table 3. As a result, it is understood that as the scan speed increases, the Δ Ep value gradually increases, and the ratio Ipa/Ipc of the anode to cathode peak current becomes further away from 1.

TABLE 3 Nitrogen-doped crystalline diamond films [ Fe (CN) ]₆]^3-/4-Electrochemical performance

The carrier velocities of electrons and holes are estimated using transient current techniques, and carrier mobility is obtained using time-of-flight and hall effect measurements. The results are shown in Table 4.

TABLE 4 Carrier velocity and Carrier mobility

Example 3 preparation of a crystalline form diamond nitrogen-doped semiconductor composite

For comparison, this example also used the prepared diamond single crystal prepared in example 1 as a substrate material, performed pretreatment and nitrogen-doped diamond growth using the method described in example 2, and measured the semiconductor properties, the results of which are shown in table 5.

TABLE 5 comparison of growth conditions and electrical properties of the crystal form nitrogen-doped diamond

As can be seen from the results of tables 4 and 5, the electrical properties and the semiconductor properties of the nitrogen-doped crystalline diamond prepared in example 2 were optimized.

All documents referred to herein are incorporated by reference into this application as if each were individually incorporated by reference. Furthermore, it should be understood that various changes and modifications of the present invention can be made by those skilled in the art after reading the above teachings of the present invention, and these equivalents also fall within the scope of the present invention as defined by the appended claims.

Claims (2)

1. A preparation method of a nitrogen-doped crystal form diamond semiconductor composite material is characterized by comprising the following steps:

s1, the IIa type diamond crystal prepared by the temperature gradient method is as follows:

s11, selecting the size of 0.5 multiplied by 0.5mm²The graphite as seed crystal, the mass ratio is 64:36 FeNi as catalyst, using temperature gradient method to grow diamond,

s12, utilizing a mass ratio of 1: 0.063 of Ti/Cu as denitrifier for removing nitrogen, preparing IIa type diamond monocrystal;

s2, using IIa type diamond crystal obtained in step S1 as substrate material and CH₄Ar and NH₃As a gas source and the volume ratio of the gas source is CH₄：Ar：NH₃And (6) =2:82:16, and growing the nitrogen-doped crystal diamond on the {111} plane of the substrate material by adopting a microwave plasma chemical vapor deposition method.

2. The method according to claim 1, wherein step S2 specifically includes:

s21, grinding the diamond single crystal prepared in the step S1 on 1.5 μm diamond powder to generate fine and uniform scratches on the surface of the diamond single crystal, then putting the diamond single crystal into ethanol suspension of the diamond powder for ultrasonic treatment for 30min, finally taking out the diamond single crystal, washing the diamond single crystal clean, drying the diamond single crystal to be used as a substrate material,

s22, placing the substrate material on a diamond-coated quartz plate at the center of the quartz tube reactor for contacting a plasma ball generated by microwave discharge;

s23, using CH₄And Ar as a gas source, NH₃As a doping source of N, the nitrogen-doped crystal form diamond film is grown on the {111} surface of the substrate material.

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