Method for evaluating feasibility of diamond co-doping system

Abstract

The invention provides a method for evaluating the feasibility of a diamond co-doping system, and the method comprises the steps: constructing a model of the diamond co-doping system which comprises at least one co-doping compound; on the basis of the diamond co-doping system model, forming energy, binding energy and thermodynamic transition energy level of a co-doping compound of the diamond co-doping system are determined; according to the relation between the formation energy and a first preset condition, the relation between the binding energy and a second preset condition and the relation between the thermodynamic transition energy level and a third preset condition, the doping feasibility degree of the co-doped compound in the diamond lattice is determined, the first preset condition represents the difficulty degree of formation of the co-doped compound in the diamond lattice, and the second preset condition represents the difficulty degree of formation of the co-doped compound in the diamond lattice. The second preset condition represents the bonding stability degree of the co-doped compound, the third preset condition represents that the thermodynamic transition energy level is a shallow energy level, and the thermodynamic transition energy levels of other compounds or single-element impurities existing in diamond lattices cannot be shallow energy levels with other polarities.

Description

Technical Field

[0001] The invention relates to the field of theoretical calculation of diamond doping systems, and in particular to a method for evaluating the feasibility of a diamond co-doping system. Background Art

[0002] Diamond has great potential for application in high-frequency, high-temperature and high-power electronic devices due to its excellent physical and chemical properties, such as extremely high carrier mobility (electron mobility is 4500 cm² / (V·s) and hole mobility is 3800 cm² / (V·s) at room temperature), electric field breakdown strength of 10 MV / cm, and high thermal conductivity of about 2000 W / (m·K). In addition, diamond also has characteristics such as radiation resistance and chemical inertness. However, the ultra-wide band gap of diamond of about 5.47 eV limits its application in electronic devices.

[0003] The key to preparing diamond semiconductor devices is to achieve efficient p-type and n-type doping. Currently, the commonly used single-element doping methods use boron (p-type) and phosphorus (n-type), but the deeper impurity energy levels introduced by these dopants limit the application potential of the material at room temperature. Although a variety of co-doping systems that may provide shallow impurity energy levels have been predicted in theory, there has been no experimental report on the successful realization of diamond co-doping systems with effective conductivity. Summary of the invention

[0004] In view of this, the present invention provides a method for evaluating the feasibility of a diamond co-doping system. Through theoretical calculation, the feasibility of a selected diamond co-doping system is evaluated, which can effectively reduce experimental costs and accelerate research progress.

[0005] The embodiment of the present invention provides a method for evaluating the feasibility of a diamond co-doping system, comprising: constructing a model of a diamond co-doping system, wherein the diamond co-doping system comprises at least one co-doping compound; determining the formation energy, binding energy, and thermodynamic transition energy level of the co-doping compound of the diamond co-doping system based on the diamond co-doping system model; determining an evaluation result of the diamond co-doping system according to the relationship between the formation energy and a first preset condition, the binding energy and a second preset condition, and the thermodynamic transition energy level and a third preset condition, wherein the first preset condition characterizes the ease of formation of the co-doping compound in a diamond lattice, the second preset condition characterizes the stability of the binding of the co-doping compound, the third preset condition characterizes that the thermodynamic transition energy level is a shallow energy level, and the thermodynamic transition energy level of the compound or single element impurity other than the co-doping compound in the diamond lattice cannot be a shallow energy level of other polarities, and the evaluation result characterizes the doping feasibility of the co-doping compound in the diamond lattice.

[0006] According to an embodiment of the present invention, constructing a model of a diamond co-doping system includes: using a density functional method to perform structural optimization on a diamond primitive cell, and determining a target lattice constant of the diamond primitive cell whose total energy reaches a target convergence value; expanding the structurally optimized diamond primitive cell into an intrinsic diamond cubic supercell, so that the intrinsic diamond cubic supercell can accommodate a co-doped composite; after replacing or adding specific atoms in the intrinsic diamond cubic supercell to form a co-doped composite, respectively performing structural optimization of an electrically neutral doping system and a charged doping system to form a model of a diamond co-doping system.

[0007] According to an embodiment of the present invention, the side lengths of the intrinsic diamond cubic supercells in the diamond co-doping system model are at least three times the target lattice constant.

[0008] According to an embodiment of the present invention, a diamond co-doping system model is constructed, including: for the diamond primitive cell, a k-point grid of [8×8×8] is used for calculation, and the total energy convergence tolerance is less than 10 -8 eV; for the intrinsic diamond cubic supercell, a [2×2×2] k-point grid was used for the calculation, and the total energy convergence tolerance was less than 10 -6 eV.

[0009] According to an embodiment of the present invention, constructing a model of a diamond co-doping system includes: using a labeled reference method or a hybrid functional method to reduce the band gap underestimation error in the model.

[0010] According to an embodiment of the present invention, the first preset condition indicates that the formation energy of the co-doped complex is a positive value and is less than the first preset value, the second preset condition indicates that the binding energy of the co-doped complex is a positive value and is greater than the second preset value, and the third preset condition indicates that the absolute value of the thermodynamic transition energy level of the co-doped complex is less than the third preset value.

[0011] According to an embodiment of the present invention, the diamond co-doping system includes at least two co-doping compounds, and the evaluation method further includes: respectively calculating the formation energy, binding energy, and thermodynamic transition energy level of each of the at least two co-doping compounds; comparing the difference between the formation energy, binding energy, and thermodynamic transition energy level of each co-doping compound and the first preset value, the second preset value, and the third preset value to determine the doping feasibility of each co-doping compound in the diamond lattice.

[0012] According to an embodiment of the present invention, the formation energy of the co-doped composite is obtained according to the addition and subtraction of the energy change value caused by the introduction of the co-doped composite into the diamond co-doping system, the energy contributed by the chemical potential change, the energy contributed by the charge change and the energy contributed by the correction term; the binding energy of the co-doped composite is expressed as the difference between the sum of the formation energies of the single elements constituting the co-doped composite and the formation energy of the co-doped composite; the thermodynamic transition energy level is expressed as the difference between the formation energies of different charge states under the same Fermi level conditions.

[0013] According to an embodiment of the present invention, the correction term adopts a Madelung correction or a factor-effective-size (FNV) correction.

[0014] According to an embodiment of the present invention, the formation energy, binding energy, and thermodynamic transition energy level of the co-doped composite of the diamond co-doping system are determined, including: when each single element does not have a suitable charge state at the same Fermi energy level within the diamond lattice band gap, the binding energy is calculated using a neutral charge state, otherwise, the binding energy is calculated using a charged state.

[0015] According to the feasibility assessment method of the diamond co-doping system according to the embodiment of the present invention, by constructing a model of the diamond co-doping system, the formation energy, binding energy and thermodynamic transition energy level of the co-doped composite are accurately calculated based on the model, and corresponding preset conditions are set respectively, so that the doping feasibility of the co-doped composite in the diamond lattice can be scientifically, comprehensively and accurately assessed. This method is more accurate and efficient than traditional experimental methods, and can reduce experimental costs and cycles. At the same time, the method helps to discover and optimize diamond co-doping systems with excellent performance, thereby promoting the research and development of new diamond-based materials. This is of great significance for improving the performance of diamond materials and expanding their application fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0017] Figure 1 A flowchart schematically shows a method for evaluating the feasibility of a diamond co-doping system according to an embodiment of the present invention;

[0018] Figure 2 A flowchart schematically shows a method for evaluating the feasibility of a diamond co-doping system doped with Ga and N elements according to an embodiment of the present invention;

[0019] Figure 3 A schematic diagram showing a local lattice structure of a composite according to an embodiment of the present invention after structural optimization in a diamond supercell;

[0020] Figure 4The diagram schematically shows the variation of the formation energy of the composite according to an embodiment of the present invention in a diamond supercell with the Fermi energy. DETAILED DESCRIPTION

[0021] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0022] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0023] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0024] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0025] Figure 1 The flowchart schematically shows a method for evaluating the feasibility of a diamond co-doping system according to an embodiment of the present invention.

[0026] like Figure 1 As shown, a method for evaluating the feasibility of a diamond co-doping system may include steps S110 to S130:

[0027] In step S110 , a model of a diamond co-doping system is constructed, where the diamond co-doping system includes at least one co-doping compound.

[0028] Diamond is the hardest substance in nature. Its crystal structure is composed of carbon atoms tightly arranged in the form of tetrahedrons, forming a stable covalent bond lattice. Diamond co-doping system refers to a special structural system formed by introducing two or more different doping elements into the diamond crystal structure at the same time. For example, doping elements X and Y form a co-doped composite XY. This system can significantly regulate the physical and chemical properties of diamond, such as conductivity, magnetism, and optical properties, by changing the local atomic composition and arrangement in the diamond lattice. Doping elements include but are not limited to gallium (Ga), boron (B), nitrogen (N), phosphorus (P), silicon (Si), etc. For example, boron doping can increase the conductivity of diamond, while nitrogen doping can change its optical properties, but the present invention does not limit the specific doping elements.

[0029] The model of the diamond co-doping system can be constructed using crystal structure simulation software, which can provide powerful tools to create, optimize and visualize crystal structures. When constructing the model of the diamond co-doping system and performing calculations, the density functional theory (DFT) method based on first principles can be used. DFT is one of the first principles methods. It transforms the ground state property problem of the multi-electron system into the problem of solving the motion of a single electron in the effective potential field, thereby greatly simplifying the calculation process. DFT can calculate the electronic structure of the diamond co-doping system, including the band structure, state density, charge distribution, etc. The total energy, formation energy, binding energy, etc. of the co-doping system can be calculated. These energy parameters can reflect the difficulty of the doping process and the stability of the doping system. DFT can also be used to optimize the crystal structure of the co-doping system and find the stable configuration with the lowest energy. This helps to simulate and predict the properties of the doping system more accurately. The relevant content of DFT calculation will be further introduced later.

[0030] In step S120, based on the diamond co-doping system model, the formation energy, binding energy, and thermodynamic transition energy level of the co-doping complex of the diamond co-doping system are determined.

[0031] In the co-doped diamond system, the formation energy is the minimum energy required to introduce the doping element into the diamond lattice, the binding energy can reflect the interaction strength between atoms in the co-doped complex, and the thermodynamic transition level refers to the energy level change caused by the doping element, which may affect the conductivity and optical properties of diamond. The formation energy, binding energy, and thermodynamic transition level can be calculated in turn by the above DFT method, and can be compared with relevant experimental results.

[0032] In step S130, the evaluation result of the diamond co-doping system is determined according to the relationship between the formation energy and the first preset condition, the binding energy and the second preset condition, and the thermodynamic transition energy level and the third preset condition.

[0033] The first preset condition characterizes the difficulty of forming the co-doped composite in the diamond lattice, the second preset condition characterizes the stability of the bonding of the co-doped composite, and the third preset condition characterizes that the thermodynamic transition energy level is a shallow energy level, and the thermodynamic transition energy level of the composite or single element impurity other than the co-doped composite in the diamond lattice cannot be a shallow energy level of other polarities. The evaluation result characterizes the feasibility of doping the co-doped composite in the diamond lattice.

[0034] For example, if the formation of the co-doped compound XY in the diamond lattice can meet the first preset condition, it means that it is easier to form in the diamond lattice, and the doping concentration is usually higher, that is, the doping process is more favorable. If the binding energy of the co-doped compound XY in the diamond lattice meets the second preset condition, it means that the interaction between the atoms inside the compound is stronger, that is, the compound is more stable. Shallow energy levels usually refer to energy levels close to the edge of the valence band or conduction band, which have a significant effect on the electrical properties of the material. Thermodynamic transition energy levels of other possible compounds or single element impurities in the diamond lattice ensure that they are not shallow energy levels of other polarities to avoid adverse effects on the properties of the co-doped compound. When the co-doped compound XY meets the first, second, and third preset conditions at the same time, it can be considered that the compound has a higher doping scenario in the diamond lattice, that is, the doping feasibility is high. The first, second, and third preset conditions can be a specific value or a range of values, which can be set by technicians as needed. In this way, the doping feasibility of the co-doped compound in the diamond lattice can be scientifically, comprehensively, and accurately evaluated without conducting experiments. This method is more accurate and efficient than the traditional experimental method, and can reduce the experimental cost and cycle. At the same time, this method helps to discover and optimize diamond co-doping systems with excellent performance, thereby promoting the research and development of new diamond-based materials. This is of great significance for improving the performance of diamond materials and expanding their application areas.

[0035] Please continue reading Figure 1 On the basis of the above embodiment, step S110 may include: using a density functional method to perform structural optimization on a diamond primitive cell, and determining a target lattice constant of a diamond primitive cell whose total energy reaches a target convergence value; expanding the structurally optimized diamond primitive cell into an intrinsic diamond cubic supercell, so that the intrinsic diamond cubic supercell can accommodate a co-doped composite; after replacing or adding specific atoms in the intrinsic diamond cubic supercell to form a co-doped composite, respectively performing structural optimization of an electrically neutral doping system and a charged doping system to form a model of a diamond co-doping system.

[0036] The DFT method is used to optimize the structure of the diamond primitive cell, the purpose of which is to determine the lattice constant of the diamond primitive cell that minimizes the total energy. First, an initial diamond primitive cell model is selected and the corresponding calculation parameters are set. The initial lattice constant can be queried through experimental values ​​or literature data. The calculation parameters can be set in the simulation software, such as the cutoff energy, exchange correlation function, and k-point grid. Then, the structure of the diamond primitive cell is optimized by changing the initial lattice constant. For example, the lattice constant is adjusted to minimize the total energy of the system by maintaining the lattice symmetry. When the total energy reaches the minimum convergence value, the structural optimization is completed. The lattice constant at this time is the target lattice constant, which can be recorded as a0.

[0037] Next, based on the structurally optimized diamond primitive cell, a sufficiently large diamond supercell (i.e., an intrinsic diamond cubic supercell) is constructed to accommodate the desired co-doped composite. Preferably, the side lengths of the intrinsic diamond cubic supercell are at least three times the target lattice constant, i.e., greater than 3 a0 (i.e., the number of atoms in the supercell is at least 216). A larger supercell helps to fully relax each atom during the structural optimization process.

[0038] For different system sizes (such as primitive cells and supercells), it is usually necessary to adjust the density of the k-point grid to balance the calculation accuracy and calculation cost. In other words, the selection of k-points needs to be determined through a series of convergence tests. The larger the number of k-points, the more convergence to a certain value will be achieved, but the calculation time will be greatly extended. Regarding the value of the k-point grid, n k-points can be used for calculation in a certain dimension, n = round(2π|bi| / c), where round() represents the integer in the brackets, bi represents the reciprocal lattice basis vector in this dimension, and c should be less than 0.5 Å for semiconductors. -1 .

[0039] For the diamond primitive cell, due to its small size, its first Brillouin zone volume is larger, so more k-point mesh sampling is required to accurately describe its electronic structure. For the intrinsic diamond cubic supercell, due to the increase in real space volume, the first Brillouin zone in reciprocal space becomes smaller. Therefore, compared with the diamond primitive cell, a smaller number of k-point meshes can be used for calculations to save computing resources. For example, the diamond primitive cell can be calculated using a k-point mesh of [8×8×8] with a total energy convergence tolerance of less than 10 -8 eV; for the intrinsic diamond cubic supercell, a [2×2×2] k-point grid was used for the calculation, and the total energy convergence tolerance was less than 10 -6 eV.

[0040] In the process of constructing a diamond supercell, the total energy E of the system can be obtained by DFT calculation. tot [bulk], band gap width E g and the valence band top position E v In the DFT method, the generalized gradient approximation (GGA) or the local density approximation (LDA) can be used to approximate the interaction potential between electrons. However, these two methods tend to underestimate the band gap (i.e., the energy difference between the top of the valence band and the bottom of the conduction band) of the material when dealing with the electronic structure of semiconductors and insulators. To reduce the impact of the band gap underestimation error, the marker method can be used; or a more accurate method such as the HSE hybrid functional can be used.

[0041] Next, the predicted co-doped complex (such as XY, where X and Y represent two chemical elements) is introduced into the intrinsic diamond cubic supercell, and the total energy E of the electrically neutral doping system is obtained by structural optimization calculation. 0 [XY]. Then, the electrostatic charge of the doping system is set to q (for example, electrostatic charges 1+ and 1- correspond to n-type doping and p-type doping, respectively). The structure is also optimized and the total energy E of the charged system is obtained. q [XY].

[0042] Please continue reading Figure 1 In step S120, the formation energy of the co-doped composite can be obtained by adding and subtracting the energy change value caused by the introduction of the co-doped composite into the diamond co-doping system, the energy contributed by the chemical potential change, the energy contributed by the charge change, and the energy contributed by the correction term.

[0043] As an example, the formation energy of an impurity complex XY with charge q calculated by DFT can be expressed as:

[0044]

[0045] In the formula, E f [(XY)q ] means that the defect (XY) is included by calculation q The formation energy of the supercell, E tot [bulk] represents the total energy of a perfect lattice with supercells of the same size, an integer n i represents the number of atoms of type i (host atoms or impurity atoms) added or removed in the supercell, μ i represents the chemical potential corresponding to these elements. The chemical potential represents the energy of exchanging atoms with the (atomic) pool. The analogy of the "charge" chemical potential is given by the electronic chemical potential, which can be seen as the Fermi energy E F . E corr represents a correction term that takes into account finite K-point sampling in the case of shallow-level impurities, or elastic or electrostatic interactions between supercells.

[0046] It should be emphasized that the defect formation energy should always be positive, otherwise the host lattice (i.e., intrinsic crystal) will be unstable. The Coulomb correlation error correction caused by the introduction of periodic boundary conditions and background charge in DFT calculations can be simply made using the Madelung correction, or by using methods such as the effective size correction (FNV).

[0047] Please continue reading Figure 1 In step S120, the binding energy of the co-doped composite can be expressed as the difference between the sum of the formation energies of the single elements constituting the co-doped composite and the formation energy of the co-doped composite.

[0048] As an example, the binding energy of an impurity complex XY with charge q calculated using DFT can be expressed as:

[0049]

[0050] In the formula, represents the neutral charge state binding energy of the co-doped complex, , , denote the formation energies of single element X with charge q1, single element Y with charge q2, and co-doped complex with charge q, respectively, and .

[0051] In some embodiments, when each single element does not have a suitable charge state at the same Fermi level within the diamond lattice band gap, the neutral charge state is used to calculate the binding energy. Otherwise, the charged state needs to be strictly used to calculate the binding energy, that is, the above formula (2).

[0052] The binding energy of the neutral charge state is calculated according to the following formula:

[0053]

[0054] In the formula, represents the neutral charge state binding energy of the co-doped complex, X and Y represent the single elements constituting the co-doped complex, , , They represent the formation energies of X single element, Y single element, and co-doped complexes, respectively.

[0055] Please continue reading Figure 1 In step S120, the thermodynamic transition energy level is expressed as the difference in formation energy when the Fermi levels of the charge states are equal.

[0056] As an example, the thermodynamic transition energy level (i.e., impurity energy level) of the diamond co-doped system XY calculated using DFT can be expressed as: defined as the difference in formation energy when the Fermi levels of charge states q1 and q2 are equal:

[0057]

[0058] In the formula, represents the thermodynamic transition energy level, It represents the formation energy of impurity XY with charge state q1 when Fermi level EF=0, It represents the formation energy of impurity XY with charge state q2 when the Fermi level EF=0.

[0059] Through the above formula, the formation energy, binding energy and thermodynamic transition energy level of the co-doped composite of the diamond co-doped system can be determined respectively. Accordingly, the first, second and third preset conditions can be quantified to compare the magnitude relationship between them.

[0060] Please continue reading Figure 1 , in step S130, the first preset condition indicates that the formation energy of the co-doped composite is positive and less than the first preset value. The second preset condition indicates that the binding energy of the co-doped composite is positive and greater than the second preset value. The third preset condition indicates that the absolute value of the thermodynamic transition energy level of the co-doped composite is less than the third preset value. In other words, the formation energy of the co-doped composite must be positive and should be as low as possible. The lower the formation energy, the less energy is required to introduce the co-doped composite into the diamond lattice, and the easier it is to increase the concentration of doped atoms, thereby better improving the physical properties. At the same time, the binding energy of the co-doped composite should be as high as possible, and the higher the binding energy, the more stable the co-doped composite formed. For n-type and p-type, the values ​​of the thermodynamic transition energy levels of the co-doped composite are positive and negative, and the lower the absolute value, the shallower the energy level, thereby better improving the conductivity of the diamond co-doped system.

[0061] By comparing the formation energy, binding energy, and thermodynamic transition energy level of the co-doped complex with the first, second, and third preset values ​​in turn, a more accurate evaluation result can be obtained in a quantitative manner. The specific numerical values ​​of the first, second, and third preset values ​​can be set and adjusted according to empirical values ​​or public data, and the present invention does not make specific limitations. It is understandable that the smaller the first preset value is set, the larger the second preset value is set, and the smaller the third preset value is set, when the formation energy, binding energy, and thermodynamic transition energy level of the co-doped complex can meet these preset values, it indicates that the co-doped complex has a higher doping prospect.

[0062] Generally, two or more elements are doped in a diamond co-doping system, and there may be multiple forms of co-doped composites. The formation energy, binding energy, and thermodynamic transition energy level of each of these co-doped composites can be calculated separately, and the difference between the formation energy, binding energy, and thermodynamic transition energy level of each co-doped composite and the first preset value, the second preset value, and the third preset value can be compared to determine the doping feasibility of each co-doped composite in the diamond lattice. In this way, it is possible to quickly find which one or several co-doped composites have a high doping feasibility among multiple co-doped composites formed by the same element.

[0063] The present invention will be further described below by taking doping two elements Ga and N in a diamond lattice as a specific embodiment and combining the above embodiments.

[0064] Figure 2 The flowchart schematically shows a method for evaluating the feasibility of a diamond co-doping system doped with Ga and N elements according to an embodiment of the present invention. Figure 3 The local lattice structure diagram of the composite according to an embodiment of the present invention after structural optimization in a diamond supercell is schematically shown. Figure 4 The diagram schematically shows the variation of the formation energy of the composite according to an embodiment of the present invention in a diamond supercell with the Fermi energy.

[0065] like Figure 2 As shown, the method for evaluating the feasibility of a diamond co-doping system doped with Ga and N elements may include steps S21 to S26.

[0066] Step S21: Construct a diamond co-doping system model. First, determine the theoretical optimal lattice constant a0, then establish an intrinsic diamond cubic supercell, and calculate the total energy E[bulk], band gap width Eg, and valence band top position Ev of the system through density functional theory. Finally, introduce the predicted co-doping compound NGaN into the intrinsic diamond cubic supercell, set the system electrostatic charge to 0 and 1+ optimized structure, and calculate the total energy E[bulk] 0 [NGaN] and E 1+ [NGaN].

[0067] Step S22: Calculate the formation energy of the co-doped system NGaN The specific calculation method can be found in formula (1) above and will not be repeated here.

[0068] Step S23: Calculate the binding energy of the co-doped system NGaN The specific calculation method can be found in formula (2) above and will not be repeated here.

[0069] Step S24: Calculate the thermodynamic transition energy level of the co-doping system NGaN The specific calculation method can be found in formula (4) above and will not be repeated here.

[0070] Step S25: Calculate the relevant parameters of other possible composites. For example, consider the composites NN, Ga-Ga, N-Ga, N-Ga-N, Ga-N-Ga, NN-Ga and Ga-Ga-N, whose lattice structures can be as follows: Figure 3 As shown in (c) to (i), Figure 3 (a) and (b) are lattice structures doped with single elements N and Ga, respectively. Then, the formation energy, binding energy and impurity energy level (i.e., thermodynamic transition energy level) of these complexes are calculated in sequence according to the above steps S22 to S24. The formation energy of the complex is as follows: Figure 3 shown.

[0071] Step S26: Compare the calculation results and evaluate the overall feasibility. The comparison results are shown in Table 1, where CBM (Conduction Band Minimum) and VBM (Valence Band Maximum) refer to the conduction band bottom and valence band top, respectively.

[0072] Table 1

[0073]

[0074] From the comparison results in Table 1, it can be seen that in terms of binding energy, these complexes in diamond have a certain thermal stability. For impurity energy levels, the NGaN complex in diamond has a shallow donor energy level, similar to phosphorus-doped diamond; while the other complexes are all deep energy levels. For formation energy, the NGaN complex in diamond has a medium level. Fortunately, the several complexes with lower formation energy are all deep energy level impurities and will not have a significant compensation effect on NGaN. Therefore, NGaN in diamond has a certain prospect of doping.

[0075] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for evaluating the feasibility of a diamond co-doping system, characterized in that: include: constructing a model of a diamond co-doped system, the diamond co-doped system comprising at least one co-doped composite; Based on the diamond co-doping system model, determining the formation energy, binding energy, and thermodynamic transition energy level of the co-doped composite of the diamond co-doping system; Determine the evaluation result of the diamond co-doping system according to the relationship between the formation energy and the first preset condition, the binding energy and the second preset condition, and the thermodynamic transition energy level and the third preset condition, Among them, the first preset condition characterizes the difficulty of forming the co-doped composite in the diamond lattice, the second preset condition characterizes the stability of the bonding of the co-doped composite, the third preset condition characterizes that the thermodynamic transition energy level is a shallow energy level, and the thermodynamic transition energy level of the composite or single element impurity other than the co-doped composite in the diamond lattice cannot be a shallow energy level of other polarities, and the evaluation result characterizes the feasibility of doping the co-doped composite in the diamond lattice.

2. The evaluation method according to claim 1, characterized in that: The model for constructing the diamond co-doping system includes: The density functional method is used to optimize the structure of the diamond primitive cell and determine the target lattice constant of the diamond primitive cell whose total energy reaches the target convergence value; Expanding the structurally optimized diamond primitive cell into an intrinsic diamond cubic supercell, so that the intrinsic diamond cubic supercell accommodates the co-doped composite; After replacing or adding specific atoms in the intrinsic diamond cubic supercell to form the co-doped composite, structural optimization of the electrically neutral doping system and the charged doping system is performed respectively to form an optimized model of the diamond co-doping system.

3. The evaluation method according to claim 2, characterized in that: The side lengths of the intrinsic diamond cubic supercells in the diamond co-doping system model are at least three times the target lattice constant.

4. The evaluation method according to claim 3, characterized in that: The model for constructing the diamond co-doping system comprises: For the diamond primitive cell, a k-point grid of [8 × 8 × 8] was used for the calculation, and the total energy convergence tolerance was less than 10 -8 eV; For the intrinsic diamond cubic supercell, a [2 × 2 × 2] k-point grid was used for the calculation, and the total energy convergence tolerance was less than 10 -6 eV.

5. The evaluation method according to claim 4, characterized in that: The model for constructing the diamond co-doping system comprises: The bandgap underestimation error in the model was reduced using either the labeled reference method or the hybrid functional method.

6. The evaluation method according to claim 1, characterized in that: The first preset condition indicates that the formation energy of the co-doped composite is positive and is less than a first preset value. The second preset condition indicates that the binding energy of the co-doped complex is positive and greater than a second preset value. The third preset condition indicates that the absolute value of the thermodynamic transition energy level of the co-doped composite is less than a third preset value.

7. The evaluation method according to claim 6, characterized in that: The diamond co-doping system includes at least two co-doping compounds, and the evaluation method further includes: respectively calculating the formation energy, binding energy, and thermodynamic transition energy level of each of the at least two co-doped composites; The formation energy, binding energy, and thermodynamic transition energy level of each co-doped composite are compared with the first preset value, the second preset value, and the third preset value to determine the doping feasibility of each co-doped composite in the diamond lattice.

8. The evaluation method according to claim 1, characterized in that: The formation energy of the co-doped composite is obtained by adding and subtracting the energy change value caused by the introduction of the co-doped composite into the diamond co-doping system, the energy contributed by the chemical potential change, the energy contributed by the charge change and the energy contributed by the correction term; The binding energy of the co-doped composite is expressed as the difference between the sum of the formation energies of the individual elements constituting the co-doped composite and the formation energy of the co-doped composite; The thermodynamic transition energy level is expressed as the difference in formation energies of different charge states under the same Fermi level condition.

9. The evaluation method according to claim 8, characterized in that: The correction term adopts the Madelung correction or the effective size correction.

10. The evaluation method according to claim 8, characterized in that: The determining of the formation energy, binding energy, and thermodynamic transition energy level of the co-doped composite of the diamond co-doping system comprises: When the single elements do not have a suitable charge state at the same Fermi level within the diamond lattice band gap, the neutral charge state is used to calculate the binding energy; otherwise, the charged state is used to calculate the binding energy.

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