Simulation method for improving hetero-epitaxial growth of gallium nitride on diamond substrate

Abstract

The present application relates to the technical field of diamond substrate heteroepitaxial growth of thin film, and particularly relates to a simulation method for improving diamond substrate heteroepitaxial growth of gallium nitride, and steps are as follows: a surface model of boron nitride terminal diamond thin film (111) with different thicknesses is established; the surface model is subjected to structure optimization, and the surface model after structure optimization is subjected to first principle calculation; the surface model after structure optimization is respectively subjected to a femtosecond laser field, and laser intensity, frequency parameter ranges in which a carbon-carbon bond is not excited, and a nitrogen-boron bond in boron nitride and a gallium-nitrogen bond in gallium nitride are excited are calculated; according to obtained data, different gradient temperature fields are applied to perform first principle calculation, and laser intensity, frequency and temperature ranges in which a nitrogen-boron bond in boron nitride is broken, a gallium-nitrogen bond in gallium nitride is bonded, and other bonds remain stable are obtained. The present application provides an effective method for improving growth of gallium nitride on a diamond substrate surface, and improves development and application of electrical properties of a diamond heterojunction.

Description

Technical Field

[0001] This invention relates to the technical field of heteroepitaxial growth of thin films on diamond substrates, and specifically to a simulation method for improving heteroepitaxial growth of gallium nitride on diamond substrates. Background Technology

[0002] Diamond, with its ultra-wide bandgap and high thermal conductivity, holds immense potential for applications in power devices. However, the full realization of this potential remains severely limited by the lack of a suitable material for forming heterojunctions with matching lattice and band structures. Currently, surface termination technology not only allows for the modulation of diamond band structures but also provides new avenues for diamond heterojunction growth. However, the surface of the termination layer readily adsorbs various impurities from the air, and subsequent epitaxial processes can cause varying degrees of damage to the surface termination. These issues significantly impact the quality of the heterojunction, preventing it from fully realizing its potential. Summary of the Invention

[0003] The purpose of this invention is to provide a simulation method for improving heteroepitaxial growth of gallium nitride on diamond substrates. This method can solve the problems of large lattice mismatch and poor interface growth quality in current diamond heterojunction growth. Furthermore, through first-principles and molecular dynamics simulation calculations, a suitable laser intensity, frequency, and temperature range can be obtained that allows for the breaking of nitrogen-boron bonds in boron nitride, the formation of gallium-nitrogen bonds in gallium nitride, and the maintenance of stable other bonds.

[0004] The solution adopted by this invention to achieve its objective is: a simulation method for improving the heteroepitaxial growth of gallium nitride on diamond substrates, comprising the following steps:

[0005] S1: Establish surface models of boron nitride-terminated diamond films (111) with different thicknesses, wherein boron nitride and diamond atoms are aligned at the top position, boron atoms contact carbon atoms in diamond to form boron-carbon bonds, and surface nitrogen atoms are not saturated and are suspended individually.

[0006] S2: The surface model of boron nitride terminal diamond film (111) of different thicknesses was optimized to obtain the lattice constant, bond length, bond angle and atomic position of terminal diamond;

[0007] S3: Based on density functional theory, first-principles calculations were performed on the surface models of boron nitride terminal diamond films (111) with different thicknesses after structural optimization to obtain the ground state electron density and wave function;

[0008] S4: Femtosecond laser fields were applied to the surface models of boron nitride terminal diamond films (111) with different thicknesses after structural optimization. Based on the calculation of density functional theory, different laser intensity and frequency parameters were set to calculate the range of laser intensity and frequency parameters when carbon-carbon bonds were not excited, while nitrogen-boron bonds in boron nitride and gallium-nitrogen bonds in gallium nitride were excited.

[0009] S5: Based on the laser intensity and frequency parameter ranges obtained in step S4, apply different gradient temperature fields to perform first-principles calculations to obtain the laser intensity, frequency, and temperature ranges in which the nitrogen-boron bond breaks in boron nitride, the gallium-nitrogen bond forms in gallium nitride, and other bonds remain stable.

[0010] Preferably, in step S1, the surface model comprises two layers: an upper vacuum layer and a lower growth layer with diamond as a substrate.

[0011] Preferably, the diamond substrate is divided into three parts. The first part keeps the carbon atoms fixed throughout the kinetic process, and its bottom is saturated with hydrogen atoms. The temperature of the second part is always kept consistent with the set temperature. The third part is a carbon atom and boron nitride terminal layer, which allows the surface atoms to be fully subjected to the potential field.

[0012] Preferably, in the surface model, the boron nitride terminal is connected to the diamond via carbon-boron bonds, and the terminal exposes nitrogen atoms; the gallium nitride above is connected to the terminal structure via gallium-nitrogen bonds, forming a growth layer upwards.

[0013] Preferably, in step S2, the specific process is as follows: based on the ground state surface model, with the goal of minimizing the total energy of the model, density functional theory is used to solve for all lattice constants, bond lengths, bond angles and atomic positions of the two surface models.

[0014] Preferably, step S3 specifically involves: dividing the surface model of the boron nitride terminal diamond film (111) into k-space grids using the Monkhorst-Pack method; selecting the pseudopotentials of nitrogen, boron, carbon, gallium, and hydrogen atoms as ultrasoft pseudopotentials; using the generalized gradient approximation exchange-correlated functional; and iteratively solving the Kohn-Sham equation after setting self-consistent accuracy to obtain the ground state electron density and wave function.

[0015] Preferably, step S4 is performed using Lammps software, where the polarization direction of the applied laser field is perpendicular to the model surface.

[0016] Preferably, in step S5, the molecular dynamics calculation method uses the Tersoff potential to calculate the interaction forces between atoms.

[0017] Preferably, in step S5, the entire simulation process uses an NVT system with a time step of Δx = 0.5fs and a cutoff radius of 0.8nm.

[0018] Boron nitride not only possesses many advantages similar to diamond, but also exhibits superior thermal and chemical stability. Benefiting from their extremely low lattice mismatch rates, this invention places boron nitride terminals on the diamond interface to rationally control the growth of diamond heterostructures, serving as a medium for the heterostructure between boron nitride and wide-bandgap semiconductors such as gallium nitride. This growth method will significantly improve the quality of gallium nitride heteroepitaxial growth on diamond substrates, facilitating the innovation of high-performance components and playing a crucial role in further promoting the development of electronic technology.

[0019] This invention discloses a simulation method to improve the heteroepitaxial growth of gallium nitride (GaN) on diamond substrates, primarily addressing the problem of poor quality of heterojunctions grown on single-crystal diamond substrates in existing technologies. Based on density functional theory and molecular dynamics, first-principles and molecular dynamics calculations are performed on cubic boron nitride-terminated diamond thin film models of varying thicknesses to simulate the microscopic crystal growth process under laser and temperature fields, as well as the corresponding photon absorption, valence electron transitions, and chemical bond breaking. Based on this, a method to improve the heteroepitaxial growth of GaN on diamond substrates is further proposed. The intensity, frequency, and temperature range of the femtosecond laser that promotes boron-nitrogen bond breaking in boron nitride and nitrogen-gallium bond bonding in gallium nitride are calculated. Because this invention performs surface termination treatment on the single-crystal diamond substrate, it reduces lattice mismatch in the subsequent epitaxial process and provides more dangling bonds, improving the quality of the heterojunction and enhancing the heat dissipation capacity of the device. This method can be used to fabricate high-power GaN-based microwave power devices.

[0020] The present invention has the following advantages and beneficial effects:

[0021] This invention studies a method for improving the heteroepitaxial growth of gallium nitride (GaN) on diamond substrates using laser and temperature fields. Through first-principles calculations and molecular dynamics simulations, laser and temperature fields are applied to the surface of a model for growing GaN on a boron nitride-terminated diamond substrate. The laser intensity, frequency, and temperature range are calculated to achieve the following: the nitrogen-boron bond breaks, the gallium-nitrogen bond forms, and other bonds remain stable. This provides an effective method for improving the growth of GaN on diamond substrates and its application in improving the electrical properties of diamond heterojunctions. Attached Figure Description

[0022] Figure 1 A schematic diagram of a diamond / boron nitride terminal / gallium nitride heterojunction structure for an improved simulation method of heteroepitaxial growth of gallium nitride on a diamond substrate, provided in an embodiment of the present invention;

[0023] Figure 2 The diagram illustrates the steps of a simulation method for improving heteroepitaxial growth of gallium nitride on a diamond substrate, as provided in an embodiment of the present invention. Detailed Implementation

[0024] To better understand the present invention, the following embodiments are further illustrations of the present invention, but the content of the present invention is not limited to the following embodiments.

[0025] The growth of high-quality diamond heterojunctions is of great significance for improving the electronic performance of wide-bandgap semiconductors and the development of high-power electronic devices. This invention addresses the problems of large lattice mismatch and poor interface growth quality in current diamond heterojunction growth methods. It simulates the temperature field changes during diamond-gallium nitride interface growth using first-principles calculations and molecular dynamics simulations to obtain suitable conditions for interface growth. To determine the range of laser intensity, frequency, and temperature field, Figure 1 A schematic diagram of a diamond / boron nitride terminator / gallium nitride heterojunction structure is provided for an embodiment of the present invention to illustrate a simulation method for improving heteroepitaxial growth of gallium nitride on a diamond substrate; as shown. Figure 2 As shown, this invention provides a simulation method to improve the heteroepitaxial growth of gallium nitride on diamond substrates. Based on first-principles calculations and molecular dynamics analysis, the model simulates the transitions of valence electrons, the breaking and formation of chemical bonds under the influence of changes in the laser field and temperature field, thereby further improving the growth quality of gallium nitride on boron nitride-terminated diamond surfaces.

[0026] Specifically, a simulation method for improving the heteroepitaxial growth of gallium nitride on diamond substrates includes the following steps:

[0027] S1: Surface models of (111) boron nitride-terminated diamond films of different thicknesses were established. Boron nitride and diamond atoms were aligned at their top positions. Boron atoms formed boron-carbon bonds with carbon atoms in diamond. Surface nitrogen atoms were not saturated and were suspended individually.

[0028] S2: The surface model of boron nitride terminal diamond film (111) of different thicknesses was optimized to obtain the lattice constant, bond length, bond angle and atomic position of terminal diamond;

[0029] S3: Based on density functional theory, first-principles calculations were performed on the surface models of boron nitride-terminated diamond films (111) of different thicknesses to obtain the ground-state electron density and wave function;

[0030] S4: Apply femtosecond laser fields to the optimized terminal surface model. Based on density functional theory calculations, set different laser intensity and frequency parameters to calculate the laser intensity and frequency ranges where carbon-carbon bonds are not excited, while nitrogen-boron bonds in boron nitride and gallium-nitrogen bonds in gallium nitride are excited.

[0031] S5: Based on the laser intensity and frequency parameter ranges obtained in step S4, apply different gradient temperature fields to perform first-principles calculations to obtain the laser intensity, frequency, and temperature ranges in which the nitrogen-boron bond breaks in boron nitride, the gallium-nitrogen bond forms in gallium nitride, and other bonds remain stable.

[0032] Furthermore, the surface model in step S1 is created using modeling software such as Quantum ATK. This surface model comprises two layers, with the upper layer having a thickness of [missing information]. The vacuum layer is followed by a growth layer with diamond as the substrate. The entire diamond substrate consists of 8 layers divided into 3 parts. The first part is the bottom 2 layers, where carbon atoms are kept fixed throughout the kinetic process and the bottom is saturated with hydrogen atoms. The second part is the middle 3 layers, where the atoms are calibrated using a velocity method to ensure that the temperature remains consistent with the set temperature. The third part is the surface 3 layers of carbon atoms and boron nitride terminal layers, allowing the surface atoms to be fully subjected to the potential field. Two-dimensional periodic boundary conditions are used in the X and Y directions to make the particles pseudo-infinite on the horizontal plane. In the two surface models of the (111) plane, the boron nitride terminal is connected to the diamond through carbon-boron bonds, and the terminal exposes nitrogen atoms. The gallium nitride above is connected to the terminal structure through gallium-nitrogen bonds, forming a growth layer upwards.

[0033] Further, step S2 specifically includes: using the first-principles calculation software Quantum ATK based on the ground-state surface model, with the goal of minimizing the total energy of the model and the atomic free relaxation force, to solve for all lattice constants, bond lengths, bond angles and atomic positions of the two surface models.

[0034] Further, step S3 specifically includes: using the first-principles calculation software Quantum ATK to perform k-space mesh generation on the surface model of the boron nitride terminal diamond film (111), the Monkhorst-Pack method is used to divide the mesh, the pseudopotentials of nitrogen, boron, carbon, gallium and hydrogen atoms are selected as ultrasoft pseudopotentials, the generalized gradient approximation exchange correlation functional is used, and the Kohn-Sham equation is iteratively solved after setting self-consistent accuracy to obtain the ground state electron density and wave function.

[0035] Furthermore, step S4 is performed using Lammps software, with the polarization direction of the applied laser field perpendicular to the model surface. Molecular dynamics simulations are employed, utilizing the two-body distribution function, nearest-neighbor coordination number, and atomic trajectory method to simulate the growth process.

[0036] Furthermore, in step S5, the molecular dynamics calculation method uses the Tersoff potential to calculate the interaction forces between atoms. The Tersoff potential is accurate for describing the bonding type of diamond system in SP3 and is widely used in the simulation of semiconductor material systems. It has been successfully used in the simulation calculation of many growth systems. The entire simulation process uses the NVT system with a time step of Δx = 0.5 fs and a cutoff radius of 0.8 nm.

[0037] The above description is merely a preferred embodiment of the present invention, and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A simulation method for improving heteroepitaxial growth of gallium nitride on diamond substrates, characterized in that, Includes the following steps: S1: Establish surface models of boron nitride-terminated diamond films (111) with different thicknesses, wherein boron nitride and diamond atoms are aligned at the top position, boron atoms contact carbon atoms in diamond to form boron-carbon bonds, and nitrogen atoms on the surface are not saturated and are suspended separately. In the surface model, the boron nitride terminal is connected to the diamond through carbon-boron bonds, and the terminal exposes nitrogen atoms; the gallium nitride above is connected to the terminal structure through gallium-nitrogen bonds to form a growth layer upward. S2: The surface model of the (111) face of boron nitride terminal diamond film of different thicknesses is optimized with the goal of minimizing the total energy of the model, and the lattice constant, bond length, bond angle and atomic position of the terminal diamond are obtained. S3: Based on density functional theory, first-principles calculations were performed on the surface models of the (111) plane of boron nitride terminal diamond films of different thicknesses after structural optimization to obtain the ground state electron density and wave function; S4: Femtosecond laser fields were applied to the surface models of the (111) plane of boron nitride terminal diamond films of different thicknesses after structural optimization. Based on the calculation of density functional theory, different laser intensity and frequency parameters were set to calculate the range of laser intensity and frequency parameters when carbon-carbon bonds were not excited, while nitrogen-boron bonds in boron nitride and gallium-nitrogen bonds in gallium nitride were excited. S5: Based on the laser intensity and frequency parameter ranges obtained in step S4, apply different gradient temperature fields to perform first-principles calculations to obtain the laser intensity, frequency, and temperature ranges in which the nitrogen-boron bond breaks in boron nitride, the gallium-nitrogen bond forms in gallium nitride, and other bonds remain stable.

2. The simulation method for improving heteroepitaxial growth of gallium nitride on diamond substrates according to claim 1, characterized in that: In step S1, the surface model comprises two layers: an upper vacuum layer and a lower growth layer with diamond as a substrate.

3. The simulation method for improving heteroepitaxial growth of gallium nitride on diamond substrates according to claim 2, characterized in that: The diamond substrate is divided into three parts. The first part keeps the carbon atoms fixed throughout the kinetic process and its bottom is saturated with hydrogen atoms. The temperature of the second part is always kept consistent with the set temperature. The third part is a carbon atom and boron nitride terminal layer, which allows the surface atoms to be fully subjected to the potential field.

4. The simulation method for improving heteroepitaxial growth of gallium nitride on diamond substrates according to claim 1, characterized in that: In step S2, the specific process is as follows: based on the ground state surface model, with the goal of minimizing the total energy of the model, density functional theory is used to solve for all lattice constants, bond lengths, bond angles and atomic positions of the surface model.

5. The simulation method for improving heteroepitaxial growth of gallium nitride on diamond substrates according to claim 1, characterized in that: The specific process of step S3 is as follows: the surface model of the boron nitride terminal diamond film (111) is divided into k-space grids using the Monkhorst-Pack method. The pseudopotentials of nitrogen, boron, carbon, gallium and hydrogen atoms are selected as ultrasoft pseudopotentials. The Kohn-Sham equation is solved iteratively after setting the self-consistent accuracy by using the generalized gradient approximation exchange correlation functional to obtain the ground state electron density and wave function.

6. The simulation method for improving heteroepitaxial growth of gallium nitride on diamond substrates according to claim 1, characterized in that: Step S4 is performed using the Lammps software, where the polarization direction of the applied laser field is perpendicular to the model surface.

7. The simulation method for improving heteroepitaxial growth of gallium nitride on diamond substrates according to claim 1, characterized in that: In step S5, the molecular dynamics calculation method uses the Tersoff potential to calculate the interaction forces between atoms.

8. The simulation method for improving heteroepitaxial growth of gallium nitride on diamond substrates according to claim 1, characterized in that: In step S5, the entire simulation process uses the NVT system with a time step of Δx = 0.5fs and a cutoff radius of 0.8nm.

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