A design method for two-dimensional InGaN materials based on VASP software

Abstract

The present invention discloses a design method for two-dimensional InGaN materials based on the VASP software, comprising the following steps: (1) geometrically optimizing the atomic structure model of bulk InGaN materials; (2) constructing the atomic structure model of two-dimensional InGaN: cutting out the surface from the geometrically optimized bulk InGaN materials along the c-plane, adding a vacuum layer along the c-axis direction to construct a unit cell; adding pseudo-hydrogen atoms on the surface of the two-dimensional InGaN materials, and the bonding direction of the hydrogen atoms is perpendicular to the c-axis; (3) calculating the band structure of the two-dimensional InGaN materials: first, geometrically optimizing the atomic structure model of the two-dimensional InGaN materials, then outputting the charge distribution through single-point energy calculation, and finally calculating the band structure of the two-dimensional InGaN materials and reading the charge distribution output by the single-point energy calculation. The present invention solves the problem of difficult convergence in the calculation of non-layered two-dimensional material design, reduces the time for material design, and improves the efficiency.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor material design, and particularly relates to a design method of two-dimensional InGaN material based on VASP software. Background Art

[0002] The successful exfoliation of graphene has triggered a research and development boom of two-dimensional materials. However, the currently studied graphene and two-dimensional transition metal sulfides are zero-bandgap or narrow-bandgap materials, which limit their applications in the fields of electronics and optoelectronics. Therefore, there is an urgent need to develop a two-dimensional material with adjustable bandgap.

[0003] VASP is a material simulation software based on the first-principles simulation of density functional theory, which can predict the physical properties of materials such as atomic structure, electronic structure and optical properties. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide a design method of two-dimensional InGaN material based on VASP software, which solves the problem of difficult convergence in the calculation due to the unstable electronic structure of surface atoms in the design of non-layered two-dimensional materials, reduces the time of material design and improves the efficiency.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] A design method of two-dimensional InGaN material based on VASP software, comprising the following steps:

[0007] (1) Geometric optimization of the atomic structure model of bulk In x Ga 1-x N material; where x = 0 to 1;

[0008] The geometric optimization uses the HSE06 hybrid functional to process the exchange-correlation energy of electrons;

[0009] (2) Construct the atomic structure model of two-dimensional In x Ga 1-x N material:

[0010] Cut out the surface from the geometrically optimized bulk In x Ga 1-x N material along the c-plane, and add a vacuum layer along the c-axis direction to construct a unit cell;

[0011] Add pseudo-hydrogen atoms to the surface of the two-dimensional In x Ga 1-x N material, and the bonding direction of the hydrogen atoms is perpendicular to the c-axis;

[0012] In the generated POSCAR file, the H atoms connected to N atoms and In / Ga atoms are set as H1 and H2 respectively. Generate the POTCAR file using the POTCAR files of H atoms with 0.75 electrons and 1.25 electrons, and set them as H1 and H2 respectively;

[0013] (3) Calculate the band structure of two-dimensional In x Ga 1-x N material:

[0014] First, perform geometric optimization on the atomic structure model of two-dimensional In x Ga 1-x N material. Then, output the charge distribution through single-point energy calculation. Finally, calculate the band structure of two-dimensional In x Ga 1-x N material and read the charge distribution output by the single-point energy calculation;

[0015] The geometric optimization uses the HSE06 hybrid functional to handle the exchange-correlation energy of electrons;

[0016] The single-point energy calculation uses the HSE06 hybrid functional to handle the exchange-correlation energy of electrons.

[0017] Preferably, the construction process of the atomic structure model of the bulk In x Ga 1-x N material is as follows:

[0018] Obtain the structure files of wurtzite InN and GaN from the crystal database, and calculate the lattice constants of In x Ga 1-x N;

[0019] When x < 0.5 in In x Ga 1-x N, add Ga and N atoms according to the atomic positions in GaN, confirm the In atom ratio according to the x value, and construct a supercell and replace the Ga atoms;

[0020] When x ≥ 0.5, add In and N atoms according to the atomic positions in InN, confirm the Ga atom ratio according to the x value, and construct a supercell and replace the In atoms.

[0021] Preferably, the thickness of the surface in step (2) is 1 to 5 atomic layers.

[0022] Preferably, during the geometric optimization process, the plane wave cutoff energy Encut is set to 520 eV.

[0023] Preferably, in the single-point energy calculation, the plane wave cutoff energy Encut is set to 520 eV.

[0024] Preferably, in the geometric optimization of the atomic structure model of the two-dimensional In x Ga 1-x N material, the electron step convergence criterion EDIFF is set to 1E-6.

[0025] Preferably, in the process of calculating the output charge distribution of the single-point energy in step (3), the electron step convergence criterion EDIFF is set to 1E-7.

[0026] Preferably, in the process of calculating the band structure of the two-dimensional In x Ga 1-x N material, the band calculation path is set to G-M-K-G.

[0027] Preferably, the thickness of the vacuum layer in step (2) is

[0028] Preferably, in step (3), the N-H chemical bond length Ga-H chemical bond length In-H chemical bond length is set and the bonding direction of the hydrogen atom is perpendicular to the c-axis.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] (1) The design method of the two-dimensional In x Ga 1-x N material based on the VASP software of the present invention constructs a two-dimensional material using the atomic structure model of the bulk material after geometric optimization as a template. The two-dimensional material model constructed on the basis of the optimized bulk material is closer to the stable structure, can converge faster during geometric optimization, reduces the time for material design, and improves the efficiency.

[0031] (2) The design method of the two-dimensional In x Ga 1-x N material based on the VASP software of the present invention uses the method of passivating surface dangling bonds with pseudo-hydrogen atoms with different pseudopotentials for different surface atoms, solving the problem that the calculation cannot converge due to the unstable electronic structure of surface atoms in the first-principles calculation of non-layered two-dimensional materials.

[0032] (3) The design method of the two-dimensional In x Ga 1-x N material based on the VASP software of the present invention obtains the corresponding relationship between the band structure of two-dimensional In x Ga 1-x N and the composition and structure of the material. The designed two-dimensional In x Ga 1-xN is a two-dimensional material with an ultra-wide continuous adjustable bandgap of 1.28 eV - 4.53 eV. Compared with common zero-bandgap and narrow-bandgap materials such as graphene and two-dimensional transition metal sulfides, it can achieve a wide range of applications in optoelectronic devices from near-infrared to deep ultraviolet. Brief Description of the Drawings

[0033] Figure 1 Schematic atomic structure diagram of 1 - 5 layers of two-dimensional GaN designed in Example 1 of the present invention.

[0034] Figure 2 Graph showing the variation of the bandgap of 1 - 5 layers of two-dimensional GaN with the number of layers designed in Example 1 of the present invention.

[0035] Figure 3 AFM image of two-dimensional GaN prepared in Example of the present invention. In the figure, (a) and (b) are the surface topography of the sample and the height curve corresponding to the part marked by the line respectively.

[0036] Figure 4 PL spectrum of two-dimensional GaN prepared in Example of the present invention.

[0037] Figure 5 Schematic atomic structure diagram of monolayer In 0.25 Ga 0.75 N designed in Example 2 of the present invention.

[0038] Figure 6 Schematic atomic structure diagram of monolayer In 0.25 Ga 0.75 N energy band structure diagram designed in Example 2 of the present invention.

[0039] Figure 7 Image showing the variation of the bandgap of 1 - 5 layers of two-dimensional InN with the number of layers designed in Example 3 of the present invention.

[0040] Figure 8 Schematic atomic structure diagram of monolayer In x Ga 1-x N bandgap variation curve with x, where x = 1, 0.75, 0.5, 0.25, 0 designed in Example 4 of the present invention. Detailed Description of the Invention

[0041] The following is a further detailed description of the present invention in conjunction with the embodiments, but the implementation manners of the present invention are not limited thereto.

[0042] Example 1

[0043] The design method of two-dimensional GaN material based on VASP software in this example includes the following steps:

[0044] (1) Obtain the structure file of wurtzite GaN from the crystal database as the atomic structure model for geometric optimization;

[0045] (2) Use the VASP software package to perform geometric optimization on the bulk GaN material. The geometric optimization selects the HSE06 hybrid functional to handle the exchange-correlation energy of electrons, the plane-wave cutoff energy Encut is set to 520 eV, and the k-point value is 6×6×4.

[0046] (3) Construct the atomic structure model of two-dimensional GaN material: Cut out a surface with a thickness of 1 - 5 atomic layers along the c-plane from the geometrically optimized bulk GaN material, and add a vacuum layer with a thickness of along the c-axis direction to construct the unit cell;

[0047] (4) Add pseudo-hydrogen atoms to the upper and lower surfaces of the two-dimensional GaN material, and the bonding direction of the hydrogen atoms is perpendicular to the c-axis;

[0048] (5) In the generated POSCAR file, set the H atoms connected to the N atoms and Ga atoms as H1 and H2 respectively. Generate the POTCAR file using the POTCAR file of H atoms with 0.75 electrons and 1.25 electrons, and set them as H1 and H2 respectively;

[0049] (6) Perform geometric optimization on the two-dimensional GaN material. The geometric optimization selects the HSE06 hybrid functional to handle the exchange-correlation energy of electrons, the plane-wave cutoff energy Encut is set to 520 eV, the k-point value is 6×6×1, and the electron-step convergence criterion EDIFF is set to 1E-6;

[0050] (7) Perform a single-point energy calculation on the geometrically optimized structure to output the charge distribution. The single-point energy calculation selects the HSE06 hybrid functional to handle the exchange-correlation energy of electrons, the plane-wave cutoff energy Encut is set to 520 eV, the k-point value is 6×6×1, and the electron-step convergence criterion EDIFF is set to 1E-7;

[0051] (8) Read the charge distribution output by the single-point energy calculation to calculate the band structure of two-dimensional GaN. The band structure selects the HSE06 hybrid functional to handle the exchange-correlation energy of electrons, the plane-wave cutoff energy Encut is set to 520 eV, the band calculation path is set to G-M-K-G, and use VASPKIT to generate the KPOINTS file.

[0052] Figure 1 Schematic diagram of the atomic structure of 1 - 5 layer two-dimensional GaN constructed in this embodiment.

[0053] As Figure 2As shown, the band gap of two-dimensional GaN decreases with the increase in the number of layers. The band gaps of 1-5 layer two-dimensional GaN are 4.53, 4.05, 3.75, 3.61, and 3.50 eV, respectively.

[0054] In this example, two-dimensional Ga2O3 was prepared by the method of liquid metal printing, and then it was converted into two-dimensional GaN through an ammoniation reaction. Figure 3 This is the AFM image of the two-dimensional GaN prepared in this example. Its thickness was measured to be about 1.4 nm, which is equivalent to the thickness of 5 atomic layers. Figure 4 This is the PL spectrum of the two-dimensional GaN prepared in this example. The main emission peak of the sample is located at 348 nm, and its calculated band gap is 3.56 eV, which is in good agreement with the theoretical calculation result of the 3.50 eV band gap of 5-layer two-dimensional GaN.

[0055] Example 2

[0056] The design method of monolayer In 0.25 Ga 0.75 N based on VASP software in this example includes the following steps:

[0057] (1) Obtain the structure files of wurtzite InN and GaN from the crystal database, and calculate the lattice constants of In 0.25 Ga 0.75 N accordingly: a = 0.25a InN + 0.75a GaN , c = 0.25c InN + 0.75c GaN ;

[0058] (2) Add Ga and N atoms according to the atomic positions in GaN, confirm the In atom ratio according to the x value, construct a 2×2×1 supercell and replace two Ga atoms with In atoms to obtain the bulk In 0.25 Ga 0.75 N atomic structure model;

[0059] (3) Use the VASP software package to perform geometric optimization on the bulk In 0.25 Ga 0.75 N material. The geometric optimization selects the HSE06 hybrid functional to handle the exchange-correlation energy of electrons, the plane wave cut-off energy Encut is set to 520 eV, and the k-point value is 3×3×4.

[0060] (4) Construct the atomic structure model of monolayer In 0.25 Ga 0.75 N material: Cut out the surface of a single atomic layer along the c-plane from the geometrically optimized bulk In 0.25 Ga 0.75 N material, and add a thickness of Construct a unit cell with a vacuum layer;

[0061] (5) Add pseudo-hydrogen atoms to the upper and lower surfaces of the single-layer In 0.25 Ga 0.75 N material, and the bonding direction of the hydrogen atoms is perpendicular to the c-axis; And the bonding direction of the hydrogen atoms is perpendicular to the c-axis;

[0062] (6) In the generated POSCAR file, set the H atoms connected to the N atoms and In / Ga atoms as H1 and H2 respectively, and generate a POTCAR file using the POTCAR files of H atoms with 0.75 electrons and 1.25 electrons, and set them as H1 and H2 respectively;

[0063] (7) Geometrically optimize the single-layer In 0.25 Ga 0.75 N material. For the geometric optimization, use the HSE06 hybrid functional to handle the exchange-correlation energy of electrons, set the plane-wave cutoff energy Encut to 520 eV, the k-point sampling to 3×3×1, and the electron-step convergence criterion EDIFF to 1E-6;

[0064] (8) Perform a single-point energy calculation on the geometrically optimized structure to output the charge distribution. For the single-point energy calculation, use the HSE06 hybrid functional to handle the exchange-correlation energy of electrons, set the plane-wave cutoff energy Encut to 520 eV, the k-point sampling to 3×3×1, and the electron-step convergence criterion EDIFF to 1E-7;

[0065] (9) Read the charge distribution output from the single-point energy calculation and calculate the band structure of the single-layer In 0.25 Ga 0.75 N material. For the band structure calculation, use the HSE06 hybrid functional to handle the exchange-correlation energy of electrons, set the plane-wave cutoff energy Encut to 520 eV, set the band calculation path to G-M-K-G, and generate a KPOINTS file using VASPKIT.

[0066] Figure 5 The single-layer In 0.25 Ga 0.75 N atomic structure diagram constructed in this example.

[0067] As Figure 6 shown, the band structure diagram of the single-layer In 0.25 Ga 0.75 N designed in this example shows that it has a direct bandgap of 4.14 eV.

[0068] Example 3

[0069] The design method of two-dimensional InN based on the VASP software in this example includes the following steps:

[0070] (1) Obtain the structure file of wurtzite InN from the crystal database as the atomic structure model for geometric optimization;

[0071] (2) Use the VASP software package to perform geometric optimization on the bulk InN material. For this geometric optimization, the HSE06 hybrid functional is selected to handle the exchange-correlation energy of electrons, the plane-wave cutoff energy Encut is set to 520 eV, and the k-point sampling is set to 6×6×4.

[0072] (3) Construct the atomic structure model of two-dimensional InN: Cut out a surface with a thickness of 1 - 5 atomic layers along the c-plane from the geometrically optimized bulk InN material, and add a vacuum layer with a thickness of to construct the unit cell along the c-axis direction;

[0073] (4) Add pseudo-hydrogen atoms to the upper and lower surfaces of the two-dimensional InN material, and the bonding direction of the hydrogen atoms is perpendicular to the c-axis;

[0074] (5) In the generated POSCAR file, set the H atoms connected to N atoms and In atoms as H1 and H2 respectively, and generate the POTCAR file using the POTCAR file of H atoms with 0.75 electrons and 1.25 electrons, and set them as H1 and H2 respectively;

[0075] (6) Perform geometric optimization on the two-dimensional InN material. For this geometric optimization, the HSE06 hybrid functional is selected to handle the exchange-correlation energy of electrons, the plane-wave cutoff energy Encut is set to 520 eV, the k-point sampling is set to 6×6×1, and the electron-step convergence criterion EDIFF is set to 1E-6;

[0076] (7) Perform a single-point energy calculation on the geometrically optimized structure to output the charge distribution. For this single-point energy calculation, the HSE06 hybrid functional is selected to handle the exchange-correlation energy of electrons, the plane-wave cutoff energy Encut is set to 520 eV, the k-point sampling is set to 6×6×1, and the electron-step convergence criterion EDIFF is set to 1E-7;

[0077] (8) Read the charge distribution output from the single-point energy calculation to calculate the band structure of two-dimensional InN. For this band structure calculation, the HSE06 hybrid functional is selected to handle the exchange-correlation energy of electrons, the plane-wave cutoff energy Encut is set to 520 eV, the band calculation path is set to G-M-K-G, and the KPOINTS file is generated using VASPKIT.

[0078] As Figure 7 shown, the band gap of two-dimensional InN decreases with the increase in the number of layers. The band gaps of 1 - 5 layer two-dimensional InN are 3.12, 2.25, 1.77, 1.47, and 1.28 eV respectively.

[0079] Example 4

[0080] Design method of monolayer two-dimensional In x Ga 1-x N material (x = 1, 0.75, 0.5, 0.25, 0), comprising the following steps:

[0081] (1) Geometrically optimize the atomic structure model of bulk In x Ga 1-x N material

[0082] Obtain the structure files of wurtzite InN and GaN from the crystal database, and calculate the lattice constants of In x Ga 1-x N: a = xa InN +(1 - x)a GaN c = xc InN +(1 - x)c GaN .

[0083] When x < 0.5 in In x Ga 1-x N, add Ga and N atoms according to the atomic positions in GaN, confirm the In atom ratio according to the x value, and construct a supercell and replace Ga atoms according to requirements; when x ≥ 0.5, add In and N atoms according to the atomic positions in InN, confirm the Ga atom ratio according to the x value, and construct a supercell and replace In atoms according to requirements;

[0084] For geometric optimization, use the HSE06 hybrid functional to handle the exchange-correlation energy of electrons, and set the plane-wave cutoff energy Encut to 520 eV.

[0085] (2) Construct the atomic structure model of two-dimensional In x Ga 1-x N material

[0086] Cut out a single-atom layer surface along the c-plane from the geometrically optimized atomic structure model of bulk In x Ga 1-x N material, and add a vacuum layer with a thickness of along the c-axis direction to construct a unit cell.

[0087] Add pseudo-hydrogen atoms to the upper and lower surfaces of two-dimensional In x Ga 1-x N material, and the bonding direction of the hydrogen atoms is perpendicular to the c-axis.

[0088] In the generated POSCAR file, the H atoms connected to N atoms and In / Ga atoms are set as H1 and H2 respectively. POTCAR files are generated using the H atom POTCAR files with 0.75 electrons and 1.25 electrons, and are set as H1 and H2 respectively.

[0089] (3) Calculate two-dimensional In x Ga 1-x The band structure of N materials

[0090] First, perform geometric optimization on the two-dimensional In x Ga 1-x N materials. The electronic step convergence criterion EDIFF is set to 1E-6. Then, output the charge distribution through single-point energy calculation, and the electronic step convergence criterion EDIFF is set to 1E-7.

[0091] For geometric optimization and single-point energy calculation, the HSE06 hybrid functional is used to handle the exchange-correlation energy of electrons, and the plane-wave cutoff energy Encut is set to 520 eV.

[0092] Finally, calculate the band structure of the two-dimensional In x Ga 1-x N materials, read the charge distribution output by single-point energy calculation, and the band calculation path is set to G-M-K-G.

[0093] The graph of the band gap of the monolayer In x Ga 1-x N varying with x is as Figure 8 shown.

[0094] The above embodiments are preferred embodiments of the present invention. However, the embodiments of the present invention are not limited by the described embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A design method for two-dimensional InGaN materials based on the VASP software, characterized in that It includes the following steps: (1)Geometrically optimize the atomic structure model of the bulk In x Ga 1-x N material; where x = 0 to 1; In the geometric optimization, the exchange-correlation energy of electrons is treated with the HSE06 hybrid functional; The block In x Ga 1-x The construction process of the atomic structure model of the GaN material is as follows: Retrieve the structure files of wurtzite InN and GaN from the crystal database and calculate the lattice constants of In x Ga 1-x Ga When In x Ga 1-x When x < 0.5 in InGaN, Ga and N atoms are added according to the atomic positions in GaN, the proportion of In atoms is confirmed according to the x value, and the supercell is constructed and the Ga atoms are replaced; When x≥0.5, In and N atoms are added according to the atomic positions in InN, the proportion of Ga atoms is confirmed according to the x value, and a supercell is constructed and the In atoms are replaced; (2)Construct a two-dimensional In x Ga 1-x atomic structure model of N material: Cut the surface along the c-plane from the geometrically optimized bulk In x Ga 1-x N material, and add a vacuum layer along the c-axis direction to construct a unit cell; Adding pseudo-hydrogen atoms to the surface of two-dimensional In x Ga 1-x N material, and the bonding direction of hydrogen atoms is perpendicular to the c-axis; In the generated POSCAR file, the H atoms connected to N atoms and In / Ga atoms are set as H1 and H2 respectively, and the POTCAR file is generated using the POTCAR files of H atoms with 0.75 electrons and 1.25 electrons, and are set as H1 and H2 respectively; (3) Calculate the energy band structure of two-dimensional In x Ga 1-x N material: First, the atomic structure model of two-dimensional In x Ga 1-x N material is geometrically optimized. Then, the charge distribution is output through single-point energy calculation. Finally, the band structure of two-dimensional In x Ga 1-x N material is calculated, and the charge distribution output by the single-point energy calculation is read; In the single-point energy calculation, the exchange-correlation energy of electrons is treated with the HSE06 hybrid functional.

2. The design method of two-dimensional InGaN material based on VASP software according to claim 1, wherein The thickness of the surface described in step (2) is 1 to 5 atomic layers.

3. The design method of two-dimensional InGaN material based on VASP software according to claim 1, characterized in that In the process of the geometric optimization, the plane-wave cutoff energy Encut is set to 520 eV.

4. The design method of two-dimensional InGaN material based on VASP software according to claim 1, characterized in that In the single-point energy calculation, the plane-wave cutoff energy Encut is set to 520 eV.

5. The design method of two-dimensional InGaN material based on VASP software according to claim 1, characterized in that, In the geometric optimization of the atomic structure model of the two-dimensional In x Ga 1-x N material, the electronic step convergence criterion EDIFF is set to 1E-6.

6. The design method of two-dimensional InGaN material based on VASP software according to claim 1, wherein In the process of the single-point energy calculation in step (3) for outputting the charge distribution, the electronic step convergence criterion EDIFF is set to 1E-7.

7. The design method of two-dimensional InGaN material based on VASP software according to claim 1, characterized in that During the process of calculating the band structure of the two-dimensional In x Ga 1-x N material, the band calculation path is set as G-M-K-G.

8. The design method of two-dimensional InGaN material based on VASP software according to claim 1, characterized in that The thickness of the vacuum layer described in step (2) is 20 Å.

9. The design method of two-dimensional InGaN material based on VASP software according to claim 8, characterized in that In step (3), set the bond length d of the N-H bond N-H = 1.05 Å, the bond length d of the Ga-H bond Ga-H = 1.58 Å, the bond length d of the In-H bond In-H = 1.78 Å, and the bonding direction of the hydrogen atom is perpendicular to the c-axis.

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