A GeSn alloy energy band calculation method and system

Abstract

The present invention belongs to the technical field related to semiconductor materials, and discloses a method and system for calculating energy bands of a GeSn alloy. The method comprises: obtaining a parameter file of structurally optimized Ge; performing cell expansion and Sn doping on the structurally optimized Ge, establishing a POSCAR input file of a target GeSn alloy, establishing a POTCAR input file of the GeSn alloy according to cutoff inner and outer diameters of Ge and cutoff inner and outer diameters of Sn, wherein the cutoff inner diameter of Ge has a value range of 1.80 to 1.90 and the outer diameter has a value range of 3.20 to 3.25, and the cutoff inner diameter of Sn has a value range of 1.40 to 1.50 and the outer diameter has a value range of 4.10 to 4.20, and running a vasp program to perform self-consistent calculation on the target GeSn alloy to obtain a band gap value and a band gap type of the target GeSn alloy. The present invention can accurately simulate the electronic structure of GeSn alloys at different concentrations and accurately calculate their energy bands.

Description

Technical Field

[0001] The present invention belongs to the technical field related to semiconductor materials, and more specifically, relates to a GeSn alloy energy band calculation method and system. Background Art

[0002] As an important Group IV semiconductor material, GeSn alloys possess tunable band gap structures and high carrier mobility, making them a focus of attention in the fields of semiconductors and optoelectronic materials. Experimental results show that the band gap of GeSn alloys gradually decreases with increasing Sn concentration, and a transition from an indirect band gap to a direct band gap occurs at 6%-10%. However, the lattice mismatch and the low solubility of Sn in Ge easily lead to Sn phase separation and agglomeration, making the preparation of high-concentration GeSn alloys technically challenging. Short-range order (SRO) during analysis complicates experimental characterization, increasing the difficulty of understanding and optimizing the properties of GeSn alloys.

[0003] Therefore, theoretical simulations are necessary, and currently, electronic structure simulations are mainly performed using the empirical pseudopotential method (EPM). Gupta et al. (2013) used the virtual crystal approximation (VCA) combined with the nonlocal empirical pseudopotential method (NL-EPM), adjusted the alloy disorder correction parameter Ploc in the VCA, and found that the GeSn alloy transitions from an indirect band gap to a direct band gap at a Sn content of approximately 6.5%. Xiao et al. (2019) used the empirical pseudopotential method (EPM) combined with strain and perturbation theory to adjust the lattice constant bending parameter (θ) and the Sn-Ge pseudopotential difference, and found that the band gap transition occurs when the Sn content is between 5.81% and 8.75%.

[0004] However, although the empirical pseudopotential method (EPM) has high computational efficiency in electronic structure simulation, its dependence on empirical parameters and its accuracy limitations in processing complex materials still make it difficult to meet the needs of accurately describing the electronic structure of materials.

[0005] Therefore, how to accurately describe the electronic structure of GeSn alloys with different concentrations in theory and calculate their band gaps is of great significance for further developing high-efficiency optoelectronic devices based on GeSn, optimizing the performance of alloy materials, and exploring new semiconductor materials. Summary of the Invention

[0006] In response to the above defects or improvement needs of the prior art, the present invention provides a GeSn alloy band calculation method and system thereof, the purpose of which is to accurately calculate the band gap of GeSn alloys at different concentrations.

[0007] To achieve the above objectives, the present invention provides a method for calculating the energy band of a GeSn alloy, which comprises:

[0008] Obtaining a parameter file of Ge after structural optimization, wherein the parameter file is a CONTCAR output file output by running the vasp program to optimize the structure of Ge to minimize the Ge energy. During the optimization, the ENCUT parameter range in the INCAR input file in the vasp program is set to 380-480, the POTCAR input file selects the PAW-LDA pseudopotential of Ge provided by the vasp program, and the POSCAR input file describes the unit cell crystal model of the orthorhombic system of Ge;

[0009] The Ge after structural optimization was expanded and doped with Sn to establish the POSCAR input file of the target GeSn alloy. The POTCAR input file of the GeSn alloy was established according to the cutoff inner and outer diameters of Ge and Sn. The cutoff inner diameter of Ge ranged from 1.80 to 1.90, and the outer diameter ranged from 3.20 to 3.25. The cutoff inner diameter of Sn ranged from 1.40 to 1.50, and the outer diameter ranged from 4.10 to 4.20. The vasp program was run to perform self-consistent calculations on the target GeSn alloy to obtain the band gap value and band gap type of the target GeSn alloy.

[0010] In an optional embodiment, the cell expansion and Sn doping of the Ge after structural optimization includes:

[0011] Materials Studio software was used to expand the structure-optimized Ge and dope it with Sn.

[0012] In an optional embodiment, when cell expansion and Sn doping are performed, the distribution of Sn atoms is made uniform and no Sn-Sn bonds appear.

[0013] In an optional embodiment, when performing structural optimization on Ge and self-consistent calculation on the target GeSn alloy, the KPOINTS input file used in the vasp program limits the sampling of the Brillouin zone using the Gamma-centered mesh or Monkhorst-Packmesh method, and the product range of the K point value in the KPOINTS input file and the lattice constant in the current POSCAR input file is

[0014] In an optional embodiment, when performing structural optimization on Ge, the POTCAR input file selects the PAW-LDA pseudopotential of Ge provided by the vasp program, specifically the 4-electron Ge pseudopotential.

[0015] In an optional embodiment, when performing structural optimization on Ge, the parameter settings of the INCAR input file used in the vasp program include: EDIFFG=-0.01, EDIFF=1E-5, IBRION=2, ISIF=3, GGA=CA, ISMEAR=0, SIGMA=0.05, NELM=500, NELMDL=-7, ENCUT=400;

[0016] When performing self-consistent calculations on the target GeSn alloy, the parameter settings of the INCAR input file used in the vasp program include: LWAVE=.TRUE., LSORBIT=.TRUE., SAXIS=0 0 1.

[0017] In an optional embodiment, the cut-off inner and outer diameters of Ge are 1.86±0.01 and 3.22±0.01, respectively, and the cut-off inner and outer diameters of Sn are 1.46±0.01 and 4.15±0.01, respectively.

[0018] The present invention also provides a GeSn alloy energy band calculation system, comprising a memory and a processor, wherein the memory stores a computer program, wherein the processor implements the steps of any of the above methods when executing the computer program.

[0019] The present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of any of the above methods.

[0020] The present invention also provides a computer program product, comprising a computer program or instructions, which implement the steps of any of the above methods when executed by a processor.

[0021] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0022] The present invention uses the vasp program to calculate the energy bands of a GeSn alloy. The POSCAR input file and the POTCAR input file are two important files required for the vasp program to run. The POTCAR input file contains the pseudopotentials of various elements in the system, and the POSCAR input file describes the unit cell parameters of the calculated system. The accuracy of these two files directly affects the accuracy of the vasp program's electronic structure simulation of the GeSn alloy, thereby affecting the energy band calculation. To improve the calculation accuracy, the present invention obtains an optimized Ge parameter file, expands the structure-optimized Ge and dopes Sn, and establishes a POSCAR input file for the target GeSn alloy. This structural optimization is also based on the vasp program. By rationally selecting ENCUT for optimization, it can effectively balance the calculation cost and accuracy while ensuring the accuracy of the energy band calculation, ensuring the reliability of the electronic structure simulation results of the GeSn alloy. On the other hand, the present invention determines the cutoff inner and outer diameters of Ge and Sn respectively through specific analytical methods, and then generates a POTCAR input file for the GeSn alloy with high accuracy. Experiments show that by simulating the electronic structure of the GeSn alloy and calculating the energy bands using the above method, the band gap value gradually decreases with increasing Sn concentration, and the trend is consistent with the actual measured trend. In addition, the turning point of the band gap type transition occurs between 7.6% and 7.8% concentration, which is consistent with the actual measured turning point between 6% and 8%. It can be seen that the present invention has a good effect and can accurately simulate the electronic structure of GeSn alloys at different concentrations and accurately calculate their energy bands. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flowchart of the steps of a method for calculating the energy band of a GeSn alloy in one embodiment of the present invention;

[0024] Figure 2 is a schematic diagram of the unit cell crystal structure of Ge in one embodiment of the present invention;

[0025] Figure 3 is a flow chart of a method for determining ENCUT parameters in one embodiment of the present invention;

[0026] Figure 4 It is a curve chart showing the change trend of energy with ENCUT value;

[0027] Figure 5 is a flow chart of the steps for determining the cut-off inner and outer diameters of Ge and Sn in one embodiment of the present invention;

[0028] Figure 6 It is a schematic diagram of the structure of GeSn alloy doped with one Sn atom;

[0029] Figure 7is the cell expansion multiple, the number of Sn atoms, and the redefined lattice vector corresponding to different doping concentrations;

[0030] Figure 8 The band gaps and band gap types corresponding to Sn at different concentrations are obtained by the method proposed by the present invention. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0032] Example 1

[0033] The Vienna Ab-initio Simulation Package (vasp) is a computer program package for atomic-scale materials simulation. Its main input files are INCAR, POTCAR, POSCAR, and KPOINTS. The INCAR input file controls the properties vasp performs. The POTCAR input file contains the pseudopotentials of the various elements in the system being calculated. The POSCAR input file describes the unit cell parameters of the system being calculated (including basis vectors or translation vectors, lattice constants, atomic positions, and other information). KPOINTS describes the k-point sampling in the irreducible Brillouin zone, also known as the k-point setup. The overall process involves specifying and submitting the input files INCAR, POTCAR, POSCAR, and KPOINTS. The vasp program executes the instructions, performs the calculations, and then outputs the corresponding files.

[0034] The present invention simulates the electronic structure of GeSn alloy based on vasp program, and then calculates the energy bands of GeSn alloy under different concentrations.

[0035] Example 1

[0036] like Figure 1 FIG. 1 is a flowchart of a method for calculating the energy band of a GeSn alloy according to an embodiment of the present invention. The steps are described below.

[0037] Step S1: Obtain the parameter file of Ge after structural optimization. The parameter file is the CONTCAR output file output by running the vasp program to optimize the structure of Ge to minimize the Ge energy. During optimization, the ENCUT parameter range in the INCAR input file in the vasp program is set to 380-500, the POTCAR input file selects the PAW-LDA pseudopotential of Ge provided by the vasp program, and the POSCAR input file describes the unit cell crystal model of the orthorhombic crystal system of Ge.

[0038] Step S2: Expand the Ge after structural optimization and dope Sn to establish the POSCAR input file of the target GeSn alloy. Establish the POTCAR input file of the GeSn alloy according to the cutoff inner and outer diameters of Ge and Sn. The cutoff inner diameter of Ge ranges from 1.80 to 1.90, and the outer diameter ranges from 3.20 to 3.25. The cutoff inner diameter of Sn ranges from 1.40 to 1.50, and the outer diameter ranges from 4.10 to 4.20. Run the vasp program to perform self-consistent calculation on the target GeSn alloy to obtain the band gap value and band gap type of the target GeSn alloy.

[0039] In step S1, it is necessary to obtain the CONTCAR output file output by running the vasp program to optimize the structure of Ge to minimize the energy of Ge. The lattice parameters of the system after each movement when the ions are relaxed given by CONTCAR are the same as those of POSCAR.

[0040] It can be understood that each time the vasp program is run, four input files need to be submitted, namely INCAR, POTCAR, POSCAR and KPOINTS.

[0041] The POTCAR input file contains the pseudopotentials of various elements in the calculated system. When optimizing the structure of Ge, the POTCAR input file uses the PAW-LDA pseudopotential of Ge provided by the vasp program. Specifically, the 4-electron Ge pseudopotential is selected, for example, Ge:4e, and the generation date is October 4, 2005.

[0042] The POSCAR input file describes the unit cell parameters of the system being calculated. When optimizing the structure of Ge, you can consult the literature to find the space group, crystal structure, and atomic coordinates of Ge in its ground state, and thus establish the POSCAR input file for Ge. In this example, the orthorhombic unit cell crystal model of Ge is selected, with a space group number of 227 and 8 atoms; Figure 2 is a schematic diagram of the atomic structure of Ge, and the lattice constant is The positions of the eight Ge atoms are expressed in fractional coordinates as follows: (0.000000000, 0.000000000, 0.500000000), (0.250000000, 0.250000000, 0.750000000), (0.000000000, 0.500000000, 0.00000000), (0.250000000, 0.750000000, 0.250000000), (0.5000000000,0.000000000,0.000000000), (0.7500000000,0.250000000,0.250000000), (0.500000000,0.500000000), (0.750000000,0.750000000,0.750000000), Based on the above information, create the POSCAR input file.

[0043] KPOINTS describes the k-point sampling in the irreducible Brillouin zone, also known as the k-point setting. In this example, you can choose to sample the Brillouin zone using a Gamma-centered mesh or a Monkhorst-Pack mesh. Regarding the k-point value, a larger value improves the calculation accuracy but increases the calculation time. Therefore, you can flexibly modify the k-point value based on the specific calculation type.

[0044] The INCAR input file controls what kind of calculations vasp performs. Different calculation types require different parameters. Here, Ge needs to be structurally optimized to minimize the Ge energy. Therefore, EDIFFG, EDIFF, IBRION, ISIF, GGA, ISMEAR, SIGMA, NELM, NELMDL, NSW, and ENCUT need to be set in the INCAR input file. Among them, the parameter ENCUT is mainly used to determine the plane wave cutoff energy. This parameter is closely related to the material. For different elements, the value of ENCUT is also different. The parameter EDIFF sets the convergence standard for the electron self-consistent field calculation, that is, when the change in total energy is less than this value, it is considered that convergence is achieved. In actual practice, considering the balance between accuracy and calculation speed, it is recommended that EDIFF be less than 1E-5ev; EDIFFG is used to control the convergence standard for structural optimization and is defined as the convergence criterion for force. When the force on each atom is less than this value, the optimization is stopped. It is recommended to be greater than And it is set to a negative value. IBRION controls the algorithm for ion movement. For example, setting it to 2 means using the conjugate gradient method for geometry optimization; ISIF determines whether the unit cell shape, volume or only the atomic position is allowed to change during the structure optimization process. GGA is used to specify the type of exchange-correlation functional, such as PBE, which is used to describe the electronic interaction of the system. ISMEAR and SIGMA set the broadening method of the electronic state and its broadening parameters, and select different broadening methods in metal and semiconductor / insulator systems to obtain a better electronic state distribution. NELM and NELMDL respectively control the maximum number of steps and delay steps of self-consistent iteration to ensure the convergence of the electronic state. NSW specifies the maximum number of moving steps of the ion position and determines the maximum number of geometric changes allowed during the optimization process. The above parameters can be flexibly set according to actual conditions. In this embodiment, the settings of other parameters are also referred to as follows:

[0045] EDIFFG=-0.01, EDIFF=1E-5, IBRION=2, ISIF=3, GGA=CA, ISMEAR=0, SIGMA=0.05, NELM=500, NELMDL=-7.

[0046] For the parameter ENCUT, the present invention provides a value range of 380 to 480 for Ge, such as Figure 3 FIG. 1 is a flow chart of a method for determining ENCUT parameters in an embodiment of the present invention, and the process is as follows.

[0047] Step S11: Set the adjustment range of ENCUT to be from 200ev to 600ev, with an adjustment step of 20ev.

[0048] Step S12: Use the vasp program to perform multiple structural optimizations on Ge. The difference between the input files constructed for each structural optimization is only the ENCUT value in the INCAR input file, and the other input files are the same.

[0049] Specifically, the settings in the above example can be adopted, wherein, since the traversal is for selecting a better ENCUT parameter, the calculation accuracy can be appropriately reduced to speed up the calculation. Therefore, in this embodiment, the k points in the KPOINTS input file can be set to 9×9×9.

[0050] Specifically, you can choose to use scripts to perform structural optimization calculations.

[0051] Step S13: extract the energy after each optimization and obtain the energy variation trend with the ENCUT value.

[0052] Step S14: Select an ENCUT value with a gentle change trend.

[0053] like Figure 4The graph shows the energy variation trend as a function of ENCUT values. It can be seen that within the ENCUT range of 380 to 480, the energy changes relatively smoothly. Therefore, an ENCUT value can be selected within this range, for example, ENCUT = 400. ENCUT significantly affects the convergence speed and accuracy of the calculation. Specifically, the ENCUT parameter determines the energy cutoff of the plane wave basis set, i.e., the maximum kinetic energy of the plane waves used to expand the wave function and electron density. Selecting the appropriate ENCUT value is key to ensuring computational accuracy: a low ENCUT value may result in non-convergence or an inaccurate description of the electronic structure, while an excessively high ENCUT value significantly increases the computational effort and time. Therefore, the present invention tests the total energy variation under different ENCUT values ​​and selects an optimal ENCUT value that ensures convergence of the total energy and force while also balancing computational efficiency. This balances accuracy and computational efficiency, effectively improving computational speed during subsequent calculations.

[0054] After submitting the above four files, you can run the vasp program to optimize the structure of Ge to minimize the Ge energy. After the calculation is completed, you will get a CONTCAR output file that describes the electronic structure of Ge after optimization. When performing structural optimization this time, the calculation accuracy can be improved. In a specific embodiment, the product range of the K point value in the KPOINTS input file and the lattice constant in the current POSCAR input file is preferably For example, in this embodiment, the k points in the KPOINTS input file can be set to 19×19×19.

[0055] In one embodiment, the output CONTCAR output file describes Ge as follows:

[0056] It contains a total of eight Ge atoms, and the unit cell scaling factor is 1.0;

[0057] The three basis vectors are (5.644,0,0), (0,5.644,0) and (0,0,5.644);

[0058] The coordinates of the 8 Ge atoms are described in the form of fractional coordinates. The 8 atoms are located at (0.00000000000000000, 0.0000000000000000, 0.50000000000000000), (0.25000000000000000, 0.25000000000000000, 0.75000000000000000), (0.00000000000000000, 0.50000000000000000, 0.00000000000000000), (0.250000000000000000, 0.750000000000000000, 0.25 0000000000000),(0.50000000000000000,0.0000000000000000,0.000000000000000),(0.75000000000000000,0.250000000000000,0.2500000000 000000), (0.50000000000000000, 0.50000000000000000, 0.5000000000000000), (0.75000000000000000, 0.75000000000000000).

[0059] It is understandable that if the parameter settings of the input file are different, the CONTCAR output file will also be slightly different, but the difference is not significant.

[0060] In step S2, the electronic structure of the GeSn alloy at the target concentration is simulated by using the vasp program. The input files closely related to the electronic structure of the GeSn alloy are the POSCAR input file and the POTCAR input file.

[0061] The POTCAR input file contains the pseudopotentials of various elements in the calculated system. When performing self-consistent calculations on the target GeSn alloy, the POTCAR input file used needs to provide the pseudopotentials of Ge and Sn. In order to improve the accuracy of the pseudopotentials, the present invention calculates the cutoff inner and outer diameters of Ge and Sn by specific means. Specifically, the cutoff inner diameter of Ge is in the range of 1.80 to 1.90, and the outer diameter is in the range of 3.20 to 3.25. The cutoff inner diameter of Sn is in the range of 1.40 to 1.50, and the outer diameter is in the range of 4.10 to 4.20. Then, an accurate POTCAR input file is constructed based on the cutoff inner and outer diameters.

[0062] like Figure 5The figure shows a flow chart of the steps for determining the cut-off inner and outer diameters of Ge and Sn in one embodiment of the present invention, combined with Figure 5 The process of determining the cutoff inner and outer diameters of Ge and Sn is introduced.

[0063] Step S21: obtaining the CONTCAR output file after structural optimization of Ge as the POSCAR input file after Ge update, and generating the WAVECAR output file of Ge by performing self-consistent calculation on the structurally optimized Ge.

[0064] The WAVECAR output file gives the electronic wave function of the calculated system. It is a binary file and cannot be edited.

[0065] As you can understand, each time you run the vasp program, you need to submit four input files, namely INCAR, POTCAR, POSCAR and KPOINTS.

[0066] In this step, the CONTCAR output file after structural optimization of Ge is directly used as the POSCAR input file;

[0067] The POTCAR input file continues to use the Ge POTCAR input file mentioned in step S1, that is, select the Ge PAW-LDA pseudopotential provided by the vasp program, specifically select the 4-electron Ge pseudopotential, for example, select Ge:4e, and the generation date is October 4, 2005;

[0068] The INCAR input file is set according to the calculation type of this step, that is, the calculation of the electron wave function is performed and the WAVECAR output file is generated. For example, the INCAR input file can be set to GGA=CA, EDIFF=1E-5, ISMEAR=0, SIGMA=0.05, ENCUT=400, and LWAVE=.TRUE.

[0069] In the KPOINTS input file, continue to select Gamma-centered mesh or Monkhorst-Pack mesh for sampling the Brillouin zone. The accuracy required for self-consistent calculation is not high, so the k value can be appropriately reduced to increase the calculation speed. In this embodiment, the K point value satisfies the multiplication range of the K point value and the lattice constant of the currently calculated system, which is 30 to 40. For example, the K point value is 7×7×7.

[0070] Submit the above four input files, run the vasp program to perform self-consistent calculations on the Ge after structural optimization, and generate the WAVECAR output file of Ge.

[0071] Step S22: traverse multiple groups of Ge cutoff inner and outer diameters, substitute each group of cutoff inner and outer diameters into the shell-LDA-1 / 4 correction function, obtain the corresponding self-energy potential and update the Ge POTCAR input file, calculate the Ge band gap based on the current four Ge input files and WAVECAR output file, and select the cutoff inner and outer diameters that make the Ge band gap most consistent with the experimental band gap (0.742 eV);

[0072] In this embodiment, the cutoff inner radius traversal range of Ge is set to 0.1 to 5.0, and the outer radius traversal range is also set to 0.1 to 5.0, with an adjustment step of 0.1. Once an optimal radius combination is obtained, a refined traversal is performed, with the range set to plus or minus 0.1 of the optimal radius, with a step size of 0.01.

[0073] The obtained inner and outer diameters of Ge are 1.86 and 3.22, respectively. Depending on the difference in calculation accuracy, there may be a fluctuation of ±0.01. Moreover, according to the difference in file parameter settings and adjustment step size, the result may have a difference of less than ±0.1. Therefore, the cutoff inner diameter value range of Ge is determined to be 1.80~1.90, and the outer diameter value range is 3.20~3.25. The fluctuation range is within the acceptable range.

[0074] Step S23: Based on the current POSCAR input file of Ge, one of the eight Ge atoms in the Ge crystal model is replaced by a Sn atom to form the POSCAR input file of the GeSn alloy. The pseudopotentials of Ge and Sn are selected from the PAW-LDA pseudopotential provided by vasp to form the POTCAR input file of the GeSn alloy. Based on the four input files of the GeSn alloy, the structure of the GeSn alloy is optimized to minimize the energy of the GeSn alloy, and the CONTCAR output file of the GeSn alloy is obtained.

[0075] The current POSCAR input file of Ge is the POSCAR input file updated in step S21. The updated Ge unit cell crystal model is doped with Sn, specifically so that one of the eight Ge atoms in the Ge crystal model is replaced by a Sn atom, as shown in FIG. Figure 6 As shown, the POSCAR input file for forming the GeSn alloy.

[0076] In the POTCAR input file for GeSn alloy, the pseudopotentials of Ge and Sn are selected from the PAW-LDA pseudopotentials provided by vasp, for example, Ge: 4e, generated on October 4, 2005; Sn: 4e, generated on October 3, 2001.

[0077] The INCAR input file and KPOINTS input file of GeSn alloy can directly refer to the settings for Ge structure optimization in step S1 above.

[0078] Submit the above four input files, run the vasp program to optimize the structure of GeSn alloy, and generate the CONTCAR output file of GeSn alloy. Its lattice constant is

[0079] Step S24: Using the CONTCAR output file of the GeSn alloy as the updated POSCAR input file of the GeSn alloy, the POTCAR input file of the GeSn alloy is updated according to the cutoff inner and outer diameters of Ge and the pseudopotential of Sn, and the WAVECAR output file of the GeSn alloy is obtained through self-consistent calculation.

[0080] At this time, the settings of the KPOINTS input file and the INCAR input file can refer to the settings for the self-consistent calculation in step S21.

[0081] Step S25: Traverse multiple groups of Sn cutoff inner and outer diameters, substitute each group of cutoff inner and outer diameters into the shell-LDA-1 / 4 correction function, obtain the corresponding self-energy potential and update the POTCAR input file of the GeSn alloy, calculate the band gap of the GeSn alloy based on the current four input files and WAVECAR output file of the GeSn alloy, and select the cutoff inner and outer diameters that maximize the band gap of the GeSn alloy.

[0082] Specifically, the Tool.exe program can be used to implement the shell-LDA-1 / 4 correction and update the POTCAR input file. Specifically, the exponential factor n of the shell-LDA-1 / 4 correction function is set to 20.

[0083] In this embodiment, the cutoff inner diameter traversal range of Sn is set to 0.1 to 5.0, and the outer diameter traversal range is also set to 0.1 to 5.0, with an adjustment step of 0.1. Once an optimal radius combination is obtained, a refined traversal is performed, with the range set to plus or minus 0.1 of the optimal radius, with a step size of 0.01.

[0084] The obtained inner and outer diameters of Sn are 1.46 and 4.15, respectively. Depending on the difference in calculation accuracy, there may be a fluctuation of ±0.01. Moreover, depending on the difference in file parameter settings and adjustment step size, the result may have a difference of less than ±0.1. Therefore, the cutoff inner diameter of Sn is determined to be in the range of 1.40 to 1.50, and the outer diameter is determined to be in the range of 4.10 to 4.20. This fluctuation range is within an acceptable range.

[0085] In the above manner, the cutoff inner and outer diameters of Ge and Sn are determined.

[0086] Based on the cutoff inner and outer diameters of Ge and Sn, the POTCAR input file for GeSn alloy can be constructed.

[0087] The POSCAR input file for the GeSn alloy is created by directly expanding the optimized Ge obtained in step S1 and doping with Sn to create the POSCAR input file for the target GeSn alloy. During doping, the distribution of Sn atoms should be uniform, and no Sn-Sn bonds should appear. When expanding the cell, try to keep the lengths of the three sides as close as possible, for example, expanding the cell by 2 times: Expand cells 10 times: Specifically, Materials Studio 2019 can be used to expand the optimized Ge and dope Sn. The expansion is done by redefining the lattice vector operation to obtain the POSCAR input file of the target GeSn alloy. Figure 7 Shown are the cell expansion factor, number of Sn atoms, and redefined lattice vectors corresponding to different doping concentrations.

[0088] It is understandable that the KPOINTS input file and INCAR input file of GeSn alloy can be set according to the calculation type of this step. For example, the product range of the K point value of the KPOINTS input file and the lattice constant in the current POSCAR input file is If this condition is met, the K-point density can be optimized to balance the computational accuracy and efficiency. The INCAR input file can be set to LWAVE=.TRUE., LSORBIT=.TRUE., SAXIS=0 0 1.

[0089] Submit the above input file, run the program for self-consistent calculation, and extract the band gap type such as Figure 8 The figure shows the band gap and band gap type corresponding to different Sn concentrations obtained by the method proposed in the present invention. As the Sn concentration increases, the band gap value of the GeSn alloy gradually decreases, and the trend is consistent with the trend measured experimentally. The turning point occurs between 7.6% and 7.8%, which is consistent with the experimentally measured turning point between 6% and 8%. It can be seen that the present invention has produced a good effect.

[0090] Example 2

[0091] The present invention also relates to a GeSn alloy energy band calculation system, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0092] The system can be set up on computing devices such as desktop computers, notebooks, PDAs and cloud servers. The so-called processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The memory can be used to store computer programs and / or modules, and the processor performs various functions of the electronic device by running or executing the computer programs and / or modules stored in the memory and calling the data stored in the memory.

[0093] Example 3

[0094] The present invention also relates to a computer-readable storage medium having a computer program stored thereon, which implements the steps of the above method when the computer program is executed by a processor.

[0095] Specifically, the memory may include a high-speed random access memory, and may also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage device.

[0096] Example 4

[0097] An embodiment of the present invention provides a computer program product or computer program, which includes computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computer device to perform the steps of the method of the above embodiment of the present invention.

[0098] The technical features of the above-described embodiments may be combined in any manner. To simplify the description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. It should be noted that the phrases "in one embodiment," "for example," "and another example," etc., of the present invention are intended to illustrate the present invention and are not intended to limit the present invention.

[0099] The above-described embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A method for calculating the energy band of GeSn alloy, characterized in that: include: Obtaining a parameter file of Ge after structural optimization, wherein the parameter file is a CONTCAR output file output by running the vasp program to optimize the structure of Ge to minimize the Ge energy. During the optimization, the ENCUT parameter range in the INCAR input file in the vasp program is set to 380-480, the POTCAR input file selects the PAW-LDA pseudopotential of Ge provided by the vasp program, and the POSCAR input file describes the unit cell crystal model of the orthorhombic system of Ge; The Ge after structural optimization was expanded and doped with Sn to establish the POSCAR input file of the target GeSn alloy. The POTCAR input file of the GeSn alloy was established according to the cutoff inner and outer diameters of Ge and Sn. The cutoff inner diameter of Ge ranged from 1.80 to 1.90, and the outer diameter ranged from 3.20 to 3.

25. The cutoff inner diameter of Sn ranged from 1.40 to 1.50, and the outer diameter ranged from 4.10 to 4.

20. The vasp program was run to perform self-consistent calculations on the target GeSn alloy to obtain the band gap value and band gap type of the target GeSn alloy.

2. The GeSn alloy energy band calculation method according to claim 1, wherein: The cell expansion and Sn doping of the structure-optimized Ge comprises: Materials Studio software was used to expand the structure-optimized Ge and dope it with Sn.

3. The GeSn alloy energy band calculation method according to claim 1, characterized in that: When cell expansion and Sn doping are performed, the distribution of Sn atoms is made uniform and no Sn-Sn bonds appear.

4. The GeSn alloy energy band calculation method according to claim 1, wherein: When optimizing the structure of Ge and performing self-consistent calculations on the target GeSn alloy, the KPOINTS input file used in the vasp program limits the sampling of the Brillouin zone using the Gamma-centered mesh or Monkhorst-Pack mesh method, and the product of the K point value in the KPOINTS input file and the lattice constant in the current POSCAR input file is in the range of 5. The GeSn alloy energy band calculation method according to claim 1, wherein: When optimizing the structure of Ge, the POTCAR input file selects the PAW-LDA pseudopotential of Ge provided by the vasp program, specifically the 4-electron Ge pseudopotential.

6. The GeSn alloy energy band calculation method according to claim 1, characterized in that: When optimizing the structure of Ge, the parameter settings of the INCAR input file used in the vasp program include: EDIFFG = -0.01, EDIFF = 1E-5, IBRION = 2, ISIF = 3, GGA = CA, ISMEAR = 0, SIGMA = 0.05, NELM = 500, NELMDL = -7, ENCUT = 400; When performing self-consistent calculations on the target GeSn alloy, the parameter settings of the INCAR input file used in the vasp program include: LWAVE=.TRUE., LSORBIT=.TRUE., SAXIS=0 0 1.

7. The GeSn alloy energy band calculation method according to claim 1, characterized in that: The cutoff inner and outer diameters of Ge are 1.86±0.01 and 3.22±0.01, respectively, and the cutoff inner and outer diameters of Sn are 1.46±0.01 and 4.15±0.01, respectively.

8. A GeSn alloy energy band calculation system, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer program product comprising a computer program or instructions, characterized in that When the computer program or instruction is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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