GeSn alloy energy band calculation method and system

Abstract

The invention belongs to the related technical field of semiconductor materials, and discloses a GeSn alloy energy band calculation method and system, and the method comprises the steps: obtaining a parameter file of Ge after structure optimization; the method comprises the following steps: performing cell expansion and Sn doping on Ge subjected to structure optimization, establishing a POSCAR input file of a target GeSn alloy, establishing a POTCAR input file of the GeSn alloy according to cut-off inner and outer diameters of Ge and cut-off inner and outer diameters of Sn, enabling the cut-off inner diameter of Ge to be 1.80-1.90, the outer diameter of Ge to be 3.20-3.25, the cut-off inner diameter of Sn to be 1.40-1.50 and the outer diameter of Sn to be 4.10-4.20, running a vasp program to perform self-consistent calculation on the target GeSn alloy, and performing self-consistent calculation on the target GeSn alloy according to the cut-off inner and outer diameters of Ge and Sn. According to the method, the electronic structure of the GeSn alloy under different concentrations can be accurately simulated, and the energy band of the GeSn alloy can be accurately calculated.

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 thereof. Background Art

[0002] As an important Group IV semiconductor material, GeSn alloy has an adjustable band gap structure and high carrier mobility, which makes it attract much attention in the field of semiconductor and optoelectronic materials. Experimental results show that with the increase of Sn concentration, the band gap of GeSn alloy gradually decreases, and a transition from indirect band gap to direct band gap occurs at 6%-10%. However, due to the lattice mismatch and the low solubility of Sn in Ge, which easily leads to phase separation and agglomeration of Sn, the preparation of high-concentration GeSn alloy is technically challenging; the short-range order phenomenon (SRO) in the analysis process complicates the experimental characterization and increases the difficulty of understanding and optimizing the performance of GeSn alloy.

[0003] Therefore, theoretical simulation calculations are needed. Currently, electronic structure simulation is mainly carried out through the empirical pseudopotential method (EPM). Gupta et al. (2013) used the virtual crystal approximation (VCA) combined with the non-local empirical pseudopotential method (NL-EPM), adjusted the alloy disorder correction parameter Ploc in the VCA, and found that the GeSn alloy changed from an indirect band gap to a direct band gap when the Sn content was about 6.5%. Xiao et al. (2019) used the empirical pseudopotential method (EPM) combined with strain and perturbation theory, adjusted the lattice constant bending parameter (θ) and the Sn-Ge pseudopotential difference, and found that the band gap transition was achieved when the Sn content was between 5.81% and 8.75%.

[0004] However, although the empirical pseudopotential method (EPM) has high computational efficiency in electronic structure simulation, its reliance on empirical parameters and its accuracy limitations in dealing with 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 view of the above defects or improvement needs of the prior art, the present invention provides a GeSn alloy energy band calculation method and system thereof, which aims to accurately calculate the band gap of GeSn alloys at different concentrations.

[0007] To achieve the above object, 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 a vasp program to perform structural optimization on Ge so as to minimize the energy of Ge, during which 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 primitive cell crystal model of the orthorhombic system of Ge;

[0009] The Ge after structural optimization is expanded and doped with Sn to establish the POSCAR input file of the target GeSn alloy. The POTCAR input file of the GeSn alloy is established according to the cutoff inner and outer diameters of Ge and Sn. The cutoff inner diameter of Ge is in the range of 1.80-1.90, and the outer diameter is in the range of 3.20-3.25. The cutoff inner diameter of Sn is in the range of 1.40-1.50, and the outer diameter is in the range of 4.10-4.20. The vasp program is 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 step of expanding the structure-optimized Ge and doping Sn includes:

[0011] Materials Studio software was used to expand the structure-optimized Ge and dope 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 the structure of Ge is optimized and the target GeSn alloy is self-consistently calculated, the KPOINTS input file used in the vasp program limits the sampling of the Brillouin zone by 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 selects the 4-electron Ge pseudopotential.

[0015] In an optional embodiment, 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;

[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 when the computer program is executed by a processor, the steps of any of the above methods are implemented.

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

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

[0022] The present invention calls the vasp program to calculate the energy band of the GeSn alloy. The POSCAR input file and the POTCAR input file are two important files required for the operation of the vasp program. The POTCAR input file contains the pseudopotentials of various elements in the system. 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 to simulate the electronic structure of the GeSn alloy, thereby affecting the calculation of the energy band. In order to improve the calculation accuracy, the present invention obtains the parameter file of the optimized Ge on the one hand, expands the cell and dopes Sn on the Ge after structural optimization, and establishes the POSCAR input file of the target GeSn alloy. The structural optimization is also based on the vasp program. By reasonably selecting ENCUT for optimization, the calculation cost and accuracy can be effectively balanced under the premise of ensuring the accuracy of the energy band calculation, and the electronic structure simulation result of the GeSn alloy can be ensured to be reliable; on the other hand, the present invention determines the cut-off inner and outer diameters of Ge and Sn respectively through specific analysis means, and then the POTCAR input file of the GeSn alloy can be generated with high accuracy. Experiments show that by simulating the electronic structure of the GeSn alloy and calculating the energy band through the above method, the band gap value gradually decreases with the increase of Sn concentration, and the trend is consistent with the actual measured trend. The turning point of the band gap type transition occurs when the concentration is between 7.6% and 7.8%, 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, can accurately simulate the electronic structure of the GeSn alloy at different concentrations, and accurately calculate its energy band. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart 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 crystal structure of a Ge unit cell 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 diagram showing the trend of energy changing with the value of ENCUT;

[0027] Figure 5 is a flow chart of the steps of determining the cut-off inner and outer diameters of Ge and the cut-off inner and outer diameters of 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 7are the cell expansion multiples, the number of Sn atoms, and the redefined lattice vectors corresponding to different doping concentrations;

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

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain 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 can be combined with each other as long as they do not conflict with each other.

[0032] Example 1

[0033] Vienna Ab-initio Simulation Package vasp (abbreviated as vasp program) is a computer program package for atomic-scale material simulation. Its main input files are INCAR, POTCAR, POSCAR and KPOINTS. The INCAR input file controls what kind of calculations vasp performs. The POTCAR input file contains the pseudopotentials of various elements in the calculated system. The POSCAR input file describes the unit cell parameters of the calculated system (including basis vectors or translation vectors, lattice constants, atomic positions and other information). KPOINTS describes the k-point sampling in the irreducible Brillouin zone, i.e., the k-point setting. The overall process is to determine the input files INCAR, POTCAR, POSCAR and KPOINTS and submit them. The vasp program executes the instructions and performs calculations, 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 The figure shows a flow chart of the steps of a method for calculating the energy band of a GeSn alloy in one embodiment of the present invention, and the steps are introduced 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 energy of Ge. 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 structure-optimized Ge 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 calculations 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 the content 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 selects the PAW-LDA pseudopotential of Ge provided by the vasp program. Specifically, the 4-electron Ge pseudopotential is selected, for example, Ge: 4e is selected, and the generation date is October 4, 2005.

[0042] The POSCAR input file describes the unit cell parameters of the calculated system. When optimizing the structure of Ge, you can consult the literature to find the space group, crystal structure, and atomic coordinates of Ge in the ground state, so as to establish the POSCAR input file of Ge. In this embodiment, the primitive cell crystal model of the orthorhombic system of Ge is selected to be established, with a space group number of 227 and 8 atoms; Figure 2 is the 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), (0.750000000,0.250000000,0.250000000), (0.500000000,0.500000000,0.500000000), (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, i.e., the k-point setting. In this embodiment, you can choose to use the Gamma-centered mesh to sample the Brillouin zone, or use the Monkhorst-Pack mesh to sample the Brillouin zone. Regarding the value of the k-point, the larger the value, the higher the calculation accuracy, but the longer the calculation time. Therefore, the k-point can be flexibly modified according to the specific calculation type performed.

[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 electronic 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 situations, 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, which is defined as the convergence criterion of force. When the force on each atom is less than this value, the optimization is stopped. It is recommended to be greater than And 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 control the maximum number of steps and delay steps of self-consistent iterations, respectively, to ensure the convergence of electronic states. NSW specifies the maximum number of moving steps of the ion position, which 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, and the adjustment step is 20ev.

[0048] Step S12: Use vasp program to perform multiple structural optimizations on Ge. The difference between the input files constructed for each structural optimization is only the difference in 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, the k points in the KPOINTS input file in this embodiment 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 to 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 figure shows the trend curve of energy changing with the value of ENCUT. It can be seen that the energy changes relatively slowly in the range of 380 to 480. Therefore, ENCUT can be selected from the range of 380 to 480, for example, ENCUT = 400. ENCUT significantly affects the convergence speed and accuracy of the calculation. Specifically, the ENCUT parameter determines the energy cutoff value of the plane wave basis set, that is, the maximum kinetic energy of the plane wave used to expand the wave function and the electron density. Selecting a suitable ENCUT value is the key to ensuring the accuracy of the calculation: a lower ENCUT value may lead to non-convergence of the calculation or inaccurate description of the electronic structure, while an excessively high ENCUT value will significantly increase the amount of calculation and time. Therefore, the present invention tests the total energy change under different ENCUT values ​​and selects an optimal ENCUT value that can ensure the convergence of the total energy and force and take into account the calculation efficiency. In this way, both accuracy and calculation efficiency can be taken into account, which can effectively improve the calculation speed in the subsequent calculation process.

[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 eight Ge atoms are described in the form of fractional coordinates. The eight atoms are located at (0.00000000000000000, 0.0000000000000000, 0.50000000000000000), (0.25000000000000000, 0.2500000000000000, 0.75000000000000000), (0.0000000000000000, 0.5000000000000000, 0.000000000000000), (0.25000000000000000, 0.7500000000000000, 0.25 00000000000000), (0.50000000000000000, 0.000000000000000, 0.000000000000000), (0.75000000000000000, 0.250000000000000, 0.25000000000 000000), (0.50000000000000000, 0.5000000000000000, 0.5000000000000000), (0.75000000000000000, 0.7500000000000000).

[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 vasp program is essentially used to simulate the electronic structure of the GeSn alloy at the target concentration, and 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 the target GeSn alloy is self-consistently calculated, the POTCAR input file used needs to provide the pseudopotential of Ge and the pseudopotential of Sn. In order to improve the more accurate pseudopotential, 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, and then constructs an accurate POTCAR input file based on the cutoff inner and outer diameters.

[0062] like Figure 5FIG. 1 is a flowchart of the steps of determining the cut-off inner and outer diameters of Ge and Sn in one embodiment of the present invention, combined with FIG. 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 POTCAR input file of Ge mentioned in step S1, that is, the PAW-LDA pseudopotential of Ge provided by the vasp program is selected, and specifically the 4-electron Ge pseudopotential is selected, for example, Ge: 4e is selected, 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 electronic wave function is performed to generate the WAVECAR output file. For example, the INCAR input file can be set as GGA=CA, EDIFF=1E-5, ISMEAR=0, SIGMA=0.05, ENCUT=400, LWAVE=.TRUE.;

[0069] In the KPOINTS input file, continue to choose to use Gamma-centered mesh to sample the Brillouin zone, or use Monkhorst-Pack mesh to sample 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 value of the K point value and the lattice constant of the currently calculated system in the range of 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 cutoff inner and outer diameters of Ge, 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 Ge, calculate the band gap of Ge based on the current four input files of Ge and the WAVECAR output file, and select the cutoff inner and outer diameters that make the band gap of Ge most consistent with the experimental band gap (0.742ev);

[0072] In this embodiment, the cutoff inner diameter traversal range of Ge 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. After obtaining a set of optimal radius combinations, a refined traversal is performed, and the range is set to plus or minus 0.1 of the optimal radius, with a step of 0.01.

[0073] The obtained inner and outer diameters of Ge are 1.86 and 3.22 respectively. According to 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 of Ge is determined to be in the range of 1.80-1.90 and the outer diameter is in the range of 3.20-3.25. The fluctuation range is within an acceptable range.

[0074] Step S23: Based on the current POSCAR input file of Ge, one of the 8 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, and the structure of the GeSn alloy is optimized based on the four input files of the GeSn alloy to minimize the energy of the GeSn alloy, thereby obtaining the CONTCAR output file of the GeSn alloy.

[0075] The current POSCAR input file of Ge is the POSCAR input file updated in step S21. Sn is doped into the updated Ge unit cell crystal model, specifically, one of the eight Ge atoms in the Ge crystal model is replaced by a Sn atom, such as 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 4 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, updating the POTCAR input file of the GeSn alloy according to the cutoff inner and outer diameters of Ge and the pseudopotential of Sn, and obtaining the WAVECAR output file of the GeSn alloy 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 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. After obtaining a set of optimal radius combinations, a refined traversal is performed, and the range is set to plus or minus 0.1 of the optimal radius, with a step of 0.01.

[0084] The obtained inner and outer diameters of Sn are 1.46 and 4.15 respectively. According to 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 of Sn is determined to be in the range of 1.40-1.50 and the outer diameter is in the range of 4.10-4.20. This fluctuation range is within an acceptable range.

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

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

[0087] The POSCAR input file of GeSn alloy is to directly expand the Ge after structural optimization obtained in step S1 and dope Sn to establish the POSCAR input file of the target GeSn alloy. When doping, the distribution of Sn atoms should be uniform, and no Sn-Sn bonds should appear; when expanding the cell, try to keep the length of the three sides as close as possible, such as 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 adopts the operation of redefining the lattice vector to obtain the POSCAR input file of the target GeSn alloy. Figure 7 Shown are the cell expansion multiples, the number of Sn atoms, and the redefined lattice vectors corresponding to different doping concentrations.

[0088] It can be understood 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 value of the K point 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 calculation 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 turning point measured experimentally between 6% and 8%. It can be seen that the present invention produces 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 on computing devices such as desktop computers, notebooks, PDAs and cloud servers. The 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 can run or execute computer programs and / or modules stored in the memory, and call data stored in the memory, and various functions of the electronic device.

[0093] Example 3

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

[0096] Example 4

[0097] The embodiment of the present invention provides a computer program product or a 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 the processor executes the computer instructions, so that the computer device performs the steps of the method of the above embodiment of the present invention.

[0098] The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above-mentioned 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 "in one embodiment", "for example", "for example", etc. of the present invention are intended to illustrate the present invention, rather than to limit the present invention.

[0099] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope 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 a vasp program to perform structural optimization on Ge so as to minimize the energy of Ge, during which 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 primitive cell crystal model of the orthorhombic system of Ge; The Ge after structural optimization is expanded and doped with Sn to establish the POSCAR input file of the target GeSn alloy. The POTCAR input file of the GeSn alloy is established according to the cutoff inner and outer diameters of Ge and Sn. The cutoff inner diameter of Ge is in the range of 1.80-1.90, and the outer diameter is in the range of 3.20-3.

25. The cutoff inner diameter of Sn is in the range of 1.40-1.50, and the outer diameter is in the range of 4.10-4.

20. The vasp program is 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, characterized in that: The step of expanding the structure-optimized Ge and doping Sn comprises: Materials Studio software was used to expand the structure-optimized Ge and dope Sn.

3. The GeSn alloy energy band calculation method according to claim 1, characterized in that: When expanding the cell and doping Sn, 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, characterized in that: 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, characterized in that: 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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