In this paper,the dispersion relationship is derived by using the k·p method with the help of the perturbation theory,and we obtain the analytical expression in connection with the deformation potential.The calcu...In this paper,the dispersion relationship is derived by using the k·p method with the help of the perturbation theory,and we obtain the analytical expression in connection with the deformation potential.The calculation of the valence band of the biaxial strained Ge/（001）Si1-xGex is then performed.The results show that the first valence band edge moves up as Ge fraction x decreases,while the second valence band edge moves down.The band structures in the strained Ge/（001）Si 0.4 Ge 0.6 exhibit significant changes with x decreasing in the relaxed Ge along the [0,0,k] and the [k,0,0] directions.Furthermore,we employ a pseudo-potential total energy package（CASTEP） approach to calculate the band structure with the Ge fraction ranging from x = 0.6 to 1.Our analytical results of the splitting energy accord with the CASTEP-extracted results.The quantitative results obtained in this work can provide some theoretical references to the understanding of the strained Ge materials and the conduction channel design related to stress and orientation in the strained Ge pMOSFET.展开更多
After constructing a stress and strain model, the valence bands of in-plane biaxial tensile strained Si is calculated by k·p method. In the paper we calculate the accurate anisotropy valance bands and the splitti...After constructing a stress and strain model, the valence bands of in-plane biaxial tensile strained Si is calculated by k·p method. In the paper we calculate the accurate anisotropy valance bands and the splitting energy between light and heavy hole bands. The results show that the valance bands are highly distorted, and the anisotropy is more obvious. To obtain the density of states （DOS） effective mass, which is a very important parameter for device modeling, a DOS effective mass model of biaxial tensile strained Si is constructed based on the valance band calculation. This model can be directly used in the device model of metal-oxide semiconductor field effect transistor （MOSFET）. It also a provides valuable reference for biaxial tensile strained silicon MOSFET design.展开更多
Two-dimensional systems with chiral symmetry allow stable discrete band crossings(nodal points) in Brillouin zones.Here we study the local evolutions of these nodal points under chiral symmetry preserving perturbation...Two-dimensional systems with chiral symmetry allow stable discrete band crossings(nodal points) in Brillouin zones.Here we study the local evolutions of these nodal points under chiral symmetry preserving perturbations.We find that these evolutions can be classified by different types of local k·p models around the nodal points.Several concrete examples are calculated to illustrate our results.展开更多
通过10带k·p模型计算,设计了能够激发3μm波长的In x Ga1-x As1-y Ny/AlAs量子阱结构的量子级联激光器有源区。In x Ga1-x As1-y Ny/AlAs异质结结构具有极宽的导带阶跃(～1.5 eV),并且能够通过成熟的GaAs基工艺生长,因此采用这种...通过10带k·p模型计算,设计了能够激发3μm波长的In x Ga1-x As1-y Ny/AlAs量子阱结构的量子级联激光器有源区。In x Ga1-x As1-y Ny/AlAs异质结结构具有极宽的导带阶跃(～1.5 eV),并且能够通过成熟的GaAs基工艺生长,因此采用这种结构制作短波量子级联激光器已成为研究热点。通过计算能带结构以及相应的波函数,发现当导带带阶非常大以致于第一激发态位于氮能级之上时,电子基态以及第一激发态会分裂为两条能级。正是由于这种效应的存在,提升了激光上能级的能量而促使激发波长缩短。通过一系列计算得出了一种最优化的基于In0.2Ga0.8As0.99N0.01/AlAs的三重耦合量子阱结构。在工作电压为65 kV/cm以及室温的条件下,最短的激光波长可以达到3μm。展开更多
The Rashba effect and valley polarization provide a novel paradigm in quantum information technology. However,practical materials are scarce. Here, we found a new class of Janus monolayers VXY(X = Cl, Br, I;Y = Se, Te...The Rashba effect and valley polarization provide a novel paradigm in quantum information technology. However,practical materials are scarce. Here, we found a new class of Janus monolayers VXY(X = Cl, Br, I;Y = Se, Te) with excellent valley polarization effect. In particular, Janus VBrSe shows Zeeman type spin splitting of 14 meV, large Berry curvature of 182.73 bohr2,and, at the same time, a large Rashba parameter of 176.89 meV·?. We use the k·p theory to analyze the relationship between the lattice constant and the curvature of the Berry. The Berry curvature can be adjusted by changing the lattice parameter,which will greatly improve the transverse velocities of carriers and promote the efficiency of the valley Hall device. By applying biaxial strain onto VBrSe, we can see that there is a correlation between Berry curvature and lattice constant, which further validates the above theory. All these results provide tantalizing opportunities for efficient spintronics and valleytronics.展开更多
In this topical review, we discuss the electronic structure of free-standing silicene by comparing results obtained using different theoretical methods. Silicene is a single atomic layer of silicon similar to graphene...In this topical review, we discuss the electronic structure of free-standing silicene by comparing results obtained using different theoretical methods. Silicene is a single atomic layer of silicon similar to graphene. The interest in silicene is the same as for graphene, in being two-dimensional and possessing a Dirac cone. One advantage of silicene is due to its compatibility with current silicon electronics. Both empirical and first-principles techniques have been used to study the electronic properties of silicene. We will provide a brief overview of the parameter space for first-principles calculations.However, since the theory is standard, no extensive discussion will be included. Instead, we will emphasize what empirical methods can provide to such investigations and the current state of these theories. Finally, we will review the properties computed using both types of theories for free-standing silicene, with emphasis on areas where we have contributed.Comparisons to graphene is provided throughout.展开更多
基金Project supported by the Fundamental Research Funds for the Central Universities,China (Grant Nos. 72105499 and 72104089)the Natural Science Basic Research Plan in Shaanxi Province,China (Grant No. 2010JQ8008)
文摘In this paper,the dispersion relationship is derived by using the k·p method with the help of the perturbation theory,and we obtain the analytical expression in connection with the deformation potential.The calculation of the valence band of the biaxial strained Ge/（001）Si1-xGex is then performed.The results show that the first valence band edge moves up as Ge fraction x decreases,while the second valence band edge moves down.The band structures in the strained Ge/（001）Si 0.4 Ge 0.6 exhibit significant changes with x decreasing in the relaxed Ge along the [0,0,k] and the [k,0,0] directions.Furthermore,we employ a pseudo-potential total energy package（CASTEP） approach to calculate the band structure with the Ge fraction ranging from x = 0.6 to 1.Our analytical results of the splitting energy accord with the CASTEP-extracted results.The quantitative results obtained in this work can provide some theoretical references to the understanding of the strained Ge materials and the conduction channel design related to stress and orientation in the strained Ge pMOSFET.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60976068 and 60936005)the Cultivation Fund of the Key Scientific and Technical Innovation Project,Ministry of Education of China (Grant No. 78083)
文摘After constructing a stress and strain model, the valence bands of in-plane biaxial tensile strained Si is calculated by k·p method. In the paper we calculate the accurate anisotropy valance bands and the splitting energy between light and heavy hole bands. The results show that the valance bands are highly distorted, and the anisotropy is more obvious. To obtain the density of states （DOS） effective mass, which is a very important parameter for device modeling, a DOS effective mass model of biaxial tensile strained Si is constructed based on the valance band calculation. This model can be directly used in the device model of metal-oxide semiconductor field effect transistor （MOSFET）. It also a provides valuable reference for biaxial tensile strained silicon MOSFET design.
基金Project supported by the National Basic Research Program of China(Grant Nos.2015CB921300 and 2017YFA0303100)the National Natural Science Foundation of China(Grant Nos.1190020,11534014,and 11334012)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB07000000 and XDB28000000)
文摘Two-dimensional systems with chiral symmetry allow stable discrete band crossings(nodal points) in Brillouin zones.Here we study the local evolutions of these nodal points under chiral symmetry preserving perturbations.We find that these evolutions can be classified by different types of local k·p models around the nodal points.Several concrete examples are calculated to illustrate our results.
基金supported by the National Natural Science Foundation of China (Grant No. 52173283)Taishan Scholar Program of Shandong Province (No. ts20190939)+1 种基金the Independent Cultivation Program of Innovation Team of Jinan City (Grant No. 2021GXRC043)Science and technology program of the University of Jinan (No. XKY1912)。
文摘The Rashba effect and valley polarization provide a novel paradigm in quantum information technology. However,practical materials are scarce. Here, we found a new class of Janus monolayers VXY(X = Cl, Br, I;Y = Se, Te) with excellent valley polarization effect. In particular, Janus VBrSe shows Zeeman type spin splitting of 14 meV, large Berry curvature of 182.73 bohr2,and, at the same time, a large Rashba parameter of 176.89 meV·?. We use the k·p theory to analyze the relationship between the lattice constant and the curvature of the Berry. The Berry curvature can be adjusted by changing the lattice parameter,which will greatly improve the transverse velocities of carriers and promote the efficiency of the valley Hall device. By applying biaxial strain onto VBrSe, we can see that there is a correlation between Berry curvature and lattice constant, which further validates the above theory. All these results provide tantalizing opportunities for efficient spintronics and valleytronics.
文摘In this topical review, we discuss the electronic structure of free-standing silicene by comparing results obtained using different theoretical methods. Silicene is a single atomic layer of silicon similar to graphene. The interest in silicene is the same as for graphene, in being two-dimensional and possessing a Dirac cone. One advantage of silicene is due to its compatibility with current silicon electronics. Both empirical and first-principles techniques have been used to study the electronic properties of silicene. We will provide a brief overview of the parameter space for first-principles calculations.However, since the theory is standard, no extensive discussion will be included. Instead, we will emphasize what empirical methods can provide to such investigations and the current state of these theories. Finally, we will review the properties computed using both types of theories for free-standing silicene, with emphasis on areas where we have contributed.Comparisons to graphene is provided throughout.
