The band structure of the(InAs)i(GaAs)i strained superlattice is calculated by the self-consistent pseudopotential method.The results show that the(InAs)_(1)(GaAs)_(1) is a direct-gap superlattice.With the local densi...The band structure of the(InAs)i(GaAs)i strained superlattice is calculated by the self-consistent pseudopotential method.The results show that the(InAs)_(1)(GaAs)_(1) is a direct-gap superlattice.With the local density approximation,the band gap calculated with the room-temperature lattice constants is 0.43eV,and the corrected value is 0.91 eV,in agreement with experimental results.Because of the lattice mismatch between InAs and GaAs layers,the three-fold degenerate energy level at the top of valence band splits into two levels with a spacing of 0.29 eV.The splitting of energy level is also estimated and explained using the effective-mass theory.展开更多
The plane-wave expansion(PWE) method is employed to calculate the photonic band structures of metal/dielectric(M/D) periodic systems. We consider a one-dimensional(1D) M/D superlattice with a metal layer characterized...The plane-wave expansion(PWE) method is employed to calculate the photonic band structures of metal/dielectric(M/D) periodic systems. We consider a one-dimensional(1D) M/D superlattice with a metal layer characterized by a frequency-dependent dielectric function. To calculate the photonic band of such a system, we propose a new method and thus avoid solving the nonlinear eigenvalue equations. We obtained the frequency dispersions and the energy distributions of eigen-modes of 1D superlattices. This general method is applicable to calculate the photonic band of a broad class of physical systems, e.g. 2D and 3D M/D photonic crystals. For comparison, we present a simple introduction of the finite-difference(FD) method to calculate the same system, and the agreement turns out to be good. But the FD method cannot be applied to the TM modes of the M/D superlattice.展开更多
We have here today published an article by Professor Boulton (former Vice Principal of the University of Edinburgh) and Sir Colin Lucas (former Principal of Oxford University) regarding several issues in university ed...We have here today published an article by Professor Boulton (former Vice Principal of the University of Edinburgh) and Sir Colin Lucas (former Principal of Oxford University) regarding several issues in university education. Issues mentioned in展开更多
文摘The band structure of the(InAs)i(GaAs)i strained superlattice is calculated by the self-consistent pseudopotential method.The results show that the(InAs)_(1)(GaAs)_(1) is a direct-gap superlattice.With the local density approximation,the band gap calculated with the room-temperature lattice constants is 0.43eV,and the corrected value is 0.91 eV,in agreement with experimental results.Because of the lattice mismatch between InAs and GaAs layers,the three-fold degenerate energy level at the top of valence band splits into two levels with a spacing of 0.29 eV.The splitting of energy level is also estimated and explained using the effective-mass theory.
基金supported by the special funds for the National Basic Research Program of China(Grant No.069c031001)the National Natural Science Foundation of China(Grant No.60521001).
文摘The plane-wave expansion(PWE) method is employed to calculate the photonic band structures of metal/dielectric(M/D) periodic systems. We consider a one-dimensional(1D) M/D superlattice with a metal layer characterized by a frequency-dependent dielectric function. To calculate the photonic band of such a system, we propose a new method and thus avoid solving the nonlinear eigenvalue equations. We obtained the frequency dispersions and the energy distributions of eigen-modes of 1D superlattices. This general method is applicable to calculate the photonic band of a broad class of physical systems, e.g. 2D and 3D M/D photonic crystals. For comparison, we present a simple introduction of the finite-difference(FD) method to calculate the same system, and the agreement turns out to be good. But the FD method cannot be applied to the TM modes of the M/D superlattice.
文摘We have here today published an article by Professor Boulton (former Vice Principal of the University of Edinburgh) and Sir Colin Lucas (former Principal of Oxford University) regarding several issues in university education. Issues mentioned in
