We report the determination of parameters for the nearest-neighbor sp3s* tight-binding (TB) model for GaP, GaAs, GaSb, InP, InAs, and InSb at 0, 77, and 300 K based on the hybrid quasi-particle self-consistent GW (QSGW) calculation and their application to a type II (InAs)/(GaSb) superlattice. The effects of finite temperature have been incorporated empirically by adjusting the parameter for blending the exchange-correlation terms of the pure QSGW method and local density approximation, in addition to the usage of experimental lattice parameters. As expected, the TB band gap shrinks with temperature and asymptotically with superlattice period when it is large. In addition, a bell curve in the band gap in the case of small superlattice period and slight and remarkable anisotropy in effective masses of electron and hole, both predicted by the hybrid QSGW method, respectively, are reproduced.
We propose a new way to reduce the number of iterations required to reach self-consistency in electronic-structure calculations in the framework of the plane-wave pseudopotential method. A prediction operator is derived from the procedure to solve the Kohn-Sham equation approximately on the basis of a second-variational approach, and then combined with a variant of Broyden's algorithm. The self-consistency is reached quite efficiently not only for semiconductor surfaces but also for intermetallic compounds either with large density of states around the Fermi level or near a threshold for the occurrence of the magnetic moment. When the magnetic moment emerges, it converges more smoothly with our prediction operator than otherwise.
We report the determination of parameters in the nearest-neighbor sp 3 d 5 s * tightbinding (TB) model for nine binary compound semiconductors which consist of Al, Ga, or In and of P, As, or Sb based on the hybrid quasi-particle self-consistent GW (QSGW) calculations. We have used the determination parameters to calculate band structures and related properties of the compounds in the bulk phase relevant to mid-infrared applications and of the type-II (InAs)/(GaSb) superlattices. For the type-II (InAs)/(GaSb) superlattices with various superlattice periods, good agreement with photoluminescence measurements on the band gaps has been confirmed. Furthermore, two aspects of the band gap properties from other calculations have been reproduced: the band gap energies rising up to some superlattice periods and shrinking beyond them asymptotically. In both the bulk phase and the superlattices, erroneous flat valence bands have appeared within the nearest-neighbor sp 3 s * TB model. The present TB model has eliminated these artifacts, which are potential obstacles to design advanced superlattices.
The electronic structure transition between the semiconducting and metallic states in boron (B)-doped diamonds was elementselectively observed by soft X-ray emission and absorption spectroscopy using synchrotron radiation. For lightly B-doped diamonds, the B 2p-density of states (DOS) in the valence band was enhanced with a steep-edge feature near the Fermi level, and localized acceptor levels, which are characteristic of semiconductors, were clearly observed both in B 2p-and C 2p-DOS in the conduction bands. For heavily B-doped diamonds, the localized acceptor levels developed into extended energy levels and the new energy levels generated formed an extended conduction band structure that overlapped with the valence band. Thus, the metallic energy band structure is actually formed by heavy boron doping. These valence and conduction band structures observed by soft X-ray emission and absorption spectroscopy accounted for the electrical properties of B-doped diamonds.
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