Electronic band-edge structure, effective masses, and optical absorption of Si1-xGe x using an extended FPLAPW/VCA/LDA+U computational method

Abstract

Electronic band-edge structure and optical properties of Si 1−x Ge x are investigated theoretically emloying a full-potential linearized augmented plane wave (FPLAPW) method. The exchange-correlation potential in the local density approximation (LDA) is corrected by an on-site Coulomb potential (i.e., within the LDA+U SIC approach) acting asymmetrically on the atomic-like orbitals in the muffin-tin spheres. The electronic structure of the Si 1−x Ge x is calculated self-consistently, assuming a T d symmetrized Hamiltonian and a linear behavior of the valence-band eigenfunctions for Si, SiGe, and Ge with respect to Ge composition x, assuming randomly alloyed crystal structure. i.e., a "virtual-crystal like" approximation (VCA). We show that this approach yields accurate band-gap energies, effective masses, dielectric function, and optical properties of Si 1−x Ge x . We perform absorption measurements showing the band-gap energy for x < 0.25.

The angular- and crystal-momentum transfer through electron–phonon coupling in silicon and silicon-carbide: similarities and differences

“…Density functional theory in the local-density approximation as used by Gavrilenko et al [47] shows in general deviations from experimental data near the band gap. Valence-band states in semiconductors contributing to the electronic ground state density tend to agree with experimental shapes, although the total valence-band width may be smaller [48][49][50], which is similarly observed here comparing the calculated DOS with the RIXS differences for 6H-SiC. Note that more recent DOS calculations on 6H-SiC (for example [51,52]) find similar s-DOS and p-DOS as obtained from the calculations by Gavrilenko et al [47].…”

Computational Investigation of Electronic and Optical Properties of Si, Ge and Si1-xGex Alloys Using the FP-LMTO Method Augmented by a Plane-Wave Basis

“…To calculate the principal energy gaps for the zinc-blende structure of Si 1-x Ge x at 300 K for concentration x < 0.85, we have used the interpolation equation like 1.12-0.41x + 0.008x 2 eV, but for x > 0.85 we have used the linear 1.86 -1.2x eV. From these calculations one can state that the Si 1-x Ge x is a Si-like indirect semiconductor for x < 0.85 in good agreement with other results [25].…”

Nitrogen-electronegativity-induced bowing character in ternary zincblende Ga1−xInxN alloys

“…In general, the bandgaps relevant to the semiconductor alloys adopt one of the following four behaviors: (i) bowing behavior, as is found for the common-cation III-V and II-VI alloys [17]; (ii) linear behavior, as in the case of common-anion alloys [18]; (iii) band anti-crossing, as occurs in indirect-bandgap-based alloys (such as Si x Ge 1−x−y Sn y [5][6][7], Al x Ga 1−x As [19] and GaP x As 1−x [20]); and (iv) anomalous behavior, exemplified by the metallization observed in the highly lattice-mismatched nitride IIIV 1−x N x alloys [21][22][23]; the negative bowing behavior seen in the alloys of In x Ga 1−x As [24] and GaSb x As 1−x [25]; the anomalous behavior reported for lead chalcogenides [26], where the direct gap is found to be at the L high-symmetry point of the Brillouin zone.…”

“…On the other hand, the II-VI semiconductor alloys remain the predominantly used materials in the opto-electronics field (e.g., the ternary and quaternary alloys of the Cd(Zn)Te(Se) family) [3,4]. It has also proven possible to tune the properties of the elementary semiconductor alloys Si x Ge 1−x−y Sn y for a diversity of telecommunication applications [5][6][7].…”