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Atomic-orbital interpretation of electronic structure of III-V semiconductors: GaAs versus AlAs

P Boguslawski and I Gorczyca

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We link the electronic structures of AlAs and GaAs with the energy structures of the constituent atomic species. The electronic structures are calculated using first-principles pseudopotentials. The wavefunctions of valence and conduction bands are projected on s, p and d symmetry orbitals. The resulting information on the orbital composition of crystalline states is combined with eigenenergies of Al and Ga atoms in order to explain differences between band energies of the two semiconductors. For GaAs, the dependence of the orbital composition of wavefunctions on the wavevector is analysed in detail, and correlated with the dispersion of energy bands. The contribution of excited d orbitals to the lowest conduction states at X and L points is as high as about 50 per cent, and is responsible for the decrease of the indirect Gamma -X optical bandgap with hydrostatic pressure. The validity of the sp3 minimal-basis-set tight-binding model is evaluated.


PACS

71.20.Nr Semiconductor compounds

71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)

Subjects

Condensed matter: electrical, magnetic and optical

Semiconductors

Dates

Issue 12 (December 1994)



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