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A Tight‐Binding Calculation of Band Discontinuities in the Al x Ga 1− x As/GaAs(AlAs) Heterostructures
Author(s) -
Gushchi. A.,
Nikulin V. K.
Publication year - 1990
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221580116
Subject(s) - heterojunction , tight binding , classification of discontinuities , condensed matter physics , crystal (programming language) , alloy , hamiltonian (control theory) , dipole , materials science , band gap , direct and indirect band gaps , electronic structure , chemistry , physics , mathematics , mathematical analysis , mathematical optimization , organic chemistry , computer science , composite material , programming language
Valence (ΔE v ) and conduction (ΔE c ) band discontinuities at the Al x Ga 1− x As alloy‐GaAs(AlAs) crystal interface are calculated within the tight‐binding approximation basing on the bulk electron properties of the individual components and taking into account the presence of a dipole layer at the interface. The alloy is considered in the virtual crystal approximation using the self‐consistent parameters of the sp 3 s* Hamiltonian obtained for the GaAs and AlAs crstals. The calculated value of the ratio of Q v = ΔE v /ΔE g Γto Q c = ΔE c /ΔE g Γ , where ΔE g Γis the difference between the direct band‐gap widths for the crystal and the alloy, is found to be 0.33:0.67 for all values of the Al concentration which is in good agreement with recent optical measurements. These parameters permit to obtain within the tight binding approximation the values of concentration x at which a direct‐indirect crossover occurs in the alloy ( x c = 0.38) and a transition occurs from the first to the second type of heterojunction in the Al x Ga 1− x As/AlAs structure ( x c2 = 0.25), values being close to the experimental data.