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Author Magri, Rita ♦ Zunger, Alex
Sponsorship (US)
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Publisher The American Physical Society
Language English
Subject Keyword CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS ♦ AMPLITUDES ♦ ATOMS ♦ MATRIX ELEMENTS ♦ SUPERLATTICES ♦ SYMMETRY
Abstract Heterostructures sharing a common atom such as AlAs/GaAs/AlAs have a D{sub 2d} point-group symmetry which allows the bulk-forbidden coupling between odd-parity light-hole states (e.g., lh1) and even-parity heavy-hole states (e.g., hh2). Continuum models, such as the commonly implemented (''standard model'') {dot k}p theory miss the correct D{sub 2d} symmetry and thus produce zero coupling at the zone center. We have used the atomistic empirical pseudopotential theory to study the lh1-hh2 coupling in (001) superlattices and quantum wells of GaAs/Al{sub x}Ga{sub 1-x}As. By varying the Al concentration x of the barrier we scan a range of valence-band barrier heights {Delta}E{sub v}(x). We find the following: (i) The lh1 and hh2 states anticross at rather large quantum wells width or superlattice periods 60<n{sub c}<70 monolayers. (ii) The coupling matrix elements V{sub lh1,hh2}{sup k{sub {parallel}}=0} are small (0.02--0.07 meV) and reach a maximum value at a valence-band barrier height {Delta}E{sub v}{approx}100 meV, which corresponds to an Al composition x{sub Al}=0.2 in the barrier. (iii) The coupling matrix elements obtained from our atomistic theory are at least an order of magnitude smaller than those calculated by the phenomenological model of Ivchenko [Phys. Rev. B 54, 5852 (1996)]. (iv) The dependence of V{sub lh1,hh2} on the barrier height {Delta}E{sub v}(x) is more complicated than that suggested by the recent model of Cortez , [J. Vac. Sci. Technol. B 18, 2232 (2000)], in which V{sub lh1,hh2} is proportional to the product of {Delta}E{sub v}(x) times the amplitudes of the lh1 and hh2 envelopes at the interfaces. Thus, atomistic information is needed to establish the actual scaling.
ISSN 01631829
Educational Use Research
Learning Resource Type Article
Publisher Date 2000-10-15
Publisher Place United States
Journal Physical Review B
Volume Number 62
Issue Number 15


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