Anticrossing and coupling of light-hole and heavy-hole states in (001) GaAs/Al{sub x}Ga{sub 1-x}As heterostructures
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.
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40205618
- Journal Information:
- Physical Review B, Journal Name: Physical Review B Journal Issue: 15 Vol. 62; ISSN 0163-1829
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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