| 1. |
- Blom, Anders, et al.
(författare)
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Donor states in modulation-doped Si/SiGe heterostructures
- 2003
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 68:16: 165338
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Tidskriftsartikel (refereegranskat)abstract
- We present a unified approach for calculating the properties of shallow donors inside or outside heterostructure quantum wells. The method allows us to obtain not only the binding energies of all localized states of any symmetry, but also the energy width of the resonant states which may appear when a localized state becomes degenerate with the continuous quantum well subbands. The approach is nonvariational, and we are therefore also able to evaluate the wave functions. This is used to calculate the optical absorption spectrum, which is strongly nonisotropic due to the selection rules. The results obtained from calculations for Si/Si1-xGex quantum wells allow us to present the general behavior of the impurity states, as the donor position is varied from the center of the well to deep inside the barrier. The influence on the donor ground state from both the central-cell effect and the strain arising from the lattice mismatch is carefully considered.
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| 2. |
- Blom, Anders, et al.
(författare)
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Resonant states induced by impurities in heterostructures
- 2002
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 65:15
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Tidskriftsartikel (refereegranskat)abstract
- A study of the formation of resonant states in the conduction band, induced by impurities outside heterostructure quantum wells, is presented. We derive general expressions for the capture and scattering amplitudes, the resonance position and width, and we also calculate the effect on the energy spectrum and the density of states in the quantum well. The theory is applied to two typical impurity potentials, the zero-range potential of deep levels and the Coulomb potential. It is found that the perturbation of the density of states can be significant over wide energy intervals, and that the resonance position may behave nonmonotonically with the modulation-doping distance. The resonance width decays exponentially with the distance, but becomes of the same order as the band discontinuity as we approach close to the quantum well interface. The capture and scattering coefficients may vary by several orders of magnitude over narrow energy intervals, producing a pronounced and strong scattering mechanism.
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| 3. |
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| 4. |
- Odnoblyudov, MA, et al.
(författare)
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Resonant acceptor states in uniaxially strained semiconductors
- 2002
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Ingår i: Journal of Experimental and Theoretical Physics. - : Pleiades Publishing Ltd. - 1063-7761 .- 1090-6509. ; 94:3, s. 593-602
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Tidskriftsartikel (refereegranskat)abstract
- A new approach to calculating the parameters of resonant states is proposed, which also makes it possible to determine the probabilities of the resonant scattering and capture probabilities at the resonant state. This approach is based on the application of the method of configuration interaction, which was proposed for the first time by Fano for an analysis of field ionization of the helium atom. Following Fano, use is made of two different Hamiltonians of the initial approximation for the states of continuum and the initial local state. Following Dirac, the wave functions are constructed in the same way as in the general theory of scattering. A detailed analysis and specific calculations are made for resonant acceptor states in uniaxially strained germanium under a pressure directed along the [001] and [111] axes. (C) 2002 MAIK "Nauka/Interperiodica".
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