| 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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| 5. |
- Odnoblyudov, MA, et al.
(författare)
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Theory of a strained p-Ge resonant-state terahertz laser
- 2004
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 70:11
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Tidskriftsartikel (refereegranskat)abstract
- A theory of a strained p-Ge resonant-state THz laser is developed. A comprehensive study of the processes leading to the stimulated THz emission in strained p-Ge under an electric field applied is presented. The distribution functions of light and heavy holes are found. The scattering by optical and acoustic phonons, as well as resonant scattering by charged impurities are taken into account. The steady-state hole distribution functions are used to calculate the generation-recombination coefficients which enter into the system of rate equations for the localized states populations. The populations of localized and resonant acceptor states are found. The conditions for population inversion are investigated. The optical gain calculation is carried out taking into account main optical transitions in the THz spectrum range.
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| 6. |
- Tarakanov, YA, et al.
(författare)
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Scattering-assisted electric current in semiconductor superlattices in the Wannier-Stark regime
- 2005
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 72:12
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Tidskriftsartikel (refereegranskat)abstract
- We have used the Monte Carlo technique to investigate the mechanism of scattering-assisted charge transport in semiconductor superlattices under a strong applied electric field in the Wannier-Stark (WS) regime. The distribution function of quasi-two-dimensional carriers localized in each WS level is calculated, and the contributions of different scattering mechanisms to the total scattering probability are analyzed. Based on these results, the drift velocity is derived as a function of the applied electric field. Due to the LO-phonon-induced resonant transfer of electrons between different spatially localized WS states, our calculated I-V characteristics oscillates with clear negative differential velocity behavior. At the electric field strength such that the Bloch oscillation energy is equal to an integer multiple of the LO phonon energy, a peak appears in the I-V curve. Our theoretical result agrees with the experimental data which was obtained from analyzing the terahertz response of superlattices to picosecond optical pulse excitation.
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