A theory of resonant spin-dependent tunneling has been developed for symmetrical double-barrier structures grown of non-centrosymmetrical semiconductors. The dependence of the tunneling transparency on the spin orientation and the wave vector of electrons leads to (i) spin polarization of the transmitted carriers in an in-plane electric field, (ii) generation of an in-plane electric current under tunneling of spin-polarized carriers. These effects originated from spin-orbit coupling-induced splitting of the resonant level have been considered for double-barrier tunneling structures.
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 non-variational, and we are therefore also able to evaluate the
wave functions. This is used to calculate the optical absorption spectrum,
which is strongly non-isotropic due to the selection rules. The results
obtained from calculations for Si/Si$_{1-x}$Ge$_x$ 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.Comment: 17 pages, 10 figure
We report on the experimental evidence for terahertz (THz) lasing of boron-doped strained Si1−xGex quantum-well structures. The lasing arises under strong electric fields (300–1500 V/cm) applied parallel to interfaces. The spectrum of THz stimulated emission is presented showing the lasing wavelength near 100 μm and the modal structure caused by a resonator. The mechanism of population inversion is based on the formation of resonant acceptor states in strained SiGe layer.
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