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 detailed theoretical investigation of resonant states induced by shallow acceptors in uniaxially strained semiconductors. By applying Dirac's approach and using the Coulomb potential of an acceptor impurity, we have obtained the amplitude of resonant scattering, the probability of coherent capture and emission of holes by resonant state, and the characteristic features of the resonant state. The modified dispersion law and density-of-states of valence band by the resonant states have also been derived. The energy dependence of optical transition probability between resonant and localized impurity state have been calculated. The theoretical investigation of a new mechanism for carrier population inversion in strained semiconductors under an electric field has been presented. It has been shown that the mechanism is the result of a coherent captureemission type inelastic scattering of holes by resonant states. The calculation based on our theory for uniaxially strained p-Ge explains the recently observed lasing phenomena in THz frequency region. PRB 62 ODNOBLYUDOV, YASSIEVICH, CHISTYAKOV, AND CHAO

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