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doi: 10.1002/(SICI)1521-3951(199807)208:1<5::AID-PSSB5>3.0.CO;2-Epmid: N/A
Layered crystal lattices undergoing Peierls stresses can be looked out like supperlattices where interlayer interactions play a fundamental role in the mechanism triggering kink dislocations. A model intended to describe such systems is considered in terms of a set of anisotropic (parallel) atomic chains lying on a common substrate which mediates the interactions between the layers. The substrate potential is considered as a nonlinear periodic function of the relative displacements of interlayer atoms, and is responsible for the kink dislocation if assumed as the dominant energy along the main dislocation line. The Peierls‐Nabarro potential and the resistive stress (so called second Peierls stress) governing the migration of dislocations, are estimated.
Eglitis, R. I.; Eglitis, R. I.; Kotomin, E. A.; Kotomin, E. A.; Borstel, G.
doi: 10.1002/(SICI)1521-3951(199807)208:1<15::AID-PSSB15>3.0.CO;2-5pmid: N/A
The semi‐empirical quantum chemical INDO method has been used for cluster and large unit cell calculations of hole polarons bound to a cation vacancy in highly ionic MgO and partly covalent perovskite KNbO3. In both cases a hole is well localized on an oxygen atom displaced towards the vacancy. The calculated optical and thermal ionization energies for V−; and V0 centers are in excellent agreement with experimental data for MgO. In KNbO3 we predict the existence of one‐site and two‐site (molecular) polarons with close absorption energies (≈︂1 eV). The relevant experimental data are discussed.
Polit, J.; Sheregii, E. M.; Ivanov‐Omskii, V. I.; Sciesińska, E.; Sciesińska, J.; Gębicki, W.
doi: 10.1002/(SICI)1521-3951(199807)208:1<21::AID-PSSB21>3.0.CO;2-Rpmid: N/A
The Raman spectra for three compositions of ZnxCdyHg1−x−yTe (ZMCT) solid solution were obtained at 300 K. The experimental method allowed us to observe TO‐phonon lines. The comparison of the spectra for compositions with x = 0.02, y = 0.7 and x = 0.12, y = 0.17 shows the appearance of additional lines at 163 and 175 cm−;1 besides two lines which are observed in the range 120 to 150 cm−;1. Far Infrared Reflection Spectra (FIRS) were obtained for five compositions. Theoret‐ical models for three modes of the four‐component solid solution were constructed for the interpretation of the FIRS spectra of ZMCT. We obtained good agreement between the results of RS and FIRS which allowed us to determine the LO‐ and TO‐phonon frequencies for HgTe‐, CdTe‐ and ZnTe‐like lattices.
León‐Avila, F.; Rodríguez‐Coppola, H.; Comas, F.
doi: 10.1002/(SICI)1521-3951(199807)208:1<31::AID-PSSB31>3.0.CO;2-Ppmid: N/A
Calculations of hot electron power losses in a semiconductor quantum well are reported on the basis of a realistic phenomenological model for polar optical phonons and the corresponding Fröhlich‐type electron–phonon Hamiltonian. This model has been discussed in recent times and leads to a plausible description of such phonons. Hot electrons are taken in a steady state configuration when the temperature model is applicable. We assume a wide range of relatively low electron temperatures (25 to 100 K) and the contribution of acoustic phonons is also included. Comparison with previous theoretical and experimental work is made with the fundamental aim of evaluating the relative importance of this model for polar optical phonons for the description of power losses in a quantum well.
Yafyasov, A. M.; Ivankiv, I. M.
doi: 10.1002/(SICI)1521-3951(199807)208:1<41::AID-PSSB41>3.0.CO;2-Npmid: N/A
A new method of self‐consistent quantum calculation of the density of the space charge near the surface of a crystal is carried out for a semiconductor with parabolic dispersion law of bands. The remarkable feature is the solution of the Schrödinger equation for electrons and holes in the energy range, including both bound energy states and the states in the continuum. Voltage–capacitance dependences of MIS structures are calculated.
Betancur, F. J.; Mikhailov, I. D.; Sierra, J.
doi: 10.1002/(SICI)1521-3951(199807)208:1<51::AID-PSSB51>3.0.CO;2-Lpmid: N/A
The energies for the ground and excited states of a D0 impurity located at the center of a GaAs/Ga1−xAlxAs spherical quantum dot are calculated, in the effective‐mass approximation, as functions of the dot radius R and spatial size. We use a variational procedure and take linear combinations of Gaussian and Slater orbitals for the impurity‐envelope wave functions. A model barrier potential is proposed to study changes in the potential introduced by diffusion effects. The binding energy of a 1s2‐like D−; impurity is also studied by considering a parabolic correlation factor. It is found that the D0 and D−; binding energies increase as the dot size decreases up to a critical dot radius R = Rc and then, for R slightly smaller than Rc, the impurity wave function spreads to the barrier region and the 3D character is rapidly restored. The critical dot radius R = Rc is estimated by using the uncertainty relations.
doi: 10.1002/(SICI)1521-3951(199807)208:1<61::AID-PSSB61>3.0.CO;2-Jpmid: N/A
The solution of the Schrödinger equation is examined for the potential that is formed of two delta functions of unequal strength. An analytical expression for the transmission coefficient is derived from the solution. The transmission coefficient is shown to exhibit relative maxima and minima. Moreover, it is proved that the transmission coefficient in its maxima is larger and in its minima is smaller than the transmission coefficient for the corresponding single delta barrier.
doi: 10.1002/(SICI)1521-3951(199807)208:1<69::AID-PSSB69>3.0.CO;2-8pmid: N/A
The energy dependence of the delay time associated with tunnelling through smooth (symmetric) double and triple barriers is investigated. Sharp resonances in the delay are found to mirror resonances in the transmission rate. In the strong‐localization limit, particles with off‐resonant energies do not perceive the inner potential relief and tunnel through the given double, or triple, barrier in much the same way as they would tunnel through a simple, unstructured barrier. Verification of the derived relations through a high‐precision numerical solution of the Schrödinger equation confirms the quality of the obtained expressions in wide energy ranges up to the barrier top.
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