The equation of motion for the polarization vector for a double heterostructure of polar crystals is solved exactly within the framework of the continuum model. There exist only two types of phonon modes, the interface modes and the confined bulk modes, whose eigenvectors are obtained explicitly. Dispersion relations are derived analytically for the interface modes, while the confined bulk modes are dispersionless, a fact consistent with the model. It is also found that in Raman scattering experiments the symmetric interface modes are predominantly longitudinal optical (LO) and the antisymmetric interface modes transverse optical (TO). In the central region of the Brillouin zone, ho~ever, they both split into two branches oscillating at LO and TO frequencies, respectively. Possible reinterpretation of various experiments is briefly discussed.

We investigate mechanisms of electric-field-induced conduction in high-quality chromia crystals. A crossover is observed between space-charge limited conduction and the Frenkel-Poole mechanism with increasing temperature, with the crossover occurring in the vicinity of the Neel temperature of this material. From an analysis of the Frenkel-Poole conduction, we infer the presence of charge traps that lie approximately 0.5 eV below the conduction-band edge. Our experiments confirm the excellent dielectric properties of chromia, a result that is important for attempts to utilize this material as a “gate” dielectric in future spintronic devices.

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The binding energy of a polaron confined in the quantum well of GaAs/Ga& "Al"As double heterostructures is calculated as a function of the magnetic field applied in the direction of growth. We have also calculated the oscillator strength of electron-phonon interaction for transitions from various excited states to the ground state of the polaron. Every type of optical-phonon mode that can exist in such structures within the continuum model is considered separately. It is found that the magnetic field 0 greatly enhances the interface-phonon part of the polaron effect. For quantum wells of widths 150 A or smaller, the interface modes dominate all polaronic phenomena we have encountered when B~1 T. For 0 quantum wells of widths up to 100 A, contributions from confined bulk phonon modes are almost negligible in magnetic fields B~1 T.

Electron interactions with interface phonon modes and strictly confined bulk phonon modes are considered to calculate the resonant magnetopolaronic 1s-2p+ transition energy of a hydrogenic impurity in the quantum well of a double heterostructure.An interaction gap is predicted between the bulk LO and TO frequencies, in contrast to the Frohlich-type interaction. These results are in good agreement with recent experimental data.