Time-resolved photoluminescence is used to study low-temperature-grown (LTG) GaAs with Be doping. It is observed that the carrier trapping time in the as-grown LTG GaAs increases with Be doping. Similar effect is observed also in the annealed samples doped with less than 3×1019 cm−3 of Be. At higher doping levels, the trapping time in these samples is abruptly reduced to below 100 fs. This behavior is attributed to changes in As antisite density and the compensation effect of Be.

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GaBiAs layers with Bi content reaching 8.4% are grown by MBE technique at low temperatures. All layers were of p-type with carrier densities ranging from 3 × 10 14 to 2 × 10 15 cm −3 and resistivities exceeding 60 cm. Energy bandgap of the gallium bismide alloys as determined from spectral measurements of the optical absorption, photoconductivity and photoluminescence decreases linearly with increasing Bi content. Optical pump-terahertz probe measurements made on these layers show that the carrier density dynamics is best described by a double-exponential decay. The shorter of the time constants corresponds to the electron trapping and the longer time constant corresponds to the trap emptying times. It has been found that the electron trapping cross-section is of the same order of magnitude as the corresponding parameter for As-antisite traps in LTG GaAs; therefore, it is reasonable to assume that As antisites play a significant role in carrier recombination processes in GaBiAs, too.

We report heteroepitaxial growth of multiferroic BiFeO 3 thin films by RF magnetron sputtering on lattice-matched SrTiO3 substrates, as well as preparation and electrical properties of the heterostructures formed by growing BiFeO 3 thin films on highly conductive LaNiO 3 films and n-Si substrates. Nonlinear and rectifying current-voltage (I−U ) characteristics were revealed for the heterojunctions in a wide temperature range (T = 78-300 K).

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