Miniband charge transport was investigated by Monte Carlo simulations of electronic motion in short period superlattices of type-II energy band alignment (InAs/GaSb composition). The strong decrease of the miniband energy width when the electronic in-plane energy increases, characteristic of type-II superlattices, leads to a conductivity that is very sensitive to a magnetic field applied parallel to the axis of the superlattice. For structures with a miniband energy width greater than the optic phonon energy, the differential conductance can be changed from positive to negative by the magnetic field, due to the suppression of optic phonon emission.

We report an investigation of the optical absorption spectrum, using non-polarized light, in Pb xEu1-xTe, x=0 and x=0.095, epitaxial thick layers grown by molecular beam epitaxy (MBE). The absorption edge is described by a broad band, due to the electronic transitions from the 4f7 of Eu2+ to the states in 4f6 5d configuration, as seen previously in bulk Eu chalcogenides. When a magnetic field is applied, a narrow absorption band (full width ~50 meV) emerges from the broad one. The energy of this absorption peak red shifts when the magnetic field increases, and reaches saturation when the Eu2+ attain ferromagnetic arrangement. This behaviour can be described by a localized excitation model with d - f exchange interaction.

GaAs/AlGaAs multiple quantum well structures containing an nipi delta-doping superlattice, where the n-type doping is inserted in the quantum wells and the p-type in the barriers, have been studied in detail to evaluate their potential for use in the fabrication of amplitude modulators. It is shown that C is an adequate p-type dopant for such structures, however, little exibility is found in the growth conditions, in particular for the V to III uxes ratio, for obtaining such layers. It is also observed that the required balance between n and p type doping levels is not trivial to be achieved due to the presence of interface hole traps whose population depends on the quantum well doping concentration. In addition, the observed photoluminescence near-edge emission at room temperature occurs at essentially the same energy as that of an equivalent undoped structure. Finally, no deep level emissions are observed which could deteriorate the device performance.

The interfaces in InP=In0.53 Ga0.47As superlattices modulation doped with Si were investigated using magneto-transport, capacitance-voltage, and high resolution X-ray diffraction measurements. Results indicate that a thick interfacial layer is formed when InP is grown on top of In xGa1-xAs, and that Si atoms that fall in the interfacial layer have a high probability of not forming a shallow donor center. Using a simple theoretical model the width of the interfacial layer which was estimated to be 7±1 monolayers.