Silicon molecular beam epitaxy (MBE) has been used to prepare various Si-based structures.The first part of the work concerns hole transport in Si_1-xGe_x layers for Ge contents 0≤x≤0.36 and B-doping concentrations 2-7.5x10¹⁸ cm^-3. A factor called the Hall factor is necessary to know in order to accuractly determine the drift mobility and the free carrier concentration from Hall measurements. For hole transport it has been found that the Hall factor in Si_1-xGe_x is decreased from 0.75 to 0.33 when the Ge content x is increased from 0 to 0.36. The temperature and B-doping concentration dependencies of the Hall factor have also been determined.

The second part describes growth and characterization of Si_1-yC_y structures. Since Catoms are smaller than Si atoms, tensile strain is introduced by the incorporation of C atoms in substitutional lattice sites. A band gap reduction equal to 63 meV/% C has been found from the shift of band edge related emission in photoluminescence experiments. An accumulation of surface roughness can occur during growth and the incorporation of C atoms in substitutional sites is then reduced.

The last part is studies of growth of Er-doped Si-MBE structures. To obtain optically active Er it is necessary to use codopants like O or F. Most of the studies were done using Er obtained by evaporation of Er₂0₃ or ErF₃. Dissociation and reaction with graphite parts in the high-temperature source are important in both cases. Surface segregation of Er has been observed, but the segregation can be limited for growth with a high flourine or CO background pressure. Comparisons between measured electroluminescence and photoluminescence spectra obtained from the prepared structures have been made.