Oscillations in the vertical magneto-transport of a GaInAs-AlInAs superlattice were observed and explained as being the modulation of miniband properties. We explain that such a modulation is due to the Landau levels of the highly (Si) n+ doped regions. It is shown that phase and amplitude of these oscillations are dependent on the angle between electric and magnetic fields. This phenomenon is thus similar to the Shubnikov - de Haas effect in bulk materials, even though the active region of the superlattice is not intentionally doped. Very highly doped three-dimensional regions were grown on each side of the superlattice to allow for the process of Ohmic contact formation.