  High-quality C-doped p-type AlGaAs heterostructures with mobilities exceeding
150 000 cm$^2$/Vs are investigated by low-temperature magnetotransport
experiments. We find features of the fractional quantum Hall effect as well as
a highly resolved Shubnikov-de Haas oscillations at low magnetic fields. This
allows us to determine the densities, effective masses and mobilities of the
holes populating the spin-split subbands arising from the lack of inversion
symmetry in these structures.
