  Spin-orbit coupling is studied using the quantum interference corrections to
conductance in AlGaN/AlN/GaN two-dimensional electron systems where the carrier
density is controlled by the persistent photoconductivity effect. All the
samples studied exhibit a weak antilocalization feature with a spin-orbit field
of around 1.8 mT. The zero-field electron spin splitting energies extracted
from the weak antilocalization measurements are found to scale linearly with
the Fermi wavevector with an effective linear spin-orbit coupling parameter
5.5x10^{-13} eV m. The spin-orbit times extracted from our measurements varied
from 0.74 to 8.24 ps within the carrier density range of this experiment.

Materials Science;Mesoscale and Nanoscale Physics