  Measurements of the Hall and dissipative conductivity of a strained Ge
quantum well on a SiGe/(001)Si substrate in the quantum Hall regime are
reported. We find quantum Hall states in the Composite Fermion family and a
precursor signal at filling fraction $\nu=5/2$. We analyse the results in terms
of thermally activated quantum tunneling of carriers from one internal edge
state to another across saddle points in the long range impurity potential.
This shows that the gaps for different filling fractions closely follow the
dependence predicted by theory. We also find that the estimates of the
separation of the edge states at the saddle are in line with the expectations
of an electrostatic model in the lowest spin-polarised Landau level (LL), but
not in the spin-reversed LL where the density of quasiparticle states is not
high enough to accommodate the carriers required.
