  The cross-over from quasi-two- to quasi-one-dimensional electron transport
subject to transverse electric fields and perpendicular magnetic fields are
studied in the diffusive to quasiballistic and zero-field to quantum Hall
regime. In-plane gates and Hall-bars have been fabricated from an
InGaAs/InAlAs/InAs quantum well hosting a 2DEG with carrier density of about
6.8$\times$10$^{11}$ cm$^{-2}$, mobility of 1.8$\times$10$^5$ cm$^2$/Vs and an
effective mass of 0.042$m_e$ after illumination. Magnetotransport measurements
at temperatures down to 50 mK and fields up to 12 T yield a high effective
Land\'e-factor of |g$^*$| = 16, enabling the resolution of spin-split subbands
at magnetic fields of 2.5 T. In the quantum Hall regime, electrostatic control
of an effective constriction width enables steering of the reflection and
transmission of edge channels, allowing a separation of fully spin-polarized
edge channels at filling factors ${\nu}$ = 1 und ${\nu}$ = 2. A change in the
orientation of a transverse in-plane electric field in the constriction shifts
the transition between Zeeman-split quantum Hall plateaus by ${\Delta}$B
$\approx$ 0.1 T and is consistent with an effective magnetic field of B$_{eff}$
$\approx$ 0.13 T by spin-dependent backscattering, indicating a change in the
spin-split density of states.
