  We demonstrate tunable transverse rectification in a density-modulated
two-dimensional electron gas (2DEG). The density modulation is induced by two
surface gates, running in parallel along a narrow stripe of 2DEG. A transverse
voltage in the direction of the density modulation is observed, i.e.
perpendicular to the applied source-drain voltage. The polarity of the
transverse voltage is independent of the polarity of the source-drain voltage,
demonstrating rectification in the device. We find that the transverse voltage
$U_{y}$ depends quadratically on the applied source-drain voltage and
non-monotonically on the density modulation. The experimental results are
discussed in the framework of a diffusion thermopower model.
