  The electrical response of two-dimensional electron gas to vibrations of a
nanomechanical cantilever containing it is studied. Vibrations of
perpendicularly oriented cantilevers are experimentally shown to change
oppositely the conductivity near their bases. This indicates the piezoelectric
nature of electromechanical coupling. A physical model is developed, which
quantitatively explains the experiment. It shows that the main origin of the
conductivity change is a rapid change in the mechanical stress on the boundary
between suspended and non-suspended areas, rather than the stress itself.
