  It was shown previously that the current-carrying state of a Field Effect
Transistor with asymmetric source and drain boundary conditions may become
unstable against spontaneous generation of plasma waves [1]. By extending the
analysis to the two-dimensional case we find that the dominant instability
modes correspond to waves propagating in the direction perpendicular to the
current and localized near the boundaries. This new type of instability should
result in plasma turbulency with a broad frequency spectrum. More generally, it
is shown that a similar instability might exist, when a strong enough current
goes through a single boundary between the gated and ungated regions.
