Influence of a magnetic field on the current instability in a ballistic field-effect transistor

Abstract

A theoretical investigation is made of the plasma-wave instability mechanism in a two-dimensional (2D) electron fluid in a ballistic field-effect transistor (FET) in the presence of a perpendicular magnetic field. The 2D electron fluid in the FET channel has been treated within the framework of hydrodynamics applicable to the shallow water waves. We show that a relatively low dc current should be unstable because of magnetoplasma-wave amplification due to the reflection of the wave from the device boundaries. Just as in the absence of the magnetic field the instability occurs for $0l{\ensuremath{\upsilon}}_{0}ls$ and ${\ensuremath{\upsilon}}_{0}l\ensuremath{-}s,$ where ${\ensuremath{\upsilon}}_{0}$ is the local electron velocity and s the plasma-wave velocity. The external field B enhances this instability considerably as the imaginary part of the wave increases with B. Accordingly, the magnetic field can be used to compensate or overcome the stabilizing role of the external and/or internal friction on plasma-wave generation. Such a ballistic FET channel is a promising device for the generation of tunable electromagnetic radiation in the terahertz frequency range.