A new type of terahertz frequency range instability of DC current in "thick" ballistic field-effect transistors

Abstract

A new type of de current instability in a ballistic field-effect transistor (FET) is proposed, which emerges due to the finite thickness of the 2D current-carrying channel. The physical origin of the instability in "thick" ballistic FETs is the nonlocality of the relation between the surface electron density and field potential. The instability arises at wavelengths of the order of the characteristic scale length of this nonlocality, which is determined by the FET geometry and vanishes for infinitesimal thickness of the current-carrying channel. The dispersion equation is derived and the domain of parameters under which the system becomes unstable is determined. Estimates show that this new type of instability is promising for driving a high-gain source of THz radiation.