Currentinstability in field-effect transistors: influence of magneticfield and collisions

Abstract

A theoretical investigation is made of the plasma-wave instabilitymechanism in a two-dimensional (2D) electron fluid in a field-effecttransistor (FET) in the presence of a perpendicular magnetic field.The influence of electron collisions with impurities and/or phononsis also taken into account. The 2D electron fluid in the FETchannel is treated within the framework of hydrodynamics. Thetreatment is valid for a nondegenerate electron fluid in which themean free path for interelectronic collisions is much smaller thanthe device length and the mean free path due to impurities and/orphonons. It is shown that a relatively low direct current should beunstable because of magnetoplasma-wave amplification due to thereflection of the wave from the device boundaries. The role of anapplied magnetic field is additive: the greater the magneticfield, the larger the wave increment. In that sense an appliedmagnetic field may be used to compensate (or overcome) the subtractive role played by collisions on plasma-wave generation.Such a ballistic FET is promising for the generation of tunableelectromagnetic radiation in the terahertz frequency range.