OSCILLATIONS OF A BALLISTIC HOLE CURRENT THROUGH UNIAXIALLY COMPRESSED SEMICONDUCTOR LAYERS

The oscillations of the ballistic hole current through a thin base of a p(+)pp(+) diode compressed uniaxially in the direction of the curren t are investigated theoretically. As a result of compression, the hole dispersion relation contains sections with negative effective mass al ong the indicated direction. The current oscillations are caused by th e instability of the stationary ballistic current-carrier distribution , which contains an extensive quasineutral plasma region in which the mobile component of the charges consists of drifting carriers with neg ative effective mass. In many cases, the current oscillations possess a harmonic character, whose frequency is determined by the length of t he base and by the voltage, amounting to hundreds of gigahertz for lon g (similar to 1 mu m), weakly doped bases and several terahertz for sh ort (< 0.1 mu m), strongly doped bases. Criteria for a quasiclassical approach to the problem, which was used in the numerical modeling of t he vibrational processes described here, are found. This approach is j ustified if the ballistically injected carriers are distributed in a s ufficiently wide band of transverse momenta. (C) 1997 American Institu te of Physics.