Frequency behaviour of space-charge-wave amplifiers in GaAs

Abstract

As a consequence of the Gunn effect travelling space charge wave (SCW) amplification in n‐GaAs is possible. Within the frame of the drifted Maxwellian approach the frequency dependence of wave propagation is investigated. The applicability of this approach is thoroughly discussed. The most remarkable properties of the SCW are high gain and early onset of relaxation effects although diffusion, surprisingly, increases the limiting frequency at field strengths just above threshold. Farther above threshold the limiting frequency is much lower than for the real part of the conductivity. Gain and limiting frequency increase with electron density. A stability criterion results which for low electron densities is consistent with the usual n × L‐product of 1012 cm−2 while larger n × L‐products should be admittable at higher concentration.