Propagation and Amplification of Density Waves in Electron-Hole Plasmas in p-InSb

Abstract

Propagation and amplification of density waves in p-InSb were investigated at 77 K. The electron-hole plasma was produced by double injection and the plasma density wave perturbed in the frequency range from 2-25 MHz at the injecting contact. The density perturbation propagates through the sample as a density wave with an ambipolar density velocity. The amplitude of the wave was observed to be spacially amplified when the electric field and the injection level were sufficiently high. The amplification constant was studied as a function of the frequency and the injection level. The experimental results are compared with the theories for the instability and it is concluded that the most probable mechanisms for the observed amplification are the effect of hot electrons on the ambipolar diffusion constant and the nonuniformity of the plasma density distribution.