Hybrid mode instability in n-type polar semiconductors

Hybrid mode instability has been studied under crossed static electric field E 0 and magnetic field B 0 in n-type polar semiconductors, the wave being propagated along a direction perpendicular to both E 0 and B 0 . The analysis takes into account the effect of diffusion. The polar optical phonon scattering has been considered as the dominant scattering mechanism at 300K. The dispersion relation shows that the coupling between the two independent modes is due to the magnetic field only when the drift is neglected. The numerical analysis is made for n-GaAs with the DC electric field E 0 <200 kV m -1 such that the electrons are all in the central valley of the conduction band. The phase velocity of the unstable mode, nu phi , increases with magnetic field and attains a maximum value when electron cyclotron frequency is equal to the electron collision frequency; for higher B 0 , nu phi starts decreasing. The growth rate is considerable, decreasing with B 0 and increasing with the increase in E 0 , and is almost independent of the wavenumber k in the long wavelength region, but increases with k in the short wavelength region.