Wave Propagation in Negative Differential Conductivity Media: n-Ge

A study has been made of transverse electromagnetic wave propagation in the negative differential resistance medium provided by suitably oriented n-type germanium at 77°K. The wave frequency is chosen to fall below the critical scattering rates in this system (1 GHz), and the sample dimensions are maintained below the critical length for domain formation. Thus when the electric vector is oriented parallel to the dc biasing field, and the propagation vector is normal to the biasing field, growth of the wave is to be expected and evidence of it is presented. In addition, the real and imaginary parts of the conductivity are evaluated throughout the dc bias field range from zero to 3.5 kV/cm, for a range of resistivities.