Die transversale,negative, differentielle Leitfähigkeit von n-Germanium: Zwei 2-Tal-Modelle ihrer statischen und dynamischen Eigenschaften

Taking into account two of the four 111-energy minima of the Ge-conduction band, expressions for the field and frequency dependent transverse differential conductivityσ _yy(ω, E _x) have been derived. Forω=0, one obtains the static properties, especially information concerning the critical fieldsE _xc defined byσ _yy(0,E _xc)=0. Forω≠0, the plasma frequenciesω _p have been calculated fromσ _yy(ω, E _x). One of these goes to zero forE _x→E _xc (soft mode). The optical quantities: refractive index, extinction and reflection coefficient have also been calculated. They show anomalies in the regionE _x=E _xc. To evaluate the equations quantitatively, the intervalley and the momentum scattering rate have been derived in the last part of this work using known distribution functions.