CURRENT-VOLTAGE CHARACTERISTICS OF MANY-VALLEY SEMICONDUCTORS WITH MULTIVALUED DEPENDENCE OF THE CURRENT ON THE ELECTRIC FIELD.

The actual current-voltage characteristics are obtained for the case when a weakly heating electric current i//x flows in a classically strong transverse magnetic field H//z so that for a uniform current distribution the characteristics should be of the S-type, caused by a steep dependence of the intervalley scattering time on the heating power. It is shown that the real characteristics of n-type Ge with i//x parallel left bracket 110 right bracket and H//z parallel left bracket 110 right bracket should as a rule be single-valued. In a narrow range of electric fields, a high positive differential conductance is observed; this is associated with the fact that a high- field domain occurs near one of the surfaces parallel to the current and magnetic field, and this domain increases with the field as a result of the rapid movement towards the opposite surface of the domain walls which separates it from a weak- current domain. This type of characteristic will occur in n-type type Si with i//x parallel left bracket 100 right bracket if the intervalley scattering rate is low on the surface where the high-field domain starts to form. If the rate is not low, then a given range of currents can only be realized when there is a high negative differential conductance with a current domain which moves perpendicular to the current and the magnetic field; this should lead to oscillations at a frequency which is inversely proportional to H//z.