SELF-GENERATED NONLINEAR OSCILLATIONS IN MULTILAYER SEMICONDUCTOR HETEROSTRUCTURES

Nonlinear charge transport parallel to the layers of modulation-doped GaAs/AlxGa1-xAs heterostructures is studied theoretically and experime ntally. In the field regime of about 2 kV cm-1 we find DC-induced curr ent oscillations associated with N-shaped negative differential resist ance. We develop a dynamic model based on real space transfer of hot e lectrons from the undoped high-mobility GaAs layers to the adjacent n- doped low-mobility AlxGa1-xAs layers. In particular, we extend previou s models to multilayer structures and investigate the dependence of th e self-generated oscillations upon circuit conditions and the lattice temperature in the range T(L) = 77-200 K. In the light of the experime ntal results the theoretical predictions are analysed and discussed.