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 experimentally. In the field regime of about 2 kV cm-1 we find DC-induced current oscillations associated with N-shaped negative differential resistance. We develop a dynamic model based on real space transfer of hot electrons from the undoped high-mobility GaAs layers to the adjacent n-doped low-mobility AlxGa1-xAs layers. In particular, we extend previous models to multilayer structures and investigate the dependence of the self-generated oscillations upon circuit conditions and the lattice temperature in the range TL=77-200 K. In the light of the experimental results the theoretical predictions are analysed and discussed.