OSCILLATORY BISTABILITY OF REAL-SPACE TRANSFER IN SEMICONDUCTOR HETEROSTRUCTURES

Charge transport parallel to the layers of a modulation-doped GaAs/Al(x)Ga1-x,As heterostructure is studied theoretically. The heating of electrons by the applied electric field leads to real-space transfer of electrons from the GaAs into the adjacent Al(x)Ga1-xAs layer. For sufficiently large dc bias, spontaneous periodic 100-GHz current oscillations, and bistability and hysteretic switching transitions between oscillatory and stationary states are predicted. We present a detailed investigation of complex bifurcation scenarios as a function of the bias voltage U0 and the load resistance R(L). For large R(L) subcritical Hopf bifurcations and global bifurcations of limit cycles are displayed.