ELECTRICALLY TUNABLE GHZ OSCILLATIONS IN DOPED GAAS-ALAS SUPERLATTICES

Tunable oscillatory modes of electric-field domains in doped semicondu ctor superlattices are reported. The experimental investigations demon strate the realization of tunable, GHz frequencies in GaAs-AlAs superl attices covering the temperature region from 5 to 300 K. The orgin of the tunable oscillatory modes is determined using an analytical and a numerical modeling of the dynamics of domain formation. Three differen t oscillatory modes are found. Their presence depends on the actual sh ape of the drift velocity curve, the doping density, the boundary cond ition, and the length of the superlattice. For most bias regions, the self-sustained oscillations are due to the formation, motion, and recy cling of the domain boundary inside the superlattice. For some biases, the strengths of the low- and high-field domain change periodically i n time with the domain boundary being pinned within a few quantum well s. The dependency of the frequency on the coupling leads to the predic tion of a different type of tunable GHz oscillator based on semiconduc tor superlattices.