Abstract
High-frequency current oscillations have been observed in highly doped single quantum well structures of GaAs/AlGaAs. Several samples of the same structure, but aligned along different crystallographic directions, have been studied. The field, temperature and time dependences of these oscillations have been investigated. Various mechanisms associated with current oscillations are discussed including NDR, trapping and dual streaming, but as yet no single mechanism fully describes the observations. In some samples, the period doubling was observed, which has been related by others with routes to chaos.