Self-sustained current oscillation above 100 GHz in a GaAs/AlAs superlattice

A GaAs/AlAs superlattice with a large miniband (120 meV) showed self-sustai ned current oscillation at a frequency of 103 GHz giving rise to microwave emission (power 0.5 mW). The emission line had a linewidth of about 1 MHz a nd was tuneable by about 800 MHz. An analysis suggests that the transport i n the superlattice was mainly due to electrons in the lowest miniband and t hat the oscillation was caused by traveling dipole domains. We also observe d frequency locking of the current oscillation attributed to a synchronizat ion of domain propagation by the external high-frequency field. (C) 1999 Am erican Institute of Physics. [S0003-6951(99)02215-9].