Narrowband microwave emission by a frequency-locked current oscillation in a GaAs/AlAs superlattice

We report on frequency locking of a self-sustained current oscillation in a GaAs/AlAs wide miniband superlattice oscillator emitting microwave radiation at 23 GHz with a power of about 0.3 mW. The current oscillation was caused by travelling dipole domains and the locking was due to interaction of the domains with an external narrowband high-frequency field. We observed that the linewidth of the frequency-locked oscillation was less than 10 Hz compared to 105 Hz for the free oscillator, indicating synchronisation of the dipole domain propagation with the external field.