Observation of multiple domains in a planar Gunn diode

We have observed multiple oscillations in a planar Gunn diode fabricated using an AlGaAs/GaAs based quantum well structure. The material used was grown by molecular beam epitaxy and devices were made using electron beam lithography. The devices had a 4 mum cathode-anode distance and 60 mum width. They showed multiple oscillations at 29 GHz, 33 GHz and 35 GHz. This is the first observation of multiple frequencies in a planar quantum well structure device and may have applications as a single chip multi-frequency source.