The development of planar Gunn diodes for the realisation of MMIC oscillators

This review presents the development of planar Gunn diodes over the last few years for the implementation of millimetre-wave sources. The fabrication procedure incorporates electron beam lithography and the oscillation frequency is determined by the anode-to-cathode distance. The evolution of the material design for the maximisation of the maximum frequency of oscillation and the enhancement of the generated power is presented in this paper. The recent implementation of a planar Gunn diode with a high-electron mobility transistor on the same substrate is also described in this work.