Impedance-matching circuits were integrated on the same chip as the IMPATT diodes to produce monolithic impatt diodes for millimetre-wave applications. A drastic reduction of device-to-circuit parasitic elements was achieved by placing the external circuitry very close to the device. Oscillators fabricated in this fashion gave the highest efficiencies reported so far in the 30–35 GHz range with 28% conversion efficiency using hybrid-Read structures.