The relevance of quantum barrier devices to millimetre wave systems

A “new” range of devices based on quantum mechanical tunnelling is receiving widespread interest for applications such as multipliers, oscillators, and harmonic mixers. These devices rely on monolayer thickness control of adjacent semiconductor layers to determine the tunnelling probability of incident electrons and so the current through the device. The disassociation of the tunnel barrier thickness from the doping adjacent to the barrier in the quantum barrier devices (QBD´s), permits much more flexibility than was the case for previous Esaki tunnel diodes. Devices have been demonstrated which provide broadband room temperature negative differential resistance (NDR) up to 712 GHz. This NDR can, under appropriate circuit conditions, be used to produce oscillators and parametric amplifiers. The exploitation of these tunnel effects in new and existing devices is discussed