Heterostructure barrier varactors at submillimetre waves

We present an overview of recent results concerning quantum barrier varactors, also called heterostructure barrier varactors (Hsv). This device is normally constructed as a mesa device, with one or several thin (ca. 200 Angstrom) barriers made from a larger bandgap material. The diodes are excellent as multipliers and have several advantages over the common Schottky barrier varactor. The Hsv only generates odd harmonics of the input power, can be built to handle large powers and permits a large device area at very high frequencies. We present theoretical design and performance characteristics for triplers and quintuplers and give an overview of Hsv multiplier experiments.