Quantum well devices for millimetre wave applications

Quantum well devices exhibit strong non-linearity with very short time responses which make them attractive for non-linear applications at very high frequencies. In this paper, we review several topics concerning the design, the fabrication and the frequency evaluation of these devices. We discuss notably new proposals in order to improve their frequency and power capabilities in the context of recent progress in strained layer epitaxy and finite superlattices. Concerning fabrication, the more recent developments for integrating the device in a whisker-less technology are reported. On this basis a few selected recent achievements for demonstrating the ability of these devices to operate at very high frequency are considered. Lastly, we focus on recent advances related to the applications for the devices used as oscillators, harmonic multipliers, detectors and mixers.