Two-dimensional electron gas hot-electron mixers for millimeter waves and submillimeter waves

Abstract

Present state-of-the-art Schottky and SIS mixer receiver noise temperatures (T RX ) range from roughly 300K at 0.3 THz to 3000K at 1 THz, while TRT RX for InSb hot electron mixers varies from 300K to 500K in the same frequency range. It is natural to ascribe the much more gradual frequency dependence of T RX for the hot electron mixer to its bulk nature, which minimizes parasitic reactances. A hot electron mixer requires an electron gas with high mobility which can be heated by the LO power, and a change in the mobility or carrier concentration as a result of this heating. Smith et al. (1987) pointed out that the two-dimensional electron gas in the channel of FIFET devices at liquid helium temperatures constitutes a potentially excellent nonlinear medium of the required type, which would also attain a much wider IF bandwidth than the InSb mixer (GHz versus a few MHz).