Wide bandwidth millimeter wave mixer using a diffusion cooled two-dimensional electron gas

Very fast millimeter wave mixers have been fabricated from a high mobility two-dimensional electron gas (2DEG) in a GaAs–AlGaAs heterostructure. Using a 115 GHz local oscillator, intermediate frequency (IF) bandwidths exceeding 20 GHz have been obtained for channel lengths L of a few microns. Operating at 77 K, the IF bandwidth scales as L−2, indicating that the response speed is determined by the diffusion transit time of hot electrons to the leads.