THz-emitters based on ballistic transport in semiconductor nanostructures

A novel concept for THz-photomixers based on semiconductor nanostructures with strongly increased conversion efficiency is presented. In THz-photomixers, typically based on photoconductivity in "low-temperature-grown-GaAs." (LT-GaAs), the performance is typically limited by the (very low) photoconductive gain and depends critically on an extremely short lifetime of photo-generated charge carriers in LT-GaAs. In contrast to those devices, in our photomixer the gain does not depend on the recombination lifetime but only on the transit time and on the path length of the photo-generated electrons within suitably designed p-i-n nanostructures, which both can be optimised for (primarily) ballistic transport. In addition, impedance matching to the attached antenna can be achieved.