Optimization of a Schottky Mixer Diode for THz Heterodyne Detection

We have designed a Schottky barrier mixer diode (SBD) for use in Terahertz (THz) heterodyne receivers with a structure optimized for high cut-off frequency and minimum conversion loss. In the THz rang, the conventional formulas describing diodes characteristics are invalid for several high frequency effects such as the skin effect and plasma resonance. The relations between these effects and doping density and operation frequency were thoroughly analyzed, and the cut-off frequency and conversion loss dependence on doping density of the epitaxial layer and anode diameter of SBD were analyzed and simulated. The results indicate that in the THz range, the substrate doping density and the epitaxial layer doping density are high enough and diode diameter is small enough to improve SBDpsilas performance, and operation above the plasma frequency is not a useful option. The optimization of the SBD structure shows an excellent agreement with experiment.