Modeling and fabrication of a PTE THz mixer on epitaxial graphene

The unique hot-electron photo thermo electric properties of graphene make it an ideal platform for terahertz (THz) heterodyne mixers. However, it requires extensive computer modeling and a complex fabrication processes to make it work well. In this work, we describe an accurate computer modeling and optimized fabrication process flow for the mixers on an epitaxial graphene platform. The proposed mixer is capacitively coupled to a twin slot antenna and optimized to resonate at 650 GHz (focused on space-based astronomy). Computer simulation (3D full-wave analysis) provides a consistent operating bandwidth of 100 GHz for the graphene impedances varying from 200 Ω – 2500 Ω. We will also demonstrate the different IF extraction schemes and their impact on antenna performance. Epitaxial grown quasi-free-standing graphene on silicon carbide substrate was used for the device fabrication. Mixer device was fabricated after several steps of standard E-beam lithographic process for metal deposition, graphene etching, and dielectric deposition. We will present the characterization of the IF mixing bandwidth of our heterodyne mixer at various temperatures and the calibration of its sensitivity.