High-Quality varactors and Schottky-Diodes in SiGe:C Technology for mm-Wave and THz applications

Abstract

This paper presents the design and experimental characterization of High-Quality varactors and Schottky Diodes in SiGe:C Technology. A new layout topology for differential varactor is proposed to significantly improve its quality factor up to the Ka band. This new layout topology addresses the typical trade-off that designers often face between the quality factor and the tuning range. 2x improvement of the quality factor up to 30 GHz over conventional layout topology made of multi fingers is demonstrated. On the other side, special care has been taken to minimize parasitic capacitance between anodes to keep the tuning range stable. Measured VCO with this new type of varactor shows a reduction of 2 dB in the Phase Noise at 1 MHz from the carrier. Silicon-based Schottky Diodes arrays with Cut-Off frequencies in the THz domain are designed and fabricated. Concurrent optimization of Schottky Diode arrays geometry and electrical performances (Cutoff frequency, parasitic, Quality-factor, Sensitivity, Responsiveness, etc.) is carried out based on careful modeling and experimental characterizations. Analysis of the Schottky Diode arrays including sweep in DC-biasing conditions to control non-linearities is studied. Detection mechanisms related to the non-linear behavior are studied and figures of merit are introduced for their analysis.