Fabrication and Characterization of Quasi-Vertical Schottky Diodes with Integrated MIM Capacitors for Millimeter Wave Application 258 views

Schottky diodes are integral devices in many millimeter and sub-millimeter wave circuits. In varactor-based frequency multipliers, DC biasing of diodes is required to maximize junction capacitance swing and produce the highest conversion efficiency possible. In some topologies, applying a reverse DC bias is straightforward, but others, such as the balanced tripler with an anti-parallel diode pair, require a DC blocking capacitor to individually apply bias to each diode. While this is possible with existing methods which utilize on or off chip capacitors, an elegant solution entails integrating the capacitor directly beneath each diode structure, building upon and exploiting the existing quasi-vertical diode (QVD) structure. At the design frequency of the device, the capacitor acts as an RF short and DC open. This thesis describes a process to realize QVDs with integrated capacitor structures for biasing and RF tuning. The fabrication process is described, in addition to measurements to characterize the diode structure. By incorporating a bias connection directly to the diode’s ohmic contact, thus DC isolating the diode from ground with a dielectric, it is possible to independently apply bias to different diodes in multi-diode circuit configurations, such as mixers and frequency triplers. Prototype diodes and anti-parallel diode pairs with integrated capacitors are fabricated and characterized with on-wafer measurements up to 220 GHz. A 120 GHz on-wafer frequency tripler utilizing this structure is designed, fabricated, and measured for conversion efficiency and output power, and serves as a proof-of-concept application for this novel diode structure.

MS (Master of Science)

Schottky diode; frequency tripler; MIM capacitor

English

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2026-04-22