A 200 GHz GaAs Schottky-diode phase shifter integrated on a silicon-on-insulator substrate

A planar GaAs based Schottky-diode phase-shifter, fabricated on a silicon-on-insulator (SOI) substrate is described. To the best of the authors' knowledge, this is the first time an integrated Schottky diode circuit has been fabricated monolithically from GaAs and bonded to SOI. Previous work on GaAs-SOI wafer bonding has focused on creating optoelectronic devices that take advantage of silicon microfabrication methods. In this work, GaAs is bonded to SOI and processed to realize a fully integrated submillimeter wave phase shifter. This approach reduces the circuit profile, eases circuit assembly and allows for flexible geometry definition. The circuit described is capable of modulating the phase of a reflected signal by 180° with 8-10 dB of return loss. To achieve this phase shift, two integrated tuning elements, one in series and a second in shunt, are incorporated into the design. These elements resonate as an open and a short at different diode bias voltages and to create the resulting phase shift.