A NEW PLANAR CIRCUIT REALIZATION FOR HIGH FEQUENCY SEMICONDUCTOR COMPONENTS

A novel GaAs monolithic membrane-diode (MOMED) structure has been developed and implemented as a 2.5 THz Schottkg diode mixer. The mesa-stgle planar diode uses a rectangular anode with a T-shaped metalization and a foot-print that measures nominallg 0.2pm bg Ipn. It is integrated onto a 3pm thick bg 36P wide bg 600prn long GaAs membrane which bridges across an aperture in a monolithic all GaAs sup-port frame approxirnatelg 50pn thick. RF filter structures are incorporated on the 600 P long membrane. The membrane frame and RF circuit are coupled to an electroformed waveguide mount that places the diode across the center of a 2.5 THz full height rectangular waveguide (100x50jnn2). The mixer mount contains an inte-grated Pickett-Potter feed horn and rectangular waveguide transformer, suspended-stripline sin-l gle-mode RF filter channels to house the mem-brane, a freed waveguide backshort for RF matching and a quartz-based transformer for the desired 7-21 GHz IF output. Measurements of receiuer peflorrnance, in air, gield a TWC,lW,of 20,000 K DSB at 8.4 GHz IF using a 150K com-mercial Miteq amplifier. The receiver conversion loss measures 17 dB (including air, diplexer, IF filter and horn coupling losses), ~ielding a de-rived front-end noise temperature of approxi-mately 12,500K DSB at 2514 GHz. A COZ pumped methanol far-IR laser is used as a local oscillator at 2522 GHz and is i~”ected with a Martin-Puplett diplexer. The required local os-cillator power is below 3mW for optimum pumping, and no device damage was observed with incident power as high as 22mW. im-provements in noise temperature are expected as the devices and circuits are still being opti-mized. The mixer is baselined for flight use o