PLANAR MULTIBARRIER 80 240-GHZ HETEROSTRUCTURE BARRIER VARACTOR TRIPLERS/

Prototype planar four barrier GaAs/Al(0.7)Gao(0.3)As heterostructure b arrier varactors (HBV's) for frequency tripling from 80 to 240 GHz hav e been fabricated using a process in which the device surface channnel is etched prior to the formation of the contact pad-to-anode air-brid ge finger, Formation of the device air-bridge finger after etching the surface channel is facilitated by a trench planarization technique an d yields a device with minimal parasitic capacitances, Planar four-bar rier HBV triplers with nominal 10-mu m diameter anodes have been teste d in a crossed-waveguide tripler block; as much as 2 mW of power has b een generated at 252 GHz with a flange-to-flange tripling efficiency o f 2.5%, These devices are the first planar or multibarrier HBV tripler s reported and their output powers are nearly double that of previous whisker-contacted single-barrier HBV's.