ill./ A.F.AL11.11,16...1,1,11 Schottky barrier varactor diodes are used as frequency multipliers to supply local oscillator power for heterodyne receivers at millimeter and submillimeter wavelengths. Whisker contacted diodes have been developed which generate sufficient power at frequencies as high as 700 GHz for ground based and airborne experiments [1,2,3]. These devices have proven to be very reliable and effective, however there remains great interest in developing multipliers which are more mechanically robust, and which are capable of delivering larger amounts of power. This research is focussed on the development of planar diodes to achieve both of these important goals. It is hoped that such diodes will eventually be used in a multiplier chain to the THz frequency range.