This paper presents the fabrication and characterization of four-barrier pl
anar heterostructure-barrier-varactors (HBVs) to be used in frequency tripl
ers. The fabrication process and the DC and RF testing results are discusse
d. The measured results are evaluated by a newly developed combined genetic
algorithm/harmonic balance simulator to calculate the optimum impedance an
d output power at 255 GHz. Different HBV structures were fabricated, and a
comparison of their conversion efficiency is presented.