Millimetre-wave frequency tripling using stacked heterostructure-barrier varactors on InP

Heterostructure-barrier varactors (HBVs) reported previously had limited power output. By using a pseudomorphic In0.52Al0.48As/AlAs/In0.52Al0.48As barrier with good current blocking characteristics and stacking three MBE-grown varactor layers, we achieve a symmetric stacked varactor on InP with low leakage and high breakdown voltage (~14 V). Tripler experiments at Ka band using these varactors give 20 dBm output with 7 dB conversion loss using a waveguide multiplier, and 10.8 dBm with 11 dB conversion loss using a microstrip circuit. These are the first HBVs to demonstrate reduced device capacitance per unit area and freedom from resistive tripling effects.