GaAs single-barrier varactors for millimeter-wave triplers: guidelines for enhanced performance

Earlier single-barrier varactors (SBVs) fabricated on GaAs suffered from low Q because of leaky barriers. By placing a thin AlAs layer in the center of an Al0.4Ga0.6As barrier, and using In0.2Ga0.8As spacers, one can increase the effective barrier height, thereby achieving SBVs with both high Q and good capacitance-modulation characteristics. Simulation of a 192-GHz tripler using these varactors shows purely reactive multiplication, without the output-power saturation both predicted and observed in triplers using leaky-barrier SBVs