K. Krishnamurthi et al., GAAS SINGLE-BARRIER VARACTORS FOR MILLIMETER-WAVE TRIPLERS - GUIDELINES FOR ENHANCED PERFORMANCE, IEEE transactions on microwave theory and techniques, 42(12), 1994, pp. 2512-2516
Earlier single-barrier varactors (SBVs) fabricated on GaAs suffered fr
om low and 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 and good capacitance-modulation characteristics.
Simulation of a 192-GHz tripler using these varactors shows purely re
active multiplication, without the output-power saturation both predic
ted and observed in triplers using leaky-barrier SBVs.