High performance GaAs quasi-planar varactors for millimeter waves

A novel quasi-planar and highly reliable varactor configuration has been developed to batch fabricate fully passivated GaAs Schottky varactors with near ideal characteristics and state of the art performance. Typically, they exhibit at zero bias a junction capacitance of 0.12 pF and a cutoff frequency in excess of 700 GHz when measured at 70 GHz. As frequency doublers (∼ 35 to 70 GHz) and triplers (35 to 105 GHz), efficiencies greater than 40 and 25 percent, respectively, have been achieved. In a parametric amplifier pumped at 105 GHz and operated in the 55- to 65-GHz signal frequency band, a gain of 14 dB, a 1-dB bandwidth of 670 MHz, and a single sideband noise factor of 5.9 dB were achieved.