InP/InGaAs Photovaractor

We report a zero-bias photovaractor that operates up to 60 GHz. The capacitance change is based on the decrease of depletion width and the steep increase of the effective area after illumination. With photocurrent of 12 mA, the reactance at 60 GHz is changed by 280 times relative to the dark condition. S11 parameter fitting shows that the capacitance of a 50-μm diameter device increases by 37 times after illumination. Good agreement is achieved between theory and measured results.