Microwave Photoinduced Varactor on Silicon Substrate

In this paper, we show that when a metallic microstrip line deposited on silicon is illuminated at its end while its entry is being connected to an ultra high frequency generator, a photoinduced load is obtained at its extremity. It is proven by experimental and simulation results that this load behaves as a « photoinduced varactor ». An equivalent circuit composed of a resistance and a capacitance in parallel is found to fit the component behaviour accurately. The dependence of these discrete elements on the DC applied voltage, the frequency and the illumination optical power is highlighted. A strong non-linear variation with the DC applied voltage is pointed out.