A porous silicon JFET gas sensor: Experimental and modeling

In this work, electrical measurements and modeling of an integrated porous silicon (PS) JFET (PSJFET) gas sensor are reported. The experimental I_DS-V_DS curves were measured for different V_GS voltages, both in synthetic air and in presence of 300 ppb of NO₂. The modeling was carried out by taking both the PS layer and the FET structure into account. By best fitting the experimental data with the given model, a quantitative evaluation of the effect of NO₂ on both the PS layer and the FET structure was performed. Firstly, an indirect estimation of the PS resistance values in air (R_{PS_AIR}~31 kOmega) and in NO₂ (R_{PS_NO2}~3.2 kOmega) was achieved, in agreement with data reported in literature and acquired by direct electrical measurements on PS. Moreover, it was also estimated that exposure to 300 ppb of NO₂ resulted in a reduction of the FET channel section of ~0.2 mum, with respect to air.