CHARACTERISTICS OF DIODE HUMIDITY SENSORS BASED ON SNO2-SENSING PROPERTIES

The structure investigated consists of a surface p-n junction formed b y a planar n+ diffusion region in p-type Si substrate. The silicon sur face is covered with thermally grown SiO2 and on top of it an SnO2 lay er is deposited and electrically connected to the n+ region. A pulsed voltage V is applied to the n' region contact and the substrate-to-gro und current pulses are recorded at forward bias conditions. When water vapours are present in the air, significant and reversible variations of the current are observed (the current increases more than 2 to 3 t imes). A model is proposed for explanation of this effect based on mod ulation of the p-n junction barrier by polarized water molecules. A go od agreement between theoretical calculations and experimental data is obtained.