Gas sensing properties of pseudo-Schottky diodes on p-type indium phosphide substrates: Application to O3 and NO2 monitoring in urban ambient air

In this paper, we present a carrier exchange gas sensing mechanism on Schottky diode-type gas sensors. This modification of carrier density reflects on the artificially enhanced barrier height of the device due to the post metallization growth of a thin counter-doped semiconductor layer. Realized on p-type InP substrates, pseudo-Schottky diodes provide a n-type InP layer just beneath the Schottky metal contact which enables detection of strongly oxidizing species with no interferences coming from reducing ones. As sensitivity towards NO2 and O3 is very high even for gas concentrations commonly found into the atmosphere, these sensors can operate in real atmosphere conditions to monitor these two criteria pollutants. Limitations to their use come from response kinetics and long-term aging effects.