NO 2 sensor based on InP epitaxial thin layers

n-InP epitaxial thin layers are exposed to concentrations of a diluted oxidizing gas: NO2. In the presence of this gas, the resistance measured parallel to the surface of the InP layer, between ohmic contacts, increases. The magnitude of its variations depends on several parameters: the operating temperature, the thickness and the doping concentration level of the InP layer, and the gas concentration. A theoretical model of the action of the gas is proposed, mixing chemisorption equilibrium and surface field effect. The experimental results are in agreement with the theoretical predictions.