The Role of Quantum Confinement in Porous Silicon Gas Sensors

Quantum confinement in nanostructured porous silicon is strongly affected by surface geometry irregularities. We have developed a method based on a variational principle for calculating volume and surface electronic states in such structures. Modelling the gas-surface interaction with the variation of the confining potential, we give a clear indication that the photo-luminescence may be used as a sensing signal. A new mechanism for donor (acceptor) impurities ionization is suggested and the implication for the charge transport discussed. Finally, we show that the nanostructure surface geometrical irregularities induce a new type of carrier surface trapping which may significantly enhance the gas reactivity.