Charge storage by irradiation with UV light in non-biased MNOS structures

Charge storage in non-biased MNOS (Metal-Nitride-Oxide-Semiconductor) structures effected by irradiation with UV light has been investigated. The electrons generated by internal photoemission at the Si surface are trapped at the SiO₂Si₃N₄-interface and inside the Si₃N₄. The resulting charge storage in the insulator can be determined by capacitance technique. The observed positive voltage shift in C-V-characteristics depends on photon energy as well as on radiant exposure. The charge storage occurs in three stpes which can be related to various types of traps. The charged structure can partially be discharged by irradiation with light of less energy than needed for the storage process.