Electrical properties of thermally oxidised porous silicon

Results obtained for thermally oxidized porous silicon MOS structures are presented. In particular, fixed oxide charge densities exhibited by the oxide and high field conduction data are presented. From high-frequency (1 MHz) capacitance/voltage plots the flatband voltages were determined for a range of oxide thicknesses. The current/voltage characteristics of a 2100-Å oxide, for both polarities of gate voltage, are shown. The plot demonstrates an asymmetry in conduction with a higher electron injection from the metal. Analysis of the corresponding Fowler-Nordheim plots, taking an effective mass of electron in the oxide of 0.5, yields barrier heights to electron emission of 1.4 eV and 2.7 eV, for injection for the metal and semiconductor, respectively. The barrier height for injection from the metal into the oxide was found to be consistently lower than the value of 3.15 eV expected for aluminum on thermally grown silicon dioxide