Dynamics of metal-SiO_x and SiO_xSi interfaces and the associated instabilities in practical metal/insulator/semiconductor structures

X-ray photoelectron spectroscopy, Auger electron spectroscopy and ellipsometry measurements were performed at CrSiO_x and YbSiO_x interfaces, which are being considered for metal/insulator/semiconductor (MIS) solar cell applications. These measurements have led to a knowledge of instability mechanisms associated with MIS solar cells. The dynamics of the metal-oxide interface reduce the effective thickness of the insulating SiO_x layer. Typically, in a 3 week period after fabrication the oxide thickness decreases by about 2 Å for ytterbium MIS structures and by less than 1 Å for chromium MIS structures. A structural equilibrium is reached thereafter. To explore further the dependence of MIS Schottky barrier heights on oxide thickness variations (from about 5 to 20 Å) a comprehensive charge balance analysis was performed at a general MIS interface. This theoretical study supports experimental data on barrier heights and also on instabilities. In addition, the application of the theoretical model to the experimental barrier heights has yielded quantitative information regarding the density of interface states at the SiO_xSi interface.