Physical and electrical properties of thermally oxidized dielectrics on Si-capped Ge-on-Si substrate.

Thermal oxidation of silicon (Si)-capped germanium (Ge) epilayer on Si substrate is performed to study the effect of the physical interface on the electrical properties of Ge metal-oxide-semiconductor capacitors. During the growth and oxidation of the Si cap layer, Ge atoms diffuse through the Si cap layer, and they are oxidized to GeO2. Once the Si cap layer is consumed, more Ge suboxides are generated, resulting in the serious degradation of the capacitance-voltage characteristics. Both the positive fixed charges generated by the evaporation of GeO and the negative fixed charges induced by the formation of Si-O- dangling bonds are proposed to affect the flat-band voltage shifts. These results suggest that the deposition of a thin Si cap layer on Ge is effective in suppressing the generation of Ge sub-oxides during thermal oxidation, thereby improving the performance of Ge capacitors. [ABSTRACT FROM AUTHOR]