Interface engineering for Ge metal-oxide-semiconductor devices

Abstract High mobility semiconductors such as Ge with high- k gates may be required to enhance performance of future devices. One of the biggest challenges for the development of a Ge metal-oxide–semiconductor (MOS) technology is to find appropriate passivating materials and methodologies for the Ge/high- k interfaces. Germanium oxynitride is frequently used as a passivating interlayer in combination with HfO 2 and is found to be necessary for the fabrication of functional devices. However, it is also considered to be insufficient since electrical characteristics in capacitors are non-ideal and field effect transistors underperform, probably due to a the high density of interface defects. We show that alternative passivating rare earth oxide layers prepared by molecular beam deposition produce improved electrical characteristics and a significant reduction of the density of interface states. In the case of CeO 2 , a thick interfacial layer is spontaneously formed containing oxidized Ge, which is considered to be the key for the observed improvements.