Yttrium passivation of defects in GeO$_{2}$ and GeO$_{2}$/Ge interfaces

Abstract

Alloying amorphous GeO${2}$ with Y${2}$O${3}$ has been found experimentally to improve its chemical stability and electrical reliability as a gate dielectric in Ge-based field effect transistors. The mechanism is explained here based on density functional calculations. The GeO${2}$ reliability problem is correlated with oxygen deficiency defects, which generate gap states near the band-edges of the underlying Ge. These can be passivated through Y doping. This shifts the defect gap state out of the gap up into the GeO${2}$ conduction band, thus effectively passivating gap states in the GeO${2}$ layer.