Modulation of the charge of germanium MIS structures with fluorine-containing insulators

An insulator layer of ErF$_{3}$, YF$_{3}$, NdF$_{3}$, and TmF$_{3}$ was formed in $n$-type Ge-based MIS (metal–insulator–semiconductor) structures. It is shown that no negative effective charge is observed in these Ge MIS structures, while the degradation of electric characteristics and the rise of density of surface states leads to an increase in the positive charge. The positive charge formed at the Ge–rare-earth-element fluoride interface can compensate the negative charge of dangling bonds on the surface of Ge, which is potentially promising for modulation of the charge magnitude and sign in MIS devices based on Ge.