Ge is doped with As. Due to doping,

When germanium (Ge), a group-IV element, is doped with arsenic (As), a group-V element, it creates an n-type semiconductor. Arsenic contributes extra electrons (conduction electrons) to the material because it has five valence electrons compared to four in germanium. These extra electrons become free to conduct electricity, thus increasing the number of conduction electrons. Thus, the effect of doping Ge with As is :

the number of conduction electrons increases.