Silicon has replaced germanium since the 1960's. Si is used for all semiconductors I work with, diodes, bjt, FET, photodiode, except for the LED. An LED is made from a compund semiconductor known as a "III-V compound". The "III-V" refers to groups III & V on the periodic chart of elements. Such compounds include GaAs, GaN, GaP, etc. The emission is much higher than group IV elements like Si, Ge, SiC, etc.
Silicon is abundant, has high temperature capability, forms great oxides which insulate and stabilize the semiconductor material, and gives good performance for semiconductor devices except LEDs.
Germanium has recently been combined with silicon to produce a bjt device. The Si-Ge combo offers high beta with low rbb' (base spreading resistance). It is useful in the base region of the bjt.
Off the top of my head, that is what I can recall. I'm too young to have worked with Ge devices, but several of my bosses who mentored me did work with Ge. Ge had high leakage current, which got worse at higher temp. Their upper temp limit is less than Si. But a Ge p-n junction has a low forward voltage drop. A Ge diode/bjt drops around 0.20-0.35V across a p-n junction, vs. 0.60-0.70V for Si.
Does this help?