Which of the following metals is an important ingredient of transistors?

Transistor has semi-conductors and semi-conductors are those whose conductivity lies between metals and non-metals.

Sodium is highly reactive, thereby cannot used as semi-conductor. Gold is very less reactive metal, thereby not acts as a semi-conductor. Germanium acts as semi-conductor at a particular temperature. Osmium has a high density and extremely hard. It is very difficult to work with Osmium and is not used as semi-conductor.