Electronics - Semiconductor Principles - Discussion

For silicon it is 0.7 and germanium it is 0.3 because, for silicon the energy gap is 1.1ev, i.e the valency band and conduction band gap is 1.21ev.

Hence in order to move the electron from valency band to conduction bad we need large amount of energy in any form. If it is voltage then it require 0.7v.

And for germanium, the energy gap is 0.78ev. Hence campare to silicon it is less gap. Hence less amount of energy is required that is 0.3v.

Germanium transistors have much lower forward voltage drop (0.1 volt) than silicon transistors (0.6 volt).

For silicon its 0.7 and for germanium 0.3 is the correct answer.

Forbidden gap energy for Ge is 0.7ev and 1.1 for Si.