a) If germanium is to be used as the base semiconductor and is doped with aluminum, is the result an n-type or a p-type semiconductor and why? b) Are these impurity atoms "donors" or "acceptors"? c) Sketch an energy-level diagram showing the filled, allowed, and forbidden bands in an intrinsic semiconductor such as silicon or germanium at room temperature. Then sketch the same kind of diagram with the Al impurity atoms present as in a) above.