Question

When a piece of pure silicon is doped with aluminium then?

Answer 1

Silicon is having 4 electrons in its outermost orbit so it can make four bonds,but if it is having a unbounded electron as u are saying, & if you add aluminium to silicon crystal , as aluminium is having one electron deficiency which is fulfilled by unbounded silicon electron and it will become neutral and it will neither behave as a p-type nor as n-type.