A small percentage of impurity is added to an intrinsic semiconductor at $300 \: K$. Which one of the following statements is true for the energy band diagram shown in the following figure?
- Intrinsic semiconductor doped with pentavalent atoms to form $n$-type semiconductor.
- Intrinsic semiconductor doped with trivalent atoms to form $n$-type semiconductor.
- Intrinsic semiconductor doped with pentavalent atoms to form $p$-type semiconductor.
- Intrinsic semiconductor doped with trivalent atoms to form $p$-type semiconductor.