Consider the following statements about semiconductors.
I. | Silicon doped with electron-rich impurity is a p-type semiconductor. |
II. | Silicon doped with an electron-rich impurity is an n-type semiconductor. |
III. | Delocalised electrons increase the conductivity of doped silicon. |
IV. | An electron vacancy increases the conductivity of n-type semiconductor. |
1. I and II
2. II and III
3. III and IV
4. I and IV