Which of the following statements about doped semiconductors are correct?

1. ASilicon doped with boron is p-type, with holes as the majority carriers.
2. BIn antimony-doped silicon, the donor level lies just below the conduction band.
3. CAn n-type semiconductor carries a net negative charge because of the extra electrons.
4. DAt very high temperature the conductivity of a doped semiconductor approaches intrinsic behaviour.