Which of the following statements is/are not correct?

1. The conductance of metals decreases with an increase in temperature.
2. p-type of conduction is observed in compounds like Fe1-YO and Fe1-YS.
3. Extrinsic semiconductors are semiconductors due to thermal defects.

Intrinsic semiconductors are semiconductors due to thermal defects. At 0K, pure Si or Ge act as insulators, however at higher temperatures, some of the covalent bonds are broken and the electrons so released become free to move in the crystal and thus conduct electricity. Extrinsic semiconductors are semiconductors due to impurity defects. Si and Ge (group 14 elements) in pure state have very low electrical conductivity. Their electrical conductivity can be enhanced by the addition of traces of elements belonging to group 13 and 15. Introduction of group 13 or 15 elements to the crystal lattice of group 14 elements p-type and n-type semiconductors respectively. The process of adding impurities is called doping.