The electrons in the conduction band of a semiconductor are called .......

If the lattice constant of this semiconductor is decreased,then which of the following is correct?

$A$ solid which is not transparent to visible light and whose conductivity increases with temperature is formed by

If the lattice constant of this semiconductor decreases,which of the following is true?

Read the following statements carefully:
$Y:$ The resistivity of a semiconductor decreases with an increase in temperature.
$Z:$ In a conducting solid,the rate of collision between free electrons and ions increases with an increase in temperature.
Select the correct statement from the following:

What is the band gap energy for Germanium $(Ge)$?