$A$ transistor is a/an

When phosphorus and antimony are mixed in germanium,then:

The most commonly used material for making transistors is

The valence of an impurity added to germanium crystal in order to convert it into a $P-$type semiconductor is

What is the relation between the number density of holes $(n_h)$ and free electrons $(n_e)$ in an intrinsic semiconductor at room temperature?

In a semiconductor,the number density of intrinsic charge carriers at $27^{\circ} \text{C}$ is $1.5 \times 10^{16} \, \text{m}^{-3}$. If the semiconductor is doped with impurity atoms,the hole density increases to $4.5 \times 10^{22} \, \text{m}^{-3}$. The electron density in the doped semiconductor is $..... \times 10^{9} \, \text{m}^{-3}$.