The electron mobility in $N$-type germanium is $3900 \ cm^2/V \cdot s$ and its conductivity is $6.24 \ mho/cm$. If the effect of holes is negligible,what is the impurity concentration?

Consider an $n$-type semiconductor in which $n_e$ and $n_h$ are the number of electrons and holes,respectively.
$(A)$ Holes are minority carriers.
$(B)$ The dopant is a pentavalent atom.
$(C)$ $n_e n_h \neq n_i^2$ (where $n_i$ is the number of electrons or holes in the semiconductor when it is in its intrinsic form).
$(D)$ $n_e n_h \geq n_i^2$.
$(E)$ The holes are not generated due to the donors.
Choose the correct answer from the options given below.

In a $p$-type semiconductor,which of the following statements is true?

For pure $Ge$,the intrinsic carrier density is $10^{19} \ m^{-3}$. If donor impurity is added with a density of $10^{23} \ m^{-3}$,what will be the hole density (in $m^{-3}$)?

$P-$type semiconductor is formed when:

In a sample of pure silicon,$10^{13} \text{ atoms/cm}^3$ of phosphorus is added. If all donor atoms are active,what will be the resistivity at $20 ^oC$ if the mobility of electrons is $1200 \text{ cm}^2/\text{V} \cdot \text{s}$? (in $\Omega \cdot \text{cm}$)