If the ratio of the number density of electrons to the number density of holes in a semiconductor is $7/5$ and the ratio of their currents is $7/4$,what is the ratio of their drift velocities?

Which statement is correct regarding the charge of doped semiconductors?

What is the number density of donor atoms which must be added to a pure germanium semiconductor to make an $n$-type semiconductor of conductivity $6.4 \ \Omega^{-1} \ cm^{-1}$? The mobility of electrons in $n$-type germanium is $4 \times 10^3 \ cm^2 \ V^{-1} \ s^{-1}$. Neglect the contribution of holes to conductivity.

At a temperature of $500 \ K$,the intrinsic electron number density $(n_e)$ and hole number density $(n_h)$ in a pure semiconductor are equal to $1.5 \times 10^{16} \ m^{-3}$. Now,by adding indium impurity,the hole density $(n_h)$ increases to $4.5 \times 10^{22} \ m^{-3}$. This doped semiconductor is:

Suppose an $n$-type wafer is created by doping $Si$ crystal having $5 \times 10^{28} \text{ atoms/m}^3$ with $1 \text{ ppm}$ concentration of $As$. On the surface,$200 \text{ ppm}$ Boron is added to create a $p$-region in this wafer. Considering $n_i = 1.5 \times 10^{16} \text{ m}^{-3}$,$(i)$ Calculate the densities of the charge carriers in the $n$ and $p$ regions. $(ii)$ Comment on which charge carriers would contribute largely to the reverse saturation current when the diode is reverse biased.

Which of the following statements is incorrect?