$A$ silicon sample is made into a $p$-type semiconductor by doping. Indium atoms are added at a rate of one atom per $5 \times 10^7$ silicon atoms. If the number density of silicon is $5 \times 10^{28} \text{ atoms/m}^3$,calculate the number density of acceptor atoms per $\text{cm}^3$.

In the energy band diagram of a material shown in the figure,the open circles and filled circles denote holes and electrons,respectively. The material 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.

In an $N$-type $Ge$ semiconductor,the mobility of electrons is $5000 \ cm^2/V \cdot s$ and the conductivity is $5 \ mho/cm$. If the effect of holes is negligible,what is the concentration of impurity atoms?

The charge carriers in a $p$-type semiconductor are

To obtain a $P$-type germanium semiconductor,it must be doped with