A semiconductor is known to have an electron concentration of $8\times {10}^{13}$ cm^-3 and a hole concentration of $5\times {10}^2$ cm^-3. The semiconductor is:

1.  n-type

2.  p-type

3.  intrinsic

4.  insulator

If a small amount of aluminium is added to the silicon crystal:

Pure Si at 500 K has equal number of electron $\left(n_{\mathit{e}}\right)$ and hole $\left(n_{\mathit{h}}\right)$ concentration of $1.5\times {10}^{\mathrm{16 }}{\mathrm{m}}^{-3}.$ Doping by indium increases $n_{\mathit{h}}$ to $4.5\times {10}^{22}$ ${\mathrm{m}}^{-3}.$ The doped semiconductor is of:

A Ge specimen is doped with Al. The concentration of acceptor atoms is $~{10}^{21}$ $\mathrm{atoms}/{\mathrm{m}}^3$. Given that the intrinsic concentration of electron hole pairs is $~{10}^{19}/{\mathrm{m}}^3$, the concentration of electrons in the specimen is:

In a semiconducting material, the mobilities of electrons and holes are ${\mathrm{\mu }}_{\mathrm{e}}$ and ${\mathrm{\mu }}_{\mathrm{h}}$ respectively. Which of the following is true?
1. \(\mu_{e} > \mu _{h}\)
2. \(\mu_{e} < \mu _{h}\)
3. \(\mu_{e} = \mu _{h}\)
4. \(\mu_{e} <0; ~\mu _{h}>0\)

The net charges on $\mathrm{p}$-type semiconductor and $\mathrm{n}$-type semiconductor are, respectively:

1. Positive, negative

2. Negative, positive

3. Positive, positive

4. Zero, zero