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

Which of the following is correct for \(\mathrm{n}\)-type semiconductors?

In semiconductors, which of the following gives the law of mass action?
(where symbols have their usual meanings.)
1. \(n_i=n_e=n_h\)
2. \(n_i^2=n_en_h\)
3. \(n_h>> n_e\)
4. \(n_h<<n_e\)

The conductivity of an n-type semiconductor whose density of conduction electrons is ${\mathrm{n}}_{\mathrm{e}}$, Density of holes is ${\mathrm{n}}_{\mathrm{h}}$, Mobility of conduction electrons is ${\mathrm{m}}_{\mathrm{e}}$and Mobility of holes is ${\mathrm{m}}_{\mathrm{h}},$ will be

1.  $\mathrm{e}\left[{\mathrm{n}}_{\mathrm{e}}{\mathrm{m}}_{\mathrm{h}} + {\mathrm{n}}_{\mathrm{e}}{\mathrm{m}}_{\mathrm{e}}\right]$

2.  $\mathrm{e}\left[{\mathrm{n}}_{\mathrm{e}}{\mathrm{m}}_{\mathrm{e}} + {\mathrm{n}}_{\mathrm{h}}{\mathrm{m}}_{\mathrm{e}}\right]$

3.  ${\mathrm{en}}_{\mathrm{e}}\left[{\mathrm{m}}_{\mathrm{e}} + {\mathrm{m}}_{\mathrm{h}}\right]$

4.  $\mathrm{e}\left[{\mathrm{n}}_{\mathrm{e}}{\mathrm{m}}_{\mathrm{e}} + {\mathrm{n}}_{\mathrm{h}}{\mathrm{m}}_{\mathrm{h}}\right]$

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

C and Si both have same lattice structure,having 4 bonding electrons in each.However, C is insulator whereas Si is intrinsic semiconductor. This is because 

1. in case of C, the valence band is not completely filled at absolute zero temperature

2. in case of C,the condition band is partly filled even at absolute zero temperature 

3. the four bonding electrons in the case of C lie in the second orbit,Whereas in the case of Si they lie in the third

4 .the four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit

If a small amount of antimony is added to germanium crystal

(1) the antimony becomes an acceptor atom

(2) there will be more free electrons than holes in the semiconductor

(3) its resistance is increased

(4) it becomes a p-type semiconductor

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:

Which one of the following statement is false?

(1) Pure Si doped with trivalent impurities gives a p-type semiconductor 

(2) Majority carries in a n-type semiconductor are holes

(3) Minority carries in a p-type semiconductor are electrons

(4) The resistance of intrinsic semiconductor decreases with increase of temperature 

The cut-in voltage for silicon diode is approximately

(1) 0.2 V                       

(2) 0.6 V

(3) 1.1 V                       

(4) 1.4 V