The density of electrons and holes in a pure germanium sample at room temperature are equal and its value is 3× 1016 per m3 . On doping with aluminium, it increases to 4.5× 1022 per m3 . Then, the electron density in doped germanium is nearly,

Question

The density of electrons and holes in a pure germanium sample at room temperature are equal and its value is 3× 1016 per m3 . On doping with aluminium, it increases to 4.5× 1022 per m3 . Then, the electron density in doped germanium is nearly, (A) 2× 1010m- 3 (B) 5× 109m- 3 (C) 4.5× 10- 10m- 3 (D) 3× 109m- 3

Tardigrade Admin · Accepted Answer

The electron and hole concentration in a semiconductor in thermal equilibrium is given by, nenh=ni2 ne=(ni2/nh)=((3 × (10)16)2/4 . 5 × (10)22)≈2× (10)10m- 3 .

Q. The density of electrons and holes in a pure germanium sample at room temperature are equal and its value is $3 \times 1 0^{16}$ per $m^{3}$ . On doping with aluminium, it increases to $4.5 \times 1 0^{22}$ per $m^{3}$ . Then, the electron density in doped germanium is nearly,

$2 \times 1 0^{10} m^{- 3}$

$5 \times 1 0^{9} m^{- 3}$

$4.5 \times 1 0^{- 10} m^{- 3}$

$3 \times 1 0^{9} m^{- 3}$

The electron and hole concentration in a semiconductor in thermal equilibrium is given by,
$n_{e} n_{h} = n_{i}^{2}$
$n_{e} = \frac{n _{i}^{2}}{n _{h}} = \frac{( 3 \times ( 10 ) ^{16} ) ^{2}}{4.5 \times ( 10 ) ^{22}} \approx 2 \times (10)^{10} m^{- 3}$ .

Q. The density of electrons and holes in a pure germanium sample at room temperature are equal and its value is 3×1016 per m3 . On doping with aluminium, it increases to 4.5×1022 per m3 . Then, the electron density in doped germanium is nearly,

2×1010m−3

5×109m−3

4.5×10−10m−3

3×109m−3