Question

What is the conductivity of a semiconductor sample having electron concentration of $5\times {10}^{18}{m}^{-3}$ , hole concentration of $5\times {10}^{19}{m}^{-3}$ , electron mobility of 2.0 $m^2{v}^{-1}{s}^{-1}$ and hole mobility of 0.01 $m^2{v}^{-1}{s}^{-1}$ ?
(Take charge of electron as $1.6\times {10}^{-19}C$ )

• A. $1.68(\Omega -m{)}^{-1}$
• B. $0.59(\Omega -m{)}^{-1}$
• C. $1.83(\Omega -m{)}^{-1}$
• D. $1.20(\Omega -m{)}^{-1}$

Answer 1

The correct option is A $1.68(\Omega -m{)}^{-1}$

Given :
Hole concentration $n_h=5\times {10}^{19}{m}^{-3}$
Hole mobility ${\mu }_h=0.01m^2{v}^{-1}{s}^{-1}$
Electron concentration $n_e=5\times {10}^{18}{m}^{-3}$
Electron concentration ${\mu }_e=2m^2{v}^{-1}{s}^{-1}$
Conductivity of semiconductor $\sigma =e(n_e{\mu }_e+n_h{\mu }_h)$
$\therefore$ $\sigma =(1.6\times {10}^{-19})\left[\right(5\times {10}^{18}\left)\right(2)+(5\times {10}^{19}\left)\right(0.01\left)\right]$
$⟹\sigma =1.68(\Omega -m{)}^{-1}$