Question

A semiconductor has an electron concentration of $8\times {10}^{13}$ per ${cm}^3$ and a hole concentration of $5\times {10}^{12}$ per ${cm}^3$. The electron mobility is $25000{cm}^2{V}^{-1}{s}^{-1}$ and the hole mobility is $100{cm}^2{V}^{-1}{s}^{-1}$. Then,

• A. The semiconductor is $n-$type
• B. The conductivity is 320 m mho ${cm}^{-1}$
• C. Both (a) and (b)
• D. None of the above

Answer 1

Answer: (C)

Both (a) and (b)

$n_e=8\times {10}^{13}/c{m}^3$

$n_h=5\times {10}^{12}/c{m}^3$

${\mu }_e=25000c{m}^2/\left(Vs\right)$

${\mu }_h=100c{m}^2/\left(Vs\right)$

Since $n_e>n_h$, the semiconductor is n-type.

The conductivity of the semi conductor is $e(n_e{\mu }_e+n_h{\mu }_h)$

$=1.6\times {10}^{19}\left(\right(8\times {10}^{13}\left)\right(25000)+(5\times {10}^{12}\left)\right(100\left)\right)mho/cm$

$=0.32mhoc{m}^{-1}$

$=320mmhoc{m}^{-1}$