Pure `Si` at `500K` has equal number of electron `(n_(e))` and hole `(n_(h))` concentration of `1.5xx10^(16)m^(-3)`. Dopping by indium. Increases `n_(h)` to `4.5xx10^(22) m^(-3)`. The doped semiconductor is of

Options

A. n-type withelectron concentration
`n_e=2.5xx10^23 m^(-3)`
B. p-type having electron concentration
`n_e=5xx10^9 m^(-3)`
C. n-type withelectron concentration `n_e=5xx10^22 m^(-3)`
D. p-type with electron concentration
`n_e=2.5xx10^10 m^(-3)`

Answer

B

Explanation

`because n_hn_e=n_i^2`
`therefore n_e=n_i^2/n_h=(1.5xx10^16xx1.5xx10^16)/(4.5xx10^22)`
`therefore` Electron concentration `(n_e) = 0.5 xx 10^10 = 5xx10^9//m^3`
Thus `(4.5xx10^22) gt gt (5xx10^9)` or `n_h gt gt n_e`
Hence it is a p-type semiconductor
Doping by indium , converts pure silicon into a p-type semiconductor