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

Options

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

Answer

D

Explanation

`n_i^2 =n_en_h`
`(1.5xx10^16)^2 = n_e (4.5xx10^22)`
`rArr n_e = 0.5 xx 10^10 or n_e = 5 xx 10^(19)`
Given `n_h = 4.5 xx 10^22 rArr n_h > >n_e`
`:.` Semiconductor is p-type and `n_e = 5 xx 10^9 m^(-3)` .