Pure Si at 500 K has equal number of electron (n_e ) and hole (n_h ) concentration of 1.5 × 10^16 m^(-3). Doping by indium increases n_h to 4.5 × 10^22 m^(-3). The doped semiconductor is of

Q: Pure Si at 500 K has equal number of electron (n_e ) and hole (n_h ) concentration of 1.5 × 10¹⁶ m^-3. Doping by indium increases n_h to 4.5 × 10²² m^-3. The doped semiconductor is of

(a) n-type with electron concentration n_e = 2.5 × 10²³ m^-3

(b) p-type having electron concentration n_e = 5 × 10⁹ m^-3

(c) n-type with electron concentration n_e = 5 × 10²² m^-3

(d) p-type with electron concentration n_e = 2.5 × 10¹⁰ m^-3

Ans: (b)

Sol: n_i² = n_e n_h

(1.5 × 10¹⁶ )² = n_e (4.5 × 10²² )

n_e = 0.5 × 10¹⁰ =5 × 10⁹

n_h = 4.5 × 10²²

n_h > n_e (p-type)