Question

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

(1) n–type; with electron concentration of 5 x 10²² m^-3

(2) p–type; with electron concentration of 2.5 x 10¹⁰ m^-3

(3) n–type; with electron concentration of 2.5 x 1023 m^-3

(4) p–type; with electron concentration of 5 x 109 m^-3

Answer 1

(4) p–type; with electron concentration of 5 x 109 m^-3

Given ne = 1.5 x 10¹⁶ m^-3, nh = 4.5 x 10²² m^-3 

Let n_e be the concentration of electrons we know

Since n_h > n_e ; the material as a p–type semiconductor. The electron concentration = n_e = 5 x 10⁹ m^-3 .