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Physics Question on Semiconductor electronics: materials, devices and simple circuits

Pure silicon at 300 K has equal electron (ne_e) and hole (nh_h) concentration of 1.5×1016m−31.5 \times 10^{16} m^{-3}. Doping by indium increases nhn_h to 4.5×1022m−34.5 \times 10^{22}m^{-3} The nen_e in the doped silicon is

A

9×1059 \times 10^5

B

5×1095 \times 10^9

C

2.25×10112.25 \times 10^{11}

D

3×10193 \times 10^{19}

Answer

5×1095 \times 10^9

Explanation

Solution

In an extrinsic semiconductor
       nenh=(ni)2\, \, \, \, \, \, \, n_en_h =(n_i)^2
ne×4.5×1022=(1.5×1016)2n_e \times 4.5 \times 10^{22} =(1.5 \times 10^{16})^2
        ne=2.25×10324.5×1022\, \, \, \, \, \, \, \, n_e =\frac{2.25 \times 10^{32}}{4.5 \times 10^{22}}
        ne=5×109\, \, \, \, \, \, \, \, n_e =5 \times 10^9