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Q. 14.8  The number of silicon atoms per m3 is  5\times 10^{28}.  This is doped simultaneously with 5\times 10^{22}.  atoms per  m^{3} of Arsenic and  5\times 10^{20}  per m^{3}  atoms  of Indium. Calculate the number of electrons and holes. Given that  n_{i}=1.5\times 10^{16}\; m^{-3}.  Is the material n-type or p-type ?

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number of Silicon atoms per  m^{3}   =  5\times 10^{28}.

number of Arsenic atoms per  m^{3} =  5\times 10^{22}.

number of Indium atoms per  m^{3}  =  5\times 10^{20}

number of thermally generated electrons n_{i}=1.5\times 10^{16}\; m^{-3}.


Number of electrons

 n_e = 5 * 10 ^{22}-1.5*10^{16} = 4.99*10^{22}(approx)

number of holes is n_h 

in thermal equilibrium 



n_h= (1.5*10^{16})^2/4.99*10^{22}

n_h= 4.51 * 10^9

Now, since the number of electrons is higher than number of holes, it is an n-type semiconductor.

Posted by

Pankaj Sanodiya

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