Question

Pure silicon at 300K has equal electron $ ({{n}_{e}}) $ and hole $ ({{n}_{h}}) $ concentration of $ 1.5\times {{10}^{16}}{{m}^{-3}}. $ Doping by indium increase $ ({{n}_{h}}) $ to $ 4.5\times {{10}^{22}}{{m}^{-3}}. $ The $ ({{n}_{e}}) $ in the doped silicon is

• A. $ 9\times {{10}^{5}} $
• B. $ 5\times {{10}^{9}} $
• C. $ 2.25\times {{10}^{11}} $
• D. $ 3\times {{10}^{19}} $

Answer 1

Answer: (B)

$ {{n}_{e}}{{n}_{h}}={{({{n}_{i}})}^{2}} $ $ {{n}_{e}}\times 4.5\times {{10}^{22}}={{(1.5\times {{10}^{16}})}^{2}} $ $ {{n}_{e}}=\frac{2.25\times {{10}^{32}}}{4.5\times {{10}^{22}}} $ $ {{n}_{e}}=5\times {{10}^{9}} $