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KVPY Sample Paper KVPY Stream-SX Model Paper-15

  • question_answer
    Mobility of electrons in a semiconductor is defined as the ratio of their drift velocity to the applied electric field. If, for an n-type semiconductor, the density of electrons is \[{{10}^{19}}{{\text{m}}^{-3}}\] and their mobility is \[\text{1}\text{.6}\,\text{,}{{\text{m}}^{\text{2}}}\]/(V.s) then the resistivity of the semiconductor (since it is an n-type semiconductor contribution of holes is ignored) is close to:

    A) \[2\,\,\Omega \,m\]

    B) \[0.4\,\,\Omega m\]

    C) \[4\,\,\Omega m\]

    D) \[0.2\,\,\Omega m\]        

    Correct Answer: B

    Solution :

    \[j\,=\,\sigma \text{E}\,=\,\text{ne}{{\text{v}}_{d}}\] \[\sigma \,=\,ne\,\frac{{{v}_{d}}}{\text{E}}\,=\,ne\mu \] \[\frac{1}{\sigma }\,=\rho \,=\,\frac{1}{{{n}_{e}}e{{\mu }_{e}}\,}=\,\frac{1}{{{10}^{19}}\times 1.6\times {{10}^{-19}}\times 1.6}\,=\,0.39\]             = 0.4 Ωm.


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