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BCECE Engineering BCECE Engineering Solved Paper-2006

  • question_answer
    Carbon, silicon and germanium have four valence electrons each. These are characterized by valence and conduction bands separated by energy band gap respectively equal to \[{{({{E}_{g}})}_{C}}\] \[{{({{E}_{g}})}_{Si}}\]and \[{{({{E}_{g}})}_{Ge.}}\]. Which of the following statements is true?            

    A)  \[{{({{E}_{g}})}_{C}}={{({{E}_{g}})}_{Si}}={{({{E}_{g}})}_{Ge}}\]

    B)         \[{{({{E}_{g}})}_{C}}>{{({{E}_{g}})}_{Si}}>{{({{E}_{g}})}_{Ge}}\]

    C)         \[{{({{E}_{g}})}_{C}}<{{({{E}_{g}})}_{Ge}}>{{({{E}_{g}})}_{Si}}\]

    D)         \[{{({{E}_{g}})}_{Si}}<{{({{E}_{g}})}_{Ge}}>{{({{E}_{g}})}_{C}}\]

    Correct Answer: B

    Solution :

    Carbon (C), germanium (Ge) and silicon (Si) are semiconductors. They lie in IV A group of periodic table. Now,     \[{{({{E}_{g}})}_{C}}=5.2\,eV\]                 \[{{({{E}_{g}})}_{Ge}}=0.75\,eV\]                 \[{{({{E}_{g}})}_{Si}}=1.21\,eV\] Thus, it is obvious that \[{{({{E}_{g}})}_{C}}>{{({{E}_{g}})}_{Si}}>{{({{E}_{g}})}_{Ge}}\]


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