BCECE Medical BCECE Medical Solved Papers-2001

  • question_answer
    The impurity atom that should be added to germanium to make it n-type semiconductor is:

    A)  aluminium     

    B)  phosphorus

    C)  boron         

    D)  indium

    Correct Answer: B

    Solution :

    An n-type semiconductor is obtained by carrying out a process of doping, that is, by adding an impurity of valence-five elements to a valence-four semiconductor in order to increase the number of free (in this case negative) charge carriers. Out of the given option phosphorus is valence-five element, so it is doped in germanium (valence-four) semiconductor to make it n-type semiconductor. Note: When the doping material is added, it gives away (donates) weakly-bound outer electrons to the semiconductor atoms. This type of doping agent is also known as donor material, since it gives away some of its electrons.


You need to login to perform this action.
You will be redirected in 3 sec spinner