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Q. The impurity atom that should be added to germanium to make it n-type semiconductor

 1421  216 Bihar CECEBihar CECE 2001Semiconductor Electronics: Materials Devices and Simple Circuits Report Error

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 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.