GR0877 Problem 96
PROBLEM STATEMENT: This problem is still being typed.
SOLUTION: (D) If you impure into tetravalent germanium atom a pentavalent element such as , , or , then four of the five valence electrons introduced by impurity atoms come into contact with four neighboring atoms of and form a stable shell of eight electrons, while the fifth electron will be weakly bound to the nucleus of the impurity atom. This creates an excess of negative (-type) electron charge carriers. The only element that cannot be used to create an excess of negative charge is , since it has only three valence electrons.
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