Saturday, August 13, 2011

How can a P-type semiconductor be neutral?

Suppose we have an intrinsic semiconductor example, Germanium. Each Germanium atom in the semiconductor sees eight electrons around it. When a trivalent atom is added one of the germanium atom is removed, leaving +4 charge on the intrinsic semiconductor. When this trivalent impurity is added the three valence electrons are engaged in covalent bond formation with three germanium atoms but the fourth bond and left incomplete thus leaving a hole on that bond. Doesn't this mean that the P-type semiconductor has a net positive charge on it?

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