When pentavalent impurity atoms (like phosphorus or arsenic, which have 5 valence electrons) are added to an intrinsic semiconductor material (like silicon or germanium, which have 4 valence electrons
This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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When pentavalent impurity atoms (like phosphorus or arsenic, which have 5 valence electrons) are added to an intrinsic semiconductor material (like silicon or germanium, which have 4 valence electrons), the process is called n-type doping.
Each pentavalent impurity atom replaces a semiconductor atom in the crystal lattice. Four of its valence electrons form covalent bonds with the surrounding semiconductor atoms. The fifth valence electron is loosely bound to the impurity atom and requires very little energy to break free and become a free electron in the conduction band.
This process significantly increases the concentration of free electrons in the semiconductor, making them the majority charge carriers. The number of holes (minority carriers) might slightly decrease due to increased recombination with the newly introduced free electrons, but the dominant effect is the increase in free electrons.
Therefore, adding pentavalent impurity atoms increases the number of free electrons.
The final answer is $\boxed{\text{C) free electrons increased}}$.
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