Concepts Of Physics MCQ Edition [Volume 2]PhysicsSemiconductors and Semiconductor Devices

Suppose a semiconductor is doped with a donor impurity.

Options

AThe concentration of holes decreases.
BThe concentration of electrons increases.
CThe concentration of electrons decreases.
DThe concentration of holes increases.

Correct answer

B. The concentration of electrons increases.

Step-by-step solution

When a semiconductor is doped with a donor impurity, pentavalent atoms are added to the crystal lattice. Each donor atom provides one extra electron to the conduction band. As a result, the concentration of electrons ( n_e ) increases significantly. According to the law of mass action for semiconductors, n_e n_h = n_i^2 , where n_h is the concentration of holes and n_i is the intrinsic carrier concentration. Since n_i is constant at a given temperature, an increase in n_e leads to a decrease in the concentration of

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