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

For a semiconductor,

Options

Aat 0 K , there are no free electrons
Bthe number of free electrons grows with temperature
Cthere are no free electrons at any given temperature
Dthe number of free electrons is smaller than in a conductor

Correct answer

D. the number of free electrons is smaller than in a conductor

Step-by-step solution

At 0 K , all electrons in a semiconductor are tightly bound in the valence band, leaving the conduction band completely empty. Therefore, there are no free electrons and the semiconductor behaves as a perfect insulator. As the temperature increases, thermal energy excites electrons from the valence band across the energy gap into the conduction band. Thus, the number of free electrons grows with temperature. The number density of free electrons in a semiconductor is significantly smaller than that in a conductor, w

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