Question

Which of the following statements is true for an n-type semiconductor?

• A. The donor level lies closely below the bottom of the conduction band
• B. The donor level lies closely above the top of the valence band
• C. The donor level lies at the halfway mark of the forbidden energy gap
• D. None of the above

Answer 1

Answer: (A)

The donor level lies closely below the bottom of the conduction band

Answer 2

The donor level is found only in n-type semiconductors. The donor level lies closely below the bottom of the conduction band. In the figure shown, below conduction band there are ${{N}_{d}}$ donor levels per $c{{m}^{3}}$ of energy ${{E}_{i}}$ At low temperatures, small fraction of donors will be ionised and practically all donor levels will be filled with electrons.
Note: $\Delta E=({{E}_{C}}-{{E}_{i}})$ is called as ionisation energy of donors.