Match List-I with List-II.
| List-I | List-II |
|---|---|
| (A) Energy gap of germanium | (I) 0.05 eV |
| (B) Energy gap of silicon | (II) 0.72 eV |
| (C) Energy needed to set free the fifth electron of a donor atom in germanium | (III) 0.01 eV |
| (D) Energy needed to set free the fifth electron of a donor atom in silicon | (IV) 1.1 eV |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A)-(II), (B)-(IV), (C)-(III), (D)-(I)
The energy gap is the energy needed to take an electron from the valence band to the conduction band of the pure material. The fifth electron of a donor atom is far more loosely bound, so it needs much less energy.
(A) Energy gap of germanium — This matches (II) 0.72 eV.
(B) Energy gap of silicon — This matches (IV) 1.1 eV. Silicon has the larger gap of the two.
(C) Energy needed to set free the fifth electron of a donor atom in germanium — This matches (III) 0.01 eV.
(D) Energy needed to set free the fifth electron of a donor atom in silicon — This matches (I) 0.05 eV. In both materials this energy is very small, so the donors are ionised at room temperature.
NCERT (2026-27):
n-type semiconductor – “… For example, the energy required is ~ 0.01 eV for germanium, and 0.05 eV for silicon, to separate this electron from its atom. This is in contrast to the energy required to jump the forbidden band (about 0.72 eV for germanium and about 1.1 eV for silicon) at room temperature in the intrinsic semiconductor. …”