Identify the correct statements among the following.
(A) The number of electrons ($n_e$) is more than the number of holes ($n_h$) in intrinsic conductors.
(B) Semiconductors are elements (Si, Ge) type as well as compounds (GaAs, CdS).
(C) The number of charge carriers can be changed by 'doping' of a suitable impurity in pure semiconductors.
(D) Holes are essentially electron vacancies in a valence band.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (B), (C) and (D) only
✅ Correct statements: (B), (C), (D)
(A) ❌ Incorrect: In an intrinsic semiconductor, every electron excited to the conduction band leaves a corresponding hole in the valence band. Hence, $n_e = n_h$ and not $n_e > n_h$.
(B) ✅ Correct: Semiconductors exist as both elemental types (such as Si and Ge) and compound types (such as GaAs and CdS), exhibiting similar electrical properties.
(C) ✅ Correct: The number of charge carriers in a semiconductor can be controlled by doping it with suitable impurities. Donor impurities produce n-type and acceptor impurities produce p-type semiconductors.
(D) ✅ Correct: A hole is an electron vacancy in the valence band that behaves as a positively charged carrier, contributing to current conduction.