Electric conduction in a semiconductor occurs due to:

The correct answer is Option (3) → both electrons and holes

In a semiconductor the current is carried by two kinds of charge carriers: free electrons in the conduction band and holes in the valence band.

When an electron leaves a covalent bond it becomes free and leaves behind a vacancy (hole) with an effective charge \( +e \). Under an applied field the free electrons drift towards the positive end, and the holes effectively move towards the negative end as bound electrons from neighbouring bonds fill them. The total current is the sum of the electron current and the hole current.

    \( I = I_e + I_h \)

Even in a doped semiconductor both carriers are present; doping only makes one of them the majority carrier. The impurity ions themselves are fixed in the crystal lattice and do not carry current.

Note: A similar question was also asked in CUET (UG) 2023 on 30-05-2023 (Slot 1).

NCERT (2026-27):
Intrinsic Semiconductor – “… Semiconductors posses the unique property in which, apart from electrons, the holes also move. … The free electron moves completely independently as conduction electron and gives rise to an electron current, I_e under an applied electric field. … Under the action of an electric field, these holes move towards negative potential giving the hole current, I_h. The total current, I is thus the sum of the electron current I_e and the hole current I_h:

    \( \displaystyle I = I_e + I_h \qquad (14.2) \)”