In a pure semiconductor, concentration of electrons in conduction band is equal to the concentration of holes in valence band. In the process of conduction when an electric field is applied, the electron moves in the opposite direction of the field and occupies the position of nearest hole, so that, a new hole is created in the place of electron.

This process of electron movement and hole movement continues in the semiconductor substance. In the applied electric field, electrons move towards positive terminal of the battery and hole moves towards negative terminal of the battery.