Question

An intrinsic semiconductor at the absolute zero temperature ________.
A. Behaves like a metallic conductor
B. Behaves like an insulator
C. Has a large number of holes
D. Has a large number of electrons

Answer 1

At absolute zero temperature, the electrons will not have adequate energy to jump from the valence band to the conduction band. So no electrons are existing in the conduction band to conduct electricity. From this concept, we can choose from the required options.

Complete step by step solution:
The intrinsic semiconductor is a kind of semiconductor, which has no impurities present in it. Accordingly, the conducting electrons for an intrinsic semiconductor are the electrons that vacate the valence shell leaving behind a hole. The gap between the conduction band and the valence band, which is called the forbidden gap for an intrinsic semiconductor will be almost equal to the value of $1eV$ . At the temperature, $T = 300K$ or $T = 27^\circ C$, which is room temperature, the electrons from the valence band jump into the conduction band once it gains some amount of energy and leaves behind holes in the valence band. At the temperature, $T = 0{\mkern 1mu} K$ the electrons of the valence band will continue to be in this band only, because they don’t get sufficient energy to jump to the upper prohibited band. Since the electrons cannot jump to the conduction band at this temperature, the electricity will not be conducted. Hence the semiconductor turns out to be an insulator in nature. The intrinsic semiconductor acts as an insulator at $T = 0K$. Thus, option (A) is correct.

Note:
One of the main differences between the conductor, semiconductor, and insulator is in their conduction state. The extrinsic semiconductor is a kind of semiconductor, where the number of electrons is more than the number of holes. The intrinsic semiconductors are those which have no impurities combined in them. So unlike extrinsics, there are no totally free electrons in the case of intrinsic semiconductors. The electrons in the valence band increase their energy from the atmosphere and jump from the valence band to the conduction band.