Question Detail
Question
Which of the following is true about intrinsic semiconductor?
i. Each semiconductor atom undergoes paired sharing of electrons with four neighbouring atoms.
ii. Conduction is due equally to holes and electrons.
iii. Group V atoms in the semiconductor share four electrons with four neighbouring atoms with an extra electron.
iv. Band structure is between that of metals and insulators.
i. Each semiconductor atom undergoes paired sharing of electrons with four neighbouring atoms.
ii. Conduction is due equally to holes and electrons.
iii. Group V atoms in the semiconductor share four electrons with four neighbouring atoms with an extra electron.
iv. Band structure is between that of metals and insulators.
Correct Answer
Option B is the correct answer.
Detailed Explanation
Let's evaluate each statement for an intrinsic semiconductor:i. In intrinsic semiconductors (like Silicon or Germanium), each atom forms covalent bonds by sharing electrons with four neighboring atoms. This statement is true.ii. In an intrinsic semiconductor, electron-hole pairs are created thermally, and thus the number of free electrons in the conduction band is equal to the number of holes in the valence band. Conduction occurs due to both, and they contribute equally. This statement is true.iii. Group V atoms are donor impurities used in n-type (extrinsic) semiconductors, not intrinsic. They have five valence electrons, with one extra electron available for conduction after forming four covalent bonds. This statement is false for intrinsic semiconductors.iv. Semiconductors have a band gap that is smaller than insulators but larger than metals (where bands often overlap or have no gap). This statement is true.Therefore, statements i, ii, and iv are true.
Hint
An intrinsic semiconductor is a pure semiconductor. Consider the bonding, charge carriers, and band structure of pure silicon or germanium.