MHTCET 14 May 2023 Shift 2 Solved Paper

The correct answer is Option B, intrinsic.
Intrinsic semiconductors are materials where the electrical conductivity is derived purely from the semiconductor itself, without any external doping. The conductivity in intrinsic semiconductors occurs because of the breaking of covalent bonds at higher temperatures, which creates electron-hole pairs. These electron-hole pairs contribute to the electrical conductivity.
Here's a brief explanation of each term to clarify the concepts:
Intrinsic Semiconductors (Option B): This is the pure form of a semiconductor, such as silicon or germanium, with no impurities added. The charge carriers (electrons and holes) are generated by thermal energy breaking the covalent bonds. Electrons are excited from the valence band to the conduction band, leaving behind holes in the valence band. Both the excited electrons and the holes contribute to the charge transport in intrinsic semiconductors.
Extrinsic Semiconductors (Option D): These are impure semiconductors intentionally 'doped' with impurities to alter their electrical properties. The addition of a small amount of dopant to a semiconductor can greatly increase its conductivity. There are two types of extrinsic semiconductors:
Donor (n-type) semiconductors (Option A): These have been doped with elements that have more valence electrons than the semiconductor, typically five-valence electrons such as phosphorus or arsenic when doping silicon. These extra electrons can easily move to the conduction band and significantly increase the conductivity of the material.
Acceptor (p-type) semiconductors (Option C): These are doped with elements that have fewer valence electrons (typically three valence electrons) than the semiconductor, such as boron or aluminum when doping silicon. These create holes (positive charge carriers) in the valence band by accepting electrons that jump from the valence band, thus increasing the conductivity.
To summarize, the answer is Option B, intrinsic, because this is the term used to describe a pure semiconductor where conductivity is due solely to its own lattice structure and not influenced by impurities or added elements.