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⚛️ Physics  ·  Semiconductor Electronics  ·  NEET & JEE

Lightly doped drain (LDD) structure in short-channel MOSFETs is designed to:

Answer: Reduce hot carrier effects and drain-induced barrier lowering at drain edge.

  • A Increase the overall drive current delivered by the transistor under most conditions encountered
  • B Reduce hot carrier effects and drain-induced barrier lowering at drain edge
  • C Increase the threshold voltage required to turn on the device as frequently observed in practice
  • D Decrease the gate-to-channel capacitance of the transistor in many documented cases

Correct answer: B. Reduce hot carrier effects and drain-induced barrier lowering at drain edge

Explanation: LDD: graded doping near drain reduces peak electric field. Mitigates hot carrier injection into gate oxide, improving long-term reliability.

Conductorconduction bandvalence bandbands overlapSemiconductorconduction bandvalence bandsmall gap (~1 eV)Insulatorconduction bandvalence bandlarge gap(> 3 eV)

Conductors have overlapping bands, semiconductors have a small energy gap that can be bridged by heat or doping, and insulators have a large gap that blocks conduction.

Concept context

Band theory, p-n junction, diodes, transistors, logic gates, and integrated circuits.

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