OPSC OAS 2022 PrelimsScience & TechnologyQuestion 3
Solved previous year question from the OPSC OAS/OCS 2022 Preliminary Examination (General Studies), with the official answer key and a detailed explanation.
Question
The light emitting diode (LED) is made of
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Answer & Explanation
Correct answer: (C) GaN
- A Light Emitting Diode (LED) is a semiconductor device that emits light when electric current passes through it. LEDs are made of compound semiconductors — specifically III-V semiconductor compounds — rather than elemental semiconductors like Silicon or Germanium.
- GaN (Gallium Nitride) is one of the most important materials used in modern LEDs, particularly for blue and white LEDs. The discovery of blue LEDs using GaN was so significant that it was awarded the Nobel Prize in Physics in 2014 to Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura.
Silicon (Si) — widely used in electronics and solar cells but is an indirect bandgap semiconductor — it cannot emit light efficiently and is not used for LEDs.
Germanium (Ge) — also an indirect bandgap semiconductor — similarly cannot emit light efficiently and is not used for LEDs.
Tungsten — a metal used as a filament in incandescent bulbs — completely different technology from LEDs. Tungsten produces light by heating, while LEDs produce light by electroluminescence.
