Question:
The minimum energy gap of a semi-conductor used in manufacturing LED is
The minimum energy gap of a semi-conductor used in manufacturing LED is
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Visible light starts around Red, which corresponds to $1.8\text{ eV}$. Any band gap smaller than this drops into invisible infrared territory.
Updated On: Jun 3, 2026
- 3 eV
- 3.6 eV
- 2.8 eV
- 1.8 eV
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The Correct Option is D
Solution and Explanation
Step 1: Concept
Light Emitting Diodes (LEDs) work on the principle of injection luminescence, where photons are emitted when electrons recombine with holes across the bandgap ($E_{g}$). To emit visible light, the emitted photon energy must fall within the visible spectrum range ($1.8\text{ eV}$ to $3.0\text{ eV}$).
Step 2: Meaning
The boundary of longest visible wavelength (red light) corresponds to a photon energy of approximately $1.8\text{ eV}$. Therefore, a semiconductor must have a minimum bandgap of $1.8\text{ eV}$ to produce visible light.
Step 3: Analysis
Elemental semiconductors like Silicon ($1.1\text{ eV}$) or Germanium ($0.7\text{ eV}$) have smaller energy gaps and emit light in the infrared region. Compound semiconductors like Gallium Arsenide Phosphide (GaAsP) are specifically manufactured with a bandgap of at least $1.8\text{ eV}$ to emit visible light.
Step 4: Conclusion
Thus, the minimum energy gap required for a visible light emitting diode is 1.8 eV.
Final Answer: (D)
Light Emitting Diodes (LEDs) work on the principle of injection luminescence, where photons are emitted when electrons recombine with holes across the bandgap ($E_{g}$). To emit visible light, the emitted photon energy must fall within the visible spectrum range ($1.8\text{ eV}$ to $3.0\text{ eV}$).
Step 2: Meaning
The boundary of longest visible wavelength (red light) corresponds to a photon energy of approximately $1.8\text{ eV}$. Therefore, a semiconductor must have a minimum bandgap of $1.8\text{ eV}$ to produce visible light.
Step 3: Analysis
Elemental semiconductors like Silicon ($1.1\text{ eV}$) or Germanium ($0.7\text{ eV}$) have smaller energy gaps and emit light in the infrared region. Compound semiconductors like Gallium Arsenide Phosphide (GaAsP) are specifically manufactured with a bandgap of at least $1.8\text{ eV}$ to emit visible light.
Step 4: Conclusion
Thus, the minimum energy gap required for a visible light emitting diode is 1.8 eV.
Final Answer: (D)
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