Opto/quantum device properties: Match each device with the defining physical attribute or emission property. List I List II A. LED 1. Heavy doping (degenerate p–n junction) B. Avalanche photodiode2. Coherent radiation C. Tunnel diode 3. Spontaneous emission D. LASER 4. Current gain via impact ionization
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AA-2, B-4, C-3, D-1
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BA-2, B-3, C-1, D-4
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CA-3, B-4, C-1, D-2
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DA-2, B-1, C-4, D-3
Answer
Correct Answer: A-3, B-4, C-1, D-2
Explanation
Introduction / Context:LEDs, APDs, tunnel diodes, and LASERs are staple devices in electronics and photonics. This matching tests recognition of their core physical mechanisms.
Given Data / Assumptions:
- LED emission is spontaneous; LASER emission is coherent (stimulated).
- APD uses avalanche multiplication (current gain).
- Tunnel diode depends on heavy (degenerate) doping to enable quantum tunneling and negative resistance.
Concept / Approach:
Connect each device to the mechanism it is known for: spontaneous vs. coherent emission, avalanche gain, and tunneling due to heavy doping.
Step-by-Step Solution:
LED → spontaneous emission ⇒ A-3.APD → impact-ionization current gain ⇒ B-4.Tunnel diode → heavy doping ⇒ C-1.LASER → coherent (stimulated) emission ⇒ D-2.Verification / Alternative check:
Device I–V curves and optical spectra verify: LEDs have broad spectra; LASERs have narrow coherent output; APDs show multiplication factors M; tunnel diodes display negative resistance due to tunneling.
Why Other Options Are Wrong:
- Swapping LED with LASER confuses spontaneous versus stimulated emission.
- Attributing “current gain” to tunnel diodes ignores their primary quantum mechanism.
Common Pitfalls:
Assuming all photodiodes are alike; APDs are distinct because of avalanche multiplication and higher sensitivity requirements.
Final Answer:
A-3, B-4, C-1, D-2