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Is there a lower band-gap limit for luminescence measurements?

In my lab, we're pushing into deeper infrared photonics with narrow-gap semiconductors. As the band-gap shrinks, blackbody radiation at room temperature becomes a significant noise floor. I'm trying to understand where the practical detection limit lies for meaningful luminescence studies.

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By Seema Answered 2 years ago

This is an excellent practical challenge. The limit isn't a fixed number, but a battle against thermal noise. As you've noted, for very narrow gaps, room-temperature thermal energy (k_B T) can excite carriers, creating a strong background. I have seen this swamp signals in materials with gaps below about 0.1 eV. I would recommend that the fundamental limit is effectively set by your ability to cool the sample and detector. With cryogenic systems, you can push further, but you eventually hit detector cut-off limits. It's a trade-off between sample temperature, detector sensitivity, and the intrinsic radiative efficiency of the material itself.

 

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