The Fine-Structure Constant as a Ruler for the Band-Edge Light Absorption Strength of Bulk and Quantum-Confined Semiconductors

P. Tim Prins, Maryam Alimoradi Jazi, Niall A. Killilea, Wiel H. Evers, Pieter Geiregat, Wolfgang Heiss, Arjan J. Houtepen, Christophe Delerue, Zeger Hens, Daniel Vanmaekelbergh*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Low-dimensional semiconductors have found numerous applications in optoelectronics. However, a quantitative comparison of the absorption strength of low-dimensional versus bulk semiconductors has remained elusive. Here, we report generality in the band-edge light absorptance of semiconductors, independent of their dimensions. First, we provide atomistic tight-binding calculations that show that the absorptance of semiconductor quantum wells equals mπα (m = 1 or 2 with α as the fine-structure constant), in agreement with reported experimental results. Then, we show experimentally that a monolayer (superlattice) of quantum dots has similar absorptance, suggesting an absorptance quantum of mπα per (confined) exciton diameter. Extending this idea to bulk semiconductors, we experimentally demonstrate that an absorptance quantum equal to mπα per exciton Bohr diameter explains their widely varying absorption coefficients. We thus provided compelling evidence that the absorptance quantum πα per exciton diameter rules the band-edge absorption of all direct semiconductors, regardless of their dimension.

Original languageEnglish
Pages (from-to)9426-9432
JournalNano Letters
Volume21
Issue number22
DOIs
Publication statusPublished - 2021

Keywords

  • dielectric screening
  • fine-structure constant
  • light absorption
  • optical transitions
  • quantum coupling

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