The Fine-Structure Constant as a Ruler for the Band-Edge Light Absorption Strength of Bulk and Quantum-Confined Semiconductors
P. Tim Prins (Debye Institute)
Maryam Alimoradi Jazi (Debye Institute)
Niall A. Killilea (Friedrich-Alexander-Universität Erlangen-Nürnberg)
Wiel H. Evers (TU Delft - BN/Technici en Analisten)
Pieter Geiregat (Universiteit Gent)
Wolfgang Heiss (Friedrich-Alexander-Universität Erlangen-Nürnberg)
Arjan J. Houtepen (TU Delft - ChemE/Opto-electronic Materials)
Christophe Delerue (Université de Lille)
Zeger Hens (Universiteit Gent)
Daniel Vanmaekelbergh (Debye Institute)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
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.
help_outline