Drastically increased absorption in vertical semiconductor nanowire arrays: A non-absorbing dielectric shell makes the difference

Nicklas Anttu*, Kousar L. Namazi, Phillip M. Wu, Pengfei Yang, Hongxing Xu, H. Q. Xu, Ulf Håkanson

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

26 Citations (Scopus)

Abstract

Enhanced absorption of especially long wavelength light is needed to enable the full potential of semiconductor nanowire (NW) arrays for optoelectronic applications. We show both experimentally and theoretically that a transparent dielectric shell (Al2O3 coating) can drastically improve the absorption of light in InAs NW arrays. With an appropriate thickness of the Al2O3 shell, we achieve four times stronger absorption in the NWs compared to uncoated NWs and twice as good absorption as when the dielectric completely fills the space between the NWs. We provide detailed theoretical analysis from a combination of full electrodynamic modeling and intuitive electrostatic approximations. This reveals how the incident light penetrates better into the absorbing NW core with increasing thickness of the dielectric shell until a resonant shell thickness is reached. We provide a simple description of how to reach this strongly absorbing resonance condition, making our results easy to apply for a broad wavelength range and a multifold of semiconductor and dielectric coating material combinations.

Original languageEnglish
Pages (from-to)863-874
Number of pages12
JournalNano Research
Volume5
Issue number12
DOIs
Publication statusPublished - Dec 2012
MoE publication typeA1 Journal article-refereed

Keywords

  • absorption
  • core-shell
  • InAs
  • Nanowire array
  • photovoltaics

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