TiO 2- x -Enhanced IR Hot Carrier Based Photodetection in Metal Thin Film-Si Junctions

Nicholas A. Güsken, Alberto Lauri, Yi Li, Takayuki Matsui, Brock Doiron, Ryan Bower, Anna Regoutz, Andrei Mihai, Peter K. Petrov, Rupert F. Oulton, Lesley F. Cohen, Stefan A. Maier

Research output: Contribution to journalArticleResearchpeer-review

34 Citations (Scopus)

Abstract

We investigate titanium nitride (TiN) thin film coatings on silicon for CMOS-compatible sub-bandgap charge separation upon incident illumination, which is a key feature in the vast field of on-chip photodetection and related integrated photonic devices. Titanium nitride of tunable oxidation distributions serves as an adjustable broadband light absorber with high mechanical robustness and strong chemical resistivity. Backside-illuminated TiN on p-type Si (pSi) constitutes a self-powered and refractory alternative for photodetection, providing a photoresponsivity of about ∼1 mA/W at 1250 nm and zero bias while outperforming conventional metal coatings such as gold (Au). Our study discloses that the enhanced photoresponse of TiN/pSi in the near-infrared spectral range is directly linked to trap states in an ultrathin TiO 2-x interfacial interlayer that forms between TiN and Si. We show that a pSi substrate in conjunction with a few nanometer thick amorphous TiO 2-x film can serve as a platform for photocurrent enhancement of various other metals such as Au and Ti. Moreover, the photoresponse of Au on a TiO 2-x /pSi platform can be increased to about 4 mA/W under 0.45 V reverse bias at 1250 nm, allowing for controlled photoswitching. A clear deviation from the typically assumed Fowler-like response is observed, and an alternative mechanism is proposed to account for the metal/semiconductor TiO 2-x interlayer, capable of facilitating hole transport.

Original languageEnglish
Pages (from-to)953-960
Number of pages8
JournalACS Photonics
Volume6
Issue number4
DOIs
Publication statusPublished - 17 Apr 2019
Externally publishedYes

Keywords

  • CMOS compatible
  • hot carriers
  • sub-bandgap photodetection
  • TiN thin films
  • TiO

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