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

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34 Citations (Scopus)


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
Issue number4
Publication statusPublished - 17 Apr 2019
Externally publishedYes


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

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