Dominant enhancement mechanisms in WO3−x/CsyWO3−x nanocrystal-modified InGaAs MSM photodetectors

Determine which mechanisms—localized surface plasmon resonance (LSPR) field enhancement in the In0.53Ga0.47As layer, plasmon-induced hot-carrier injection from WO3−x or CsyWO3−x nanocrystals into the semiconductor, or antireflective scattering and photon collection due to nanocrystal films—are present and which are dominant in In0.52Al0.48As/In0.53Ga0.47As metal–semiconductor–metal photodetectors functionalized with WO3−x nanorods or CsyWO3−x hexagonal nanoprisms under the experimental conditions reported.

Background

The study demonstrates enhanced responsivity and external quantum efficiency in In0.52Al0.48As/In0.53Ga0.47As MSM photodetectors after drop-casting plasmonic WO3−x nanorods or CsyWO3−x hexagonal nanoprisms onto the active area. Spectral enhancements broadly track nanocrystal extinction features, suggesting plasmonic involvement.

The authors outline several candidate mechanisms for the observed enhancement: (1) LSPR-induced near-field amplification increasing carrier generation in the InGaAs layer; (2) injection of plasmon-induced hot carriers from the nanocrystals into the semiconductor; and (3) antireflective effects and enhanced photon collection from nanocrystal films. They note that the current data do not distinguish among these mechanisms and propose targeted experiments (e.g., insulating interlayers, varying InAlAs thickness, tuning nanocrystal doping and morphology) to isolate and evaluate their contributions.

References

Mechanisms for plasmonic response giving rise to increased photodetector EQEs have been debated in recent years. Possible mechanisms to explain our observations include: 1) LSPR modes of the NCs create stronger electric fields in the InGaAs layer of the MSM photodetector, generating charge carriers at a higher rate. 2) Plasmon-induced hot carriers are injected from the NCs into the bulk semiconductor. 3) Photon collection from scattering is increased due to the NC films forming an anti-reflective (AR) coating. It is not clear from the present data which of these mechanisms are present or dominant in our devices.

— Enhancement of Photoresponse for InGaAs Infrared Photodetectors Using Plasmonic WO3-x/CsyWO3-x Nanocrystals  (2408.10389 - Merino et al., 2024) in Discussion