Ultrasensitive and broadband MoS2 photodetector driven by ferroelectrics

Abstract: Photodetectors based on two dimensional materials have attracted growing interest. However, the sensitivity is still unsatisfactory even under high gate voltage. Here we demonstrate a MoS2 photodetector with a poly(vinylidene fluoride-trifluoroethylene) ferroelectric layer in place of the oxide layer in a traditional field effect transistor. The dark current of the photodetector is strongly suppressed by ferroelectric polarization. A high detectivity 2.21012 Jones) and photoresponsitivity (2570 A W) detector has been achieved under ZERO gate bias at a wavelength of 635 nm. Most strikingly, the band gap of few-layer MoS2 can be tuned by the ultra-high electrostatic field from the ferroelectric polarization. With this characteristic, photoresponse wavelengths of the photodetector are extended into the near infrared (0.85-1.55m). A ferroelectrics optoelectronics hybrid structure is an effective way to achieve high performance 2D electronic optoelectronic devices.

• The paper introduces a MoS2 photodetector using a P(VDF-TrFE) ferroelectric layer to achieve 2.2×10¹² Jones detectivity and 2570 A/W responsivity.
• The device fabrication employs mechanical exfoliation and ultrathin aluminum electrodes, with Raman spectroscopy confirming structural integrity and dark current suppression.
• The study shows that ferroelectric polarization enables bandgap tuning, resulting in fast photoresponse times (~1.8 ms rise, ~2 ms decay) and stable broadband infrared detection.

Insights into the MoS$_2$ Photodetector Driven by Ferroelectrics

The paper entitled "Ultrasensitive and broadband MoS$_2$ photodetector driven by ferroelectrics" presents a significant advancement in the domain of two-dimensional (2D) material-based photodetectors, leveraging the unique properties of Molybdenum Disulfide (MoS$_2$). This research introduces a photodetector configuration that substitutes the traditional oxide layer in a field-effect transistor (FET) with a poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) ferroelectric polymer. This innovation serves to optimize both performance and functionality by harnessing ferroelectric-induced polarization effects.

Key Findings and Performance Metrics

1. Ferroelectric Layer Integration:
   • The research notes the integration of a P(VDF-TrFE) ferroelectric layer within MoS$_2$ photodetectors, which dramatically suppresses dark current through remnant polarization. Notably, the resultant photodetector achieves a specific detectivity of approximately $2.2 \times 10^{12}$ Jones and a photoresponsivity of 2570 A/W at a zero gate voltage, extending photoresponse wavelengths into the near-infrared spectrum (0.85–1.55 µm).
2. Device Fabrication:
   • The MoS$_2$ layers were prepared by mechanical exfoliation, and the device architecture incorporated ultrathin aluminum electrodes atop the ferroelectric layer. Raman spectroscopy confirmed the structural integrity, with the ferroelectric properties meticulously characterized via hysteresis loops.
3. Bandgap Tuning and Device States:
   • One of the pivotal discoveries is the ability to adjust the bandgap of few-layer MoS$_2$ using the ultra-high electrostatic field generated by ferroelectric polarization. This electrostatic field encourages a fully depleted state within the semiconductor channel, thereby optimizing detectivity without requiring additional gate bias.
4. Photoresponse Characteristics:
   • The study emphasizes substantial improvements in photoresponse times, achieving a rise and decay time of approximately 1.8 ms and 2 ms respectively, suggesting potential for rapid operation cycles. Moreover, the photoresponse was stable over extended operation cycles, signifying robust device reliability.
5. Band Structure Modifications:
   • The research further explores potential band structure modifications under electric field conditions through computational studies, showing linear dependencies between bandgap energy and applied fields, thereby broadening the operational wavelengths of the photodetector.

Implications and Future Directions

This paper underscores the promise of using ferroelectric materials to engineer bandgaps and expand the functional range of 2D material-based devices. Practically, the enhanced performance metrics suggest potential applications in optical communications and advanced imaging systems. Furthermore, the research paves the way for future exploration into ferroelectric and optoelectronic hybrid devices, encouraging investigation into the physicochemical interactions at ferroelectric and semiconductor interfaces.

In conclusion, the integration of ferroelectric layers for modulating photodetector performance exemplifies a step towards next-generation telecommunications and infrared detection technologies. Upcoming studies might explore optimizing fabrication processes and exploring alternative ferroelectric materials. The efforts to mitigate device defects and enhance electrode transparency could potentially unlock even greater performance efficiencies in 2D materials' photodetectors.