Palladium Diselenide Long-Wavelength Infrared Photodetector with High Sensitivity and Stability (1902.02199v1)

Abstract: A long-wavelength infrared (IR) photodetector based on two-dimensional materials working at room temperature would have wide applications in many aspects in remote sensing, thermal imaging, biomedical optics, and medical imaging. However, sub-bandgap light detection in graphene and black phosphorus has been a long-standing scientific challenge because of low photoresponsivity, instability in the air and highdark current. In this study, we report a highly sensitive, air-stable and operable long-wavelength infrared photodetector at room temperature based on PdSe2 phototransistors and its heterostructure. A high photoresponsivity of ~42.1 AW-1 (at 10.6 {\mu}m) was demonstrated, which is an order of magnitude higher than the current record of platinum diselenide. Moreover, the dark current and noise power density were suppressed effectively by fabricating a van der Waals heterostructure. This work fundamentally contributes to establishing long-wavelength infrared detection by PdSe2 at the forefront of long-IR two-dimensional-materials-based photonics.

• The paper demonstrates a PdSe₂ photodetector achieving 42.1 A/W responsivity through a heterostructure design with MoS₂.
• It uses a self-flux synthesis method and DFT calculations to ensure excellent room-temperature stability and low dark current.
• The study underscores the potential of two-dimensional materials for scalable, ambient-stable photodetection in remote sensing and thermal imaging.

Palladium Diselenide Long-Wavelength Infrared Photodetector with High Sensitivity and Stability

The paper presents a comprehensive paper on the development and characterization of a long-wavelength infrared (LWIR) photodetector using palladium diselenide (PdSe₂), a two-dimensional material. This research addresses the limitations of existing LWIR photodetectors which often require cryogenic temperatures, complex fabrication processes, and face stability issues, particularly in ambient conditions.

The authors have synthesized high-quality single crystals of PdSe₂ through a self-flux method, achieving excellent room-temperature stability and high photoresponsivity—critical metrics for practical photodetector applications in remote sensing, thermal imaging, and medical diagnostics. Specifically, the photodetector exhibits a photoresponsivity of approximately 42.1 A/W at a wavelength of 10.6 µm, marking a notable improvement over previously reported values for other two-dimensional materials like graphene and platinum diselenide. This advancement in responsivity is attributed to the heterostructural design using PdSe₂-MoS₂, which also contributes significantly to the suppression of dark current and noise power density through effective carrier mobility and stable electronic properties.

The PdSe₂ photodetectors were shown to have a detectivity $D^*$ as high as $8.21 \times 10^{10}$ Jones, indicating superior sensitivity compared to commercial and traditional semiconductor-based detectors that operate at much lower temperatures. The heterostructure strategy effectively reduced the dark current levels and increased the photodetector efficiency. Moreover, analyses reveal that PdSe₂ showcases strong absorption in the IR range, good carrier mobility, and robust air-stability, distinguishing it from more air-sensitive materials like black phosphorus.

The research methodology included density functional theory (DFT) calculations to predict the band structure and optical properties of PdSe₂, aligning with experimental observations that demonstrated a narrow bandgap and high mobility for multi-layer configurations. The paper also utilized advanced characterization techniques like high-resolution TEM and Raman spectroscopy to ascertain structural fidelity and composition, ensuring the PdSe₂ material meets the necessary optoelectronic standards for high-performance photodetection over a broad wavelength range (450 nm to 10.6 µm).

Theoretically, the paper significantly contributes to the understanding of two-dimensional material functionalities and photoconductive mechanisms, proposing potential pathways for optimizing device performance via vdW heterostructure engineering. Practically, this research could impact the development of scalable and highly sensitive photodetectors that operate efficiently at room temperature, simplifying deployment in various applications while maintaining high performance.

Future investigations might focus on large-scale production techniques for PdSe₂ and similar materials, along with exploring their integration into complex photonic systems. This work promises further advancements in materials science, pushing forward the capability of two-dimensional materials in infrared photon detection and beyond. The comprehensive analysis and promising results outlined in the paper emphasize the viability of PdSe₂ as an exceptional candidate for next-generation optoelectronic devices.