Printed MoSe 2 /GaAs Photodetector Enabling Ultrafast and Broadband Photodetection up to 1.5 μm.

The development of high-performance and low-cost photodetectors (PDs) capable of detecting a broad range of wavelengths, from ultraviolet (UV) to near-infrared (NIR), is crucial for applications in sensing, imaging, and communication systems. This work presents a novel approach for printing a broadband PD based on a heterostructure of two-dimensional (2D) molybdenum diselenide (MoSe 2 ) and gallium arsenide (GaAs). The fabrication process involves a precise technique to print MoSe 2 nanoflower (NF) ink onto a prepatterned GaAs substrate. The resulting heterostructure exhibits unique properties, leveraging the exceptional electronic and optical characteristics of both GaAs and 2D MoSe 2 . The fabricated PD achieves an astounding on-off ratio of ∼10 5 at 5 V bias while demonstrating an exceptional on-off ratio of ∼10 4 at 0 V. The depletion region between GaAs and MoSe 2 facilitates efficient charge generation and separation and collection of photogenerated carriers. This significantly improves the performance of the PD, resulting in a notably high responsivity across the spectrum. The peak responsivity of the device is 5.25 A/W at 5 V bias under 808 nm laser excitation, which is more than an order of magnitude higher than that of any commercial NIR PDs. Furthermore, the device demonstrates an exceptional responsivity of 0.36 A/W under an external bias of 0 V. The printing technology used here offers several advantages including simplicity, scalability, and compatibility with large-scale production. Additionally, it enables precise control over the placement and integration of the MoSe 2 NF onto the GaAs substrate, ensuring uniformity and reliability in device performance. The exceptional responsivity across a broad spectral range (360-1550 nm) and the success of the printing technique make our MoSe 2 /GaAs heterostructure PD promising for future low-cost and efficient optoelectronic devices.