Printed MoSe2/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 (MoSe2) and gallium arsenide (GaAs). The fabrication process involves a precise technique to print MoSe2 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 MoSe2. The fabricated PD achieves an astounding on-off ratio of ∼105 at 5 V bias while demonstrating an exceptional on-off ratio of ∼104 at 0 V. The depletion region between GaAs and MoSe2 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 MoSe2 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 MoSe2/GaAs heterostructure PD promising for future low-cost and efficient optoelectronic devices.

A fully printed ultrafast Si/WS2 quantum dot photodetector with very high responsivity over the UV to near-infrared region.

Two-dimensional (2D) semiconducting material-based photodetectors (PDs) with high responsivity and fast photo-response are of great interest for various applications such as optical communications, biomedical imaging, security surveillance, environmental monitoring, etc. Additive manufacturing such as 2D printing is a potentially less cumbersome and cost-effective alternative to conventional microdevice fabrication processes used in the production of PDs. Here, we have fabricated a Si/WS2 quantum dot-based heterostructure PD with a very short electrode gap of 40 µm by a simple printing process. The printed p-Si/n-WS2 PD shows an excellent photo-to-dark current ratio of 5121 under 405 nm illumination (23.8 mW cm-2). The printed photodetector exhibits a peak responsivity of 126 A W-1 and a peak detectivity of 9.24 × 1012 Jones over a very broad wavelength range (300-1100 nm), which is much superior to commercial Si PDs. A high external quantum efficiency of 3.9 × 104% and an ultrafast photoresponse (7.8 µs rise time and 9.5 µs fall time) make the device an attractive candidate as an efficient photodetector. The origin of high-performance photodetection is traced to a nearly defect-free interface at the heterojunction, leading to highly efficient charge separation and high photocurrent. Finally, the 2D-printed device exhibits good photodetection even in self-powered conditions, which is very attractive.